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35 * @(#)vm_swap.c 8.5 (Berkeley) 2/17/94
36 * $FreeBSD: src/sys/vm/vm_swap.c,v 1.96.2.2 2001/10/14 18:46:47 iedowse Exp $
37 * $DragonFly: src/sys/vm/vm_swap.c,v 1.36 2007/07/20 17:21:54 dillon Exp $
42 #include <sys/param.h>
43 #include <sys/systm.h>
44 #include <sys/sysproto.h>
48 #include <sys/nlookup.h>
49 #include <sys/dmap.h> /* XXX */
50 #include <sys/vnode.h>
51 #include <sys/fcntl.h>
52 #include <sys/blist.h>
53 #include <sys/kernel.h>
59 #include <vm/vm_extern.h>
60 #include <vm/swap_pager.h>
61 #include <vm/vm_zone.h>
63 #include <sys/thread2.h>
64 #include <sys/mplock2.h>
65 #include <sys/mutex2.h>
68 * Indirect driver for multi-controller paging.
74 static struct swdevt should_be_malloced[NSWAPDEV];
75 struct swdevt *swdevt = should_be_malloced; /* exported to pstat/systat */
76 static swblk_t nswap; /* first block after the interleaved devs */
77 static struct mtx swap_mtx = MTX_INITIALIZER;
78 int nswdev = NSWAPDEV; /* exported to pstat/systat */
82 static int swapdev_strategy (struct vop_strategy_args *ap);
83 struct vnode *swapdev_vp;
86 * (struct vnode *a_vp, struct bio *b_bio)
88 * vn_strategy() for swapdev_vp. Perform swap strategy interleave device
94 swapdev_strategy(struct vop_strategy_args *ap)
96 struct bio *bio = ap->a_bio;
98 struct buf *bp = bio->bio_buf;
99 int sz, off, seg, index, blkno, nblkno;
104 sz = howmany(bp->b_bcount, PAGE_SIZE);
105 blkno = (int)(bio->bio_offset >> PAGE_SHIFT);
108 * Convert interleaved swap into per-device swap. Note that
109 * the block size is left in PAGE_SIZE'd chunks (for the newswap)
112 nbio = push_bio(bio);
115 if (off + sz > dmmax) {
116 bp->b_error = EINVAL;
117 bp->b_flags |= B_ERROR;
122 index = seg % nswdev;
124 nbio->bio_offset = (off_t)(seg * dmmax + off) << PAGE_SHIFT;
127 nbio->bio_offset = bio->bio_offset;
129 nblkno = (int)(nbio->bio_offset >> PAGE_SHIFT);
131 if (nblkno + sz > sp->sw_nblks) {
132 bp->b_error = EINVAL;
133 bp->b_flags |= B_ERROR;
134 /* I/O was never started on nbio, must biodone(bio) */
138 if (sp->sw_vp == NULL) {
139 bp->b_error = ENODEV;
140 bp->b_flags |= B_ERROR;
141 /* I/O was never started on nbio, must biodone(bio) */
147 * Issue a strategy call on the appropriate swap vnode. Note that
148 * bp->b_vp is not modified. Strategy code is always supposed to
151 * We have to use vn_strategy() here even if we know we have a
152 * device in order to properly break up requests which exceed the
153 * device's DMA limits.
155 vn_strategy(sp->sw_vp, nbio);
160 * Create a special vnode op vector for swapdev_vp - we only use
161 * vn_strategy(), everything else returns an error.
163 static struct vop_ops swapdev_vnode_vops = {
164 .vop_default = vop_defaultop,
165 .vop_strategy = swapdev_strategy
167 static struct vop_ops *swapdev_vnode_vops_p = &swapdev_vnode_vops;
169 VNODEOP_SET(swapdev_vnode_vops);
172 * swapon_args(char *name)
174 * System call swapon(name) enables swapping on device name,
175 * which must be in the swdevsw. Return EBUSY
176 * if already swapping on this device.
181 sys_swapon(struct swapon_args *uap)
183 struct thread *td = curthread;
186 struct nlookupdata nd;
192 error = priv_check(td, PRIV_ROOT);
199 error = nlookup_init(&nd, uap->name, UIO_USERSPACE, NLC_FOLLOW);
201 error = nlookup(&nd);
203 error = cache_vref(&nd.nl_nch, nd.nl_cred, &vp);
207 mtx_unlock(&swap_mtx);
211 if (vn_isdisk(vp, &error)) {
212 error = swaponvp(td, vp, 0);
213 } else if (vp->v_type == VREG && vp->v_tag == VT_NFS &&
214 (error = VOP_GETATTR(vp, &attr)) == 0) {
216 * Allow direct swapping to NFS regular files in the same
217 * way that nfs_mountroot() sets up diskless swapping.
219 error = swaponvp(td, vp, attr.va_size / DEV_BSIZE);
224 mtx_unlock(&swap_mtx);
230 * Swfree(index) frees the index'th portion of the swap map.
231 * Each of the nswdev devices provides 1/nswdev'th of the swap
232 * space, which is laid out with blocks of dmmax pages circularly
235 * The new swap code uses page-sized blocks. The old swap code used
236 * DEV_BSIZE'd chunks.
238 * XXX locking when multiple swapon's run in parallel
241 swaponvp(struct thread *td, struct vnode *vp, u_quad_t nblks)
243 swblk_t aligned_nblks;
259 error = getspecialvnode(VT_NON, NULL, &swapdev_vnode_vops_p,
262 panic("Cannot get vnode for swapdev");
263 swapdev_vp->v_type = VNON; /* Untyped */
264 vx_unlock(swapdev_vp);
267 for (sp = swdevt, index = 0 ; index < nswdev; index++, sp++) {
268 if (sp->sw_vp == vp) {
269 mtx_unlock(&swap_mtx);
276 mtx_unlock(&swap_mtx);
279 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
280 error = VOP_OPEN(vp, FREAD | FWRITE, cred, NULL);
283 mtx_unlock(&swap_mtx);
288 * v_rdev is not valid until after the VOP_OPEN() call. dev_psize()
289 * must be supported if a character device has been specified.
291 if (vp->v_type == VCHR)
296 if (nblks == 0 && dev != NULL) {
297 dpsize = dev_dpsize(dev);
299 VOP_CLOSE(vp, FREAD | FWRITE);
300 mtx_unlock(&swap_mtx);
303 nblks = (u_quad_t)dpsize;
306 VOP_CLOSE(vp, FREAD | FWRITE);
307 mtx_unlock(&swap_mtx);
312 * nblks is in DEV_BSIZE'd chunks, convert to PAGE_SIZE'd chunks.
313 * First chop nblks off to page-align it, then convert.
315 * sw->sw_nblks is in page-sized chunks now too.
317 nblks &= ~(u_quad_t)(ctodb(1) - 1);
318 nblks = dbtoc(nblks);
321 * Post-conversion nblks must not be >= BLIST_MAXBLKS, and
322 * we impose a 4-swap-device limit so we have to divide it out
323 * further. Going beyond this will result in overflows in the
326 * Post-conversion nblks must fit within a (swblk_t), which
327 * this test also ensures.
329 if (nblks > BLIST_MAXBLKS / nswdev) {
330 kprintf("exceeded maximum of %d blocks per swap unit\n",
331 (int)BLIST_MAXBLKS / nswdev);
332 VOP_CLOSE(vp, FREAD | FWRITE);
333 mtx_unlock(&swap_mtx);
338 sp->sw_dev = dev2udev(dev);
340 sp->sw_flags |= SW_FREED;
341 sp->sw_nblks = (swblk_t)nblks;
344 * nblks, nswap, and dmmax are PAGE_SIZE'd parameters now, not
345 * DEV_BSIZE'd. aligned_nblks is used to calculate the
346 * size of the swap bitmap, taking into account the stripe size.
348 aligned_nblks = (swblk_t)((nblks + (dmmax - 1)) & ~(u_long)(dmmax - 1));
350 if (aligned_nblks * nswdev > nswap)
351 nswap = aligned_nblks * nswdev;
353 if (swapblist == NULL)
354 swapblist = blist_create(nswap);
356 blist_resize(&swapblist, nswap, 0);
358 for (dvbase = dmmax; dvbase < nblks; dvbase += dmmax) {
359 blk = min(nblks - dvbase, dmmax);
360 vsbase = index * dmmax + dvbase * nswdev;
361 blist_free(swapblist, vsbase, blk);
365 swap_pager_newswap();
367 mtx_unlock(&swap_mtx);