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freebsd-dev/sys/ufs/ffs/ffs_snapshot.c
Ian Dowse f55ff3f3ef The ffs superblock includes a 128-byte region for use by temporary 
in-core pointers to summary information. An array in this region
(fs_csp) could overflow on filesystems with a very large number of
cylinder groups (~16000 on i386 with 8k blocks). When this happens,
other fields in the superblock get corrupted, and fsck refuses to
check the filesystem.

Solve this problem by replacing the fs_csp array in 'struct fs'
with a single pointer, and add padding to keep the length of the
128-byte region fixed. Update the kernel and userland utilities
to use just this single pointer.

With this change, the kernel no longer makes use of the superblock
fields 'fs_csshift' and 'fs_csmask'. Add a comment to newfs/mkfs.c
to indicate that these fields must be calculated for compatibility
with older kernels.

Reviewed by:	mckusick
2001-01-15 18:30:40 +00:00

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/*
* 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 <sys/param.h>
#include <sys/systm.h>
#include <sys/bio.h>
#include <sys/buf.h>
#include <sys/proc.h>
#include <sys/namei.h>
#include <sys/stat.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/resource.h>
#include <sys/resourcevar.h>
#include <sys/vnode.h>
#include <ufs/ufs/extattr.h>
#include <ufs/ufs/quota.h>
#include <ufs/ufs/ufsmount.h>
#include <ufs/ufs/inode.h>
#include <ufs/ufs/ufs_extern.h>
#include <ufs/ffs/fs.h>
#include <ufs/ffs/ffs_extern.h>
#define KERNCRED proc0.p_ucred
#define DEBUG 1
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 <sys/sysctl.h>
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;
void *space;
struct fs *copy_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.
*/
if ((error = VOP_BALLOC(vp, (off_t)(SBOFF), SBSIZE, KERNCRED, 0, &nbp)))
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 - 1;
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;
if (((ufs_daddr_t *)(ibp->b_data))[indiroff] != 0)
panic("ffs_snapshot: lost block");
((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.
*/
if ((error = VOP_BALLOC(vp, SBOFF, SBSIZE, KERNCRED, 0, &nbp)) != 0)
goto out1;
copy_fs = (struct fs *)(nbp->b_data + blkoff(fs, SBOFF));
bcopy(fs, copy_fs, fs->fs_sbsize);
copy_fs->fs_clean = 1;
if (fs->fs_sbsize < SBSIZE)
bzero(&nbp->b_data[blkoff(fs, SBOFF) + fs->fs_sbsize],
SBSIZE - 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;
space = fs->fs_csp;
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 - loc * fs->fs_bsize;
}
bcopy(space, nbp->b_data, size);
space = (char *)space + 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);
}
/*
* Decrement extra reference on snapshot when last name is removed.
* It will not be freed until the last open reference goes away.
*/
void
ffs_snapgone(ip)
struct inode *ip;
{
struct inode *xp;
/*
* Find snapshot in incore list.
*/
for (xp = VTOI(ip->i_devvp); xp; xp = xp->i_copyonwrite)
if (xp->i_copyonwrite == ip)
break;
if (xp == 0)
printf("ffs_snapgone: lost snapshot vnode %d\n",
ip->i_number);
else
vrele(ITOV(ip));
}
/*
* 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));
}
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