/* * Copyright 2000 Marshall Kirk McKusick. All Rights Reserved. * * Further information about snapshots can be obtained from: * * Marshall Kirk McKusick http://www.mckusick.com/softdep/ * 1614 Oxford Street mckusick@mckusick.com * Berkeley, CA 94709-1608 +1-510-843-9542 * USA * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY MARSHALL KIRK MCKUSICK ``AS IS'' AND ANY * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE * DISCLAIMED. IN NO EVENT SHALL MARSHALL KIRK MCKUSICK BE LIABLE FOR * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * @(#)ffs_snapshot.c 8.11 (McKusick) 7/23/00 * $FreeBSD$ */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define KERNCRED proc0.p_ucred #define DEBUG static int indiracct __P((struct vnode *, struct vnode *, int, ufs_daddr_t, int, int, int, int)); static int snapacct __P((struct vnode *, ufs_daddr_t *, ufs_daddr_t *)); static int readblock __P((struct buf *, daddr_t)); #ifdef DEBUG #include int snapdebug = 0; SYSCTL_INT(_debug, OID_AUTO, snapdebug, CTLFLAG_RW, &snapdebug, 0, ""); #endif /* DEBUG */ /* * Create a snapshot file and initialize it for the filesystem. */ int ffs_snapshot(mp, snapfile) struct mount *mp; char *snapfile; { ufs_daddr_t rlbn; ufs_daddr_t lbn, blkno, copyblkno, inoblks[FSMAXSNAP]; int error, cg, snaploc, indiroff, numblks; int i, size, base, len, loc, inoblkcnt; int blksperindir, flag = mp->mnt_flag; struct fs *fs = VFSTOUFS(mp)->um_fs; struct proc *p = CURPROC; struct inode *devip, *ip, *xp; struct buf *bp, *nbp, *ibp; struct vnode *vp, *devvp; struct nameidata nd; struct mount *wrtmp; struct dinode *dip; struct vattr vat; struct cg *cgp; /* * Need to serialize access to snapshot code per filesystem. */ /* * Assign a snapshot slot in the superblock. */ for (snaploc = 0; snaploc < FSMAXSNAP; snaploc++) if (fs->fs_snapinum[snaploc] == 0) break; if (snaploc == FSMAXSNAP) return (ENOSPC); /* * Create the snapshot file. */ restart: NDINIT(&nd, CREATE, LOCKPARENT | LOCKLEAF, UIO_USERSPACE, snapfile, p); if ((error = namei(&nd)) != 0) return (error); if (nd.ni_vp != NULL) { vput(nd.ni_vp); error = EEXIST; } if (nd.ni_dvp->v_mount != mp) error = EXDEV; if (error) { NDFREE(&nd, NDF_ONLY_PNBUF); if (nd.ni_dvp == nd.ni_vp) vrele(nd.ni_dvp); else vput(nd.ni_dvp); return (error); } VATTR_NULL(&vat); vat.va_type = VREG; vat.va_mode = S_IRUSR; vat.va_vaflags |= VA_EXCLUSIVE; if (VOP_GETWRITEMOUNT(nd.ni_dvp, &wrtmp)) wrtmp = NULL; if (wrtmp != mp) panic("ffs_snapshot: mount mismatch"); if (vn_start_write(NULL, &wrtmp, V_NOWAIT) != 0) { NDFREE(&nd, NDF_ONLY_PNBUF); vput(nd.ni_dvp); if ((error = vn_start_write(NULL, &wrtmp, V_XSLEEP | PCATCH)) != 0) return (error); goto restart; } VOP_LEASE(nd.ni_dvp, p, KERNCRED, LEASE_WRITE); error = VOP_CREATE(nd.ni_dvp, &nd.ni_vp, &nd.ni_cnd, &vat); vput(nd.ni_dvp); if (error) { NDFREE(&nd, NDF_ONLY_PNBUF); vn_finished_write(wrtmp); return (error); } vp = nd.ni_vp; ip = VTOI(vp); devvp = ip->i_devvp; devip = VTOI(devvp); /* * Allocate and copy the last block contents so as to be able * to set size to that of the filesystem. */ numblks = howmany(fs->fs_size, fs->fs_frag); error = VOP_BALLOC(vp, lblktosize(fs, (off_t)(numblks - 1)), fs->fs_bsize, KERNCRED, B_CLRBUF, &bp); if (error) goto out; ip->i_size = lblktosize(fs, (off_t)numblks); ip->i_flag |= IN_CHANGE | IN_UPDATE; if ((error = readblock(bp, numblks - 1)) != 0) goto out; bawrite(bp); /* * Preallocate critical data structures so that we can copy * them in without further allocation after we suspend all * operations on the filesystem. We would like to just release * the allocated buffers without writing them since they will * be filled in below once we are ready to go, but this upsets * the soft update code, so we go ahead and write the new buffers. * * Allocate all indirect blocks. Also allocate shadow copies * for each of the indirect blocks. */ for (blkno = NDADDR; blkno < numblks; blkno += NINDIR(fs)) { error = VOP_BALLOC(vp, lblktosize(fs, (off_t)blkno), fs->fs_bsize, p->p_ucred, B_METAONLY, &ibp); if (error) goto out; copyblkno = fragstoblks(fs, dbtofsb(fs, ibp->b_blkno)); bdwrite(ibp); error = VOP_BALLOC(vp, lblktosize(fs, (off_t)copyblkno), fs->fs_bsize, p->p_ucred, 0, &nbp); if (error) goto out; bawrite(nbp); } /* * Allocate shadow blocks to copy all of the other snapshot inodes * so that we will be able to expunge them from this snapshot. */ for (loc = 0, inoblkcnt = 0; loc < snaploc; loc++) { blkno = fragstoblks(fs, ino_to_fsba(fs, fs->fs_snapinum[loc])); for (i = 0; i < inoblkcnt; i++) if (inoblks[i] == blkno) break; if (i == inoblkcnt) { inoblks[inoblkcnt++] = blkno; error = VOP_BALLOC(vp, lblktosize(fs, (off_t)blkno), fs->fs_bsize, KERNCRED, 0, &nbp); if (error) goto out; bawrite(nbp); } } /* * Allocate all cylinder group blocks. */ for (cg = 0; cg < fs->fs_ncg; cg++) { error = VOP_BALLOC(vp, (off_t)(cgtod(fs, cg)) << fs->fs_fshift, fs->fs_bsize, KERNCRED, 0, &nbp); if (error) goto out; bawrite(nbp); } /* * Allocate copies for the superblock and its summary information. */ error = VOP_BALLOC(vp, (off_t)(SBOFF), fs->fs_bsize, KERNCRED, 0, &nbp); if (error) goto out; bawrite(nbp); blkno = fragstoblks(fs, fs->fs_csaddr); len = howmany(fs->fs_cssize, fs->fs_bsize); for (loc = 0; loc < len; loc++) { error = VOP_BALLOC(vp, lblktosize(fs, (off_t)(blkno + loc)), fs->fs_bsize, KERNCRED, 0, &nbp); if (error) goto out; bawrite(nbp); } /* * Change inode to snapshot type file. */ ip->i_flags |= SF_SNAPSHOT; ip->i_flag |= IN_CHANGE | IN_UPDATE; /* * Ensure that the snapshot is completely on disk. */ if ((error = VOP_FSYNC(vp, KERNCRED, MNT_WAIT, p)) != 0) goto out; /* * All allocations are done, so we can now snapshot the system. * * Suspend operation on filesystem. */ for (;;) { vn_finished_write(wrtmp); vfs_write_suspend(vp->v_mount); if (mp->mnt_kern_flag & MNTK_SUSPENDED) break; vn_start_write(NULL, &wrtmp, V_WAIT); } /* * First, copy all the cylinder group maps. All the unallocated * blocks are marked BLK_NOCOPY so that the snapshot knows that * it need not copy them if they are later written. */ len = howmany(fs->fs_fpg, fs->fs_frag); for (cg = 0; cg < fs->fs_ncg; cg++) { error = bread(ip->i_devvp, fsbtodb(fs, cgtod(fs, cg)), (int)fs->fs_cgsize, KERNCRED, &bp); if (error) { brelse(bp); goto out1; } cgp = (struct cg *)bp->b_data; if (!cg_chkmagic(cgp)) { brelse(bp); error = EIO; goto out1; } error = bread(vp, fragstoblks(fs, cgtod(fs, cg)), fs->fs_bsize, KERNCRED, &nbp); if (error) { brelse(bp); brelse(nbp); goto out1; } bcopy(bp->b_data, nbp->b_data, fs->fs_cgsize); if (fs->fs_cgsize < fs->fs_bsize) bzero(&nbp->b_data[fs->fs_cgsize], fs->fs_bsize - fs->fs_cgsize); nbp->b_flags |= B_VALIDSUSPWRT; bawrite(nbp); base = cg * fs->fs_fpg / fs->fs_frag; if (base + len > numblks) len = numblks - base; loc = 0; if (base < NDADDR) { for ( ; loc < NDADDR; loc++) { if (!ffs_isblock(fs, cg_blksfree(cgp), loc)) continue; ip->i_db[loc] = BLK_NOCOPY; } } error = VOP_BALLOC(vp, lblktosize(fs, (off_t)(base + loc)), fs->fs_bsize, KERNCRED, B_METAONLY, &ibp); if (error) { brelse(bp); goto out1; } indiroff = (base + loc - NDADDR) % NINDIR(fs); for ( ; loc < len; loc++, indiroff++) { if (indiroff >= NINDIR(fs)) { ibp->b_flags |= B_VALIDSUSPWRT; bawrite(ibp); error = VOP_BALLOC(vp, lblktosize(fs, (off_t)(base + loc)), fs->fs_bsize, KERNCRED, B_METAONLY, &ibp); if (error) { brelse(bp); goto out1; } indiroff = 0; } if (!ffs_isblock(fs, cg_blksfree(cgp), loc)) continue; ((ufs_daddr_t *)(ibp->b_data))[indiroff] = BLK_NOCOPY; } bqrelse(bp); ibp->b_flags |= B_VALIDSUSPWRT; bdwrite(ibp); } /* * Snapshot the superblock and its summary information. */ error = VOP_BALLOC(vp, (off_t)(SBOFF), fs->fs_bsize, KERNCRED, 0, &nbp); if (error) goto out1; bcopy(fs, nbp->b_data, fs->fs_sbsize); ((struct fs *)(nbp->b_data))->fs_clean = 1; if (fs->fs_sbsize < fs->fs_bsize) bzero(&nbp->b_data[fs->fs_sbsize], fs->fs_bsize - fs->fs_sbsize); nbp->b_flags |= B_VALIDSUSPWRT; bawrite(nbp); blkno = fragstoblks(fs, fs->fs_csaddr); len = howmany(fs->fs_cssize, fs->fs_bsize) - 1; size = fs->fs_bsize; for (loc = 0; loc <= len; loc++) { error = VOP_BALLOC(vp, lblktosize(fs, (off_t)(blkno + loc)), fs->fs_bsize, KERNCRED, 0, &nbp); if (error) goto out1; if (loc == len) { readblock(nbp, blkno + loc); size = fs->fs_cssize % fs->fs_bsize; } bcopy(fs->fs_csp[loc], nbp->b_data, size); nbp->b_flags |= B_VALIDSUSPWRT; bawrite(nbp); } /* * Copy the shadow blocks for the snapshot inodes so that * the copies can can be expunged. */ for (loc = 0; loc < inoblkcnt; loc++) { error = VOP_BALLOC(vp, lblktosize(fs, (off_t)inoblks[loc]), fs->fs_bsize, KERNCRED, 0, &nbp); if (error) goto out1; readblock(nbp, inoblks[loc]); nbp->b_flags |= B_VALIDSUSPWRT; bdwrite(nbp); } /* * Copy allocation information from other snapshots and then * expunge them from the view of the current snapshot. */ for (xp = devip->i_copyonwrite; xp; xp = xp->i_copyonwrite) { /* * Before expunging a snapshot inode, note all the * blocks that it claims with BLK_SNAP so that fsck will * be able to account for those blocks properly and so * that this snapshot knows that it need not copy them * if the other snapshot holding them is freed. */ if ((error = snapacct(vp, &xp->i_db[0], &xp->i_ib[NIADDR])) !=0) goto out1; blksperindir = 1; lbn = -NDADDR; len = numblks - NDADDR; rlbn = NDADDR; for (i = 0; len > 0 && i < NIADDR; i++) { error = indiracct(vp, ITOV(xp), i, xp->i_ib[i], lbn, rlbn, len, blksperindir); if (error) goto out1; blksperindir *= NINDIR(fs); lbn -= blksperindir + 1; len -= blksperindir; rlbn += blksperindir; } /* * Set copied snapshot inode to be a zero length file. */ blkno = fragstoblks(fs, ino_to_fsba(fs, xp->i_number)); error = VOP_BALLOC(vp, lblktosize(fs, (off_t)blkno), fs->fs_bsize, KERNCRED, 0, &nbp); if (error) goto out1; dip = (struct dinode *)nbp->b_data + ino_to_fsbo(fs, xp->i_number); dip->di_size = 0; dip->di_blocks = 0; dip->di_flags &= ~SF_SNAPSHOT; bzero(&dip->di_db[0], (NDADDR + NIADDR) * sizeof(ufs_daddr_t)); nbp->b_flags |= B_VALIDSUSPWRT; bdwrite(nbp); } /* * Copy all indirect blocks to their shadows (allocated above) * to avoid deadlock in ffs_copyonwrite. */ for (blkno = NDADDR; blkno < numblks; blkno += NINDIR(fs)) { error = VOP_BALLOC(vp, lblktosize(fs, (off_t)blkno), fs->fs_bsize, p->p_ucred, B_METAONLY, &ibp); if (error) goto out1; copyblkno = fragstoblks(fs, dbtofsb(fs, ibp->b_blkno)); bqrelse(ibp); error = VOP_BALLOC(vp, lblktosize(fs, (off_t)copyblkno), fs->fs_bsize, p->p_ucred, 0, &nbp); if (error) goto out1; error = VOP_BALLOC(vp, lblktosize(fs, (off_t)blkno), fs->fs_bsize, p->p_ucred, B_METAONLY, &ibp); if (error) { brelse(nbp); goto out1; } bcopy(ibp->b_data, nbp->b_data, fs->fs_bsize); bqrelse(ibp); nbp->b_flags |= B_VALIDSUSPWRT; bawrite(nbp); } /* * Record snapshot inode. Since this is the newest snapshot, * it must be placed at the end of the list. */ fs->fs_snapinum[snaploc] = ip->i_number; if (ip->i_copyonwrite != 0) panic("ffs_snapshot: %d already on list", ip->i_number); if (devip->i_copyonwrite == 0) { devvp->v_flag |= VCOPYONWRITE; devip->i_copyonwrite = ip; } else { for (xp = devip->i_copyonwrite; xp->i_copyonwrite != 0; ) xp = xp->i_copyonwrite; xp->i_copyonwrite = ip; } vp->v_flag |= VSYSTEM; /* * Resume operation on filesystem. */ out1: vfs_write_resume(vp->v_mount); vn_start_write(NULL, &wrtmp, V_WAIT); out: mp->mnt_flag = flag; (void) VOP_FSYNC(vp, KERNCRED, MNT_WAIT, p); if (error) vput(vp); else VOP_UNLOCK(vp, 0, p); vn_finished_write(wrtmp); return (error); } /* * Descend an indirect block chain for vnode cancelvp accounting for all * its indirect blocks in snapvp. */ static int indiracct(snapvp, cancelvp, level, blkno, lbn, rlbn, remblks, blksperindir) struct vnode *snapvp; struct vnode *cancelvp; int level; ufs_daddr_t blkno; int lbn; int rlbn; int remblks; int blksperindir; { int subblksperindir, error, last, num, i; struct indir indirs[NIADDR + 2]; ufs_daddr_t *bap; struct buf *bp; struct fs *fs; if ((error = ufs_getlbns(cancelvp, rlbn, indirs, &num)) != 0) return (error); if (lbn != indirs[num - 1 - level].in_lbn || blkno == 0 || num < 2) panic("indiracct: botched params"); /* * We have to expand bread here since it will deadlock looking * up the block number for any blocks that are not in the cache. */ fs = VTOI(cancelvp)->i_fs; bp = getblk(cancelvp, lbn, fs->fs_bsize, 0, 0); bp->b_blkno = fsbtodb(fs, blkno); if ((bp->b_flags & (B_DONE | B_DELWRI)) == 0 && (error = readblock(bp, fragstoblks(fs, blkno)))) { brelse(bp); return (error); } /* * Account for the block pointers in this indirect block. */ last = howmany(remblks, blksperindir); if (last > NINDIR(fs)) last = NINDIR(fs); if (snapvp != cancelvp) { bap = (ufs_daddr_t *)bp->b_data; } else { MALLOC(bap, ufs_daddr_t *, fs->fs_bsize, M_DEVBUF, M_WAITOK); bcopy(bp->b_data, (caddr_t)bap, fs->fs_bsize); bqrelse(bp); } error = snapacct(snapvp, &bap[0], &bap[last]); if (error || level == 0) goto out; /* * Account for the block pointers in each of the indirect blocks * in the levels below us. */ subblksperindir = blksperindir / NINDIR(fs); for (lbn++, level--, i = 0; i < last; i++) { error = indiracct(snapvp, cancelvp, level, bap[i], lbn, rlbn, remblks, subblksperindir); if (error) goto out; rlbn += blksperindir; lbn -= blksperindir; remblks -= blksperindir; } out: if (snapvp != cancelvp) bqrelse(bp); else FREE(bap, M_DEVBUF); return (error); } /* * Account for a set of blocks allocated in a snapshot inode. */ static int snapacct(vp, oldblkp, lastblkp) struct vnode *vp; ufs_daddr_t *oldblkp, *lastblkp; { struct inode *ip = VTOI(vp); struct fs *fs = ip->i_fs; ufs_daddr_t lbn, blkno, *blkp; struct buf *ibp; int error; for ( ; oldblkp < lastblkp; oldblkp++) { blkno = *oldblkp; if (blkno == 0 || blkno == BLK_NOCOPY || blkno == BLK_SNAP) continue; lbn = fragstoblks(fs, blkno); if (lbn < NDADDR) { blkp = &ip->i_db[lbn]; ip->i_flag |= IN_CHANGE | IN_UPDATE; } else { error = VOP_BALLOC(vp, lblktosize(fs, (off_t)lbn), fs->fs_bsize, KERNCRED, B_METAONLY, &ibp); if (error) return (error); blkp = &((ufs_daddr_t *)(ibp->b_data)) [(lbn - NDADDR) % NINDIR(fs)]; } if (*blkp != 0) panic("snapacct: bad block"); *blkp = BLK_SNAP; if (lbn >= NDADDR) { ibp->b_flags |= B_VALIDSUSPWRT; bdwrite(ibp); } } return (0); } /* * Prepare a snapshot file for being removed. */ void ffs_snapremove(vp) struct vnode *vp; { struct inode *ip, *xp; struct vnode *devvp; struct buf *ibp; struct fs *fs; ufs_daddr_t blkno, dblk; int error, snaploc, loc, last; ip = VTOI(vp); fs = ip->i_fs; /* * Delete snapshot inode from superblock. Keep list dense. */ for (snaploc = 0; snaploc < FSMAXSNAP; snaploc++) if (fs->fs_snapinum[snaploc] == ip->i_number) break; if (snaploc < FSMAXSNAP) { for (snaploc++; snaploc < FSMAXSNAP; snaploc++) { if (fs->fs_snapinum[snaploc] == 0) break; fs->fs_snapinum[snaploc - 1] = fs->fs_snapinum[snaploc]; } fs->fs_snapinum[snaploc - 1] = 0; } /* * Delete from incore list. * Clear copy-on-write flag if last snapshot. */ devvp = ip->i_devvp; for (xp = VTOI(devvp); xp; xp = xp->i_copyonwrite) { if (xp->i_copyonwrite != ip) continue; xp->i_copyonwrite = ip->i_copyonwrite; ip->i_copyonwrite = 0; break; } if (xp == 0) printf("ffs_snapremove: lost snapshot vnode %d\n", ip->i_number); if (VTOI(devvp)->i_copyonwrite == 0) devvp->v_flag &= ~VCOPYONWRITE; /* * Clear all BLK_NOCOPY fields. Pass any block claims to other * snapshots that want them (see ffs_snapblkfree below). */ for (blkno = 1; blkno < NDADDR; blkno++) { dblk = ip->i_db[blkno]; if (dblk == BLK_NOCOPY || dblk == BLK_SNAP || (dblk == blkstofrags(fs, blkno) && ffs_snapblkfree(ip, dblk, fs->fs_bsize))) ip->i_db[blkno] = 0; } for (blkno = NDADDR; blkno < fs->fs_size; blkno += NINDIR(fs)) { error = VOP_BALLOC(vp, lblktosize(fs, (off_t)blkno), fs->fs_bsize, KERNCRED, B_METAONLY, &ibp); if (error) continue; if ((last = fs->fs_size - blkno) > NINDIR(fs)) last = NINDIR(fs); for (loc = 0; loc < last; loc++) { dblk = ((ufs_daddr_t *)(ibp->b_data))[loc]; if (dblk == BLK_NOCOPY || dblk == BLK_SNAP || (dblk == blkstofrags(fs, blkno) && ffs_snapblkfree(ip, dblk, fs->fs_bsize))) ((ufs_daddr_t *)(ibp->b_data))[loc] = 0; } bawrite(ibp); } /* * Clear snapshot flag and drop reference. */ ip->i_flags &= ~SF_SNAPSHOT; ip->i_flag |= IN_CHANGE | IN_UPDATE; } /* * Notification that a block is being freed. Return zero if the free * should be allowed to proceed. Return non-zero if the snapshot file * wants to claim the block. The block will be claimed if it is an * uncopied part of one of the snapshots. It will be freed if it is * either a BLK_NOCOPY or has already been copied in all of the snapshots. * If a fragment is being freed, then all snapshots that care about * it must make a copy since a snapshot file can only claim full sized * blocks. Note that if more than one snapshot file maps the block, * we can pick one at random to claim it. Since none of the snapshots * can change, we are assurred that they will all see the same unmodified * image. When deleting a snapshot file (see ffs_snapremove above), we * must push any of these claimed blocks to one of the other snapshots * that maps it. These claimed blocks are easily identified as they will * have a block number equal to their logical block number within the * snapshot. A copied block can never have this property because they * must always have been allocated from a BLK_NOCOPY location. */ int ffs_snapblkfree(freeip, bno, size) struct inode *freeip; ufs_daddr_t bno; long size; { struct buf *ibp, *cbp, *savedcbp = 0; struct fs *fs = freeip->i_fs; struct proc *p = CURPROC; struct inode *ip; struct vnode *vp; ufs_daddr_t lbn, blkno; int indiroff = 0, error = 0, claimedblk = 0; lbn = fragstoblks(fs, bno); for (ip = VTOI(freeip->i_devvp)->i_copyonwrite; ip; ip = ip->i_copyonwrite) { vp = ITOV(ip); /* * Lookup block being written. */ if (lbn < NDADDR) { blkno = ip->i_db[lbn]; } else { vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p); p->p_flag |= P_COWINPROGRESS; error = VOP_BALLOC(vp, lblktosize(fs, (off_t)lbn), fs->fs_bsize, KERNCRED, B_METAONLY, &ibp); p->p_flag &= ~P_COWINPROGRESS; VOP_UNLOCK(vp, 0, p); if (error) break; indiroff = (lbn - NDADDR) % NINDIR(fs); blkno = ((ufs_daddr_t *)(ibp->b_data))[indiroff]; } /* * Check to see if block needs to be copied. */ switch (blkno) { /* * If the snapshot has already copied the block (default), * or does not care about the block, it is not needed. */ default: case BLK_NOCOPY: if (lbn >= NDADDR) bqrelse(ibp); continue; /* * No previous snapshot claimed the block, so it will be * freed and become a BLK_NOCOPY (don't care) for us. */ case BLK_SNAP: if (claimedblk) panic("snapblkfree: inconsistent block type"); vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p); if (lbn < NDADDR) { ip->i_db[lbn] = BLK_NOCOPY; ip->i_flag |= IN_CHANGE | IN_UPDATE; } else { ((ufs_daddr_t *)(ibp->b_data))[indiroff] = BLK_NOCOPY; bdwrite(ibp); } VOP_UNLOCK(vp, 0, p); continue; /* * A block that we map is being freed. If it has not been * claimed yet, we will claim or copy it (below). */ case 0: claimedblk = 1; break; } /* * If this is a full size block, we will just grab it * and assign it to the snapshot inode. Otherwise we * will proceed to copy it. See explanation for this * routine as to why only a single snapshot needs to * claim this block. */ if (size == fs->fs_bsize) { #ifdef DEBUG if (snapdebug) printf("%s %d lbn %d from inum %d\n", "Grabonremove: snapino", ip->i_number, lbn, freeip->i_number); #endif vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p); if (lbn < NDADDR) { ip->i_db[lbn] = bno; } else { ((ufs_daddr_t *)(ibp->b_data))[indiroff] = bno; bdwrite(ibp); } ip->i_blocks += btodb(size); ip->i_flag |= IN_CHANGE | IN_UPDATE; VOP_UNLOCK(vp, 0, p); return (1); } if (lbn >= NDADDR) bqrelse(ibp); /* * Allocate the block into which to do the copy. Note that this * allocation will never require any additional allocations for * the snapshot inode. */ vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p); p->p_flag |= P_COWINPROGRESS; error = VOP_BALLOC(vp, lblktosize(fs, (off_t)lbn), fs->fs_bsize, KERNCRED, 0, &cbp); p->p_flag &= ~P_COWINPROGRESS; VOP_UNLOCK(vp, 0, p); if (error) break; #ifdef DEBUG if (snapdebug) printf("%s%d lbn %d for inum %d size %ld to blkno %d\n", "Copyonremove: snapino ", ip->i_number, lbn, freeip->i_number, size, cbp->b_blkno); #endif /* * If we have already read the old block contents, then * simply copy them to the new block. */ if (savedcbp != 0) { bcopy(savedcbp->b_data, cbp->b_data, fs->fs_bsize); bawrite(cbp); continue; } /* * Otherwise, read the old block contents into the buffer. */ if ((error = readblock(cbp, lbn)) != 0) break; savedcbp = cbp; } if (savedcbp) bawrite(savedcbp); /* * If we have been unable to allocate a block in which to do * the copy, then return non-zero so that the fragment will * not be freed. Although space will be lost, the snapshot * will stay consistent. */ return (error); } /* * Associate snapshot files when mounting. */ void ffs_snapshot_mount(mp) struct mount *mp; { struct ufsmount *ump = VFSTOUFS(mp); struct fs *fs = ump->um_fs; struct proc *p = CURPROC; struct inode *ip, **listtailp; struct vnode *vp; int error, snaploc, loc; listtailp = &VTOI(ump->um_devvp)->i_copyonwrite; for (snaploc = 0; snaploc < FSMAXSNAP; snaploc++) { if (fs->fs_snapinum[snaploc] == 0) return; if ((error = VFS_VGET(mp, fs->fs_snapinum[snaploc], &vp)) != 0){ printf("ffs_snapshot_mount: vget failed %d\n", error); continue; } ip = VTOI(vp); if ((ip->i_flags & SF_SNAPSHOT) == 0) { printf("ffs_snapshot_mount: non-snapshot inode %d\n", fs->fs_snapinum[snaploc]); vput(vp); for (loc = snaploc + 1; loc < FSMAXSNAP; loc++) { if (fs->fs_snapinum[loc] == 0) break; fs->fs_snapinum[loc - 1] = fs->fs_snapinum[loc]; } fs->fs_snapinum[loc - 1] = 0; snaploc--; continue; } if (ip->i_copyonwrite != 0) panic("ffs_snapshot_mount: %d already on list", ip->i_number); *listtailp = ip; listtailp = &ip->i_copyonwrite; vp->v_flag |= VSYSTEM; VOP_UNLOCK(vp, 0, p); ump->um_devvp->v_flag |= VCOPYONWRITE; } } /* * Disassociate snapshot files when unmounting. */ void ffs_snapshot_unmount(mp) struct mount *mp; { struct ufsmount *ump = VFSTOUFS(mp); struct inode *devip = VTOI(ump->um_devvp); struct inode *xp; while ((xp = devip->i_copyonwrite) != 0) { devip->i_copyonwrite = xp->i_copyonwrite; xp->i_copyonwrite = 0; if (xp->i_effnlink > 0) vrele(ITOV(xp)); } ump->um_devvp->v_flag &= ~VCOPYONWRITE; } /* * Check for need to copy block that is about to be written, * copying the block if necessary. */ int ffs_copyonwrite(ap) struct vop_copyonwrite_args /* { struct vnode *a_vp; struct buf *a_bp; } */ *ap; { struct buf *ibp, *cbp, *savedcbp = 0, *bp = ap->a_bp; struct fs *fs = VTOI(bp->b_vp)->i_fs; struct proc *p = CURPROC; struct inode *ip; struct vnode *vp; ufs_daddr_t lbn, blkno; int indiroff, error = 0; lbn = fragstoblks(fs, dbtofsb(fs, bp->b_blkno)); if (p->p_flag & P_COWINPROGRESS) panic("ffs_copyonwrite: recursive call"); for (ip = VTOI(ap->a_vp)->i_copyonwrite; ip; ip = ip->i_copyonwrite) { vp = ITOV(ip); /* * We ensure that everything of our own that needs to be * copied will be done at the time that ffs_snapshot is * called. Thus we can skip the check here which can * deadlock in doing the lookup in VOP_BALLOC. */ if (bp->b_vp == vp) continue; /* * Check to see if block needs to be copied. We have to * be able to do the VOP_BALLOC without blocking, otherwise * we may get in a deadlock with another process also * trying to allocate. If we find outselves unable to * get the buffer lock, we unlock the snapshot vnode, * sleep briefly, and try again. */ retry: vn_lock(vp, LK_SHARED | LK_RETRY, p); if (lbn < NDADDR) { blkno = ip->i_db[lbn]; } else { p->p_flag |= P_COWINPROGRESS; error = VOP_BALLOC(vp, lblktosize(fs, (off_t)lbn), fs->fs_bsize, KERNCRED, B_METAONLY | B_NOWAIT, &ibp); p->p_flag &= ~P_COWINPROGRESS; if (error) { VOP_UNLOCK(vp, 0, p); if (error != EWOULDBLOCK) break; tsleep(vp, p->p_usrpri, "nap", 1); goto retry; } indiroff = (lbn - NDADDR) % NINDIR(fs); blkno = ((ufs_daddr_t *)(ibp->b_data))[indiroff]; bqrelse(ibp); } #ifdef DIAGNOSTIC if (blkno == BLK_SNAP && bp->b_lblkno >= 0) panic("ffs_copyonwrite: bad copy block"); #endif if (blkno != 0) { VOP_UNLOCK(vp, 0, p); continue; } /* * Allocate the block into which to do the copy. Note that this * allocation will never require any additional allocations for * the snapshot inode. */ p->p_flag |= P_COWINPROGRESS; error = VOP_BALLOC(vp, lblktosize(fs, (off_t)lbn), fs->fs_bsize, KERNCRED, B_NOWAIT, &cbp); p->p_flag &= ~P_COWINPROGRESS; VOP_UNLOCK(vp, 0, p); if (error) { if (error != EWOULDBLOCK) break; tsleep(vp, p->p_usrpri, "nap", 1); goto retry; } #ifdef DEBUG if (snapdebug) { printf("Copyonwrite: snapino %d lbn %d for ", ip->i_number, lbn); if (bp->b_vp == ap->a_vp) printf("fs metadata"); else printf("inum %d", VTOI(bp->b_vp)->i_number); printf(" lblkno %d to blkno %d\n", bp->b_lblkno, cbp->b_blkno); } #endif /* * If we have already read the old block contents, then * simply copy them to the new block. */ if (savedcbp != 0) { bcopy(savedcbp->b_data, cbp->b_data, fs->fs_bsize); bawrite(cbp); continue; } /* * Otherwise, read the old block contents into the buffer. */ if ((error = readblock(cbp, lbn)) != 0) break; savedcbp = cbp; } if (savedcbp) bawrite(savedcbp); return (error); } /* * Read the specified block into the given buffer. * Much of this boiler-plate comes from bwrite(). */ static int readblock(bp, lbn) struct buf *bp; daddr_t lbn; { struct uio auio; struct iovec aiov; struct proc *p = CURPROC; struct inode *ip = VTOI(bp->b_vp); aiov.iov_base = bp->b_data; aiov.iov_len = bp->b_bcount; auio.uio_iov = &aiov; auio.uio_iovcnt = 1; auio.uio_offset = dbtob(fsbtodb(ip->i_fs, blkstofrags(ip->i_fs, lbn))); auio.uio_resid = bp->b_bcount; auio.uio_rw = UIO_READ; auio.uio_segflg = UIO_SYSSPACE; auio.uio_procp = p; return (physio(ip->i_devvp->v_rdev, &auio, 0)); }