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freebsd-dev/sys/ufs/ffs/ffs_snapshot.c
Kirk McKusick a0595d0249 Add a flags parameter to VFS_VGET to pass through the desired 
locking flags when acquiring a vnode. The immediate purpose is
to allow polling lock requests (LK_NOWAIT) needed by soft updates
to avoid deadlock when enlisting other processes to help with
the background cleanup. For the future it will allow the use of
shared locks for read access to vnodes. This change touches a
lot of files as it affects most filesystems within the system.
It has been well tested on FFS, loopback, and CD-ROM filesystems.
only lightly on the others, so if you find a problem there, please
let me (mckusick@mckusick.com) know.
2002-03-17 01:25:47 +00:00

1398 lines
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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/conf.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 thread0.td_ucred
#define DEBUG 1
static int cgaccount __P((int, struct vnode *, struct buf *, int));
static int expunge __P((struct vnode *, struct inode *, struct fs *,
int (*) __P((struct vnode *, ufs_daddr_t *, ufs_daddr_t *, struct fs *,
ufs_daddr_t, int)), int));
static int indiracct __P((struct vnode *, struct vnode *, int, ufs_daddr_t,
int, int, int, int, struct fs *, int (*) __P((struct vnode *,
ufs_daddr_t *, ufs_daddr_t *, struct fs *, ufs_daddr_t, int)), int));
static int fullacct __P((struct vnode *, ufs_daddr_t *, ufs_daddr_t *,
struct fs *, ufs_daddr_t, int));
static int snapacct __P((struct vnode *, ufs_daddr_t *, ufs_daddr_t *,
struct fs *, ufs_daddr_t, int));
static int mapacct __P((struct vnode *, ufs_daddr_t *, ufs_daddr_t *,
struct fs *, ufs_daddr_t, int));
static int ffs_copyonwrite __P((struct vnode *, struct buf *));
static int readblock __P((struct buf *, daddr_t));
/*
* To ensure the consistency of snapshots across crashes, we must
* synchronously write out copied blocks before allowing the
* originals to be modified. Because of the rather severe speed
* penalty that this imposes, the following flag allows this
* crash persistence to be disabled.
*/
int dopersistence = 0;
#ifdef DEBUG
#include <sys/sysctl.h>
SYSCTL_INT(_debug, OID_AUTO, dopersistence, CTLFLAG_RW, &dopersistence, 0, "");
int snapdebug = 0;
SYSCTL_INT(_debug, OID_AUTO, snapdebug, CTLFLAG_RW, &snapdebug, 0, "");
int collectsnapstats = 0;
SYSCTL_INT(_debug, OID_AUTO, collectsnapstats, CTLFLAG_RW, &collectsnapstats,
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 blkno;
int error, cg, snaploc, numblks;
int i, size, len, loc;
int flag = mp->mnt_flag;
struct timespec starttime = {0, 0}, endtime;
char saved_nice = 0;
long redo = 0;
int32_t *lp;
void *space;
struct fs *copy_fs = NULL, *fs = VFSTOUFS(mp)->um_fs;
struct snaphead *snaphead;
struct thread *td = curthread;
struct inode *ip, *xp;
struct buf *bp, *nbp, *ibp, *sbp = NULL;
struct nameidata nd;
struct mount *wrtmp;
struct vattr vat;
struct vnode *vp, *xvp, *nvp;
/*
* 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, td);
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, td, 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);
/*
* 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 = UFS_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 and mark all of them as not
* needing to be copied.
*/
for (blkno = NDADDR; blkno < numblks; blkno += NINDIR(fs)) {
error = UFS_BALLOC(vp, lblktosize(fs, (off_t)blkno),
fs->fs_bsize, td->td_ucred, B_METAONLY, &ibp);
if (error)
goto out;
bdwrite(ibp);
}
/*
* Allocate copies for the superblock and its summary information.
*/
error = UFS_BALLOC(vp, (off_t)(SBOFF), SBSIZE, 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 = UFS_BALLOC(vp, lblktosize(fs, (off_t)(blkno + loc)),
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 = UFS_BALLOC(vp, (off_t)(cgtod(fs, cg)) << fs->fs_fshift,
fs->fs_bsize, KERNCRED, 0, &nbp);
if (error)
goto out;
bdwrite(nbp);
}
/*
* Copy all the cylinder group maps. Although the
* filesystem is still active, we hope that only a few
* cylinder groups will change between now and when we
* suspend operations. Thus, we will be able to quickly
* touch up the few cylinder groups that changed during
* the suspension period.
*/
len = howmany(fs->fs_ncg, NBBY);
MALLOC(fs->fs_active, int *, len, M_DEVBUF, M_WAITOK);
bzero(fs->fs_active, len);
for (cg = 0; cg < fs->fs_ncg; cg++) {
error = bread(vp, fragstoblks(fs, cgtod(fs, cg)), fs->fs_bsize,
KERNCRED, &nbp);
if (error) {
brelse(nbp);
goto out;
}
error = cgaccount(cg, vp, nbp, 1);
bawrite(nbp);
if (error)
goto out;
}
/*
* 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, td)) != 0)
goto out;
/*
* All allocations are done, so we can now snapshot the system.
*
* Recind nice scheduling while running with the filesystem suspended.
*/
if (td->td_ksegrp->kg_nice > 0) {
saved_nice = td->td_ksegrp->kg_nice;
td->td_ksegrp->kg_nice = 0;
}
/*
* 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);
}
if (collectsnapstats)
nanotime(&starttime);
/*
* First, copy all the cylinder group maps that have changed.
*/
for (cg = 0; cg < fs->fs_ncg; cg++) {
if ((ACTIVECGNUM(fs, cg) & ACTIVECGOFF(cg)) != 0)
continue;
redo++;
error = bread(vp, fragstoblks(fs, cgtod(fs, cg)), fs->fs_bsize,
KERNCRED, &nbp);
if (error) {
brelse(nbp);
goto out1;
}
error = cgaccount(cg, vp, nbp, 2);
bawrite(nbp);
if (error)
goto out1;
}
/*
* Grab a copy of the superblock and its summary information.
* We delay writing it until the suspension is released below.
*/
error = bread(vp, lblkno(fs, SBOFF), fs->fs_bsize, KERNCRED, &sbp);
if (error) {
brelse(sbp);
sbp = NULL;
goto out1;
}
copy_fs = (struct fs *)(sbp->b_data + blkoff(fs, SBOFF));
bcopy(fs, copy_fs, fs->fs_sbsize);
if ((fs->fs_flags & (FS_UNCLEAN | FS_NEEDSFSCK)) == 0)
copy_fs->fs_clean = 1;
if (fs->fs_sbsize < SBSIZE)
bzero(&sbp->b_data[blkoff(fs, SBOFF) + fs->fs_sbsize],
SBSIZE - fs->fs_sbsize);
size = blkroundup(fs, fs->fs_cssize);
if (fs->fs_contigsumsize > 0)
size += fs->fs_ncg * sizeof(int32_t);
space = malloc((u_long)size, M_UFSMNT, M_WAITOK);
copy_fs->fs_csp = space;
bcopy(fs->fs_csp, copy_fs->fs_csp, fs->fs_cssize);
(char *)space += fs->fs_cssize;
loc = howmany(fs->fs_cssize, fs->fs_fsize);
i = fs->fs_frag - loc % fs->fs_frag;
len = (i == fs->fs_frag) ? 0 : i * fs->fs_fsize;
if (len > 0) {
if ((error = bread(ip->i_devvp,
fsbtodb(fs, fs->fs_csaddr + loc),
len, KERNCRED, &bp)) != 0) {
brelse(bp);
free(copy_fs->fs_csp, M_UFSMNT);
bawrite(sbp);
sbp = NULL;
goto out1;
}
bcopy(bp->b_data, space, (u_int)len);
(char *)space += len;
bp->b_flags |= B_INVAL | B_NOCACHE;
brelse(bp);
}
if (fs->fs_contigsumsize > 0) {
copy_fs->fs_maxcluster = lp = space;
for (i = 0; i < fs->fs_ncg; i++)
*lp++ = fs->fs_contigsumsize;
}
/*
* We must check for active files that have been unlinked
* (e.g., with a zero link count). We have to expunge all
* trace of these files from the snapshot so that they are
* not reclaimed prematurely by fsck or unnecessarily dumped.
* We turn off the MNTK_SUSPENDED flag to avoid a panic from
* spec_strategy about writing on a suspended filesystem.
*/
mp->mnt_kern_flag &= ~MNTK_SUSPENDED;
mtx_lock(&mntvnode_mtx);
loop:
for (xvp = TAILQ_FIRST(&mp->mnt_nvnodelist); xvp; xvp = nvp) {
/*
* Make sure this vnode wasn't reclaimed in getnewvnode().
* Start over if it has (it won't be on the list anymore).
*/
if (xvp->v_mount != mp)
goto loop;
nvp = TAILQ_NEXT(xvp, v_nmntvnodes);
mtx_unlock(&mntvnode_mtx);
mtx_lock(&xvp->v_interlock);
if (xvp->v_usecount == 0 || xvp->v_type == VNON ||
(VOP_GETATTR(xvp, &vat, td->td_proc->p_ucred, td) == 0 &&
vat.va_nlink > 0)) {
mtx_unlock(&xvp->v_interlock);
mtx_lock(&mntvnode_mtx);
continue;
}
if (snapdebug)
vprint("ffs_snapshot: busy vnode", xvp);
if (vn_lock(xvp, LK_EXCLUSIVE | LK_INTERLOCK, td) != 0)
goto loop;
xp = VTOI(xvp);
/*
* If there is a fragment, clear it here.
*/
blkno = 0;
loc = howmany(xp->i_size, fs->fs_bsize) - 1;
if (loc < NDADDR) {
len = fragroundup(fs, blkoff(fs, xp->i_size));
if (len < fs->fs_bsize) {
ffs_blkfree(copy_fs, vp, xp->i_db[loc], len,
xp->i_number);
blkno = xp->i_db[loc];
xp->i_db[loc] = 0;
}
}
error = expunge(vp, xp, copy_fs, fullacct, BLK_NOCOPY);
if (blkno)
xp->i_db[loc] = blkno;
if (!error)
error = ffs_freefile(copy_fs, vp, xp->i_number,
xp->i_mode);
VOP_UNLOCK(xvp, 0, td);
if (error) {
free(copy_fs->fs_csp, M_UFSMNT);
bawrite(sbp);
sbp = NULL;
goto out1;
}
mtx_lock(&mntvnode_mtx);
}
mtx_unlock(&mntvnode_mtx);
/*
* 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_nextsnap.tqe_prev != 0)
panic("ffs_snapshot: %d already on list", ip->i_number);
snaphead = &ip->i_devvp->v_rdev->si_snapshots;
TAILQ_INSERT_TAIL(snaphead, ip, i_nextsnap);
ip->i_devvp->v_rdev->si_copyonwrite = ffs_copyonwrite;
ip->i_devvp->v_flag |= VCOPYONWRITE;
vp->v_flag |= VSYSTEM;
out1:
/*
* Resume operation on filesystem.
*/
vfs_write_resume(vp->v_mount);
if (saved_nice > 0)
td->td_ksegrp->kg_nice = saved_nice;
vn_start_write(NULL, &wrtmp, V_WAIT);
if (collectsnapstats && starttime.tv_sec > 0) {
nanotime(&endtime);
timespecsub(&endtime, &starttime);
printf("%s: suspended %d.%03ld sec, redo %ld of %d\n",
vp->v_mount->mnt_stat.f_mntonname, endtime.tv_sec,
endtime.tv_nsec / 1000000, redo, fs->fs_ncg);
}
if (sbp == NULL)
goto out;
/*
* Copy allocation information from all the snapshots in
* this snapshot and then expunge them from its view.
*/
snaphead = &ip->i_devvp->v_rdev->si_snapshots;
TAILQ_FOREACH(xp, snaphead, i_nextsnap) {
if (xp == ip)
break;
if ((error = expunge(vp, xp, fs, snapacct, BLK_SNAP)) != 0) {
fs->fs_snapinum[snaploc] = 0;
goto done;
}
}
/*
* Expunge the blocks used by the snapshots from the set of
* blocks marked as used in the snapshot bitmaps.
*/
if ((error = expunge(vp, ip, copy_fs, mapacct, BLK_SNAP)) != 0) {
fs->fs_snapinum[snaploc] = 0;
goto done;
}
/*
* Write the superblock and its summary information
* to the snapshot.
*/
blkno = fragstoblks(fs, fs->fs_csaddr);
len = howmany(fs->fs_cssize, fs->fs_bsize);
space = copy_fs->fs_csp;
for (loc = 0; loc < len; loc++) {
error = bread(vp, blkno + loc, fs->fs_bsize, KERNCRED, &nbp);
if (error) {
brelse(nbp);
fs->fs_snapinum[snaploc] = 0;
goto done;
}
bcopy(space, nbp->b_data, fs->fs_bsize);
space = (char *)space + fs->fs_bsize;
bawrite(nbp);
}
done:
free(copy_fs->fs_csp, M_UFSMNT);
bawrite(sbp);
out:
if (fs->fs_active != 0) {
FREE(fs->fs_active, M_DEVBUF);
fs->fs_active = 0;
}
mp->mnt_flag = flag;
if (error)
(void) UFS_TRUNCATE(vp, (off_t)0, 0, NOCRED, td);
(void) VOP_FSYNC(vp, KERNCRED, MNT_WAIT, td);
if (error)
vput(vp);
else
VOP_UNLOCK(vp, 0, td);
vn_finished_write(wrtmp);
return (error);
}
/*
* Copy a cylinder group map. All the unallocated blocks are marked
* BLK_NOCOPY so that the snapshot knows that it need not copy them
* if they are later written. If passno is one, then this is a first
* pass, so only setting needs to be done. If passno is 2, then this
* is a revision to a previous pass which must be undone as the
* replacement pass is done.
*/
static int
cgaccount(cg, vp, nbp, passno)
int cg;
struct vnode *vp;
struct buf *nbp;
int passno;
{
struct buf *bp, *ibp;
struct inode *ip;
struct cg *cgp;
struct fs *fs;
int error, numblks, base, len, loc, indiroff;
ip = VTOI(vp);
fs = ip->i_fs;
error = bread(ip->i_devvp, fsbtodb(fs, cgtod(fs, cg)),
(int)fs->fs_cgsize, KERNCRED, &bp);
if (error) {
brelse(bp);
return (error);
}
cgp = (struct cg *)bp->b_data;
if (!cg_chkmagic(cgp)) {
brelse(bp);
return (EIO);
}
atomic_set_int(&ACTIVECGNUM(fs, cg), ACTIVECGOFF(cg));
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);
if (passno == 2)
nbp->b_flags |= B_VALIDSUSPWRT;
numblks = howmany(fs->fs_size, fs->fs_frag);
len = howmany(fs->fs_fpg, fs->fs_frag);
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))
ip->i_db[loc] = BLK_NOCOPY;
else if (passno == 2 && ip->i_db[loc] == BLK_NOCOPY)
ip->i_db[loc] = 0;
else if (passno == 1 && ip->i_db[loc] == BLK_NOCOPY)
panic("ffs_snapshot: lost direct block");
}
}
error = UFS_BALLOC(vp, lblktosize(fs, (off_t)(base + loc)),
fs->fs_bsize, KERNCRED, B_METAONLY, &ibp);
if (error) {
brelse(bp);
return (error);
}
indiroff = (base + loc - NDADDR) % NINDIR(fs);
for ( ; loc < len; loc++, indiroff++) {
if (indiroff >= NINDIR(fs)) {
if (passno == 2)
ibp->b_flags |= B_VALIDSUSPWRT;
bawrite(ibp);
error = UFS_BALLOC(vp,
lblktosize(fs, (off_t)(base + loc)),
fs->fs_bsize, KERNCRED, B_METAONLY, &ibp);
if (error) {
brelse(bp);
return (error);
}
indiroff = 0;
}
if (ffs_isblock(fs, cg_blksfree(cgp), loc))
((ufs_daddr_t *)(ibp->b_data))[indiroff] = BLK_NOCOPY;
else if (passno == 2 &&
((ufs_daddr_t *)(ibp->b_data))[indiroff] == BLK_NOCOPY)
((ufs_daddr_t *)(ibp->b_data))[indiroff] = 0;
else if (passno == 1 &&
((ufs_daddr_t *)(ibp->b_data))[indiroff] == BLK_NOCOPY)
panic("ffs_snapshot: lost indirect block");
}
bqrelse(bp);
if (passno == 2)
ibp->b_flags |= B_VALIDSUSPWRT;
bdwrite(ibp);
return (0);
}
/*
* 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.
*/
static int
expunge(snapvp, cancelip, fs, acctfunc, expungetype)
struct vnode *snapvp;
struct inode *cancelip;
struct fs *fs;
int (*acctfunc) __P((struct vnode *, ufs_daddr_t *, ufs_daddr_t *,
struct fs *, ufs_daddr_t, int));
int expungetype;
{
int i, len, error, numblks, blksperindir;
ufs_daddr_t lbn, rlbn, blkno, indiroff;
struct thread *td = curthread;
struct dinode *dip;
struct buf *bp;
numblks = howmany(cancelip->i_size, fs->fs_bsize);
if ((error = (*acctfunc)(snapvp, &cancelip->i_db[0],
&cancelip->i_ib[NIADDR], fs, 0, expungetype)))
return (error);
blksperindir = 1;
lbn = -NDADDR;
len = numblks - NDADDR;
rlbn = NDADDR;
for (i = 0; len > 0 && i < NIADDR; i++) {
error = indiracct(snapvp, ITOV(cancelip), i, cancelip->i_ib[i],
lbn, rlbn, len, blksperindir, fs, acctfunc, expungetype);
if (error)
return (error);
blksperindir *= NINDIR(fs);
lbn -= blksperindir + 1;
len -= blksperindir;
rlbn += blksperindir;
}
/*
* Prepare to expunge the inode. If its inode block has not
* yet been copied, then allocate and fill the copy.
*/
lbn = fragstoblks(fs, ino_to_fsba(fs, cancelip->i_number));
blkno = 0;
if (lbn < NDADDR) {
blkno = cancelip->i_db[lbn];
} else {
td->td_proc->p_flag |= P_COWINPROGRESS;
error = UFS_BALLOC(snapvp, lblktosize(fs, (off_t)lbn),
fs->fs_bsize, KERNCRED, B_METAONLY, &bp);
td->td_proc->p_flag &= ~P_COWINPROGRESS;
if (error)
return (error);
indiroff = (lbn - NDADDR) % NINDIR(fs);
blkno = ((ufs_daddr_t *)(bp->b_data))[indiroff];
bqrelse(bp);
}
error = UFS_BALLOC(snapvp, lblktosize(fs, (off_t)lbn),
fs->fs_bsize, KERNCRED, 0, &bp);
if (error)
return (error);
if (blkno == 0 && (error = readblock(bp, lbn)))
return (error);
/*
* Set a snapshot inode to be a zero length file, regular files
* to be completely unallocated.
*/
dip = (struct dinode *)bp->b_data + ino_to_fsbo(fs, cancelip->i_number);
if (expungetype == BLK_NOCOPY)
dip->di_mode = 0;
dip->di_size = 0;
dip->di_blocks = 0;
dip->di_flags &= ~SF_SNAPSHOT;
bzero(&dip->di_db[0], (NDADDR + NIADDR) * sizeof(ufs_daddr_t));
bdwrite(bp);
return (0);
}
/*
* 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, fs,
acctfunc, expungetype)
struct vnode *snapvp;
struct vnode *cancelvp;
int level;
ufs_daddr_t blkno;
int lbn;
int rlbn;
int remblks;
int blksperindir;
struct fs *fs;
int (*acctfunc) __P((struct vnode *, ufs_daddr_t *, ufs_daddr_t *,
struct fs *, ufs_daddr_t, int));
int expungetype;
{
int subblksperindir, error, last, num, i;
struct indir indirs[NIADDR + 2];
ufs_daddr_t *bap;
struct buf *bp;
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.
*/
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);
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 = (*acctfunc)(snapvp, &bap[0], &bap[last], fs, rlbn, expungetype);
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, fs, acctfunc, expungetype);
if (error)
goto out;
rlbn += blksperindir;
lbn -= blksperindir;
remblks -= blksperindir;
}
out:
FREE(bap, M_DEVBUF);
return (error);
}
/*
* Do both snap accounting and map accounting.
*/
static int
fullacct(vp, oldblkp, lastblkp, fs, lblkno, expungetype)
struct vnode *vp;
ufs_daddr_t *oldblkp, *lastblkp;
struct fs *fs;
ufs_daddr_t lblkno;
int expungetype; /* BLK_SNAP or BLK_NOCOPY */
{
int error;
if ((error = snapacct(vp, oldblkp, lastblkp, fs, lblkno, expungetype)))
return (error);
return (mapacct(vp, oldblkp, lastblkp, fs, lblkno, expungetype));
}
/*
* Identify a set of blocks allocated in a snapshot inode.
*/
static int
snapacct(vp, oldblkp, lastblkp, fs, lblkno, expungetype)
struct vnode *vp;
ufs_daddr_t *oldblkp, *lastblkp;
struct fs *fs;
ufs_daddr_t lblkno;
int expungetype; /* BLK_SNAP or BLK_NOCOPY */
{
struct inode *ip = VTOI(vp);
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 = UFS_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 we are expunging a snapshot vnode and we
* find a block marked BLK_NOCOPY, then it is
* one that has been allocated to this snapshot after
* we took our current snapshot and can be ignored.
*/
if (expungetype == BLK_SNAP && *blkp == BLK_NOCOPY) {
if (lbn >= NDADDR)
brelse(ibp);
} else {
if (*blkp != 0)
panic("snapacct: bad block");
*blkp = expungetype;
if (lbn >= NDADDR)
bdwrite(ibp);
}
}
return (0);
}
/*
* Account for a set of blocks allocated in a snapshot inode.
*/
static int
mapacct(vp, oldblkp, lastblkp, fs, lblkno, expungetype)
struct vnode *vp;
ufs_daddr_t *oldblkp, *lastblkp;
struct fs *fs;
ufs_daddr_t lblkno;
int expungetype;
{
ufs_daddr_t blkno;
ino_t inum;
inum = VTOI(vp)->i_number;
for ( ; oldblkp < lastblkp; oldblkp++, lblkno++) {
blkno = *oldblkp;
if (blkno == 0 || blkno == BLK_NOCOPY)
continue;
if (blkno == BLK_SNAP)
blkno = blkstofrags(fs, lblkno);
ffs_blkfree(fs, vp, blkno, fs->fs_bsize, inum);
}
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;
struct fs *fs;
int snaploc;
/*
* Find snapshot in incore list.
*/
TAILQ_FOREACH(xp, &ip->i_devvp->v_rdev->si_snapshots, i_nextsnap)
if (xp == ip)
break;
if (xp == 0)
printf("ffs_snapgone: lost snapshot vnode %d\n",
ip->i_number);
else
vrele(ITOV(ip));
/*
* Delete snapshot inode from superblock. Keep list dense.
*/
fs = ip->i_fs;
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;
}
}
/*
* Prepare a snapshot file for being removed.
*/
void
ffs_snapremove(vp)
struct vnode *vp;
{
struct inode *ip;
struct vnode *devvp;
struct buf *ibp;
struct fs *fs;
ufs_daddr_t blkno, dblk;
int error, numblks, loc, last;
ip = VTOI(vp);
fs = ip->i_fs;
/*
* If active, delete from incore list (this snapshot may
* already have been in the process of being deleted, so
* would not have been active).
*
* Clear copy-on-write flag if last snapshot.
*/
if (ip->i_nextsnap.tqe_prev != 0) {
devvp = ip->i_devvp;
TAILQ_REMOVE(&devvp->v_rdev->si_snapshots, ip, i_nextsnap);
ip->i_nextsnap.tqe_prev = 0;
if (TAILQ_FIRST(&devvp->v_rdev->si_snapshots) == 0) {
devvp->v_rdev->si_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)
ip->i_db[blkno] = 0;
else if ((dblk == blkstofrags(fs, blkno) &&
ffs_snapblkfree(fs, ip->i_devvp, dblk, fs->fs_bsize,
ip->i_number))) {
ip->i_blocks -= btodb(fs->fs_bsize);
ip->i_db[blkno] = 0;
}
}
numblks = howmany(ip->i_size, fs->fs_bsize);
for (blkno = NDADDR; blkno < numblks; blkno += NINDIR(fs)) {
error = UFS_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)
((ufs_daddr_t *)(ibp->b_data))[loc] = 0;
else if ((dblk == blkstofrags(fs, blkno) &&
ffs_snapblkfree(fs, ip->i_devvp, dblk,
fs->fs_bsize, ip->i_number))) {
ip->i_blocks -= btodb(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(fs, devvp, bno, size, inum)
struct fs *fs;
struct vnode *devvp;
ufs_daddr_t bno;
long size;
ino_t inum;
{
struct buf *ibp, *cbp, *savedcbp = 0;
struct thread *td = curthread;
struct inode *ip;
struct vnode *vp;
ufs_daddr_t lbn, blkno;
int indiroff = 0, error = 0, claimedblk = 0;
struct snaphead *snaphead;
lbn = fragstoblks(fs, bno);
snaphead = &devvp->v_rdev->si_snapshots;
TAILQ_FOREACH(ip, snaphead, i_nextsnap) {
vp = ITOV(ip);
/*
* Lookup block being written.
*/
if (lbn < NDADDR) {
blkno = ip->i_db[lbn];
} else {
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td);
td->td_proc->p_flag |= P_COWINPROGRESS;
error = UFS_BALLOC(vp, lblktosize(fs, (off_t)lbn),
fs->fs_bsize, KERNCRED, B_METAONLY, &ibp);
td->td_proc->p_flag &= ~P_COWINPROGRESS;
VOP_UNLOCK(vp, 0, td);
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, td);
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, td);
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,
inum);
#endif
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td);
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, td);
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, td);
td->td_proc->p_flag |= P_COWINPROGRESS;
error = UFS_BALLOC(vp, lblktosize(fs, (off_t)lbn),
fs->fs_bsize, KERNCRED, 0, &cbp);
td->td_proc->p_flag &= ~P_COWINPROGRESS;
if (error) {
VOP_UNLOCK(vp, 0, td);
break;
}
#ifdef DEBUG
if (snapdebug)
printf("%s%d lbn %d for inum %d size %ld to blkno %lld\n",
"Copyonremove: snapino ", ip->i_number, lbn,
inum, size, cbp->b_blkno);
#endif
/*
* If we have already read the old block contents, then
* simply copy them to the new block. Note that we need
* to synchronously write snapshots that have not been
* unlinked, and hence will be visible after a crash,
* to ensure their integrity.
*/
if (savedcbp != 0) {
bcopy(savedcbp->b_data, cbp->b_data, fs->fs_bsize);
bawrite(cbp);
if (dopersistence && ip->i_effnlink > 0)
(void) VOP_FSYNC(vp, KERNCRED, MNT_WAIT, td);
VOP_UNLOCK(vp, 0, td);
continue;
}
/*
* Otherwise, read the old block contents into the buffer.
*/
if ((error = readblock(cbp, lbn)) != 0) {
bzero(cbp->b_data, fs->fs_bsize);
bawrite(cbp);
if (dopersistence && ip->i_effnlink > 0)
(void) VOP_FSYNC(vp, KERNCRED, MNT_WAIT, td);
VOP_UNLOCK(vp, 0, td);
break;
}
VOP_UNLOCK(vp, 0, td);
savedcbp = cbp;
}
/*
* Note that we need to synchronously write snapshots that
* have not been unlinked, and hence will be visible after
* a crash, to ensure their integrity.
*/
if (savedcbp) {
vp = savedcbp->b_vp;
bawrite(savedcbp);
if (dopersistence && VTOI(vp)->i_effnlink > 0) {
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td);
(void) VOP_FSYNC(vp, KERNCRED, MNT_WAIT, td);
VOP_UNLOCK(vp, 0, td);
}
}
/*
* 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 thread *td = curthread;
struct snaphead *snaphead;
struct vnode *vp;
struct inode *ip;
int error, snaploc, loc;
snaphead = &ump->um_devvp->v_rdev->si_snapshots;
for (snaploc = 0; snaploc < FSMAXSNAP; snaploc++) {
if (fs->fs_snapinum[snaploc] == 0)
return;
if ((error = VFS_VGET(mp, fs->fs_snapinum[snaploc],
LK_EXCLUSIVE, &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_nextsnap.tqe_prev != 0)
panic("ffs_snapshot_mount: %d already on list",
ip->i_number);
else
TAILQ_INSERT_TAIL(snaphead, ip, i_nextsnap);
vp->v_flag |= VSYSTEM;
ump->um_devvp->v_rdev->si_copyonwrite = ffs_copyonwrite;
ump->um_devvp->v_flag |= VCOPYONWRITE;
VOP_UNLOCK(vp, 0, td);
}
}
/*
* Disassociate snapshot files when unmounting.
*/
void
ffs_snapshot_unmount(mp)
struct mount *mp;
{
struct ufsmount *ump = VFSTOUFS(mp);
struct snaphead *snaphead = &ump->um_devvp->v_rdev->si_snapshots;
struct inode *xp;
while ((xp = TAILQ_FIRST(snaphead)) != 0) {
TAILQ_REMOVE(snaphead, xp, i_nextsnap);
xp->i_nextsnap.tqe_prev = 0;
if (xp->i_effnlink > 0)
vrele(ITOV(xp));
}
ump->um_devvp->v_rdev->si_copyonwrite = 0;
ump->um_devvp->v_flag &= ~VCOPYONWRITE;
}
/*
* Check for need to copy block that is about to be written,
* copying the block if necessary.
*/
static int
ffs_copyonwrite(devvp, bp)
struct vnode *devvp;
struct buf *bp;
{
struct buf *ibp, *cbp, *savedcbp = 0;
struct thread *td = curthread;
struct fs *fs;
struct inode *ip;
struct vnode *vp;
ufs_daddr_t lbn, blkno;
int indiroff, error = 0;
fs = TAILQ_FIRST(&devvp->v_rdev->si_snapshots)->i_fs;
lbn = fragstoblks(fs, dbtofsb(fs, bp->b_blkno));
if (td->td_proc->p_flag & P_COWINPROGRESS)
panic("ffs_copyonwrite: recursive call");
TAILQ_FOREACH(ip, &devvp->v_rdev->si_snapshots, i_nextsnap) {
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 UFS_BALLOC.
*/
if (bp->b_vp == vp)
continue;
/*
* Check to see if block needs to be copied. We have to
* be able to do the UFS_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_EXCLUSIVE | LK_RETRY, td);
if (lbn < NDADDR) {
blkno = ip->i_db[lbn];
} else {
td->td_proc->p_flag |= P_COWINPROGRESS;
error = UFS_BALLOC(vp, lblktosize(fs, (off_t)lbn),
fs->fs_bsize, KERNCRED, B_METAONLY | B_NOWAIT, &ibp);
td->td_proc->p_flag &= ~P_COWINPROGRESS;
if (error) {
VOP_UNLOCK(vp, 0, td);
if (error != EWOULDBLOCK)
break;
tsleep(vp, td->td_ksegrp->kg_user_pri, "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, td);
continue;
}
/*
* Allocate the block into which to do the copy. Note that this
* allocation will never require any additional allocations for
* the snapshot inode.
*/
td->td_proc->p_flag |= P_COWINPROGRESS;
error = UFS_BALLOC(vp, lblktosize(fs, (off_t)lbn),
fs->fs_bsize, KERNCRED, B_NOWAIT, &cbp);
td->td_proc->p_flag &= ~P_COWINPROGRESS;
if (error) {
VOP_UNLOCK(vp, 0, td);
if (error != EWOULDBLOCK)
break;
tsleep(vp, td->td_ksegrp->kg_user_pri, "nap", 1);
goto retry;
}
#ifdef DEBUG
if (snapdebug) {
printf("Copyonwrite: snapino %d lbn %d for ",
ip->i_number, lbn);
if (bp->b_vp == devvp)
printf("fs metadata");
else
printf("inum %d", VTOI(bp->b_vp)->i_number);
printf(" lblkno %lld to blkno %lld\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. Note that we need
* to synchronously write snapshots that have not been
* unlinked, and hence will be visible after a crash,
* to ensure their integrity.
*/
if (savedcbp != 0) {
bcopy(savedcbp->b_data, cbp->b_data, fs->fs_bsize);
bawrite(cbp);
if (dopersistence && ip->i_effnlink > 0)
(void) VOP_FSYNC(vp, KERNCRED, MNT_WAIT, td);
VOP_UNLOCK(vp, 0, td);
continue;
}
/*
* Otherwise, read the old block contents into the buffer.
*/
if ((error = readblock(cbp, lbn)) != 0) {
bzero(cbp->b_data, fs->fs_bsize);
bawrite(cbp);
if (dopersistence && ip->i_effnlink > 0)
(void) VOP_FSYNC(vp, KERNCRED, MNT_WAIT, td);
VOP_UNLOCK(vp, 0, td);
break;
}
savedcbp = cbp;
VOP_UNLOCK(vp, 0, td);
}
/*
* Note that we need to synchronously write snapshots that
* have not been unlinked, and hence will be visible after
* a crash, to ensure their integrity.
*/
if (savedcbp) {
vp = savedcbp->b_vp;
bawrite(savedcbp);
if (dopersistence && VTOI(vp)->i_effnlink > 0) {
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td);
(void) VOP_FSYNC(vp, KERNCRED, MNT_WAIT, td);
VOP_UNLOCK(vp, 0, td);
}
}
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 thread *td = curthread;
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_td = td;
return (physio(ip->i_devvp->v_rdev, &auio, 0));
}
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