2 * Copyright (c) 1994,1997 John S. Dyson
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
8 * 1. Redistributions of source code must retain the above copyright
9 * notice immediately at the beginning of the file, without modification,
10 * this list of conditions, and the following disclaimer.
11 * 2. Absolutely no warranty of function or purpose is made by the author
14 * $FreeBSD: src/sys/kern/vfs_bio.c,v 1.242.2.20 2003/05/28 18:38:10 alc Exp $
18 * this file contains a new buffer I/O scheme implementing a coherent
19 * VM object and buffer cache scheme. Pains have been taken to make
20 * sure that the performance degradation associated with schemes such
21 * as this is not realized.
23 * Author: John S. Dyson
24 * Significant help during the development and debugging phases
25 * had been provided by David Greenman, also of the FreeBSD core team.
27 * see man buf(9) for more info.
30 #include <sys/param.h>
31 #include <sys/systm.h>
34 #include <sys/devicestat.h>
35 #include <sys/eventhandler.h>
37 #include <sys/malloc.h>
38 #include <sys/mount.h>
39 #include <sys/kernel.h>
40 #include <sys/kthread.h>
42 #include <sys/reboot.h>
43 #include <sys/resourcevar.h>
44 #include <sys/sysctl.h>
45 #include <sys/vmmeter.h>
46 #include <sys/vnode.h>
47 #include <sys/dsched.h>
49 #include <vm/vm_param.h>
50 #include <vm/vm_kern.h>
51 #include <vm/vm_pageout.h>
52 #include <vm/vm_page.h>
53 #include <vm/vm_object.h>
54 #include <vm/vm_extern.h>
55 #include <vm/vm_map.h>
56 #include <vm/vm_pager.h>
57 #include <vm/swap_pager.h>
60 #include <sys/thread2.h>
61 #include <sys/spinlock2.h>
62 #include <sys/mplock2.h>
63 #include <vm/vm_page2.h>
74 BQUEUE_NONE, /* not on any queue */
75 BQUEUE_LOCKED, /* locked buffers */
76 BQUEUE_CLEAN, /* non-B_DELWRI buffers */
77 BQUEUE_DIRTY, /* B_DELWRI buffers */
78 BQUEUE_DIRTY_HW, /* B_DELWRI buffers - heavy weight */
79 BQUEUE_EMPTYKVA, /* empty buffer headers with KVA assignment */
80 BQUEUE_EMPTY, /* empty buffer headers */
82 BUFFER_QUEUES /* number of buffer queues */
85 typedef enum bufq_type bufq_type_t;
87 #define BD_WAKE_SIZE 16384
88 #define BD_WAKE_MASK (BD_WAKE_SIZE - 1)
90 TAILQ_HEAD(bqueues, buf) bufqueues[BUFFER_QUEUES];
91 static struct spinlock bufqspin = SPINLOCK_INITIALIZER(&bufqspin);
92 static struct spinlock bufcspin = SPINLOCK_INITIALIZER(&bufcspin);
94 static MALLOC_DEFINE(M_BIOBUF, "BIO buffer", "BIO buffer");
96 struct buf *buf; /* buffer header pool */
98 static void vfs_clean_pages(struct buf *bp);
99 static void vfs_clean_one_page(struct buf *bp, int pageno, vm_page_t m);
100 static void vfs_dirty_one_page(struct buf *bp, int pageno, vm_page_t m);
101 static void vfs_vmio_release(struct buf *bp);
102 static int flushbufqueues(bufq_type_t q);
103 static vm_page_t bio_page_alloc(vm_object_t obj, vm_pindex_t pg, int deficit);
105 static void bd_signal(int totalspace);
106 static void buf_daemon(void);
107 static void buf_daemon_hw(void);
110 * bogus page -- for I/O to/from partially complete buffers
111 * this is a temporary solution to the problem, but it is not
112 * really that bad. it would be better to split the buffer
113 * for input in the case of buffers partially already in memory,
114 * but the code is intricate enough already.
116 vm_page_t bogus_page;
119 * These are all static, but make the ones we export globals so we do
120 * not need to use compiler magic.
122 long bufspace; /* locked by buffer_map */
124 static long bufmallocspace; /* atomic ops */
125 long maxbufmallocspace, lobufspace, hibufspace;
126 static int bufreusecnt, bufdefragcnt, buffreekvacnt;
127 static long lorunningspace;
128 static long hirunningspace;
129 static int runningbufreq; /* locked by bufcspin */
130 static long dirtybufspace; /* locked by bufcspin */
131 static int dirtybufcount; /* locked by bufcspin */
132 static long dirtybufspacehw; /* locked by bufcspin */
133 static int dirtybufcounthw; /* locked by bufcspin */
134 static long runningbufspace; /* locked by bufcspin */
135 static int runningbufcount; /* locked by bufcspin */
136 long lodirtybufspace;
137 long hidirtybufspace;
138 static int getnewbufcalls;
139 static int getnewbufrestarts;
140 static int recoverbufcalls;
141 static int needsbuffer; /* locked by bufcspin */
142 static int bd_request; /* locked by bufcspin */
143 static int bd_request_hw; /* locked by bufcspin */
144 static u_int bd_wake_ary[BD_WAKE_SIZE];
145 static u_int bd_wake_index;
146 static u_int vm_cycle_point = 40; /* 23-36 will migrate more act->inact */
147 static int debug_commit;
149 static struct thread *bufdaemon_td;
150 static struct thread *bufdaemonhw_td;
151 static u_int lowmempgallocs;
152 static u_int lowmempgfails;
155 * Sysctls for operational control of the buffer cache.
157 SYSCTL_LONG(_vfs, OID_AUTO, lodirtybufspace, CTLFLAG_RW, &lodirtybufspace, 0,
158 "Number of dirty buffers to flush before bufdaemon becomes inactive");
159 SYSCTL_LONG(_vfs, OID_AUTO, hidirtybufspace, CTLFLAG_RW, &hidirtybufspace, 0,
160 "High watermark used to trigger explicit flushing of dirty buffers");
161 SYSCTL_LONG(_vfs, OID_AUTO, lorunningspace, CTLFLAG_RW, &lorunningspace, 0,
162 "Minimum amount of buffer space required for active I/O");
163 SYSCTL_LONG(_vfs, OID_AUTO, hirunningspace, CTLFLAG_RW, &hirunningspace, 0,
164 "Maximum amount of buffer space to usable for active I/O");
165 SYSCTL_UINT(_vfs, OID_AUTO, lowmempgallocs, CTLFLAG_RW, &lowmempgallocs, 0,
166 "Page allocations done during periods of very low free memory");
167 SYSCTL_UINT(_vfs, OID_AUTO, lowmempgfails, CTLFLAG_RW, &lowmempgfails, 0,
168 "Page allocations which failed during periods of very low free memory");
169 SYSCTL_UINT(_vfs, OID_AUTO, vm_cycle_point, CTLFLAG_RW, &vm_cycle_point, 0,
170 "Recycle pages to active or inactive queue transition pt 0-64");
172 * Sysctls determining current state of the buffer cache.
174 SYSCTL_INT(_vfs, OID_AUTO, nbuf, CTLFLAG_RD, &nbuf, 0,
175 "Total number of buffers in buffer cache");
176 SYSCTL_LONG(_vfs, OID_AUTO, dirtybufspace, CTLFLAG_RD, &dirtybufspace, 0,
177 "Pending bytes of dirty buffers (all)");
178 SYSCTL_LONG(_vfs, OID_AUTO, dirtybufspacehw, CTLFLAG_RD, &dirtybufspacehw, 0,
179 "Pending bytes of dirty buffers (heavy weight)");
180 SYSCTL_INT(_vfs, OID_AUTO, dirtybufcount, CTLFLAG_RD, &dirtybufcount, 0,
181 "Pending number of dirty buffers");
182 SYSCTL_INT(_vfs, OID_AUTO, dirtybufcounthw, CTLFLAG_RD, &dirtybufcounthw, 0,
183 "Pending number of dirty buffers (heavy weight)");
184 SYSCTL_LONG(_vfs, OID_AUTO, runningbufspace, CTLFLAG_RD, &runningbufspace, 0,
185 "I/O bytes currently in progress due to asynchronous writes");
186 SYSCTL_INT(_vfs, OID_AUTO, runningbufcount, CTLFLAG_RD, &runningbufcount, 0,
187 "I/O buffers currently in progress due to asynchronous writes");
188 SYSCTL_LONG(_vfs, OID_AUTO, maxbufspace, CTLFLAG_RD, &maxbufspace, 0,
189 "Hard limit on maximum amount of memory usable for buffer space");
190 SYSCTL_LONG(_vfs, OID_AUTO, hibufspace, CTLFLAG_RD, &hibufspace, 0,
191 "Soft limit on maximum amount of memory usable for buffer space");
192 SYSCTL_LONG(_vfs, OID_AUTO, lobufspace, CTLFLAG_RD, &lobufspace, 0,
193 "Minimum amount of memory to reserve for system buffer space");
194 SYSCTL_LONG(_vfs, OID_AUTO, bufspace, CTLFLAG_RD, &bufspace, 0,
195 "Amount of memory available for buffers");
196 SYSCTL_LONG(_vfs, OID_AUTO, maxmallocbufspace, CTLFLAG_RD, &maxbufmallocspace,
197 0, "Maximum amount of memory reserved for buffers using malloc");
198 SYSCTL_LONG(_vfs, OID_AUTO, bufmallocspace, CTLFLAG_RD, &bufmallocspace, 0,
199 "Amount of memory left for buffers using malloc-scheme");
200 SYSCTL_INT(_vfs, OID_AUTO, getnewbufcalls, CTLFLAG_RD, &getnewbufcalls, 0,
201 "New buffer header acquisition requests");
202 SYSCTL_INT(_vfs, OID_AUTO, getnewbufrestarts, CTLFLAG_RD, &getnewbufrestarts,
203 0, "New buffer header acquisition restarts");
204 SYSCTL_INT(_vfs, OID_AUTO, recoverbufcalls, CTLFLAG_RD, &recoverbufcalls, 0,
205 "Recover VM space in an emergency");
206 SYSCTL_INT(_vfs, OID_AUTO, bufdefragcnt, CTLFLAG_RD, &bufdefragcnt, 0,
207 "Buffer acquisition restarts due to fragmented buffer map");
208 SYSCTL_INT(_vfs, OID_AUTO, buffreekvacnt, CTLFLAG_RD, &buffreekvacnt, 0,
209 "Amount of time KVA space was deallocated in an arbitrary buffer");
210 SYSCTL_INT(_vfs, OID_AUTO, bufreusecnt, CTLFLAG_RD, &bufreusecnt, 0,
211 "Amount of time buffer re-use operations were successful");
212 SYSCTL_INT(_vfs, OID_AUTO, debug_commit, CTLFLAG_RW, &debug_commit, 0, "");
213 SYSCTL_INT(_debug_sizeof, OID_AUTO, buf, CTLFLAG_RD, 0, sizeof(struct buf),
214 "sizeof(struct buf)");
216 char *buf_wmesg = BUF_WMESG;
218 #define VFS_BIO_NEED_ANY 0x01 /* any freeable buffer */
219 #define VFS_BIO_NEED_UNUSED02 0x02
220 #define VFS_BIO_NEED_UNUSED04 0x04
221 #define VFS_BIO_NEED_BUFSPACE 0x08 /* wait for buf space, lo hysteresis */
226 * Called when buffer space is potentially available for recovery.
227 * getnewbuf() will block on this flag when it is unable to free
228 * sufficient buffer space. Buffer space becomes recoverable when
229 * bp's get placed back in the queues.
235 * If someone is waiting for BUF space, wake them up. Even
236 * though we haven't freed the kva space yet, the waiting
237 * process will be able to now.
239 spin_lock(&bufcspin);
240 if (needsbuffer & VFS_BIO_NEED_BUFSPACE) {
241 needsbuffer &= ~VFS_BIO_NEED_BUFSPACE;
242 spin_unlock(&bufcspin);
243 wakeup(&needsbuffer);
245 spin_unlock(&bufcspin);
252 * Accounting for I/O in progress.
256 runningbufwakeup(struct buf *bp)
261 if ((totalspace = bp->b_runningbufspace) != 0) {
262 spin_lock(&bufcspin);
263 runningbufspace -= totalspace;
265 bp->b_runningbufspace = 0;
268 * see waitrunningbufspace() for limit test.
270 limit = hirunningspace * 3 / 6;
271 if (runningbufreq && runningbufspace <= limit) {
273 spin_unlock(&bufcspin);
274 wakeup(&runningbufreq);
276 spin_unlock(&bufcspin);
278 bd_signal(totalspace);
285 * Called when a buffer has been added to one of the free queues to
286 * account for the buffer and to wakeup anyone waiting for free buffers.
287 * This typically occurs when large amounts of metadata are being handled
288 * by the buffer cache ( else buffer space runs out first, usually ).
295 spin_lock(&bufcspin);
297 needsbuffer &= ~VFS_BIO_NEED_ANY;
298 spin_unlock(&bufcspin);
299 wakeup(&needsbuffer);
301 spin_unlock(&bufcspin);
306 * waitrunningbufspace()
308 * If runningbufspace exceeds 4/6 hirunningspace we block until
309 * runningbufspace drops to 3/6 hirunningspace. We also block if another
310 * thread blocked here in order to be fair, even if runningbufspace
311 * is now lower than the limit.
313 * The caller may be using this function to block in a tight loop, we
314 * must block while runningbufspace is greater than at least
315 * hirunningspace * 3 / 6.
318 waitrunningbufspace(void)
320 long limit = hirunningspace * 4 / 6;
322 if (runningbufspace > limit || runningbufreq) {
323 spin_lock(&bufcspin);
324 while (runningbufspace > limit || runningbufreq) {
326 ssleep(&runningbufreq, &bufcspin, 0, "wdrn1", 0);
328 spin_unlock(&bufcspin);
333 * buf_dirty_count_severe:
335 * Return true if we have too many dirty buffers.
338 buf_dirty_count_severe(void)
340 return (runningbufspace + dirtybufspace >= hidirtybufspace ||
341 dirtybufcount >= nbuf / 2);
345 * Return true if the amount of running I/O is severe and BIOQ should
349 buf_runningbufspace_severe(void)
351 return (runningbufspace >= hirunningspace * 4 / 6);
355 * vfs_buf_test_cache:
357 * Called when a buffer is extended. This function clears the B_CACHE
358 * bit if the newly extended portion of the buffer does not contain
361 * NOTE! Dirty VM pages are not processed into dirty (B_DELWRI) buffer
362 * cache buffers. The VM pages remain dirty, as someone had mmap()'d
363 * them while a clean buffer was present.
367 vfs_buf_test_cache(struct buf *bp,
368 vm_ooffset_t foff, vm_offset_t off, vm_offset_t size,
371 if (bp->b_flags & B_CACHE) {
372 int base = (foff + off) & PAGE_MASK;
373 if (vm_page_is_valid(m, base, size) == 0)
374 bp->b_flags &= ~B_CACHE;
381 * Spank the buf_daemon[_hw] if the total dirty buffer space exceeds the
390 if (dirtybufspace < lodirtybufspace && dirtybufcount < nbuf / 2)
393 if (bd_request == 0 &&
394 (dirtybufspace - dirtybufspacehw > lodirtybufspace / 2 ||
395 dirtybufcount - dirtybufcounthw >= nbuf / 2)) {
396 spin_lock(&bufcspin);
398 spin_unlock(&bufcspin);
401 if (bd_request_hw == 0 &&
402 (dirtybufspacehw > lodirtybufspace / 2 ||
403 dirtybufcounthw >= nbuf / 2)) {
404 spin_lock(&bufcspin);
406 spin_unlock(&bufcspin);
407 wakeup(&bd_request_hw);
414 * Get the buf_daemon heated up when the number of running and dirty
415 * buffers exceeds the mid-point.
417 * Return the total number of dirty bytes past the second mid point
418 * as a measure of how much excess dirty data there is in the system.
429 mid1 = lodirtybufspace + (hidirtybufspace - lodirtybufspace) / 2;
431 totalspace = runningbufspace + dirtybufspace;
432 if (totalspace >= mid1 || dirtybufcount >= nbuf / 2) {
434 mid2 = mid1 + (hidirtybufspace - mid1) / 2;
435 if (totalspace >= mid2)
436 return(totalspace - mid2);
444 * Wait for the buffer cache to flush (totalspace) bytes worth of
445 * buffers, then return.
447 * Regardless this function blocks while the number of dirty buffers
448 * exceeds hidirtybufspace.
453 bd_wait(int totalspace)
458 if (curthread == bufdaemonhw_td || curthread == bufdaemon_td)
461 while (totalspace > 0) {
463 if (totalspace > runningbufspace + dirtybufspace)
464 totalspace = runningbufspace + dirtybufspace;
465 count = totalspace / BKVASIZE;
466 if (count >= BD_WAKE_SIZE)
467 count = BD_WAKE_SIZE - 1;
469 spin_lock(&bufcspin);
470 i = (bd_wake_index + count) & BD_WAKE_MASK;
474 * This is not a strict interlock, so we play a bit loose
475 * with locking access to dirtybufspace*
477 tsleep_interlock(&bd_wake_ary[i], 0);
478 spin_unlock(&bufcspin);
479 tsleep(&bd_wake_ary[i], PINTERLOCKED, "flstik", hz);
481 totalspace = runningbufspace + dirtybufspace - hidirtybufspace;
488 * This function is called whenever runningbufspace or dirtybufspace
489 * is reduced. Track threads waiting for run+dirty buffer I/O
495 bd_signal(int totalspace)
499 if (totalspace > 0) {
500 if (totalspace > BKVASIZE * BD_WAKE_SIZE)
501 totalspace = BKVASIZE * BD_WAKE_SIZE;
502 spin_lock(&bufcspin);
503 while (totalspace > 0) {
506 if (bd_wake_ary[i]) {
508 spin_unlock(&bufcspin);
509 wakeup(&bd_wake_ary[i]);
510 spin_lock(&bufcspin);
512 totalspace -= BKVASIZE;
514 spin_unlock(&bufcspin);
519 * BIO tracking support routines.
521 * Release a ref on a bio_track. Wakeup requests are atomically released
522 * along with the last reference so bk_active will never wind up set to
529 bio_track_rel(struct bio_track *track)
537 active = track->bk_active;
538 if (active == 1 && atomic_cmpset_int(&track->bk_active, 1, 0))
542 * Full-on. Note that the wait flag is only atomically released on
543 * the 1->0 count transition.
545 * We check for a negative count transition using bit 30 since bit 31
546 * has a different meaning.
549 desired = (active & 0x7FFFFFFF) - 1;
551 desired |= active & 0x80000000;
552 if (atomic_cmpset_int(&track->bk_active, active, desired)) {
553 if (desired & 0x40000000)
554 panic("bio_track_rel: bad count: %p\n", track);
555 if (active & 0x80000000)
559 active = track->bk_active;
564 * Wait for the tracking count to reach 0.
566 * Use atomic ops such that the wait flag is only set atomically when
567 * bk_active is non-zero.
572 bio_track_wait(struct bio_track *track, int slp_flags, int slp_timo)
581 if (track->bk_active == 0)
585 * Full-on. Note that the wait flag may only be atomically set if
586 * the active count is non-zero.
588 * NOTE: We cannot optimize active == desired since a wakeup could
589 * clear active prior to our tsleep_interlock().
592 while ((active = track->bk_active) != 0) {
594 desired = active | 0x80000000;
595 tsleep_interlock(track, slp_flags);
596 if (atomic_cmpset_int(&track->bk_active, active, desired)) {
597 error = tsleep(track, slp_flags | PINTERLOCKED,
609 * Load time initialisation of the buffer cache, called from machine
610 * dependant initialization code.
616 vm_offset_t bogus_offset;
619 /* next, make a null set of free lists */
620 for (i = 0; i < BUFFER_QUEUES; i++)
621 TAILQ_INIT(&bufqueues[i]);
623 /* finally, initialize each buffer header and stick on empty q */
624 for (i = 0; i < nbuf; i++) {
626 bzero(bp, sizeof *bp);
627 bp->b_flags = B_INVAL; /* we're just an empty header */
628 bp->b_cmd = BUF_CMD_DONE;
629 bp->b_qindex = BQUEUE_EMPTY;
631 xio_init(&bp->b_xio);
633 TAILQ_INSERT_TAIL(&bufqueues[BQUEUE_EMPTY], bp, b_freelist);
637 * maxbufspace is the absolute maximum amount of buffer space we are
638 * allowed to reserve in KVM and in real terms. The absolute maximum
639 * is nominally used by buf_daemon. hibufspace is the nominal maximum
640 * used by most other processes. The differential is required to
641 * ensure that buf_daemon is able to run when other processes might
642 * be blocked waiting for buffer space.
644 * maxbufspace is based on BKVASIZE. Allocating buffers larger then
645 * this may result in KVM fragmentation which is not handled optimally
648 maxbufspace = (long)nbuf * BKVASIZE;
649 hibufspace = imax(3 * maxbufspace / 4, maxbufspace - MAXBSIZE * 10);
650 lobufspace = hibufspace - MAXBSIZE;
652 lorunningspace = 512 * 1024;
653 /* hirunningspace -- see below */
656 * Limit the amount of malloc memory since it is wired permanently
657 * into the kernel space. Even though this is accounted for in
658 * the buffer allocation, we don't want the malloced region to grow
659 * uncontrolled. The malloc scheme improves memory utilization
660 * significantly on average (small) directories.
662 maxbufmallocspace = hibufspace / 20;
665 * Reduce the chance of a deadlock occuring by limiting the number
666 * of delayed-write dirty buffers we allow to stack up.
668 * We don't want too much actually queued to the device at once
669 * (XXX this needs to be per-mount!), because the buffers will
670 * wind up locked for a very long period of time while the I/O
673 hidirtybufspace = hibufspace / 2; /* dirty + running */
674 hirunningspace = hibufspace / 16; /* locked & queued to device */
675 if (hirunningspace < 1024 * 1024)
676 hirunningspace = 1024 * 1024;
681 lodirtybufspace = hidirtybufspace / 2;
684 * Maximum number of async ops initiated per buf_daemon loop. This is
685 * somewhat of a hack at the moment, we really need to limit ourselves
686 * based on the number of bytes of I/O in-transit that were initiated
690 bogus_offset = kmem_alloc_pageable(&kernel_map, PAGE_SIZE);
691 vm_object_hold(&kernel_object);
692 bogus_page = vm_page_alloc(&kernel_object,
693 (bogus_offset >> PAGE_SHIFT),
695 vm_object_drop(&kernel_object);
696 vmstats.v_wire_count++;
701 * Initialize the embedded bio structures, typically used by
702 * deprecated code which tries to allocate its own struct bufs.
705 initbufbio(struct buf *bp)
707 bp->b_bio1.bio_buf = bp;
708 bp->b_bio1.bio_prev = NULL;
709 bp->b_bio1.bio_offset = NOOFFSET;
710 bp->b_bio1.bio_next = &bp->b_bio2;
711 bp->b_bio1.bio_done = NULL;
712 bp->b_bio1.bio_flags = 0;
714 bp->b_bio2.bio_buf = bp;
715 bp->b_bio2.bio_prev = &bp->b_bio1;
716 bp->b_bio2.bio_offset = NOOFFSET;
717 bp->b_bio2.bio_next = NULL;
718 bp->b_bio2.bio_done = NULL;
719 bp->b_bio2.bio_flags = 0;
725 * Reinitialize the embedded bio structures as well as any additional
726 * translation cache layers.
729 reinitbufbio(struct buf *bp)
733 for (bio = &bp->b_bio1; bio; bio = bio->bio_next) {
734 bio->bio_done = NULL;
735 bio->bio_offset = NOOFFSET;
740 * Undo the effects of an initbufbio().
743 uninitbufbio(struct buf *bp)
750 * Push another BIO layer onto an existing BIO and return it. The new
751 * BIO layer may already exist, holding cached translation data.
754 push_bio(struct bio *bio)
758 if ((nbio = bio->bio_next) == NULL) {
759 int index = bio - &bio->bio_buf->b_bio_array[0];
760 if (index >= NBUF_BIO - 1) {
761 panic("push_bio: too many layers bp %p\n",
764 nbio = &bio->bio_buf->b_bio_array[index + 1];
765 bio->bio_next = nbio;
766 nbio->bio_prev = bio;
767 nbio->bio_buf = bio->bio_buf;
768 nbio->bio_offset = NOOFFSET;
769 nbio->bio_done = NULL;
770 nbio->bio_next = NULL;
772 KKASSERT(nbio->bio_done == NULL);
777 * Pop a BIO translation layer, returning the previous layer. The
778 * must have been previously pushed.
781 pop_bio(struct bio *bio)
783 return(bio->bio_prev);
787 clearbiocache(struct bio *bio)
790 bio->bio_offset = NOOFFSET;
798 * Free the KVA allocation for buffer 'bp'.
800 * Must be called from a critical section as this is the only locking for
803 * Since this call frees up buffer space, we call bufspacewakeup().
808 bfreekva(struct buf *bp)
814 count = vm_map_entry_reserve(MAP_RESERVE_COUNT);
815 vm_map_lock(&buffer_map);
816 bufspace -= bp->b_kvasize;
817 vm_map_delete(&buffer_map,
818 (vm_offset_t) bp->b_kvabase,
819 (vm_offset_t) bp->b_kvabase + bp->b_kvasize,
822 vm_map_unlock(&buffer_map);
823 vm_map_entry_release(count);
825 bp->b_kvabase = NULL;
833 * Remove the buffer from the appropriate free list.
836 _bremfree(struct buf *bp)
838 if (bp->b_qindex != BQUEUE_NONE) {
839 KASSERT(BUF_REFCNTNB(bp) == 1,
840 ("bremfree: bp %p not locked",bp));
841 TAILQ_REMOVE(&bufqueues[bp->b_qindex], bp, b_freelist);
842 bp->b_qindex = BQUEUE_NONE;
844 if (BUF_REFCNTNB(bp) <= 1)
845 panic("bremfree: removing a buffer not on a queue");
850 bremfree(struct buf *bp)
852 spin_lock(&bufqspin);
854 spin_unlock(&bufqspin);
858 bremfree_locked(struct buf *bp)
864 * This version of bread issues any required I/O asyncnronously and
865 * makes a callback on completion.
867 * The callback must check whether BIO_DONE is set in the bio and issue
868 * the bpdone(bp, 0) if it isn't. The callback is responsible for clearing
869 * BIO_DONE and disposing of the I/O (bqrelse()ing it).
872 breadcb(struct vnode *vp, off_t loffset, int size,
873 void (*func)(struct bio *), void *arg)
877 bp = getblk(vp, loffset, size, 0, 0);
879 /* if not found in cache, do some I/O */
880 if ((bp->b_flags & B_CACHE) == 0) {
881 bp->b_flags &= ~(B_ERROR | B_EINTR | B_INVAL);
882 bp->b_cmd = BUF_CMD_READ;
883 bp->b_bio1.bio_done = func;
884 bp->b_bio1.bio_caller_info1.ptr = arg;
885 vfs_busy_pages(vp, bp);
887 vn_strategy(vp, &bp->b_bio1);
890 * Since we are issuing the callback synchronously it cannot
891 * race the BIO_DONE, so no need for atomic ops here.
893 /*bp->b_bio1.bio_done = func;*/
894 bp->b_bio1.bio_caller_info1.ptr = arg;
895 bp->b_bio1.bio_flags |= BIO_DONE;
903 * breadnx() - Terminal function for bread() and breadn().
905 * This function will start asynchronous I/O on read-ahead blocks as well
906 * as satisfy the primary request.
908 * We must clear B_ERROR and B_INVAL prior to initiating I/O. If B_CACHE is
909 * set, the buffer is valid and we do not have to do anything.
912 breadnx(struct vnode *vp, off_t loffset, int size, off_t *raoffset,
913 int *rabsize, int cnt, struct buf **bpp)
915 struct buf *bp, *rabp;
917 int rv = 0, readwait = 0;
922 *bpp = bp = getblk(vp, loffset, size, 0, 0);
924 /* if not found in cache, do some I/O */
925 if ((bp->b_flags & B_CACHE) == 0) {
926 bp->b_flags &= ~(B_ERROR | B_EINTR | B_INVAL);
927 bp->b_cmd = BUF_CMD_READ;
928 bp->b_bio1.bio_done = biodone_sync;
929 bp->b_bio1.bio_flags |= BIO_SYNC;
930 vfs_busy_pages(vp, bp);
931 vn_strategy(vp, &bp->b_bio1);
935 for (i = 0; i < cnt; i++, raoffset++, rabsize++) {
936 if (inmem(vp, *raoffset))
938 rabp = getblk(vp, *raoffset, *rabsize, 0, 0);
940 if ((rabp->b_flags & B_CACHE) == 0) {
941 rabp->b_flags &= ~(B_ERROR | B_EINTR | B_INVAL);
942 rabp->b_cmd = BUF_CMD_READ;
943 vfs_busy_pages(vp, rabp);
945 vn_strategy(vp, &rabp->b_bio1);
951 rv = biowait(&bp->b_bio1, "biord");
958 * Synchronous write, waits for completion.
960 * Write, release buffer on completion. (Done by iodone
961 * if async). Do not bother writing anything if the buffer
964 * Note that we set B_CACHE here, indicating that buffer is
965 * fully valid and thus cacheable. This is true even of NFS
966 * now so we set it generally. This could be set either here
967 * or in biodone() since the I/O is synchronous. We put it
971 bwrite(struct buf *bp)
975 if (bp->b_flags & B_INVAL) {
979 if (BUF_REFCNTNB(bp) == 0)
980 panic("bwrite: buffer is not busy???");
982 /* Mark the buffer clean */
985 bp->b_flags &= ~(B_ERROR | B_EINTR);
986 bp->b_flags |= B_CACHE;
987 bp->b_cmd = BUF_CMD_WRITE;
988 bp->b_bio1.bio_done = biodone_sync;
989 bp->b_bio1.bio_flags |= BIO_SYNC;
990 vfs_busy_pages(bp->b_vp, bp);
993 * Normal bwrites pipeline writes. NOTE: b_bufsize is only
994 * valid for vnode-backed buffers.
996 bsetrunningbufspace(bp, bp->b_bufsize);
997 vn_strategy(bp->b_vp, &bp->b_bio1);
998 error = biowait(&bp->b_bio1, "biows");
1007 * Asynchronous write. Start output on a buffer, but do not wait for
1008 * it to complete. The buffer is released when the output completes.
1010 * bwrite() ( or the VOP routine anyway ) is responsible for handling
1011 * B_INVAL buffers. Not us.
1014 bawrite(struct buf *bp)
1016 if (bp->b_flags & B_INVAL) {
1020 if (BUF_REFCNTNB(bp) == 0)
1021 panic("bwrite: buffer is not busy???");
1023 /* Mark the buffer clean */
1026 bp->b_flags &= ~(B_ERROR | B_EINTR);
1027 bp->b_flags |= B_CACHE;
1028 bp->b_cmd = BUF_CMD_WRITE;
1029 KKASSERT(bp->b_bio1.bio_done == NULL);
1030 vfs_busy_pages(bp->b_vp, bp);
1033 * Normal bwrites pipeline writes. NOTE: b_bufsize is only
1034 * valid for vnode-backed buffers.
1036 bsetrunningbufspace(bp, bp->b_bufsize);
1038 vn_strategy(bp->b_vp, &bp->b_bio1);
1044 * Ordered write. Start output on a buffer, and flag it so that the
1045 * device will write it in the order it was queued. The buffer is
1046 * released when the output completes. bwrite() ( or the VOP routine
1047 * anyway ) is responsible for handling B_INVAL buffers.
1050 bowrite(struct buf *bp)
1052 bp->b_flags |= B_ORDERED;
1060 * Delayed write. (Buffer is marked dirty). Do not bother writing
1061 * anything if the buffer is marked invalid.
1063 * Note that since the buffer must be completely valid, we can safely
1064 * set B_CACHE. In fact, we have to set B_CACHE here rather then in
1065 * biodone() in order to prevent getblk from writing the buffer
1066 * out synchronously.
1069 bdwrite(struct buf *bp)
1071 if (BUF_REFCNTNB(bp) == 0)
1072 panic("bdwrite: buffer is not busy");
1074 if (bp->b_flags & B_INVAL) {
1080 if (dsched_is_clear_buf_priv(bp))
1084 * Set B_CACHE, indicating that the buffer is fully valid. This is
1085 * true even of NFS now.
1087 bp->b_flags |= B_CACHE;
1090 * This bmap keeps the system from needing to do the bmap later,
1091 * perhaps when the system is attempting to do a sync. Since it
1092 * is likely that the indirect block -- or whatever other datastructure
1093 * that the filesystem needs is still in memory now, it is a good
1094 * thing to do this. Note also, that if the pageout daemon is
1095 * requesting a sync -- there might not be enough memory to do
1096 * the bmap then... So, this is important to do.
1098 if (bp->b_bio2.bio_offset == NOOFFSET) {
1099 VOP_BMAP(bp->b_vp, bp->b_loffset, &bp->b_bio2.bio_offset,
1100 NULL, NULL, BUF_CMD_WRITE);
1104 * Because the underlying pages may still be mapped and
1105 * writable trying to set the dirty buffer (b_dirtyoff/end)
1106 * range here will be inaccurate.
1108 * However, we must still clean the pages to satisfy the
1109 * vnode_pager and pageout daemon, so theythink the pages
1110 * have been "cleaned". What has really occured is that
1111 * they've been earmarked for later writing by the buffer
1114 * So we get the b_dirtyoff/end update but will not actually
1115 * depend on it (NFS that is) until the pages are busied for
1118 vfs_clean_pages(bp);
1122 * note: we cannot initiate I/O from a bdwrite even if we wanted to,
1123 * due to the softdep code.
1128 * Fake write - return pages to VM system as dirty, leave the buffer clean.
1129 * This is used by tmpfs.
1131 * It is important for any VFS using this routine to NOT use it for
1132 * IO_SYNC or IO_ASYNC operations which occur when the system really
1133 * wants to flush VM pages to backing store.
1136 buwrite(struct buf *bp)
1142 * Only works for VMIO buffers. If the buffer is already
1143 * marked for delayed-write we can't avoid the bdwrite().
1145 if ((bp->b_flags & B_VMIO) == 0 || (bp->b_flags & B_DELWRI)) {
1151 * Set valid & dirty.
1153 for (i = 0; i < bp->b_xio.xio_npages; i++) {
1154 m = bp->b_xio.xio_pages[i];
1155 vfs_dirty_one_page(bp, i, m);
1163 * Turn buffer into delayed write request by marking it B_DELWRI.
1164 * B_RELBUF and B_NOCACHE must be cleared.
1166 * We reassign the buffer to itself to properly update it in the
1167 * dirty/clean lists.
1169 * Must be called from a critical section.
1170 * The buffer must be on BQUEUE_NONE.
1173 bdirty(struct buf *bp)
1175 KASSERT(bp->b_qindex == BQUEUE_NONE, ("bdirty: buffer %p still on queue %d", bp, bp->b_qindex));
1176 if (bp->b_flags & B_NOCACHE) {
1177 kprintf("bdirty: clearing B_NOCACHE on buf %p\n", bp);
1178 bp->b_flags &= ~B_NOCACHE;
1180 if (bp->b_flags & B_INVAL) {
1181 kprintf("bdirty: warning, dirtying invalid buffer %p\n", bp);
1183 bp->b_flags &= ~B_RELBUF;
1185 if ((bp->b_flags & B_DELWRI) == 0) {
1186 lwkt_gettoken(&bp->b_vp->v_token);
1187 bp->b_flags |= B_DELWRI;
1189 lwkt_reltoken(&bp->b_vp->v_token);
1191 spin_lock(&bufcspin);
1193 dirtybufspace += bp->b_bufsize;
1194 if (bp->b_flags & B_HEAVY) {
1196 dirtybufspacehw += bp->b_bufsize;
1198 spin_unlock(&bufcspin);
1205 * Set B_HEAVY, indicating that this is a heavy-weight buffer that
1206 * needs to be flushed with a different buf_daemon thread to avoid
1207 * deadlocks. B_HEAVY also imposes restrictions in getnewbuf().
1210 bheavy(struct buf *bp)
1212 if ((bp->b_flags & B_HEAVY) == 0) {
1213 bp->b_flags |= B_HEAVY;
1214 if (bp->b_flags & B_DELWRI) {
1215 spin_lock(&bufcspin);
1217 dirtybufspacehw += bp->b_bufsize;
1218 spin_unlock(&bufcspin);
1226 * Clear B_DELWRI for buffer.
1228 * Must be called from a critical section.
1230 * The buffer is typically on BQUEUE_NONE but there is one case in
1231 * brelse() that calls this function after placing the buffer on
1232 * a different queue.
1237 bundirty(struct buf *bp)
1239 if (bp->b_flags & B_DELWRI) {
1240 lwkt_gettoken(&bp->b_vp->v_token);
1241 bp->b_flags &= ~B_DELWRI;
1243 lwkt_reltoken(&bp->b_vp->v_token);
1245 spin_lock(&bufcspin);
1247 dirtybufspace -= bp->b_bufsize;
1248 if (bp->b_flags & B_HEAVY) {
1250 dirtybufspacehw -= bp->b_bufsize;
1252 spin_unlock(&bufcspin);
1254 bd_signal(bp->b_bufsize);
1257 * Since it is now being written, we can clear its deferred write flag.
1259 bp->b_flags &= ~B_DEFERRED;
1263 * Set the b_runningbufspace field, used to track how much I/O is
1264 * in progress at any given moment.
1267 bsetrunningbufspace(struct buf *bp, int bytes)
1269 bp->b_runningbufspace = bytes;
1271 spin_lock(&bufcspin);
1272 runningbufspace += bytes;
1274 spin_unlock(&bufcspin);
1281 * Release a busy buffer and, if requested, free its resources. The
1282 * buffer will be stashed in the appropriate bufqueue[] allowing it
1283 * to be accessed later as a cache entity or reused for other purposes.
1288 brelse(struct buf *bp)
1291 int saved_flags = bp->b_flags;
1294 KASSERT(!(bp->b_flags & (B_CLUSTER|B_PAGING)), ("brelse: inappropriate B_PAGING or B_CLUSTER bp %p", bp));
1297 * If B_NOCACHE is set we are being asked to destroy the buffer and
1298 * its backing store. Clear B_DELWRI.
1300 * B_NOCACHE is set in two cases: (1) when the caller really wants
1301 * to destroy the buffer and backing store and (2) when the caller
1302 * wants to destroy the buffer and backing store after a write
1305 if ((bp->b_flags & (B_NOCACHE|B_DELWRI)) == (B_NOCACHE|B_DELWRI)) {
1309 if ((bp->b_flags & (B_INVAL | B_DELWRI)) == B_DELWRI) {
1311 * A re-dirtied buffer is only subject to destruction
1312 * by B_INVAL. B_ERROR and B_NOCACHE are ignored.
1314 /* leave buffer intact */
1315 } else if ((bp->b_flags & (B_NOCACHE | B_INVAL | B_ERROR)) ||
1316 (bp->b_bufsize <= 0)) {
1318 * Either a failed read or we were asked to free or not
1319 * cache the buffer. This path is reached with B_DELWRI
1320 * set only if B_INVAL is already set. B_NOCACHE governs
1321 * backing store destruction.
1323 * NOTE: HAMMER will set B_LOCKED in buf_deallocate if the
1324 * buffer cannot be immediately freed.
1326 bp->b_flags |= B_INVAL;
1327 if (LIST_FIRST(&bp->b_dep) != NULL)
1329 if (bp->b_flags & B_DELWRI) {
1330 spin_lock(&bufcspin);
1332 dirtybufspace -= bp->b_bufsize;
1333 if (bp->b_flags & B_HEAVY) {
1335 dirtybufspacehw -= bp->b_bufsize;
1337 spin_unlock(&bufcspin);
1339 bd_signal(bp->b_bufsize);
1341 bp->b_flags &= ~(B_DELWRI | B_CACHE);
1345 * We must clear B_RELBUF if B_DELWRI or B_LOCKED is set,
1346 * or if b_refs is non-zero.
1348 * If vfs_vmio_release() is called with either bit set, the
1349 * underlying pages may wind up getting freed causing a previous
1350 * write (bdwrite()) to get 'lost' because pages associated with
1351 * a B_DELWRI bp are marked clean. Pages associated with a
1352 * B_LOCKED buffer may be mapped by the filesystem.
1354 * If we want to release the buffer ourselves (rather then the
1355 * originator asking us to release it), give the originator a
1356 * chance to countermand the release by setting B_LOCKED.
1358 * We still allow the B_INVAL case to call vfs_vmio_release(), even
1359 * if B_DELWRI is set.
1361 * If B_DELWRI is not set we may have to set B_RELBUF if we are low
1362 * on pages to return pages to the VM page queues.
1364 if ((bp->b_flags & (B_DELWRI | B_LOCKED)) || bp->b_refs) {
1365 bp->b_flags &= ~B_RELBUF;
1366 } else if (vm_page_count_severe()) {
1367 if (LIST_FIRST(&bp->b_dep) != NULL)
1368 buf_deallocate(bp); /* can set B_LOCKED */
1369 if (bp->b_flags & (B_DELWRI | B_LOCKED))
1370 bp->b_flags &= ~B_RELBUF;
1372 bp->b_flags |= B_RELBUF;
1376 * Make sure b_cmd is clear. It may have already been cleared by
1379 * At this point destroying the buffer is governed by the B_INVAL
1380 * or B_RELBUF flags.
1382 bp->b_cmd = BUF_CMD_DONE;
1383 dsched_exit_buf(bp);
1386 * VMIO buffer rundown. Make sure the VM page array is restored
1387 * after an I/O may have replaces some of the pages with bogus pages
1388 * in order to not destroy dirty pages in a fill-in read.
1390 * Note that due to the code above, if a buffer is marked B_DELWRI
1391 * then the B_RELBUF and B_NOCACHE bits will always be clear.
1392 * B_INVAL may still be set, however.
1394 * For clean buffers, B_INVAL or B_RELBUF will destroy the buffer
1395 * but not the backing store. B_NOCACHE will destroy the backing
1398 * Note that dirty NFS buffers contain byte-granular write ranges
1399 * and should not be destroyed w/ B_INVAL even if the backing store
1402 if (bp->b_flags & B_VMIO) {
1404 * Rundown for VMIO buffers which are not dirty NFS buffers.
1416 * Get the base offset and length of the buffer. Note that
1417 * in the VMIO case if the buffer block size is not
1418 * page-aligned then b_data pointer may not be page-aligned.
1419 * But our b_xio.xio_pages array *IS* page aligned.
1421 * block sizes less then DEV_BSIZE (usually 512) are not
1422 * supported due to the page granularity bits (m->valid,
1423 * m->dirty, etc...).
1425 * See man buf(9) for more information
1428 resid = bp->b_bufsize;
1429 foff = bp->b_loffset;
1431 for (i = 0; i < bp->b_xio.xio_npages; i++) {
1432 m = bp->b_xio.xio_pages[i];
1433 vm_page_flag_clear(m, PG_ZERO);
1435 * If we hit a bogus page, fixup *all* of them
1436 * now. Note that we left these pages wired
1437 * when we removed them so they had better exist,
1438 * and they cannot be ripped out from under us so
1439 * no critical section protection is necessary.
1441 if (m == bogus_page) {
1443 poff = OFF_TO_IDX(bp->b_loffset);
1445 vm_object_hold(obj);
1446 for (j = i; j < bp->b_xio.xio_npages; j++) {
1449 mtmp = bp->b_xio.xio_pages[j];
1450 if (mtmp == bogus_page) {
1451 mtmp = vm_page_lookup(obj, poff + j);
1453 panic("brelse: page missing");
1455 bp->b_xio.xio_pages[j] = mtmp;
1458 bp->b_flags &= ~B_HASBOGUS;
1459 vm_object_drop(obj);
1461 if ((bp->b_flags & B_INVAL) == 0) {
1462 pmap_qenter(trunc_page((vm_offset_t)bp->b_data),
1463 bp->b_xio.xio_pages, bp->b_xio.xio_npages);
1465 m = bp->b_xio.xio_pages[i];
1469 * Invalidate the backing store if B_NOCACHE is set
1470 * (e.g. used with vinvalbuf()). If this is NFS
1471 * we impose a requirement that the block size be
1472 * a multiple of PAGE_SIZE and create a temporary
1473 * hack to basically invalidate the whole page. The
1474 * problem is that NFS uses really odd buffer sizes
1475 * especially when tracking piecemeal writes and
1476 * it also vinvalbuf()'s a lot, which would result
1477 * in only partial page validation and invalidation
1478 * here. If the file page is mmap()'d, however,
1479 * all the valid bits get set so after we invalidate
1480 * here we would end up with weird m->valid values
1481 * like 0xfc. nfs_getpages() can't handle this so
1482 * we clear all the valid bits for the NFS case
1483 * instead of just some of them.
1485 * The real bug is the VM system having to set m->valid
1486 * to VM_PAGE_BITS_ALL for faulted-in pages, which
1487 * itself is an artifact of the whole 512-byte
1488 * granular mess that exists to support odd block
1489 * sizes and UFS meta-data block sizes (e.g. 6144).
1490 * A complete rewrite is required.
1494 if (bp->b_flags & (B_NOCACHE|B_ERROR)) {
1495 int poffset = foff & PAGE_MASK;
1498 presid = PAGE_SIZE - poffset;
1499 if (bp->b_vp->v_tag == VT_NFS &&
1500 bp->b_vp->v_type == VREG) {
1502 } else if (presid > resid) {
1505 KASSERT(presid >= 0, ("brelse: extra page"));
1506 vm_page_set_invalid(m, poffset, presid);
1509 * Also make sure any swap cache is removed
1510 * as it is now stale (HAMMER in particular
1511 * uses B_NOCACHE to deal with buffer
1514 swap_pager_unswapped(m);
1516 resid -= PAGE_SIZE - (foff & PAGE_MASK);
1517 foff = (foff + PAGE_SIZE) & ~(off_t)PAGE_MASK;
1519 if (bp->b_flags & (B_INVAL | B_RELBUF))
1520 vfs_vmio_release(bp);
1523 * Rundown for non-VMIO buffers.
1525 if (bp->b_flags & (B_INVAL | B_RELBUF)) {
1528 KKASSERT (LIST_FIRST(&bp->b_dep) == NULL);
1534 if (bp->b_qindex != BQUEUE_NONE)
1535 panic("brelse: free buffer onto another queue???");
1536 if (BUF_REFCNTNB(bp) > 1) {
1537 /* Temporary panic to verify exclusive locking */
1538 /* This panic goes away when we allow shared refs */
1539 panic("brelse: multiple refs");
1545 * Figure out the correct queue to place the cleaned up buffer on.
1546 * Buffers placed in the EMPTY or EMPTYKVA had better already be
1547 * disassociated from their vnode.
1549 spin_lock(&bufqspin);
1550 if (bp->b_flags & B_LOCKED) {
1552 * Buffers that are locked are placed in the locked queue
1553 * immediately, regardless of their state.
1555 bp->b_qindex = BQUEUE_LOCKED;
1556 TAILQ_INSERT_TAIL(&bufqueues[BQUEUE_LOCKED], bp, b_freelist);
1557 } else if (bp->b_bufsize == 0) {
1559 * Buffers with no memory. Due to conditionals near the top
1560 * of brelse() such buffers should probably already be
1561 * marked B_INVAL and disassociated from their vnode.
1563 bp->b_flags |= B_INVAL;
1564 KASSERT(bp->b_vp == NULL, ("bp1 %p flags %08x/%08x vnode %p unexpectededly still associated!", bp, saved_flags, bp->b_flags, bp->b_vp));
1565 KKASSERT((bp->b_flags & B_HASHED) == 0);
1566 if (bp->b_kvasize) {
1567 bp->b_qindex = BQUEUE_EMPTYKVA;
1569 bp->b_qindex = BQUEUE_EMPTY;
1571 TAILQ_INSERT_HEAD(&bufqueues[bp->b_qindex], bp, b_freelist);
1572 } else if (bp->b_flags & (B_INVAL | B_NOCACHE | B_RELBUF)) {
1574 * Buffers with junk contents. Again these buffers had better
1575 * already be disassociated from their vnode.
1577 KASSERT(bp->b_vp == NULL, ("bp2 %p flags %08x/%08x vnode %p unexpectededly still associated!", bp, saved_flags, bp->b_flags, bp->b_vp));
1578 KKASSERT((bp->b_flags & B_HASHED) == 0);
1579 bp->b_flags |= B_INVAL;
1580 bp->b_qindex = BQUEUE_CLEAN;
1581 TAILQ_INSERT_HEAD(&bufqueues[BQUEUE_CLEAN], bp, b_freelist);
1584 * Remaining buffers. These buffers are still associated with
1587 switch(bp->b_flags & (B_DELWRI|B_HEAVY)) {
1589 bp->b_qindex = BQUEUE_DIRTY;
1590 TAILQ_INSERT_TAIL(&bufqueues[BQUEUE_DIRTY], bp, b_freelist);
1592 case B_DELWRI | B_HEAVY:
1593 bp->b_qindex = BQUEUE_DIRTY_HW;
1594 TAILQ_INSERT_TAIL(&bufqueues[BQUEUE_DIRTY_HW], bp,
1599 * NOTE: Buffers are always placed at the end of the
1600 * queue. If B_AGE is not set the buffer will cycle
1601 * through the queue twice.
1603 bp->b_qindex = BQUEUE_CLEAN;
1604 TAILQ_INSERT_TAIL(&bufqueues[BQUEUE_CLEAN], bp, b_freelist);
1608 spin_unlock(&bufqspin);
1611 * If B_INVAL, clear B_DELWRI. We've already placed the buffer
1612 * on the correct queue.
1614 if ((bp->b_flags & (B_INVAL|B_DELWRI)) == (B_INVAL|B_DELWRI))
1618 * The bp is on an appropriate queue unless locked. If it is not
1619 * locked or dirty we can wakeup threads waiting for buffer space.
1621 * We've already handled the B_INVAL case ( B_DELWRI will be clear
1622 * if B_INVAL is set ).
1624 if ((bp->b_flags & (B_LOCKED|B_DELWRI)) == 0)
1628 * Something we can maybe free or reuse
1630 if (bp->b_bufsize || bp->b_kvasize)
1634 * Clean up temporary flags and unlock the buffer.
1636 bp->b_flags &= ~(B_ORDERED | B_NOCACHE | B_RELBUF | B_DIRECT);
1643 * Release a buffer back to the appropriate queue but do not try to free
1644 * it. The buffer is expected to be used again soon.
1646 * bqrelse() is used by bdwrite() to requeue a delayed write, and used by
1647 * biodone() to requeue an async I/O on completion. It is also used when
1648 * known good buffers need to be requeued but we think we may need the data
1651 * XXX we should be able to leave the B_RELBUF hint set on completion.
1656 bqrelse(struct buf *bp)
1658 KASSERT(!(bp->b_flags & (B_CLUSTER|B_PAGING)), ("bqrelse: inappropriate B_PAGING or B_CLUSTER bp %p", bp));
1660 if (bp->b_qindex != BQUEUE_NONE)
1661 panic("bqrelse: free buffer onto another queue???");
1662 if (BUF_REFCNTNB(bp) > 1) {
1663 /* do not release to free list */
1664 panic("bqrelse: multiple refs");
1668 buf_act_advance(bp);
1670 spin_lock(&bufqspin);
1671 if (bp->b_flags & B_LOCKED) {
1673 * Locked buffers are released to the locked queue. However,
1674 * if the buffer is dirty it will first go into the dirty
1675 * queue and later on after the I/O completes successfully it
1676 * will be released to the locked queue.
1678 bp->b_qindex = BQUEUE_LOCKED;
1679 TAILQ_INSERT_TAIL(&bufqueues[BQUEUE_LOCKED], bp, b_freelist);
1680 } else if (bp->b_flags & B_DELWRI) {
1681 bp->b_qindex = (bp->b_flags & B_HEAVY) ?
1682 BQUEUE_DIRTY_HW : BQUEUE_DIRTY;
1683 TAILQ_INSERT_TAIL(&bufqueues[bp->b_qindex], bp, b_freelist);
1684 } else if (vm_page_count_severe()) {
1686 * We are too low on memory, we have to try to free the
1687 * buffer (most importantly: the wired pages making up its
1688 * backing store) *now*.
1690 spin_unlock(&bufqspin);
1694 bp->b_qindex = BQUEUE_CLEAN;
1695 TAILQ_INSERT_TAIL(&bufqueues[BQUEUE_CLEAN], bp, b_freelist);
1697 spin_unlock(&bufqspin);
1699 if ((bp->b_flags & B_LOCKED) == 0 &&
1700 ((bp->b_flags & B_INVAL) || (bp->b_flags & B_DELWRI) == 0)) {
1705 * Something we can maybe free or reuse.
1707 if (bp->b_bufsize && !(bp->b_flags & B_DELWRI))
1711 * Final cleanup and unlock. Clear bits that are only used while a
1712 * buffer is actively locked.
1714 bp->b_flags &= ~(B_ORDERED | B_NOCACHE | B_RELBUF);
1715 dsched_exit_buf(bp);
1720 * Hold a buffer, preventing it from being reused. This will prevent
1721 * normal B_RELBUF operations on the buffer but will not prevent B_INVAL
1722 * operations. If a B_INVAL operation occurs the buffer will remain held
1723 * but the underlying pages may get ripped out.
1725 * These functions are typically used in VOP_READ/VOP_WRITE functions
1726 * to hold a buffer during a copyin or copyout, preventing deadlocks
1727 * or recursive lock panics when read()/write() is used over mmap()'d
1730 * NOTE: bqhold() requires that the buffer be locked at the time of the
1731 * hold. bqdrop() has no requirements other than the buffer having
1732 * previously been held.
1735 bqhold(struct buf *bp)
1737 atomic_add_int(&bp->b_refs, 1);
1741 bqdrop(struct buf *bp)
1743 KKASSERT(bp->b_refs > 0);
1744 atomic_add_int(&bp->b_refs, -1);
1750 * Return backing pages held by the buffer 'bp' back to the VM system
1751 * if possible. The pages are freed if they are no longer valid or
1752 * attempt to free if it was used for direct I/O otherwise they are
1753 * sent to the page cache.
1755 * Pages that were marked busy are left alone and skipped.
1757 * The KVA mapping (b_data) for the underlying pages is removed by
1761 vfs_vmio_release(struct buf *bp)
1766 for (i = 0; i < bp->b_xio.xio_npages; i++) {
1767 m = bp->b_xio.xio_pages[i];
1768 bp->b_xio.xio_pages[i] = NULL;
1770 vm_page_busy_wait(m, FALSE, "vmiopg");
1773 * The VFS is telling us this is not a meta-data buffer
1774 * even if it is backed by a block device.
1776 if (bp->b_flags & B_NOTMETA)
1777 vm_page_flag_set(m, PG_NOTMETA);
1780 * This is a very important bit of code. We try to track
1781 * VM page use whether the pages are wired into the buffer
1782 * cache or not. While wired into the buffer cache the
1783 * bp tracks the act_count.
1785 * We can choose to place unwired pages on the inactive
1786 * queue (0) or active queue (1). If we place too many
1787 * on the active queue the queue will cycle the act_count
1788 * on pages we'd like to keep, just from single-use pages
1789 * (such as when doing a tar-up or file scan).
1791 if (bp->b_act_count < vm_cycle_point)
1792 vm_page_unwire(m, 0);
1794 vm_page_unwire(m, 1);
1797 * We don't mess with busy pages, it is the responsibility
1798 * of the process that busied the pages to deal with them.
1800 * However, the caller may have marked the page invalid and
1801 * we must still make sure the page is no longer mapped.
1803 if ((m->flags & PG_BUSY) || (m->busy != 0)) {
1804 vm_page_protect(m, VM_PROT_NONE);
1809 if (m->wire_count == 0) {
1810 vm_page_flag_clear(m, PG_ZERO);
1812 * Might as well free the page if we can and it has
1813 * no valid data. We also free the page if the
1814 * buffer was used for direct I/O.
1817 if ((bp->b_flags & B_ASYNC) == 0 && !m->valid &&
1818 m->hold_count == 0) {
1819 vm_page_protect(m, VM_PROT_NONE);
1824 * Cache the page if we are really low on free
1827 * Also bypass the active and inactive queues
1828 * if B_NOTMETA is set. This flag is set by HAMMER
1829 * on a regular file buffer when double buffering
1830 * is enabled or on a block device buffer representing
1831 * file data when double buffering is not enabled.
1832 * The flag prevents two copies of the same data from
1833 * being cached for long periods of time.
1835 if (bp->b_flags & B_DIRECT) {
1837 vm_page_try_to_free(m);
1838 } else if ((bp->b_flags & B_NOTMETA) ||
1839 vm_page_count_severe()) {
1840 m->act_count = bp->b_act_count;
1842 vm_page_try_to_cache(m);
1844 m->act_count = bp->b_act_count;
1852 pmap_qremove(trunc_page((vm_offset_t) bp->b_data),
1853 bp->b_xio.xio_npages);
1854 if (bp->b_bufsize) {
1858 bp->b_xio.xio_npages = 0;
1859 bp->b_flags &= ~B_VMIO;
1860 KKASSERT (LIST_FIRST(&bp->b_dep) == NULL);
1868 * Implement clustered async writes for clearing out B_DELWRI buffers.
1869 * This is much better then the old way of writing only one buffer at
1870 * a time. Note that we may not be presented with the buffers in the
1871 * correct order, so we search for the cluster in both directions.
1873 * The buffer is locked on call.
1876 vfs_bio_awrite(struct buf *bp)
1880 off_t loffset = bp->b_loffset;
1881 struct vnode *vp = bp->b_vp;
1888 * right now we support clustered writing only to regular files. If
1889 * we find a clusterable block we could be in the middle of a cluster
1890 * rather then at the beginning.
1892 * NOTE: b_bio1 contains the logical loffset and is aliased
1893 * to b_loffset. b_bio2 contains the translated block number.
1895 if ((vp->v_type == VREG) &&
1896 (vp->v_mount != 0) && /* Only on nodes that have the size info */
1897 (bp->b_flags & (B_CLUSTEROK | B_INVAL)) == B_CLUSTEROK) {
1899 size = vp->v_mount->mnt_stat.f_iosize;
1901 for (i = size; i < MAXPHYS; i += size) {
1902 if ((bpa = findblk(vp, loffset + i, FINDBLK_TEST)) &&
1903 BUF_REFCNT(bpa) == 0 &&
1904 ((bpa->b_flags & (B_DELWRI | B_CLUSTEROK | B_INVAL)) ==
1905 (B_DELWRI | B_CLUSTEROK)) &&
1906 (bpa->b_bufsize == size)) {
1907 if ((bpa->b_bio2.bio_offset == NOOFFSET) ||
1908 (bpa->b_bio2.bio_offset !=
1909 bp->b_bio2.bio_offset + i))
1915 for (j = size; i + j <= MAXPHYS && j <= loffset; j += size) {
1916 if ((bpa = findblk(vp, loffset - j, FINDBLK_TEST)) &&
1917 BUF_REFCNT(bpa) == 0 &&
1918 ((bpa->b_flags & (B_DELWRI | B_CLUSTEROK | B_INVAL)) ==
1919 (B_DELWRI | B_CLUSTEROK)) &&
1920 (bpa->b_bufsize == size)) {
1921 if ((bpa->b_bio2.bio_offset == NOOFFSET) ||
1922 (bpa->b_bio2.bio_offset !=
1923 bp->b_bio2.bio_offset - j))
1933 * this is a possible cluster write
1935 if (nbytes != size) {
1937 nwritten = cluster_wbuild(vp, size,
1938 loffset - j, nbytes);
1944 * default (old) behavior, writing out only one block
1946 * XXX returns b_bufsize instead of b_bcount for nwritten?
1948 nwritten = bp->b_bufsize;
1958 * Find and initialize a new buffer header, freeing up existing buffers
1959 * in the bufqueues as necessary. The new buffer is returned locked.
1961 * Important: B_INVAL is not set. If the caller wishes to throw the
1962 * buffer away, the caller must set B_INVAL prior to calling brelse().
1965 * We have insufficient buffer headers
1966 * We have insufficient buffer space
1967 * buffer_map is too fragmented ( space reservation fails )
1968 * If we have to flush dirty buffers ( but we try to avoid this )
1970 * To avoid VFS layer recursion we do not flush dirty buffers ourselves.
1971 * Instead we ask the buf daemon to do it for us. We attempt to
1972 * avoid piecemeal wakeups of the pageout daemon.
1977 getnewbuf(int blkflags, int slptimeo, int size, int maxsize)
1983 int slpflags = (blkflags & GETBLK_PCATCH) ? PCATCH : 0;
1984 static int flushingbufs;
1987 * We can't afford to block since we might be holding a vnode lock,
1988 * which may prevent system daemons from running. We deal with
1989 * low-memory situations by proactively returning memory and running
1990 * async I/O rather then sync I/O.
1994 --getnewbufrestarts;
1996 ++getnewbufrestarts;
1999 * Setup for scan. If we do not have enough free buffers,
2000 * we setup a degenerate case that immediately fails. Note
2001 * that if we are specially marked process, we are allowed to
2002 * dip into our reserves.
2004 * The scanning sequence is nominally: EMPTY->EMPTYKVA->CLEAN
2006 * We start with EMPTYKVA. If the list is empty we backup to EMPTY.
2007 * However, there are a number of cases (defragging, reusing, ...)
2008 * where we cannot backup.
2010 nqindex = BQUEUE_EMPTYKVA;
2011 spin_lock(&bufqspin);
2012 nbp = TAILQ_FIRST(&bufqueues[BQUEUE_EMPTYKVA]);
2016 * If no EMPTYKVA buffers and we are either
2017 * defragging or reusing, locate a CLEAN buffer
2018 * to free or reuse. If bufspace useage is low
2019 * skip this step so we can allocate a new buffer.
2021 if (defrag || bufspace >= lobufspace) {
2022 nqindex = BQUEUE_CLEAN;
2023 nbp = TAILQ_FIRST(&bufqueues[BQUEUE_CLEAN]);
2027 * If we could not find or were not allowed to reuse a
2028 * CLEAN buffer, check to see if it is ok to use an EMPTY
2029 * buffer. We can only use an EMPTY buffer if allocating
2030 * its KVA would not otherwise run us out of buffer space.
2032 if (nbp == NULL && defrag == 0 &&
2033 bufspace + maxsize < hibufspace) {
2034 nqindex = BQUEUE_EMPTY;
2035 nbp = TAILQ_FIRST(&bufqueues[BQUEUE_EMPTY]);
2040 * Run scan, possibly freeing data and/or kva mappings on the fly
2043 * WARNING! bufqspin is held!
2045 while ((bp = nbp) != NULL) {
2046 int qindex = nqindex;
2048 nbp = TAILQ_NEXT(bp, b_freelist);
2051 * BQUEUE_CLEAN - B_AGE special case. If not set the bp
2052 * cycles through the queue twice before being selected.
2054 if (qindex == BQUEUE_CLEAN &&
2055 (bp->b_flags & B_AGE) == 0 && nbp) {
2056 bp->b_flags |= B_AGE;
2057 TAILQ_REMOVE(&bufqueues[qindex], bp, b_freelist);
2058 TAILQ_INSERT_TAIL(&bufqueues[qindex], bp, b_freelist);
2063 * Calculate next bp ( we can only use it if we do not block
2064 * or do other fancy things ).
2069 nqindex = BQUEUE_EMPTYKVA;
2070 if ((nbp = TAILQ_FIRST(&bufqueues[BQUEUE_EMPTYKVA])))
2073 case BQUEUE_EMPTYKVA:
2074 nqindex = BQUEUE_CLEAN;
2075 if ((nbp = TAILQ_FIRST(&bufqueues[BQUEUE_CLEAN])))
2089 KASSERT(bp->b_qindex == qindex,
2090 ("getnewbuf: inconsistent queue %d bp %p", qindex, bp));
2093 * Note: we no longer distinguish between VMIO and non-VMIO
2096 KASSERT((bp->b_flags & B_DELWRI) == 0,
2097 ("delwri buffer %p found in queue %d", bp, qindex));
2100 * Do not try to reuse a buffer with a non-zero b_refs.
2101 * This is an unsynchronized test. A synchronized test
2102 * is also performed after we lock the buffer.
2108 * If we are defragging then we need a buffer with
2109 * b_kvasize != 0. XXX this situation should no longer
2110 * occur, if defrag is non-zero the buffer's b_kvasize
2111 * should also be non-zero at this point. XXX
2113 if (defrag && bp->b_kvasize == 0) {
2114 kprintf("Warning: defrag empty buffer %p\n", bp);
2119 * Start freeing the bp. This is somewhat involved. nbp
2120 * remains valid only for BQUEUE_EMPTY[KVA] bp's. Buffers
2121 * on the clean list must be disassociated from their
2122 * current vnode. Buffers on the empty[kva] lists have
2123 * already been disassociated.
2125 * b_refs is checked after locking along with queue changes.
2126 * We must check here to deal with zero->nonzero transitions
2127 * made by the owner of the buffer lock, which is used by
2128 * VFS's to hold the buffer while issuing an unlocked
2129 * uiomove()s. We cannot invalidate the buffer's pages
2130 * for this case. Once we successfully lock a buffer the
2131 * only 0->1 transitions of b_refs will occur via findblk().
2133 * We must also check for queue changes after successful
2134 * locking as the current lock holder may dispose of the
2135 * buffer and change its queue.
2137 if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT) != 0) {
2138 spin_unlock(&bufqspin);
2139 tsleep(&bd_request, 0, "gnbxxx", (hz + 99) / 100);
2142 if (bp->b_qindex != qindex || bp->b_refs) {
2143 spin_unlock(&bufqspin);
2147 bremfree_locked(bp);
2148 spin_unlock(&bufqspin);
2151 * Dependancies must be handled before we disassociate the
2154 * NOTE: HAMMER will set B_LOCKED if the buffer cannot
2155 * be immediately disassociated. HAMMER then becomes
2156 * responsible for releasing the buffer.
2158 * NOTE: bufqspin is UNLOCKED now.
2160 if (LIST_FIRST(&bp->b_dep) != NULL) {
2162 if (bp->b_flags & B_LOCKED) {
2166 KKASSERT(LIST_FIRST(&bp->b_dep) == NULL);
2169 if (qindex == BQUEUE_CLEAN) {
2170 if (bp->b_flags & B_VMIO)
2171 vfs_vmio_release(bp);
2177 * NOTE: nbp is now entirely invalid. We can only restart
2178 * the scan from this point on.
2180 * Get the rest of the buffer freed up. b_kva* is still
2181 * valid after this operation.
2183 KASSERT(bp->b_vp == NULL,
2184 ("bp3 %p flags %08x vnode %p qindex %d "
2185 "unexpectededly still associated!",
2186 bp, bp->b_flags, bp->b_vp, qindex));
2187 KKASSERT((bp->b_flags & B_HASHED) == 0);
2190 * critical section protection is not required when
2191 * scrapping a buffer's contents because it is already
2197 bp->b_flags = B_BNOCLIP;
2198 bp->b_cmd = BUF_CMD_DONE;
2203 bp->b_xio.xio_npages = 0;
2204 bp->b_dirtyoff = bp->b_dirtyend = 0;
2205 bp->b_act_count = ACT_INIT;
2207 KKASSERT(LIST_FIRST(&bp->b_dep) == NULL);
2209 if (blkflags & GETBLK_BHEAVY)
2210 bp->b_flags |= B_HEAVY;
2213 * If we are defragging then free the buffer.
2216 bp->b_flags |= B_INVAL;
2224 * If we are overcomitted then recover the buffer and its
2225 * KVM space. This occurs in rare situations when multiple
2226 * processes are blocked in getnewbuf() or allocbuf().
2228 if (bufspace >= hibufspace)
2230 if (flushingbufs && bp->b_kvasize != 0) {
2231 bp->b_flags |= B_INVAL;
2236 if (bufspace < lobufspace)
2240 * b_refs can transition to a non-zero value while we hold
2241 * the buffer locked due to a findblk(). Our brelvp() above
2242 * interlocked any future possible transitions due to
2245 * If we find b_refs to be non-zero we can destroy the
2246 * buffer's contents but we cannot yet reuse the buffer.
2249 bp->b_flags |= B_INVAL;
2255 /* NOT REACHED, bufqspin not held */
2259 * If we exhausted our list, sleep as appropriate. We may have to
2260 * wakeup various daemons and write out some dirty buffers.
2262 * Generally we are sleeping due to insufficient buffer space.
2264 * NOTE: bufqspin is held if bp is NULL, else it is not held.
2270 spin_unlock(&bufqspin);
2272 flags = VFS_BIO_NEED_BUFSPACE;
2274 } else if (bufspace >= hibufspace) {
2276 flags = VFS_BIO_NEED_BUFSPACE;
2279 flags = VFS_BIO_NEED_ANY;
2282 bd_speedup(); /* heeeelp */
2283 spin_lock(&bufcspin);
2284 needsbuffer |= flags;
2285 while (needsbuffer & flags) {
2286 if (ssleep(&needsbuffer, &bufcspin,
2287 slpflags, waitmsg, slptimeo)) {
2288 spin_unlock(&bufcspin);
2292 spin_unlock(&bufcspin);
2295 * We finally have a valid bp. We aren't quite out of the
2296 * woods, we still have to reserve kva space. In order
2297 * to keep fragmentation sane we only allocate kva in
2300 * (bufqspin is not held)
2302 maxsize = (maxsize + BKVAMASK) & ~BKVAMASK;
2304 if (maxsize != bp->b_kvasize) {
2305 vm_offset_t addr = 0;
2310 count = vm_map_entry_reserve(MAP_RESERVE_COUNT);
2311 vm_map_lock(&buffer_map);
2313 if (vm_map_findspace(&buffer_map,
2314 vm_map_min(&buffer_map), maxsize,
2315 maxsize, 0, &addr)) {
2317 * Uh oh. Buffer map is too fragmented. We
2318 * must defragment the map.
2320 vm_map_unlock(&buffer_map);
2321 vm_map_entry_release(count);
2324 bp->b_flags |= B_INVAL;
2329 vm_map_insert(&buffer_map, &count,
2331 addr, addr + maxsize,
2333 VM_PROT_ALL, VM_PROT_ALL,
2336 bp->b_kvabase = (caddr_t) addr;
2337 bp->b_kvasize = maxsize;
2338 bufspace += bp->b_kvasize;
2341 vm_map_unlock(&buffer_map);
2342 vm_map_entry_release(count);
2344 bp->b_data = bp->b_kvabase;
2350 * This routine is called in an emergency to recover VM pages from the
2351 * buffer cache by cashing in clean buffers. The idea is to recover
2352 * enough pages to be able to satisfy a stuck bio_page_alloc().
2357 recoverbufpages(void)
2364 spin_lock(&bufqspin);
2365 while (bytes < MAXBSIZE) {
2366 bp = TAILQ_FIRST(&bufqueues[BQUEUE_CLEAN]);
2371 * BQUEUE_CLEAN - B_AGE special case. If not set the bp
2372 * cycles through the queue twice before being selected.
2374 if ((bp->b_flags & B_AGE) == 0 && TAILQ_NEXT(bp, b_freelist)) {
2375 bp->b_flags |= B_AGE;
2376 TAILQ_REMOVE(&bufqueues[BQUEUE_CLEAN], bp, b_freelist);
2377 TAILQ_INSERT_TAIL(&bufqueues[BQUEUE_CLEAN],
2385 KKASSERT(bp->b_qindex == BQUEUE_CLEAN);
2386 KKASSERT((bp->b_flags & B_DELWRI) == 0);
2389 * Start freeing the bp. This is somewhat involved.
2391 * Buffers on the clean list must be disassociated from
2392 * their current vnode
2395 if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT) != 0) {
2396 kprintf("recoverbufpages: warning, locked buf %p, "
2399 ssleep(&bd_request, &bufqspin, 0, "gnbxxx", hz / 100);
2402 if (bp->b_qindex != BQUEUE_CLEAN) {
2403 kprintf("recoverbufpages: warning, BUF_LOCK blocked "
2404 "unexpectedly on buf %p index %d, race "
2410 bremfree_locked(bp);
2411 spin_unlock(&bufqspin);
2414 * Dependancies must be handled before we disassociate the
2417 * NOTE: HAMMER will set B_LOCKED if the buffer cannot
2418 * be immediately disassociated. HAMMER then becomes
2419 * responsible for releasing the buffer.
2421 if (LIST_FIRST(&bp->b_dep) != NULL) {
2423 if (bp->b_flags & B_LOCKED) {
2425 spin_lock(&bufqspin);
2428 KKASSERT(LIST_FIRST(&bp->b_dep) == NULL);
2431 bytes += bp->b_bufsize;
2433 if (bp->b_flags & B_VMIO) {
2434 bp->b_flags |= B_DIRECT; /* try to free pages */
2435 vfs_vmio_release(bp);
2440 KKASSERT(bp->b_vp == NULL);
2441 KKASSERT((bp->b_flags & B_HASHED) == 0);
2444 * critical section protection is not required when
2445 * scrapping a buffer's contents because it is already
2451 bp->b_flags = B_BNOCLIP;
2452 bp->b_cmd = BUF_CMD_DONE;
2457 bp->b_xio.xio_npages = 0;
2458 bp->b_dirtyoff = bp->b_dirtyend = 0;
2460 KKASSERT(LIST_FIRST(&bp->b_dep) == NULL);
2462 bp->b_flags |= B_INVAL;
2465 spin_lock(&bufqspin);
2467 spin_unlock(&bufqspin);
2474 * Buffer flushing daemon. Buffers are normally flushed by the
2475 * update daemon but if it cannot keep up this process starts to
2476 * take the load in an attempt to prevent getnewbuf() from blocking.
2478 * Once a flush is initiated it does not stop until the number
2479 * of buffers falls below lodirtybuffers, but we will wake up anyone
2480 * waiting at the mid-point.
2483 static struct kproc_desc buf_kp = {
2488 SYSINIT(bufdaemon, SI_SUB_KTHREAD_BUF, SI_ORDER_FIRST,
2489 kproc_start, &buf_kp)
2491 static struct kproc_desc bufhw_kp = {
2496 SYSINIT(bufdaemon_hw, SI_SUB_KTHREAD_BUF, SI_ORDER_FIRST,
2497 kproc_start, &bufhw_kp)
2508 * This process needs to be suspended prior to shutdown sync.
2510 EVENTHANDLER_REGISTER(shutdown_pre_sync, shutdown_kproc,
2511 bufdaemon_td, SHUTDOWN_PRI_LAST);
2512 curthread->td_flags |= TDF_SYSTHREAD;
2515 * This process is allowed to take the buffer cache to the limit
2518 kproc_suspend_loop();
2521 * Do the flush as long as the number of dirty buffers
2522 * (including those running) exceeds lodirtybufspace.
2524 * When flushing limit running I/O to hirunningspace
2525 * Do the flush. Limit the amount of in-transit I/O we
2526 * allow to build up, otherwise we would completely saturate
2527 * the I/O system. Wakeup any waiting processes before we
2528 * normally would so they can run in parallel with our drain.
2530 * Our aggregate normal+HW lo water mark is lodirtybufspace,
2531 * but because we split the operation into two threads we
2532 * have to cut it in half for each thread.
2534 waitrunningbufspace();
2535 limit = lodirtybufspace / 2;
2536 while (runningbufspace + dirtybufspace > limit ||
2537 dirtybufcount - dirtybufcounthw >= nbuf / 2) {
2538 if (flushbufqueues(BQUEUE_DIRTY) == 0)
2540 if (runningbufspace < hirunningspace)
2542 waitrunningbufspace();
2546 * We reached our low water mark, reset the
2547 * request and sleep until we are needed again.
2548 * The sleep is just so the suspend code works.
2550 spin_lock(&bufcspin);
2551 if (bd_request == 0)
2552 ssleep(&bd_request, &bufcspin, 0, "psleep", hz);
2554 spin_unlock(&bufcspin);
2567 * This process needs to be suspended prior to shutdown sync.
2569 EVENTHANDLER_REGISTER(shutdown_pre_sync, shutdown_kproc,
2570 bufdaemonhw_td, SHUTDOWN_PRI_LAST);
2571 curthread->td_flags |= TDF_SYSTHREAD;
2574 * This process is allowed to take the buffer cache to the limit
2577 kproc_suspend_loop();
2580 * Do the flush. Limit the amount of in-transit I/O we
2581 * allow to build up, otherwise we would completely saturate
2582 * the I/O system. Wakeup any waiting processes before we
2583 * normally would so they can run in parallel with our drain.
2585 * Once we decide to flush push the queued I/O up to
2586 * hirunningspace in order to trigger bursting by the bioq
2589 * Our aggregate normal+HW lo water mark is lodirtybufspace,
2590 * but because we split the operation into two threads we
2591 * have to cut it in half for each thread.
2593 waitrunningbufspace();
2594 limit = lodirtybufspace / 2;
2595 while (runningbufspace + dirtybufspacehw > limit ||
2596 dirtybufcounthw >= nbuf / 2) {
2597 if (flushbufqueues(BQUEUE_DIRTY_HW) == 0)
2599 if (runningbufspace < hirunningspace)
2601 waitrunningbufspace();
2605 * We reached our low water mark, reset the
2606 * request and sleep until we are needed again.
2607 * The sleep is just so the suspend code works.
2609 spin_lock(&bufcspin);
2610 if (bd_request_hw == 0)
2611 ssleep(&bd_request_hw, &bufcspin, 0, "psleep", hz);
2613 spin_unlock(&bufcspin);
2620 * Try to flush a buffer in the dirty queue. We must be careful to
2621 * free up B_INVAL buffers instead of write them, which NFS is
2622 * particularly sensitive to.
2624 * B_RELBUF may only be set by VFSs. We do set B_AGE to indicate
2625 * that we really want to try to get the buffer out and reuse it
2626 * due to the write load on the machine.
2628 * We must lock the buffer in order to check its validity before we
2629 * can mess with its contents. bufqspin isn't enough.
2632 flushbufqueues(bufq_type_t q)
2638 spin_lock(&bufqspin);
2641 bp = TAILQ_FIRST(&bufqueues[q]);
2643 if ((bp->b_flags & B_DELWRI) == 0) {
2644 kprintf("Unexpected clean buffer %p\n", bp);
2645 bp = TAILQ_NEXT(bp, b_freelist);
2648 if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT)) {
2649 bp = TAILQ_NEXT(bp, b_freelist);
2652 KKASSERT(bp->b_qindex == q);
2655 * Must recheck B_DELWRI after successfully locking
2658 if ((bp->b_flags & B_DELWRI) == 0) {
2660 bp = TAILQ_NEXT(bp, b_freelist);
2664 if (bp->b_flags & B_INVAL) {
2666 spin_unlock(&bufqspin);
2673 spin_unlock(&bufqspin);
2677 if (LIST_FIRST(&bp->b_dep) != NULL &&
2678 (bp->b_flags & B_DEFERRED) == 0 &&
2679 buf_countdeps(bp, 0)) {
2680 spin_lock(&bufqspin);
2682 TAILQ_REMOVE(&bufqueues[q], bp, b_freelist);
2683 TAILQ_INSERT_TAIL(&bufqueues[q], bp, b_freelist);
2684 bp->b_flags |= B_DEFERRED;
2686 bp = TAILQ_FIRST(&bufqueues[q]);
2691 * If the buffer has a dependancy, buf_checkwrite() must
2692 * also return 0 for us to be able to initate the write.
2694 * If the buffer is flagged B_ERROR it may be requeued
2695 * over and over again, we try to avoid a live lock.
2697 * NOTE: buf_checkwrite is MPSAFE.
2699 if (LIST_FIRST(&bp->b_dep) != NULL && buf_checkwrite(bp)) {
2702 } else if (bp->b_flags & B_ERROR) {
2703 tsleep(bp, 0, "bioer", 1);
2704 bp->b_flags &= ~B_AGE;
2707 bp->b_flags |= B_AGE;
2714 spin_unlock(&bufqspin);
2721 * Returns true if no I/O is needed to access the associated VM object.
2722 * This is like findblk except it also hunts around in the VM system for
2725 * Note that we ignore vm_page_free() races from interrupts against our
2726 * lookup, since if the caller is not protected our return value will not
2727 * be any more valid then otherwise once we exit the critical section.
2730 inmem(struct vnode *vp, off_t loffset)
2733 vm_offset_t toff, tinc, size;
2737 if (findblk(vp, loffset, FINDBLK_TEST))
2739 if (vp->v_mount == NULL)
2741 if ((obj = vp->v_object) == NULL)
2745 if (size > vp->v_mount->mnt_stat.f_iosize)
2746 size = vp->v_mount->mnt_stat.f_iosize;
2748 vm_object_hold(obj);
2749 for (toff = 0; toff < vp->v_mount->mnt_stat.f_iosize; toff += tinc) {
2750 m = vm_page_lookup(obj, OFF_TO_IDX(loffset + toff));
2756 if (tinc > PAGE_SIZE - ((toff + loffset) & PAGE_MASK))
2757 tinc = PAGE_SIZE - ((toff + loffset) & PAGE_MASK);
2758 if (vm_page_is_valid(m,
2759 (vm_offset_t) ((toff + loffset) & PAGE_MASK), tinc) == 0) {
2764 vm_object_drop(obj);
2771 * Locate and return the specified buffer. Unless flagged otherwise,
2772 * a locked buffer will be returned if it exists or NULL if it does not.
2774 * findblk()'d buffers are still on the bufqueues and if you intend
2775 * to use your (locked NON-TEST) buffer you need to bremfree(bp)
2776 * and possibly do other stuff to it.
2778 * FINDBLK_TEST - Do not lock the buffer. The caller is responsible
2779 * for locking the buffer and ensuring that it remains
2780 * the desired buffer after locking.
2782 * FINDBLK_NBLOCK - Lock the buffer non-blocking. If we are unable
2783 * to acquire the lock we return NULL, even if the
2786 * FINDBLK_REF - Returns the buffer ref'd, which prevents normal
2787 * reuse by getnewbuf() but does not prevent
2788 * disassociation (B_INVAL). Used to avoid deadlocks
2789 * against random (vp,loffset)s due to reassignment.
2791 * (0) - Lock the buffer blocking.
2796 findblk(struct vnode *vp, off_t loffset, int flags)
2801 lkflags = LK_EXCLUSIVE;
2802 if (flags & FINDBLK_NBLOCK)
2803 lkflags |= LK_NOWAIT;
2807 * Lookup. Ref the buf while holding v_token to prevent
2808 * reuse (but does not prevent diassociation).
2810 lwkt_gettoken_shared(&vp->v_token);
2811 bp = buf_rb_hash_RB_LOOKUP(&vp->v_rbhash_tree, loffset);
2813 lwkt_reltoken(&vp->v_token);
2817 lwkt_reltoken(&vp->v_token);
2820 * If testing only break and return bp, do not lock.
2822 if (flags & FINDBLK_TEST)
2826 * Lock the buffer, return an error if the lock fails.
2827 * (only FINDBLK_NBLOCK can cause the lock to fail).
2829 if (BUF_LOCK(bp, lkflags)) {
2830 atomic_subtract_int(&bp->b_refs, 1);
2831 /* bp = NULL; not needed */
2836 * Revalidate the locked buf before allowing it to be
2839 if (bp->b_vp == vp && bp->b_loffset == loffset)
2841 atomic_subtract_int(&bp->b_refs, 1);
2848 if ((flags & FINDBLK_REF) == 0)
2849 atomic_subtract_int(&bp->b_refs, 1);
2856 * Similar to getblk() except only returns the buffer if it is
2857 * B_CACHE and requires no other manipulation. Otherwise NULL
2860 * If B_RAM is set the buffer might be just fine, but we return
2861 * NULL anyway because we want the code to fall through to the
2862 * cluster read. Otherwise read-ahead breaks.
2864 * If blksize is 0 the buffer cache buffer must already be fully
2867 * If blksize is non-zero getblk() will be used, allowing a buffer
2868 * to be reinstantiated from its VM backing store. The buffer must
2869 * still be fully cached after reinstantiation to be returned.
2872 getcacheblk(struct vnode *vp, off_t loffset, int blksize)
2877 bp = getblk(vp, loffset, blksize, 0, 0);
2879 if ((bp->b_flags & (B_INVAL | B_CACHE | B_RAM)) ==
2881 bp->b_flags &= ~B_AGE;
2888 bp = findblk(vp, loffset, 0);
2890 if ((bp->b_flags & (B_INVAL | B_CACHE | B_RAM)) ==
2892 bp->b_flags &= ~B_AGE;
2906 * Get a block given a specified block and offset into a file/device.
2907 * B_INVAL may or may not be set on return. The caller should clear
2908 * B_INVAL prior to initiating a READ.
2910 * IT IS IMPORTANT TO UNDERSTAND THAT IF YOU CALL GETBLK() AND B_CACHE
2911 * IS NOT SET, YOU MUST INITIALIZE THE RETURNED BUFFER, ISSUE A READ,
2912 * OR SET B_INVAL BEFORE RETIRING IT. If you retire a getblk'd buffer
2913 * without doing any of those things the system will likely believe
2914 * the buffer to be valid (especially if it is not B_VMIO), and the
2915 * next getblk() will return the buffer with B_CACHE set.
2917 * For a non-VMIO buffer, B_CACHE is set to the opposite of B_INVAL for
2918 * an existing buffer.
2920 * For a VMIO buffer, B_CACHE is modified according to the backing VM.
2921 * If getblk()ing a previously 0-sized invalid buffer, B_CACHE is set
2922 * and then cleared based on the backing VM. If the previous buffer is
2923 * non-0-sized but invalid, B_CACHE will be cleared.
2925 * If getblk() must create a new buffer, the new buffer is returned with
2926 * both B_INVAL and B_CACHE clear unless it is a VMIO buffer, in which
2927 * case it is returned with B_INVAL clear and B_CACHE set based on the
2930 * getblk() also forces a bwrite() for any B_DELWRI buffer whos
2931 * B_CACHE bit is clear.
2933 * What this means, basically, is that the caller should use B_CACHE to
2934 * determine whether the buffer is fully valid or not and should clear
2935 * B_INVAL prior to issuing a read. If the caller intends to validate
2936 * the buffer by loading its data area with something, the caller needs
2937 * to clear B_INVAL. If the caller does this without issuing an I/O,
2938 * the caller should set B_CACHE ( as an optimization ), else the caller
2939 * should issue the I/O and biodone() will set B_CACHE if the I/O was
2940 * a write attempt or if it was a successfull read. If the caller
2941 * intends to issue a READ, the caller must clear B_INVAL and B_ERROR
2942 * prior to issuing the READ. biodone() will *not* clear B_INVAL.
2946 * GETBLK_PCATCH - catch signal if blocked, can cause NULL return
2947 * GETBLK_BHEAVY - heavy-weight buffer cache buffer
2952 getblk(struct vnode *vp, off_t loffset, int size, int blkflags, int slptimeo)
2955 int slpflags = (blkflags & GETBLK_PCATCH) ? PCATCH : 0;
2959 if (size > MAXBSIZE)
2960 panic("getblk: size(%d) > MAXBSIZE(%d)", size, MAXBSIZE);
2961 if (vp->v_object == NULL)
2962 panic("getblk: vnode %p has no object!", vp);
2965 if ((bp = findblk(vp, loffset, FINDBLK_REF | FINDBLK_TEST)) != NULL) {
2967 * The buffer was found in the cache, but we need to lock it.
2968 * We must acquire a ref on the bp to prevent reuse, but
2969 * this will not prevent disassociation (brelvp()) so we
2970 * must recheck (vp,loffset) after acquiring the lock.
2972 * Without the ref the buffer could potentially be reused
2973 * before we acquire the lock and create a deadlock
2974 * situation between the thread trying to reuse the buffer
2975 * and us due to the fact that we would wind up blocking
2976 * on a random (vp,loffset).
2978 if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT)) {
2979 if (blkflags & GETBLK_NOWAIT) {
2983 lkflags = LK_EXCLUSIVE | LK_SLEEPFAIL;
2984 if (blkflags & GETBLK_PCATCH)
2985 lkflags |= LK_PCATCH;
2986 error = BUF_TIMELOCK(bp, lkflags, "getblk", slptimeo);
2989 if (error == ENOLCK)
2993 /* buffer may have changed on us */
2998 * Once the buffer has been locked, make sure we didn't race
2999 * a buffer recyclement. Buffers that are no longer hashed
3000 * will have b_vp == NULL, so this takes care of that check
3003 if (bp->b_vp != vp || bp->b_loffset != loffset) {
3004 kprintf("Warning buffer %p (vp %p loffset %lld) "
3006 bp, vp, (long long)loffset);
3012 * If SZMATCH any pre-existing buffer must be of the requested
3013 * size or NULL is returned. The caller absolutely does not
3014 * want getblk() to bwrite() the buffer on a size mismatch.
3016 if ((blkflags & GETBLK_SZMATCH) && size != bp->b_bcount) {
3022 * All vnode-based buffers must be backed by a VM object.
3024 KKASSERT(bp->b_flags & B_VMIO);
3025 KKASSERT(bp->b_cmd == BUF_CMD_DONE);
3026 bp->b_flags &= ~B_AGE;
3029 * Make sure that B_INVAL buffers do not have a cached
3030 * block number translation.
3032 if ((bp->b_flags & B_INVAL) && (bp->b_bio2.bio_offset != NOOFFSET)) {
3033 kprintf("Warning invalid buffer %p (vp %p loffset %lld)"
3034 " did not have cleared bio_offset cache\n",
3035 bp, vp, (long long)loffset);
3036 clearbiocache(&bp->b_bio2);
3040 * The buffer is locked. B_CACHE is cleared if the buffer is
3043 if (bp->b_flags & B_INVAL)
3044 bp->b_flags &= ~B_CACHE;
3048 * Any size inconsistancy with a dirty buffer or a buffer
3049 * with a softupdates dependancy must be resolved. Resizing
3050 * the buffer in such circumstances can lead to problems.
3052 * Dirty or dependant buffers are written synchronously.
3053 * Other types of buffers are simply released and
3054 * reconstituted as they may be backed by valid, dirty VM
3055 * pages (but not marked B_DELWRI).
3057 * NFS NOTE: NFS buffers which straddle EOF are oddly-sized
3058 * and may be left over from a prior truncation (and thus
3059 * no longer represent the actual EOF point), so we
3060 * definitely do not want to B_NOCACHE the backing store.
3062 if (size != bp->b_bcount) {
3063 if (bp->b_flags & B_DELWRI) {
3064 bp->b_flags |= B_RELBUF;
3066 } else if (LIST_FIRST(&bp->b_dep)) {
3067 bp->b_flags |= B_RELBUF;
3070 bp->b_flags |= B_RELBUF;
3075 KKASSERT(size <= bp->b_kvasize);
3076 KASSERT(bp->b_loffset != NOOFFSET,
3077 ("getblk: no buffer offset"));
3080 * A buffer with B_DELWRI set and B_CACHE clear must
3081 * be committed before we can return the buffer in
3082 * order to prevent the caller from issuing a read
3083 * ( due to B_CACHE not being set ) and overwriting
3086 * Most callers, including NFS and FFS, need this to
3087 * operate properly either because they assume they
3088 * can issue a read if B_CACHE is not set, or because
3089 * ( for example ) an uncached B_DELWRI might loop due
3090 * to softupdates re-dirtying the buffer. In the latter
3091 * case, B_CACHE is set after the first write completes,
3092 * preventing further loops.
3094 * NOTE! b*write() sets B_CACHE. If we cleared B_CACHE
3095 * above while extending the buffer, we cannot allow the
3096 * buffer to remain with B_CACHE set after the write
3097 * completes or it will represent a corrupt state. To
3098 * deal with this we set B_NOCACHE to scrap the buffer
3101 * XXX Should this be B_RELBUF instead of B_NOCACHE?
3102 * I'm not even sure this state is still possible
3103 * now that getblk() writes out any dirty buffers
3106 * We might be able to do something fancy, like setting
3107 * B_CACHE in bwrite() except if B_DELWRI is already set,
3108 * so the below call doesn't set B_CACHE, but that gets real
3109 * confusing. This is much easier.
3112 if ((bp->b_flags & (B_CACHE|B_DELWRI)) == B_DELWRI) {
3113 kprintf("getblk: Warning, bp %p loff=%jx DELWRI set "
3114 "and CACHE clear, b_flags %08x\n",
3115 bp, (intmax_t)bp->b_loffset, bp->b_flags);
3116 bp->b_flags |= B_NOCACHE;
3122 * Buffer is not in-core, create new buffer. The buffer
3123 * returned by getnewbuf() is locked. Note that the returned
3124 * buffer is also considered valid (not marked B_INVAL).
3126 * Calculating the offset for the I/O requires figuring out
3127 * the block size. We use DEV_BSIZE for VBLK or VCHR and
3128 * the mount's f_iosize otherwise. If the vnode does not
3129 * have an associated mount we assume that the passed size is
3132 * Note that vn_isdisk() cannot be used here since it may
3133 * return a failure for numerous reasons. Note that the
3134 * buffer size may be larger then the block size (the caller
3135 * will use block numbers with the proper multiple). Beware
3136 * of using any v_* fields which are part of unions. In
3137 * particular, in DragonFly the mount point overloading
3138 * mechanism uses the namecache only and the underlying
3139 * directory vnode is not a special case.
3143 if (vp->v_type == VBLK || vp->v_type == VCHR)
3145 else if (vp->v_mount)
3146 bsize = vp->v_mount->mnt_stat.f_iosize;
3150 maxsize = size + (loffset & PAGE_MASK);
3151 maxsize = imax(maxsize, bsize);
3153 bp = getnewbuf(blkflags, slptimeo, size, maxsize);
3155 if (slpflags || slptimeo)
3161 * Atomically insert the buffer into the hash, so that it can
3162 * be found by findblk().
3164 * If bgetvp() returns non-zero a collision occured, and the
3165 * bp will not be associated with the vnode.
3167 * Make sure the translation layer has been cleared.
3169 bp->b_loffset = loffset;
3170 bp->b_bio2.bio_offset = NOOFFSET;
3171 /* bp->b_bio2.bio_next = NULL; */
3173 if (bgetvp(vp, bp, size)) {
3174 bp->b_flags |= B_INVAL;
3180 * All vnode-based buffers must be backed by a VM object.
3182 KKASSERT(vp->v_object != NULL);
3183 bp->b_flags |= B_VMIO;
3184 KKASSERT(bp->b_cmd == BUF_CMD_DONE);
3188 KKASSERT(dsched_is_clear_buf_priv(bp));
3195 * Reacquire a buffer that was previously released to the locked queue,
3196 * or reacquire a buffer which is interlocked by having bioops->io_deallocate
3197 * set B_LOCKED (which handles the acquisition race).
3199 * To this end, either B_LOCKED must be set or the dependancy list must be
3205 regetblk(struct buf *bp)
3207 KKASSERT((bp->b_flags & B_LOCKED) || LIST_FIRST(&bp->b_dep) != NULL);
3208 BUF_LOCK(bp, LK_EXCLUSIVE | LK_RETRY);
3215 * Get an empty, disassociated buffer of given size. The buffer is
3216 * initially set to B_INVAL.
3218 * critical section protection is not required for the allocbuf()
3219 * call because races are impossible here.
3229 maxsize = (size + BKVAMASK) & ~BKVAMASK;
3231 while ((bp = getnewbuf(0, 0, size, maxsize)) == 0)
3234 bp->b_flags |= B_INVAL; /* b_dep cleared by getnewbuf() */
3235 KKASSERT(dsched_is_clear_buf_priv(bp));
3243 * This code constitutes the buffer memory from either anonymous system
3244 * memory (in the case of non-VMIO operations) or from an associated
3245 * VM object (in the case of VMIO operations). This code is able to
3246 * resize a buffer up or down.
3248 * Note that this code is tricky, and has many complications to resolve
3249 * deadlock or inconsistant data situations. Tread lightly!!!
3250 * There are B_CACHE and B_DELWRI interactions that must be dealt with by
3251 * the caller. Calling this code willy nilly can result in the loss of
3254 * allocbuf() only adjusts B_CACHE for VMIO buffers. getblk() deals with
3255 * B_CACHE for the non-VMIO case.
3257 * This routine does not need to be called from a critical section but you
3258 * must own the buffer.
3263 allocbuf(struct buf *bp, int size)
3265 int newbsize, mbsize;
3268 if (BUF_REFCNT(bp) == 0)
3269 panic("allocbuf: buffer not busy");
3271 if (bp->b_kvasize < size)
3272 panic("allocbuf: buffer too small");
3274 if ((bp->b_flags & B_VMIO) == 0) {
3278 * Just get anonymous memory from the kernel. Don't
3279 * mess with B_CACHE.
3281 mbsize = (size + DEV_BSIZE - 1) & ~(DEV_BSIZE - 1);
3282 if (bp->b_flags & B_MALLOC)
3285 newbsize = round_page(size);
3287 if (newbsize < bp->b_bufsize) {
3289 * Malloced buffers are not shrunk
3291 if (bp->b_flags & B_MALLOC) {
3293 bp->b_bcount = size;
3295 kfree(bp->b_data, M_BIOBUF);
3296 if (bp->b_bufsize) {
3297 atomic_subtract_long(&bufmallocspace, bp->b_bufsize);
3301 bp->b_data = bp->b_kvabase;
3303 bp->b_flags &= ~B_MALLOC;
3309 (vm_offset_t) bp->b_data + newbsize,
3310 (vm_offset_t) bp->b_data + bp->b_bufsize);
3311 } else if (newbsize > bp->b_bufsize) {
3313 * We only use malloced memory on the first allocation.
3314 * and revert to page-allocated memory when the buffer
3317 if ((bufmallocspace < maxbufmallocspace) &&
3318 (bp->b_bufsize == 0) &&
3319 (mbsize <= PAGE_SIZE/2)) {
3321 bp->b_data = kmalloc(mbsize, M_BIOBUF, M_WAITOK);
3322 bp->b_bufsize = mbsize;
3323 bp->b_bcount = size;
3324 bp->b_flags |= B_MALLOC;
3325 atomic_add_long(&bufmallocspace, mbsize);
3331 * If the buffer is growing on its other-than-first
3332 * allocation, then we revert to the page-allocation
3335 if (bp->b_flags & B_MALLOC) {
3336 origbuf = bp->b_data;
3337 origbufsize = bp->b_bufsize;
3338 bp->b_data = bp->b_kvabase;
3339 if (bp->b_bufsize) {
3340 atomic_subtract_long(&bufmallocspace,
3345 bp->b_flags &= ~B_MALLOC;
3346 newbsize = round_page(newbsize);
3350 (vm_offset_t) bp->b_data + bp->b_bufsize,
3351 (vm_offset_t) bp->b_data + newbsize);
3353 bcopy(origbuf, bp->b_data, origbufsize);
3354 kfree(origbuf, M_BIOBUF);
3361 newbsize = (size + DEV_BSIZE - 1) & ~(DEV_BSIZE - 1);
3362 desiredpages = ((int)(bp->b_loffset & PAGE_MASK) +
3363 newbsize + PAGE_MASK) >> PAGE_SHIFT;
3364 KKASSERT(desiredpages <= XIO_INTERNAL_PAGES);
3366 if (bp->b_flags & B_MALLOC)
3367 panic("allocbuf: VMIO buffer can't be malloced");
3369 * Set B_CACHE initially if buffer is 0 length or will become
3372 if (size == 0 || bp->b_bufsize == 0)
3373 bp->b_flags |= B_CACHE;
3375 if (newbsize < bp->b_bufsize) {
3377 * DEV_BSIZE aligned new buffer size is less then the
3378 * DEV_BSIZE aligned existing buffer size. Figure out
3379 * if we have to remove any pages.
3381 if (desiredpages < bp->b_xio.xio_npages) {
3382 for (i = desiredpages; i < bp->b_xio.xio_npages; i++) {
3384 * the page is not freed here -- it
3385 * is the responsibility of
3386 * vnode_pager_setsize
3388 m = bp->b_xio.xio_pages[i];
3389 KASSERT(m != bogus_page,
3390 ("allocbuf: bogus page found"));
3391 vm_page_busy_wait(m, TRUE, "biodep");
3392 bp->b_xio.xio_pages[i] = NULL;
3393 vm_page_unwire(m, 0);
3396 pmap_qremove((vm_offset_t) trunc_page((vm_offset_t)bp->b_data) +
3397 (desiredpages << PAGE_SHIFT), (bp->b_xio.xio_npages - desiredpages));
3398 bp->b_xio.xio_npages = desiredpages;
3400 } else if (size > bp->b_bcount) {
3402 * We are growing the buffer, possibly in a
3403 * byte-granular fashion.
3411 * Step 1, bring in the VM pages from the object,
3412 * allocating them if necessary. We must clear
3413 * B_CACHE if these pages are not valid for the
3414 * range covered by the buffer.
3416 * critical section protection is required to protect
3417 * against interrupts unbusying and freeing pages
3418 * between our vm_page_lookup() and our
3419 * busycheck/wiring call.
3424 vm_object_hold(obj);
3425 while (bp->b_xio.xio_npages < desiredpages) {
3430 pi = OFF_TO_IDX(bp->b_loffset) +
3431 bp->b_xio.xio_npages;
3434 * Blocking on m->busy might lead to a
3437 * vm_fault->getpages->cluster_read->allocbuf
3439 m = vm_page_lookup_busy_try(obj, pi, FALSE,
3442 vm_page_sleep_busy(m, FALSE, "pgtblk");
3447 * note: must allocate system pages
3448 * since blocking here could intefere
3449 * with paging I/O, no matter which
3452 m = bio_page_alloc(obj, pi, desiredpages - bp->b_xio.xio_npages);
3455 vm_page_flag_clear(m, PG_ZERO);
3457 bp->b_flags &= ~B_CACHE;
3458 bp->b_xio.xio_pages[bp->b_xio.xio_npages] = m;
3459 ++bp->b_xio.xio_npages;
3465 * We found a page and were able to busy it.
3467 vm_page_flag_clear(m, PG_ZERO);
3470 bp->b_xio.xio_pages[bp->b_xio.xio_npages] = m;
3471 ++bp->b_xio.xio_npages;
3472 if (bp->b_act_count < m->act_count)
3473 bp->b_act_count = m->act_count;
3475 vm_object_drop(obj);
3478 * Step 2. We've loaded the pages into the buffer,
3479 * we have to figure out if we can still have B_CACHE
3480 * set. Note that B_CACHE is set according to the
3481 * byte-granular range ( bcount and size ), not the
3482 * aligned range ( newbsize ).
3484 * The VM test is against m->valid, which is DEV_BSIZE
3485 * aligned. Needless to say, the validity of the data
3486 * needs to also be DEV_BSIZE aligned. Note that this
3487 * fails with NFS if the server or some other client
3488 * extends the file's EOF. If our buffer is resized,
3489 * B_CACHE may remain set! XXX
3492 toff = bp->b_bcount;
3493 tinc = PAGE_SIZE - ((bp->b_loffset + toff) & PAGE_MASK);
3495 while ((bp->b_flags & B_CACHE) && toff < size) {
3498 if (tinc > (size - toff))
3501 pi = ((bp->b_loffset & PAGE_MASK) + toff) >>
3509 bp->b_xio.xio_pages[pi]
3516 * Step 3, fixup the KVM pmap. Remember that
3517 * bp->b_data is relative to bp->b_loffset, but
3518 * bp->b_loffset may be offset into the first page.
3521 bp->b_data = (caddr_t)
3522 trunc_page((vm_offset_t)bp->b_data);
3524 (vm_offset_t)bp->b_data,
3525 bp->b_xio.xio_pages,
3526 bp->b_xio.xio_npages
3528 bp->b_data = (caddr_t)((vm_offset_t)bp->b_data |
3529 (vm_offset_t)(bp->b_loffset & PAGE_MASK));
3533 /* adjust space use on already-dirty buffer */
3534 if (bp->b_flags & B_DELWRI) {
3535 spin_lock(&bufcspin);
3536 dirtybufspace += newbsize - bp->b_bufsize;
3537 if (bp->b_flags & B_HEAVY)
3538 dirtybufspacehw += newbsize - bp->b_bufsize;
3539 spin_unlock(&bufcspin);
3541 if (newbsize < bp->b_bufsize)
3543 bp->b_bufsize = newbsize; /* actual buffer allocation */
3544 bp->b_bcount = size; /* requested buffer size */
3551 * Wait for buffer I/O completion, returning error status. B_EINTR
3552 * is converted into an EINTR error but not cleared (since a chain
3553 * of biowait() calls may occur).
3555 * On return bpdone() will have been called but the buffer will remain
3556 * locked and will not have been brelse()'d.
3558 * NOTE! If a timeout is specified and ETIMEDOUT occurs the I/O is
3559 * likely still in progress on return.
3561 * NOTE! This operation is on a BIO, not a BUF.
3563 * NOTE! BIO_DONE is cleared by vn_strategy()
3568 _biowait(struct bio *bio, const char *wmesg, int to)
3570 struct buf *bp = bio->bio_buf;
3575 KKASSERT(bio == &bp->b_bio1);
3577 flags = bio->bio_flags;
3578 if (flags & BIO_DONE)
3580 nflags = flags | BIO_WANT;
3581 tsleep_interlock(bio, 0);
3582 if (atomic_cmpset_int(&bio->bio_flags, flags, nflags)) {
3584 error = tsleep(bio, PINTERLOCKED, wmesg, to);
3585 else if (bp->b_cmd == BUF_CMD_READ)
3586 error = tsleep(bio, PINTERLOCKED, "biord", to);
3588 error = tsleep(bio, PINTERLOCKED, "biowr", to);
3590 kprintf("tsleep error biowait %d\n", error);
3599 KKASSERT(bp->b_cmd == BUF_CMD_DONE);
3600 bio->bio_flags &= ~(BIO_DONE | BIO_SYNC);
3601 if (bp->b_flags & B_EINTR)
3603 if (bp->b_flags & B_ERROR)
3604 return (bp->b_error ? bp->b_error : EIO);
3609 biowait(struct bio *bio, const char *wmesg)
3611 return(_biowait(bio, wmesg, 0));
3615 biowait_timeout(struct bio *bio, const char *wmesg, int to)
3617 return(_biowait(bio, wmesg, to));
3621 * This associates a tracking count with an I/O. vn_strategy() and
3622 * dev_dstrategy() do this automatically but there are a few cases
3623 * where a vnode or device layer is bypassed when a block translation
3624 * is cached. In such cases bio_start_transaction() may be called on
3625 * the bypassed layers so the system gets an I/O in progress indication
3626 * for those higher layers.
3629 bio_start_transaction(struct bio *bio, struct bio_track *track)
3631 bio->bio_track = track;
3632 if (dsched_is_clear_buf_priv(bio->bio_buf))
3633 dsched_new_buf(bio->bio_buf);
3634 bio_track_ref(track);
3638 * Initiate I/O on a vnode.
3640 * SWAPCACHE OPERATION:
3642 * Real buffer cache buffers have a non-NULL bp->b_vp. Unfortunately
3643 * devfs also uses b_vp for fake buffers so we also have to check
3644 * that B_PAGING is 0. In this case the passed 'vp' is probably the
3645 * underlying block device. The swap assignments are related to the
3646 * buffer cache buffer's b_vp, not the passed vp.
3648 * The passed vp == bp->b_vp only in the case where the strategy call
3649 * is made on the vp itself for its own buffers (a regular file or
3650 * block device vp). The filesystem usually then re-calls vn_strategy()
3651 * after translating the request to an underlying device.
3653 * Cluster buffers set B_CLUSTER and the passed vp is the vp of the
3654 * underlying buffer cache buffers.
3656 * We can only deal with page-aligned buffers at the moment, because
3657 * we can't tell what the real dirty state for pages straddling a buffer
3660 * In order to call swap_pager_strategy() we must provide the VM object
3661 * and base offset for the underlying buffer cache pages so it can find
3665 vn_strategy(struct vnode *vp, struct bio *bio)
3667 struct bio_track *track;
3668 struct buf *bp = bio->bio_buf;
3670 KKASSERT(bp->b_cmd != BUF_CMD_DONE);
3673 * Set when an I/O is issued on the bp. Cleared by consumers
3674 * (aka HAMMER), allowing the consumer to determine if I/O had
3675 * actually occurred.
3677 bp->b_flags |= B_IODEBUG;
3680 * Handle the swap cache intercept.
3682 if (vn_cache_strategy(vp, bio))
3686 * Otherwise do the operation through the filesystem
3688 if (bp->b_cmd == BUF_CMD_READ)
3689 track = &vp->v_track_read;
3691 track = &vp->v_track_write;
3692 KKASSERT((bio->bio_flags & BIO_DONE) == 0);
3693 bio->bio_track = track;
3694 if (dsched_is_clear_buf_priv(bio->bio_buf))
3695 dsched_new_buf(bio->bio_buf);
3696 bio_track_ref(track);
3697 vop_strategy(*vp->v_ops, vp, bio);
3700 static void vn_cache_strategy_callback(struct bio *bio);
3703 vn_cache_strategy(struct vnode *vp, struct bio *bio)
3705 struct buf *bp = bio->bio_buf;
3712 * Is this buffer cache buffer suitable for reading from
3715 if (vm_swapcache_read_enable == 0 ||
3716 bp->b_cmd != BUF_CMD_READ ||
3717 ((bp->b_flags & B_CLUSTER) == 0 &&
3718 (bp->b_vp == NULL || (bp->b_flags & B_PAGING))) ||
3719 ((int)bp->b_loffset & PAGE_MASK) != 0 ||
3720 (bp->b_bcount & PAGE_MASK) != 0) {
3725 * Figure out the original VM object (it will match the underlying
3726 * VM pages). Note that swap cached data uses page indices relative
3727 * to that object, not relative to bio->bio_offset.
3729 if (bp->b_flags & B_CLUSTER)
3730 object = vp->v_object;
3732 object = bp->b_vp->v_object;
3735 * In order to be able to use the swap cache all underlying VM
3736 * pages must be marked as such, and we can't have any bogus pages.
3738 for (i = 0; i < bp->b_xio.xio_npages; ++i) {
3739 m = bp->b_xio.xio_pages[i];
3740 if ((m->flags & PG_SWAPPED) == 0)
3742 if (m == bogus_page)
3747 * If we are good then issue the I/O using swap_pager_strategy().
3749 * We can only do this if the buffer actually supports object-backed
3750 * I/O. If it doesn't npages will be 0.
3752 if (i && i == bp->b_xio.xio_npages) {
3753 m = bp->b_xio.xio_pages[0];
3754 nbio = push_bio(bio);
3755 nbio->bio_done = vn_cache_strategy_callback;
3756 nbio->bio_offset = ptoa(m->pindex);
3757 KKASSERT(m->object == object);
3758 swap_pager_strategy(object, nbio);
3765 * This is a bit of a hack but since the vn_cache_strategy() function can
3766 * override a VFS's strategy function we must make sure that the bio, which
3767 * is probably bio2, doesn't leak an unexpected offset value back to the
3768 * filesystem. The filesystem (e.g. UFS) might otherwise assume that the
3769 * bio went through its own file strategy function and the the bio2 offset
3770 * is a cached disk offset when, in fact, it isn't.
3773 vn_cache_strategy_callback(struct bio *bio)
3775 bio->bio_offset = NOOFFSET;
3776 biodone(pop_bio(bio));
3782 * Finish I/O on a buffer after all BIOs have been processed.
3783 * Called when the bio chain is exhausted or by biowait. If called
3784 * by biowait, elseit is typically 0.
3786 * bpdone is also responsible for setting B_CACHE in a B_VMIO bp.
3787 * In a non-VMIO bp, B_CACHE will be set on the next getblk()
3788 * assuming B_INVAL is clear.
3790 * For the VMIO case, we set B_CACHE if the op was a read and no
3791 * read error occured, or if the op was a write. B_CACHE is never
3792 * set if the buffer is invalid or otherwise uncacheable.
3794 * bpdone does not mess with B_INVAL, allowing the I/O routine or the
3795 * initiator to leave B_INVAL set to brelse the buffer out of existance
3796 * in the biodone routine.
3799 bpdone(struct buf *bp, int elseit)
3803 KASSERT(BUF_REFCNTNB(bp) > 0,
3804 ("biodone: bp %p not busy %d", bp, BUF_REFCNTNB(bp)));
3805 KASSERT(bp->b_cmd != BUF_CMD_DONE,
3806 ("biodone: bp %p already done!", bp));
3809 * No more BIOs are left. All completion functions have been dealt
3810 * with, now we clean up the buffer.
3813 bp->b_cmd = BUF_CMD_DONE;
3816 * Only reads and writes are processed past this point.
3818 if (cmd != BUF_CMD_READ && cmd != BUF_CMD_WRITE) {
3819 if (cmd == BUF_CMD_FREEBLKS)
3820 bp->b_flags |= B_NOCACHE;
3827 * Warning: softupdates may re-dirty the buffer, and HAMMER can do
3828 * a lot worse. XXX - move this above the clearing of b_cmd
3830 if (LIST_FIRST(&bp->b_dep) != NULL)
3831 buf_complete(bp); /* MPSAFE */
3834 * A failed write must re-dirty the buffer unless B_INVAL
3835 * was set. Only applicable to normal buffers (with VPs).
3836 * vinum buffers may not have a vp.
3838 if (cmd == BUF_CMD_WRITE &&
3839 (bp->b_flags & (B_ERROR | B_INVAL)) == B_ERROR) {
3840 bp->b_flags &= ~B_NOCACHE;
3845 if (bp->b_flags & B_VMIO) {
3851 struct vnode *vp = bp->b_vp;
3855 #if defined(VFS_BIO_DEBUG)
3856 if (vp->v_auxrefs == 0)
3857 panic("biodone: zero vnode hold count");
3858 if ((vp->v_flag & VOBJBUF) == 0)
3859 panic("biodone: vnode is not setup for merged cache");
3862 foff = bp->b_loffset;
3863 KASSERT(foff != NOOFFSET, ("biodone: no buffer offset"));
3864 KASSERT(obj != NULL, ("biodone: missing VM object"));
3866 #if defined(VFS_BIO_DEBUG)
3867 if (obj->paging_in_progress < bp->b_xio.xio_npages) {
3868 kprintf("biodone: paging in progress(%d) < "
3869 "bp->b_xio.xio_npages(%d)\n",
3870 obj->paging_in_progress,
3871 bp->b_xio.xio_npages);
3876 * Set B_CACHE if the op was a normal read and no error
3877 * occured. B_CACHE is set for writes in the b*write()
3880 iosize = bp->b_bcount - bp->b_resid;
3881 if (cmd == BUF_CMD_READ &&
3882 (bp->b_flags & (B_INVAL|B_NOCACHE|B_ERROR)) == 0) {
3883 bp->b_flags |= B_CACHE;
3886 vm_object_hold(obj);
3887 for (i = 0; i < bp->b_xio.xio_npages; i++) {
3891 resid = ((foff + PAGE_SIZE) & ~(off_t)PAGE_MASK) - foff;
3896 * cleanup bogus pages, restoring the originals. Since
3897 * the originals should still be wired, we don't have
3898 * to worry about interrupt/freeing races destroying
3899 * the VM object association.
3901 m = bp->b_xio.xio_pages[i];
3902 if (m == bogus_page) {
3904 m = vm_page_lookup(obj, OFF_TO_IDX(foff));
3906 panic("biodone: page disappeared");
3907 bp->b_xio.xio_pages[i] = m;
3908 pmap_qenter(trunc_page((vm_offset_t)bp->b_data),
3909 bp->b_xio.xio_pages, bp->b_xio.xio_npages);
3911 #if defined(VFS_BIO_DEBUG)
3912 if (OFF_TO_IDX(foff) != m->pindex) {
3913 kprintf("biodone: foff(%lu)/m->pindex(%ld) "
3915 (unsigned long)foff, (long)m->pindex);
3920 * In the write case, the valid and clean bits are
3921 * already changed correctly (see bdwrite()), so we
3922 * only need to do this here in the read case.
3924 vm_page_busy_wait(m, FALSE, "bpdpgw");
3925 if (cmd == BUF_CMD_READ && !bogusflag && resid > 0) {
3926 vfs_clean_one_page(bp, i, m);
3928 vm_page_flag_clear(m, PG_ZERO);
3931 * when debugging new filesystems or buffer I/O
3932 * methods, this is the most common error that pops
3933 * up. if you see this, you have not set the page
3934 * busy flag correctly!!!
3937 kprintf("biodone: page busy < 0, "
3938 "pindex: %d, foff: 0x(%x,%x), "
3939 "resid: %d, index: %d\n",
3940 (int) m->pindex, (int)(foff >> 32),
3941 (int) foff & 0xffffffff, resid, i);
3942 if (!vn_isdisk(vp, NULL))
3943 kprintf(" iosize: %ld, loffset: %lld, "
3944 "flags: 0x%08x, npages: %d\n",
3945 bp->b_vp->v_mount->mnt_stat.f_iosize,
3946 (long long)bp->b_loffset,
3947 bp->b_flags, bp->b_xio.xio_npages);
3949 kprintf(" VDEV, loffset: %lld, flags: 0x%08x, npages: %d\n",
3950 (long long)bp->b_loffset,
3951 bp->b_flags, bp->b_xio.xio_npages);
3952 kprintf(" valid: 0x%x, dirty: 0x%x, wired: %d\n",
3953 m->valid, m->dirty, m->wire_count);
3954 panic("biodone: page busy < 0");
3956 vm_page_io_finish(m);
3958 vm_object_pip_wakeup(obj);
3959 foff = (foff + PAGE_SIZE) & ~(off_t)PAGE_MASK;
3962 bp->b_flags &= ~B_HASBOGUS;
3963 vm_object_drop(obj);
3967 * Finish up by releasing the buffer. There are no more synchronous
3968 * or asynchronous completions, those were handled by bio_done
3972 if (bp->b_flags & (B_NOCACHE|B_INVAL|B_ERROR|B_RELBUF))
3983 biodone(struct bio *bio)
3985 struct buf *bp = bio->bio_buf;
3987 runningbufwakeup(bp);
3990 * Run up the chain of BIO's. Leave b_cmd intact for the duration.
3993 biodone_t *done_func;
3994 struct bio_track *track;
3997 * BIO tracking. Most but not all BIOs are tracked.
3999 if ((track = bio->bio_track) != NULL) {
4000 bio_track_rel(track);
4001 bio->bio_track = NULL;
4005 * A bio_done function terminates the loop. The function
4006 * will be responsible for any further chaining and/or
4007 * buffer management.
4009 * WARNING! The done function can deallocate the buffer!
4011 if ((done_func = bio->bio_done) != NULL) {
4012 bio->bio_done = NULL;
4016 bio = bio->bio_prev;
4020 * If we've run out of bio's do normal [a]synchronous completion.
4026 * Synchronous biodone - this terminates a synchronous BIO.
4028 * bpdone() is called with elseit=FALSE, leaving the buffer completed
4029 * but still locked. The caller must brelse() the buffer after waiting
4033 biodone_sync(struct bio *bio)
4035 struct buf *bp = bio->bio_buf;
4039 KKASSERT(bio == &bp->b_bio1);
4043 flags = bio->bio_flags;
4044 nflags = (flags | BIO_DONE) & ~BIO_WANT;
4046 if (atomic_cmpset_int(&bio->bio_flags, flags, nflags)) {
4047 if (flags & BIO_WANT)
4057 * This routine is called in lieu of iodone in the case of
4058 * incomplete I/O. This keeps the busy status for pages
4062 vfs_unbusy_pages(struct buf *bp)
4066 runningbufwakeup(bp);
4068 if (bp->b_flags & B_VMIO) {
4069 struct vnode *vp = bp->b_vp;
4073 vm_object_hold(obj);
4075 for (i = 0; i < bp->b_xio.xio_npages; i++) {
4076 vm_page_t m = bp->b_xio.xio_pages[i];
4079 * When restoring bogus changes the original pages
4080 * should still be wired, so we are in no danger of
4081 * losing the object association and do not need
4082 * critical section protection particularly.
4084 if (m == bogus_page) {
4085 m = vm_page_lookup(obj, OFF_TO_IDX(bp->b_loffset) + i);
4087 panic("vfs_unbusy_pages: page missing");
4089 bp->b_xio.xio_pages[i] = m;
4090 pmap_qenter(trunc_page((vm_offset_t)bp->b_data),
4091 bp->b_xio.xio_pages, bp->b_xio.xio_npages);
4093 vm_page_busy_wait(m, FALSE, "bpdpgw");
4094 vm_page_flag_clear(m, PG_ZERO);
4095 vm_page_io_finish(m);
4097 vm_object_pip_wakeup(obj);
4099 bp->b_flags &= ~B_HASBOGUS;
4100 vm_object_drop(obj);
4107 * This routine is called before a device strategy routine.
4108 * It is used to tell the VM system that paging I/O is in
4109 * progress, and treat the pages associated with the buffer
4110 * almost as being PG_BUSY. Also the object 'paging_in_progress'
4111 * flag is handled to make sure that the object doesn't become
4114 * Since I/O has not been initiated yet, certain buffer flags
4115 * such as B_ERROR or B_INVAL may be in an inconsistant state
4116 * and should be ignored.
4121 vfs_busy_pages(struct vnode *vp, struct buf *bp)
4124 struct lwp *lp = curthread->td_lwp;
4127 * The buffer's I/O command must already be set. If reading,
4128 * B_CACHE must be 0 (double check against callers only doing
4129 * I/O when B_CACHE is 0).
4131 KKASSERT(bp->b_cmd != BUF_CMD_DONE);
4132 KKASSERT(bp->b_cmd == BUF_CMD_WRITE || (bp->b_flags & B_CACHE) == 0);
4134 if (bp->b_flags & B_VMIO) {
4138 KASSERT(bp->b_loffset != NOOFFSET,
4139 ("vfs_busy_pages: no buffer offset"));
4142 * Busy all the pages. We have to busy them all at once
4143 * to avoid deadlocks.
4146 for (i = 0; i < bp->b_xio.xio_npages; i++) {
4147 vm_page_t m = bp->b_xio.xio_pages[i];
4149 if (vm_page_busy_try(m, FALSE)) {
4150 vm_page_sleep_busy(m, FALSE, "vbpage");
4152 vm_page_wakeup(bp->b_xio.xio_pages[i]);
4158 * Setup for I/O, soft-busy the page right now because
4159 * the next loop may block.
4161 for (i = 0; i < bp->b_xio.xio_npages; i++) {
4162 vm_page_t m = bp->b_xio.xio_pages[i];
4164 vm_page_flag_clear(m, PG_ZERO);
4165 if ((bp->b_flags & B_CLUSTER) == 0) {
4166 vm_object_pip_add(obj, 1);
4167 vm_page_io_start(m);
4172 * Adjust protections for I/O and do bogus-page mapping.
4173 * Assume that vm_page_protect() can block (it can block
4174 * if VM_PROT_NONE, don't take any chances regardless).
4176 * In particular note that for writes we must incorporate
4177 * page dirtyness from the VM system into the buffer's
4180 * For reads we theoretically must incorporate page dirtyness
4181 * from the VM system to determine if the page needs bogus
4182 * replacement, but we shortcut the test by simply checking
4183 * that all m->valid bits are set, indicating that the page
4184 * is fully valid and does not need to be re-read. For any
4185 * VM system dirtyness the page will also be fully valid
4186 * since it was mapped at one point.
4189 for (i = 0; i < bp->b_xio.xio_npages; i++) {
4190 vm_page_t m = bp->b_xio.xio_pages[i];
4192 vm_page_flag_clear(m, PG_ZERO); /* XXX */
4193 if (bp->b_cmd == BUF_CMD_WRITE) {
4195 * When readying a vnode-backed buffer for
4196 * a write we must zero-fill any invalid
4197 * portions of the backing VM pages, mark
4198 * it valid and clear related dirty bits.
4200 * vfs_clean_one_page() incorporates any
4201 * VM dirtyness and updates the b_dirtyoff
4202 * range (after we've made the page RO).
4204 * It is also expected that the pmap modified
4205 * bit has already been cleared by the
4206 * vm_page_protect(). We may not be able
4207 * to clear all dirty bits for a page if it
4208 * was also memory mapped (NFS).
4210 * Finally be sure to unassign any swap-cache
4211 * backing store as it is now stale.
4213 vm_page_protect(m, VM_PROT_READ);
4214 vfs_clean_one_page(bp, i, m);
4215 swap_pager_unswapped(m);
4216 } else if (m->valid == VM_PAGE_BITS_ALL) {
4218 * When readying a vnode-backed buffer for
4219 * read we must replace any dirty pages with
4220 * a bogus page so dirty data is not destroyed
4221 * when filling gaps.
4223 * To avoid testing whether the page is
4224 * dirty we instead test that the page was
4225 * at some point mapped (m->valid fully
4226 * valid) with the understanding that
4227 * this also covers the dirty case.
4229 bp->b_xio.xio_pages[i] = bogus_page;
4230 bp->b_flags |= B_HASBOGUS;
4232 } else if (m->valid & m->dirty) {
4234 * This case should not occur as partial
4235 * dirtyment can only happen if the buffer
4236 * is B_CACHE, and this code is not entered
4237 * if the buffer is B_CACHE.
4239 kprintf("Warning: vfs_busy_pages - page not "
4240 "fully valid! loff=%jx bpf=%08x "
4241 "idx=%d val=%02x dir=%02x\n",
4242 (intmax_t)bp->b_loffset, bp->b_flags,
4243 i, m->valid, m->dirty);
4244 vm_page_protect(m, VM_PROT_NONE);
4247 * The page is not valid and can be made
4250 vm_page_protect(m, VM_PROT_NONE);
4255 pmap_qenter(trunc_page((vm_offset_t)bp->b_data),
4256 bp->b_xio.xio_pages, bp->b_xio.xio_npages);
4261 * This is the easiest place to put the process accounting for the I/O
4265 if (bp->b_cmd == BUF_CMD_READ)
4266 lp->lwp_ru.ru_inblock++;
4268 lp->lwp_ru.ru_oublock++;
4273 * Tell the VM system that the pages associated with this buffer
4274 * are clean. This is used for delayed writes where the data is
4275 * going to go to disk eventually without additional VM intevention.
4277 * NOTE: While we only really need to clean through to b_bcount, we
4278 * just go ahead and clean through to b_bufsize.
4281 vfs_clean_pages(struct buf *bp)
4286 if ((bp->b_flags & B_VMIO) == 0)
4289 KASSERT(bp->b_loffset != NOOFFSET,
4290 ("vfs_clean_pages: no buffer offset"));
4292 for (i = 0; i < bp->b_xio.xio_npages; i++) {
4293 m = bp->b_xio.xio_pages[i];
4294 vfs_clean_one_page(bp, i, m);
4299 * vfs_clean_one_page:
4301 * Set the valid bits and clear the dirty bits in a page within a
4302 * buffer. The range is restricted to the buffer's size and the
4303 * buffer's logical offset might index into the first page.
4305 * The caller has busied or soft-busied the page and it is not mapped,
4306 * test and incorporate the dirty bits into b_dirtyoff/end before
4307 * clearing them. Note that we need to clear the pmap modified bits
4308 * after determining the the page was dirty, vm_page_set_validclean()
4309 * does not do it for us.
4311 * This routine is typically called after a read completes (dirty should
4312 * be zero in that case as we are not called on bogus-replace pages),
4313 * or before a write is initiated.
4316 vfs_clean_one_page(struct buf *bp, int pageno, vm_page_t m)
4324 * Calculate offset range within the page but relative to buffer's
4325 * loffset. loffset might be offset into the first page.
4327 xoff = (int)bp->b_loffset & PAGE_MASK; /* loffset offset into pg 0 */
4328 bcount = bp->b_bcount + xoff; /* offset adjusted */
4334 soff = (pageno << PAGE_SHIFT);
4335 eoff = soff + PAGE_SIZE;
4343 * Test dirty bits and adjust b_dirtyoff/end.
4345 * If dirty pages are incorporated into the bp any prior
4346 * B_NEEDCOMMIT state (NFS) must be cleared because the
4347 * caller has not taken into account the new dirty data.
4349 * If the page was memory mapped the dirty bits might go beyond the
4350 * end of the buffer, but we can't really make the assumption that
4351 * a file EOF straddles the buffer (even though this is the case for
4352 * NFS if B_NEEDCOMMIT is also set). So for the purposes of clearing
4353 * B_NEEDCOMMIT we only test the dirty bits covered by the buffer.
4354 * This also saves some console spam.
4356 * When clearing B_NEEDCOMMIT we must also clear B_CLUSTEROK,
4357 * NFS can handle huge commits but not huge writes.
4359 vm_page_test_dirty(m);
4361 if ((bp->b_flags & B_NEEDCOMMIT) &&
4362 (m->dirty & vm_page_bits(soff & PAGE_MASK, eoff - soff))) {
4364 kprintf("Warning: vfs_clean_one_page: bp %p "
4365 "loff=%jx,%d flgs=%08x clr B_NEEDCOMMIT"
4366 " cmd %d vd %02x/%02x x/s/e %d %d %d "
4368 bp, (intmax_t)bp->b_loffset, bp->b_bcount,
4369 bp->b_flags, bp->b_cmd,
4370 m->valid, m->dirty, xoff, soff, eoff,
4371 bp->b_dirtyoff, bp->b_dirtyend);
4372 bp->b_flags &= ~(B_NEEDCOMMIT | B_CLUSTEROK);
4374 print_backtrace(-1);
4377 * Only clear the pmap modified bits if ALL the dirty bits
4378 * are set, otherwise the system might mis-clear portions
4381 if (m->dirty == VM_PAGE_BITS_ALL &&
4382 (bp->b_flags & B_NEEDCOMMIT) == 0) {
4383 pmap_clear_modify(m);
4385 if (bp->b_dirtyoff > soff - xoff)
4386 bp->b_dirtyoff = soff - xoff;
4387 if (bp->b_dirtyend < eoff - xoff)
4388 bp->b_dirtyend = eoff - xoff;
4392 * Set related valid bits, clear related dirty bits.
4393 * Does not mess with the pmap modified bit.
4395 * WARNING! We cannot just clear all of m->dirty here as the
4396 * buffer cache buffers may use a DEV_BSIZE'd aligned
4397 * block size, or have an odd size (e.g. NFS at file EOF).
4398 * The putpages code can clear m->dirty to 0.
4400 * If a VOP_WRITE generates a buffer cache buffer which
4401 * covers the same space as mapped writable pages the
4402 * buffer flush might not be able to clear all the dirty
4403 * bits and still require a putpages from the VM system
4406 * WARNING! vm_page_set_validclean() currently assumes vm_token
4407 * is held. The page might not be busied (bdwrite() case).
4408 * XXX remove this comment once we've validated that this
4409 * is no longer an issue.
4411 vm_page_set_validclean(m, soff & PAGE_MASK, eoff - soff);
4415 * Similar to vfs_clean_one_page() but sets the bits to valid and dirty.
4416 * The page data is assumed to be valid (there is no zeroing here).
4419 vfs_dirty_one_page(struct buf *bp, int pageno, vm_page_t m)
4427 * Calculate offset range within the page but relative to buffer's
4428 * loffset. loffset might be offset into the first page.
4430 xoff = (int)bp->b_loffset & PAGE_MASK; /* loffset offset into pg 0 */
4431 bcount = bp->b_bcount + xoff; /* offset adjusted */
4437 soff = (pageno << PAGE_SHIFT);
4438 eoff = soff + PAGE_SIZE;
4444 vm_page_set_validdirty(m, soff & PAGE_MASK, eoff - soff);
4450 * Clear a buffer. This routine essentially fakes an I/O, so we need
4451 * to clear B_ERROR and B_INVAL.
4453 * Note that while we only theoretically need to clear through b_bcount,
4454 * we go ahead and clear through b_bufsize.
4458 vfs_bio_clrbuf(struct buf *bp)
4462 if ((bp->b_flags & (B_VMIO | B_MALLOC)) == B_VMIO) {
4463 bp->b_flags &= ~(B_INVAL | B_EINTR | B_ERROR);
4464 if ((bp->b_xio.xio_npages == 1) && (bp->b_bufsize < PAGE_SIZE) &&
4465 (bp->b_loffset & PAGE_MASK) == 0) {
4466 mask = (1 << (bp->b_bufsize / DEV_BSIZE)) - 1;
4467 if ((bp->b_xio.xio_pages[0]->valid & mask) == mask) {
4471 if (((bp->b_xio.xio_pages[0]->flags & PG_ZERO) == 0) &&
4472 ((bp->b_xio.xio_pages[0]->valid & mask) == 0)) {
4473 bzero(bp->b_data, bp->b_bufsize);
4474 bp->b_xio.xio_pages[0]->valid |= mask;
4480 for(i=0;i<bp->b_xio.xio_npages;i++,sa=ea) {
4481 int j = ((vm_offset_t)sa & PAGE_MASK) / DEV_BSIZE;
4482 ea = (caddr_t)trunc_page((vm_offset_t)sa + PAGE_SIZE);
4483 ea = (caddr_t)(vm_offset_t)ulmin(
4484 (u_long)(vm_offset_t)ea,
4485 (u_long)(vm_offset_t)bp->b_data + bp->b_bufsize);
4486 mask = ((1 << ((ea - sa) / DEV_BSIZE)) - 1) << j;
4487 if ((bp->b_xio.xio_pages[i]->valid & mask) == mask)
4489 if ((bp->b_xio.xio_pages[i]->valid & mask) == 0) {
4490 if ((bp->b_xio.xio_pages[i]->flags & PG_ZERO) == 0) {
4494 for (; sa < ea; sa += DEV_BSIZE, j++) {
4495 if (((bp->b_xio.xio_pages[i]->flags & PG_ZERO) == 0) &&
4496 (bp->b_xio.xio_pages[i]->valid & (1<<j)) == 0)
4497 bzero(sa, DEV_BSIZE);
4500 bp->b_xio.xio_pages[i]->valid |= mask;
4501 vm_page_flag_clear(bp->b_xio.xio_pages[i], PG_ZERO);
4510 * vm_hold_load_pages:
4512 * Load pages into the buffer's address space. The pages are
4513 * allocated from the kernel object in order to reduce interference
4514 * with the any VM paging I/O activity. The range of loaded
4515 * pages will be wired.
4517 * If a page cannot be allocated, the 'pagedaemon' is woken up to
4518 * retrieve the full range (to - from) of pages.
4523 vm_hold_load_pages(struct buf *bp, vm_offset_t from, vm_offset_t to)
4529 to = round_page(to);
4530 from = round_page(from);
4531 index = (from - trunc_page((vm_offset_t)bp->b_data)) >> PAGE_SHIFT;
4536 * Note: must allocate system pages since blocking here
4537 * could intefere with paging I/O, no matter which
4540 vm_object_hold(&kernel_object);
4541 p = bio_page_alloc(&kernel_object, pg >> PAGE_SHIFT,
4542 (vm_pindex_t)((to - pg) >> PAGE_SHIFT));
4543 vm_object_drop(&kernel_object);
4546 p->valid = VM_PAGE_BITS_ALL;
4547 vm_page_flag_clear(p, PG_ZERO);
4548 pmap_kenter(pg, VM_PAGE_TO_PHYS(p));
4549 bp->b_xio.xio_pages[index] = p;
4556 bp->b_xio.xio_npages = index;
4560 * Allocate pages for a buffer cache buffer.
4562 * Under extremely severe memory conditions even allocating out of the
4563 * system reserve can fail. If this occurs we must allocate out of the
4564 * interrupt reserve to avoid a deadlock with the pageout daemon.
4566 * The pageout daemon can run (putpages -> VOP_WRITE -> getblk -> allocbuf).
4567 * If the buffer cache's vm_page_alloc() fails a vm_wait() can deadlock
4568 * against the pageout daemon if pages are not freed from other sources.
4570 * If NULL is returned the caller is expected to retry (typically check if
4571 * the page already exists on retry before trying to allocate one).
4575 bio_page_alloc(vm_object_t obj, vm_pindex_t pg, int deficit)
4579 ASSERT_LWKT_TOKEN_HELD(vm_object_token(obj));
4582 * Try a normal allocation, allow use of system reserve.
4584 p = vm_page_alloc(obj, pg, VM_ALLOC_NORMAL | VM_ALLOC_SYSTEM |
4590 * The normal allocation failed and we clearly have a page
4591 * deficit. Try to reclaim some clean VM pages directly
4592 * from the buffer cache.
4594 vm_pageout_deficit += deficit;
4598 * We may have blocked, the caller will know what to do if the
4601 if (vm_page_lookup(obj, pg)) {
4606 * Only system threads can use the interrupt reserve
4608 if ((curthread->td_flags & TDF_SYSTHREAD) == 0) {
4615 * Allocate and allow use of the interrupt reserve.
4617 * If after all that we still can't allocate a VM page we are
4618 * in real trouble, but we slog on anyway hoping that the system
4621 p = vm_page_alloc(obj, pg, VM_ALLOC_NORMAL | VM_ALLOC_SYSTEM |
4622 VM_ALLOC_INTERRUPT | VM_ALLOC_NULL_OK);
4624 if (vm_page_count_severe()) {
4626 vm_wait(hz / 20 + 1);
4628 } else if (vm_page_lookup(obj, pg) == NULL) {
4629 kprintf("bio_page_alloc: Memory exhausted during bufcache "
4630 "page allocation\n");
4638 * vm_hold_free_pages:
4640 * Return pages associated with the buffer back to the VM system.
4642 * The range of pages underlying the buffer's address space will
4643 * be unmapped and un-wired.
4648 vm_hold_free_pages(struct buf *bp, vm_offset_t from, vm_offset_t to)
4652 int index, newnpages;
4654 from = round_page(from);
4655 to = round_page(to);
4656 index = (from - trunc_page((vm_offset_t)bp->b_data)) >> PAGE_SHIFT;
4659 for (pg = from; pg < to; pg += PAGE_SIZE, index++) {
4660 p = bp->b_xio.xio_pages[index];
4661 if (p && (index < bp->b_xio.xio_npages)) {
4663 kprintf("vm_hold_free_pages: doffset: %lld, "
4665 (long long)bp->b_bio2.bio_offset,
4666 (long long)bp->b_loffset);
4668 bp->b_xio.xio_pages[index] = NULL;
4670 vm_page_busy_wait(p, FALSE, "vmhldpg");
4671 vm_page_unwire(p, 0);
4675 bp->b_xio.xio_npages = newnpages;
4681 * Map a user buffer into KVM via a pbuf. On return the buffer's
4682 * b_data, b_bufsize, and b_bcount will be set, and its XIO page array
4686 vmapbuf(struct buf *bp, caddr_t udata, int bytes)
4697 * bp had better have a command and it better be a pbuf.
4699 KKASSERT(bp->b_cmd != BUF_CMD_DONE);
4700 KKASSERT(bp->b_flags & B_PAGING);
4701 KKASSERT(bp->b_kvabase);
4707 * Map the user data into KVM. Mappings have to be page-aligned.
4709 addr = (caddr_t)trunc_page((vm_offset_t)udata);
4712 vmprot = VM_PROT_READ;
4713 if (bp->b_cmd == BUF_CMD_READ)
4714 vmprot |= VM_PROT_WRITE;
4716 while (addr < udata + bytes) {
4718 * Do the vm_fault if needed; do the copy-on-write thing
4719 * when reading stuff off device into memory.
4721 * vm_fault_page*() returns a held VM page.
4723 va = (addr >= udata) ? (vm_offset_t)addr : (vm_offset_t)udata;
4724 va = trunc_page(va);
4726 m = vm_fault_page_quick(va, vmprot, &error);
4728 for (i = 0; i < pidx; ++i) {
4729 vm_page_unhold(bp->b_xio.xio_pages[i]);
4730 bp->b_xio.xio_pages[i] = NULL;
4734 bp->b_xio.xio_pages[pidx] = m;
4740 * Map the page array and set the buffer fields to point to
4741 * the mapped data buffer.
4743 if (pidx > btoc(MAXPHYS))
4744 panic("vmapbuf: mapped more than MAXPHYS");
4745 pmap_qenter((vm_offset_t)bp->b_kvabase, bp->b_xio.xio_pages, pidx);
4747 bp->b_xio.xio_npages = pidx;
4748 bp->b_data = bp->b_kvabase + ((int)(intptr_t)udata & PAGE_MASK);
4749 bp->b_bcount = bytes;
4750 bp->b_bufsize = bytes;
4757 * Free the io map PTEs associated with this IO operation.
4758 * We also invalidate the TLB entries and restore the original b_addr.
4761 vunmapbuf(struct buf *bp)
4766 KKASSERT(bp->b_flags & B_PAGING);
4768 npages = bp->b_xio.xio_npages;
4769 pmap_qremove(trunc_page((vm_offset_t)bp->b_data), npages);
4770 for (pidx = 0; pidx < npages; ++pidx) {
4771 vm_page_unhold(bp->b_xio.xio_pages[pidx]);
4772 bp->b_xio.xio_pages[pidx] = NULL;
4774 bp->b_xio.xio_npages = 0;
4775 bp->b_data = bp->b_kvabase;
4779 * Scan all buffers in the system and issue the callback.
4782 scan_all_buffers(int (*callback)(struct buf *, void *), void *info)
4788 for (n = 0; n < nbuf; ++n) {
4789 if ((error = callback(&buf[n], info)) < 0) {
4799 * nestiobuf_iodone: biodone callback for nested buffers and propagate
4800 * completion to the master buffer.
4803 nestiobuf_iodone(struct bio *bio)
4806 struct buf *mbp, *bp;
4807 struct devstat *stats;
4812 mbio = bio->bio_caller_info1.ptr;
4813 stats = bio->bio_caller_info2.ptr;
4814 mbp = mbio->bio_buf;
4816 KKASSERT(bp->b_bcount <= bp->b_bufsize);
4817 KKASSERT(mbp != bp);
4819 error = bp->b_error;
4820 if (bp->b_error == 0 &&
4821 (bp->b_bcount < bp->b_bufsize || bp->b_resid > 0)) {
4823 * Not all got transfered, raise an error. We have no way to
4824 * propagate these conditions to mbp.
4829 donebytes = bp->b_bufsize;
4833 nestiobuf_done(mbio, donebytes, error, stats);
4837 nestiobuf_done(struct bio *mbio, int donebytes, int error, struct devstat *stats)
4841 mbp = mbio->bio_buf;
4843 KKASSERT((int)(intptr_t)mbio->bio_driver_info > 0);
4846 * If an error occured, propagate it to the master buffer.
4848 * Several biodone()s may wind up running concurrently so
4849 * use an atomic op to adjust b_flags.
4852 mbp->b_error = error;
4853 atomic_set_int(&mbp->b_flags, B_ERROR);
4857 * Decrement the operations in progress counter and terminate the
4858 * I/O if this was the last bit.
4860 if (atomic_fetchadd_int((int *)&mbio->bio_driver_info, -1) == 1) {
4863 devstat_end_transaction_buf(stats, mbp);
4869 * Initialize a nestiobuf for use. Set an initial count of 1 to prevent
4870 * the mbio from being biodone()'d while we are still adding sub-bios to
4874 nestiobuf_init(struct bio *bio)
4876 bio->bio_driver_info = (void *)1;
4880 * The BIOs added to the nestedio have already been started, remove the
4881 * count that placeheld our mbio and biodone() it if the count would
4885 nestiobuf_start(struct bio *mbio)
4887 struct buf *mbp = mbio->bio_buf;
4890 * Decrement the operations in progress counter and terminate the
4891 * I/O if this was the last bit.
4893 if (atomic_fetchadd_int((int *)&mbio->bio_driver_info, -1) == 1) {
4894 if (mbp->b_flags & B_ERROR)
4895 mbp->b_resid = mbp->b_bcount;
4903 * Set an intermediate error prior to calling nestiobuf_start()
4906 nestiobuf_error(struct bio *mbio, int error)
4908 struct buf *mbp = mbio->bio_buf;
4911 mbp->b_error = error;
4912 atomic_set_int(&mbp->b_flags, B_ERROR);
4917 * nestiobuf_add: setup a "nested" buffer.
4919 * => 'mbp' is a "master" buffer which is being divided into sub pieces.
4920 * => 'bp' should be a buffer allocated by getiobuf.
4921 * => 'offset' is a byte offset in the master buffer.
4922 * => 'size' is a size in bytes of this nested buffer.
4925 nestiobuf_add(struct bio *mbio, struct buf *bp, int offset, size_t size, struct devstat *stats)
4927 struct buf *mbp = mbio->bio_buf;
4928 struct vnode *vp = mbp->b_vp;
4930 KKASSERT(mbp->b_bcount >= offset + size);
4932 atomic_add_int((int *)&mbio->bio_driver_info, 1);
4934 /* kernel needs to own the lock for it to be released in biodone */
4937 bp->b_cmd = mbp->b_cmd;
4938 bp->b_bio1.bio_done = nestiobuf_iodone;
4939 bp->b_data = (char *)mbp->b_data + offset;
4940 bp->b_resid = bp->b_bcount = size;
4941 bp->b_bufsize = bp->b_bcount;
4943 bp->b_bio1.bio_track = NULL;
4944 bp->b_bio1.bio_caller_info1.ptr = mbio;
4945 bp->b_bio1.bio_caller_info2.ptr = stats;
4949 * print out statistics from the current status of the buffer pool
4950 * this can be toggeled by the system control option debug.syncprt
4959 int counts[(MAXBSIZE / PAGE_SIZE) + 1];
4960 static char *bname[3] = { "LOCKED", "LRU", "AGE" };
4962 for (dp = bufqueues, i = 0; dp < &bufqueues[3]; dp++, i++) {
4964 for (j = 0; j <= MAXBSIZE/PAGE_SIZE; j++)
4967 spin_lock(&bufqspin);
4968 TAILQ_FOREACH(bp, dp, b_freelist) {
4969 counts[bp->b_bufsize/PAGE_SIZE]++;
4972 spin_unlock(&bufqspin);
4974 kprintf("%s: total-%d", bname[i], count);
4975 for (j = 0; j <= MAXBSIZE/PAGE_SIZE; j++)
4977 kprintf(", %d-%d", j * PAGE_SIZE, counts[j]);
4985 DB_SHOW_COMMAND(buffer, db_show_buffer)
4988 struct buf *bp = (struct buf *)addr;
4991 db_printf("usage: show buffer <addr>\n");
4995 db_printf("b_flags = 0x%b\n", (u_int)bp->b_flags, PRINT_BUF_FLAGS);
4996 db_printf("b_cmd = %d\n", bp->b_cmd);
4997 db_printf("b_error = %d, b_bufsize = %d, b_bcount = %d, "
4998 "b_resid = %d\n, b_data = %p, "
4999 "bio_offset(disk) = %lld, bio_offset(phys) = %lld\n",
5000 bp->b_error, bp->b_bufsize, bp->b_bcount, bp->b_resid,
5002 (long long)bp->b_bio2.bio_offset,
5003 (long long)(bp->b_bio2.bio_next ?
5004 bp->b_bio2.bio_next->bio_offset : (off_t)-1));
5005 if (bp->b_xio.xio_npages) {
5007 db_printf("b_xio.xio_npages = %d, pages(OBJ, IDX, PA): ",
5008 bp->b_xio.xio_npages);
5009 for (i = 0; i < bp->b_xio.xio_npages; i++) {
5011 m = bp->b_xio.xio_pages[i];
5012 db_printf("(%p, 0x%lx, 0x%lx)", (void *)m->object,
5013 (u_long)m->pindex, (u_long)VM_PAGE_TO_PHYS(m));
5014 if ((i + 1) < bp->b_xio.xio_npages)