2 * Copyright (c) 2007 The DragonFly Project. All rights reserved.
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in
15 * the documentation and/or other materials provided with the
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19 * from this software without specific, prior written permission.
21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * $DragonFly: src/sys/vfs/hammer/hammer_io.c,v 1.1 2007/11/07 00:43:24 dillon Exp $
37 * IO Primitives and buffer cache management
39 * All major data-tracking structures in HAMMER contain a struct hammer_io
40 * which is used to manage their backing store. We use filesystem buffers
41 * for backing store and we leave them passively associated with their
44 * If the kernel tries to release a passively associated buf which we cannot
45 * yet let go we set B_LOCKED in the buffer and then actively released it
50 #include <sys/fcntl.h>
51 #include <sys/nlookup.h>
56 * Helper routine which disassociates a buffer cache buf from a
59 * If the io structures indicates that the buffer is not in a released
60 * state we must dispose of it.
63 hammer_io_disassociate(union hammer_io_structure *io)
65 struct buf *bp = io->io.bp;
69 LIST_INIT(&bp->b_dep); /* clear the association */
71 modified = io->io.modified;
72 released = io->io.released;
75 case HAMMER_STRUCTURE_VOLUME:
76 io->volume.ondisk = NULL;
77 io->volume.alist.meta = NULL;
80 case HAMMER_STRUCTURE_SUPERCL:
81 io->supercl.ondisk = NULL;
82 io->supercl.alist.meta = NULL;
85 case HAMMER_STRUCTURE_CLUSTER:
86 io->cluster.ondisk = NULL;
87 io->cluster.alist_master.meta = NULL;
88 io->cluster.alist_btree.meta = NULL;
89 io->cluster.alist_record.meta = NULL;
90 io->cluster.alist_mdata.meta = NULL;
93 case HAMMER_STRUCTURE_BUFFER:
94 io->buffer.ondisk = NULL;
95 io->buffer.alist.meta = NULL;
100 * 'io' now invalid. If the buffer was not released we have to
103 * disassociate can be called via hammer_io_checkwrite() with
104 * the buffer in a released state (possibly with no lock held
105 * at all, in fact). Don't mess with it if we are in a released
117 * Load bp for a HAMMER structure.
120 hammer_io_read(struct vnode *devvp, struct hammer_io *io)
125 if ((bp = io->bp) == NULL) {
126 error = bread(devvp, io->offset, HAMMER_BUFSIZE, &io->bp);
129 bp->b_ops = &hammer_bioops;
130 LIST_INSERT_HEAD(&bp->b_dep, &io->worklist, node);
133 io->modified = 0; /* no new modifications yet */
134 io->released = 0; /* we hold an active lock on bp */
142 * Similar to hammer_io_read() but returns a zero'd out buffer instead.
143 * vfs_bio_clrbuf() is kinda nasty, enforce serialization against background
144 * I/O so we can call it.
147 hammer_io_new(struct vnode *devvp, struct hammer_io *io)
151 if ((bp = io->bp) == NULL) {
152 io->bp = getblk(devvp, io->offset, HAMMER_BUFSIZE, 0, 0);
154 bp->b_ops = &hammer_bioops;
155 LIST_INSERT_HEAD(&bp->b_dep, &io->worklist, node);
156 io->released = 0; /* we hold an active lock on bp */
171 * Release the IO buffer on the last reference to a hammer structure. At
172 * this time the lock still has a reference.
174 * We flush and disassociate the bp if flush is non-zero or if the kernel
175 * tried to free/reuse the buffer.
178 hammer_io_release(struct hammer_io *io, int flush)
180 union hammer_io_structure *iou = (void *)io;
183 if ((bp = io->bp) != NULL) {
184 if (bp->b_flags & B_LOCKED) {
186 * The kernel wanted the buffer but couldn't get it,
189 KKASSERT(io->released);
193 bp->b_flags &= ~B_LOCKED;
194 hammer_io_disassociate(iou);
195 } else if (io->released == 0) {
197 * We are holding a real lock on the buffer, release
198 * it passively (hammer_io_deallocate is called
199 * when the kernel really wants to reuse the buffer).
202 hammer_io_disassociate(iou);
211 } else if (io->modified && (bp->b_flags & B_DELWRI) == 0) {
213 * We are holding the buffer passively but made
214 * modifications to it. The kernel has not initiated
215 * I/O (else B_LOCKED would have been set), so just
216 * check whether B_DELWRI is set. Since we still
217 * have lock references on the HAMMER structure the
218 * kernel cannot throw the buffer away.
220 * We have to do this to avoid the situation where
221 * the buffer is not marked B_DELWRI when modified
222 * and in a released state, otherwise the kernel
223 * will never try to flush the modified buffer!
229 hammer_io_disassociate(iou);
236 * We are holding the buffer passively but were
237 * asked to disassociate and flush it.
242 hammer_io_disassociate(iou);
243 /* io->released ignored */
244 } /* else just leave it associated in a released state */
253 * Pre and post I/O callbacks. No buffer munging is done so there is
254 * nothing to do here.
256 static void hammer_io_deallocate(struct buf *bp);
259 hammer_io_start(struct buf *bp)
264 hammer_io_complete(struct buf *bp)
269 * Callback from kernel when it wishes to deallocate a passively
270 * associated structure. This can only occur if the buffer is
271 * passively associated with the structure.
273 * If we cannot disassociate we set B_LOCKED to prevent the buffer
274 * from getting reused.
277 hammer_io_deallocate(struct buf *bp)
279 union hammer_io_structure *io = (void *)LIST_FIRST(&bp->b_dep);
281 /* XXX memory interlock, spinlock to sync cpus */
283 KKASSERT(io->io.released);
285 if (io->io.lock.refs) {
286 bp->b_flags |= B_LOCKED;
288 hammer_lock(&io->io.lock);
289 KKASSERT(io->io.lock.refs == 1);
290 switch(io->io.type) {
291 case HAMMER_STRUCTURE_VOLUME:
292 hammer_put_volume(&io->volume, 1);
294 case HAMMER_STRUCTURE_SUPERCL:
295 hammer_put_supercl(&io->supercl, 1);
297 case HAMMER_STRUCTURE_CLUSTER:
298 hammer_put_cluster(&io->cluster, 1);
300 case HAMMER_STRUCTURE_BUFFER:
301 hammer_put_buffer(&io->buffer, 1);
304 /* NOTE: io may be invalid (kfree'd) here */
310 hammer_io_fsync(struct vnode *vp)
316 * NOTE: will not be called unless we tell the kernel about the
317 * bioops. Unused... we use the mount's VFS_SYNC instead.
320 hammer_io_sync(struct mount *mp)
326 hammer_io_movedeps(struct buf *bp1, struct buf *bp2)
331 * I/O pre-check for reading and writing. HAMMER only uses this for
332 * B_CACHE buffers so checkread just shouldn't happen, but if it does
335 * Writing is a different case. We don't want to write out a buffer
336 * that HAMMER may be modifying passively.
339 hammer_io_checkread(struct buf *bp)
345 hammer_io_checkwrite(struct buf *bp)
347 union hammer_io_structure *io = (void *)LIST_FIRST(&bp->b_dep);
349 if (io->io.lock.refs) {
350 bp->b_flags |= B_LOCKED;
353 KKASSERT(bp->b_flags & B_DELWRI);
354 hammer_io_disassociate(io);
361 * Return non-zero if we wish to delay the kernel's attempt to flush
362 * this buffer to disk.
365 hammer_io_countdeps(struct buf *bp, int n)
370 struct bio_ops hammer_bioops = {
371 .io_start = hammer_io_start,
372 .io_complete = hammer_io_complete,
373 .io_deallocate = hammer_io_deallocate,
374 .io_fsync = hammer_io_fsync,
375 .io_sync = hammer_io_sync,
376 .io_movedeps = hammer_io_movedeps,
377 .io_countdeps = hammer_io_countdeps,
378 .io_checkread = hammer_io_checkread,
379 .io_checkwrite = hammer_io_checkwrite,