ufs_snap.c revision 7c478bd95313f5f23a4c958a745db2134aa03244
/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License, Version 1.0 only
* (the "License"). You may not use this file except in compliance
* with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 2004 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
#pragma ident "%Z%%M% %I% %E% SMI"
#include <sys/systm.h>
#include <sys/types.h>
#include <sys/vnode.h>
#include <sys/file.h>
#include <sys/buf.h>
#include <sys/ddi.h>
#include <sys/errno.h>
#include <sys/cmn_err.h>
#include <sys/fs/ufs_inode.h>
#include <sys/fs/ufs_filio.h>
#include <sys/fs/ufs_snap.h>
#include <sys/fssnap_if.h>
#include <sys/sysmacros.h>
#include <sys/modctl.h>
#include <sys/fs/ufs_bio.h>
#include <sys/debug.h>
#include <sys/kmem.h>
#include <sys/inttypes.h>
#include <sys/vfs.h>
#include <sys/disp.h>
#include <sys/atomic.h>
#include <sys/conf.h>
#include <sys/param.h>
#include <sys/policy.h>
static int ufs_snap_init_backfile(int *, int, vnode_t ***, struct ufsvfs *);
static void release_backing_vnodes(vnode_t ***, int);
static int ufs_snap_find_candidates(void *, struct ufsvfs *, int);
/*
* Create a snapshot on a file system
*/
int
ufs_snap_create(struct vnode *vp, struct fiosnapcreate_multi *fiosnapp,
cred_t *cr)
{
int error = 0;
struct ufsvfs *ufsvfsp = VTOI(vp)->i_ufsvfs;
struct fs *fs = ufsvfsp->vfs_fs;
vnode_t **bfvpp = NULL;
struct lockfs lf;
void *snapid = NULL;
u_offset_t nchunks;
uint_t chunksize, fragsperchunk;
/*
* Only privilege processes can create a snapshot for now. This
* would be better if it was based on the permissions of the device
* file.
*/
if (secpolicy_fs_config(cr, ufsvfsp->vfs_vfs) != 0)
return (EPERM);
/*
* There is no reason to make a snapshot of a read-only file system
*/
if (fs->fs_ronly) {
fiosnapp->error = FIOCOW_EREADONLY;
return (EROFS);
}
/*
* Initialize the backing files to store old data. This assumes any
* preallocation and setup has been done already.
* ufs_snap_init_backfile() allocates and returns a pointer to
* a null-terminated array of vnodes in bfvpp.
*/
error = ufs_snap_init_backfile(fiosnapp->backfiledesc,
fiosnapp->backfilecount, &bfvpp, ufsvfsp);
if (error) {
fiosnapp->error = FIOCOW_EBACKFILE;
return (error);
}
/*
* File system must be write locked to prevent updates while
* the snapshot is being established.
*/
if ((error = ufs_fiolfss(vp, &lf)) != 0) {
release_backing_vnodes(&bfvpp, fiosnapp->backfilecount);
return (error);
}
if (!LOCKFS_IS_ULOCK(&lf)) {
release_backing_vnodes(&bfvpp, fiosnapp->backfilecount);
fiosnapp->error = FIOCOW_EULOCK;
return (EINVAL);
}
lf.lf_lock = LOCKFS_WLOCK;
lf.lf_flags = 0;
lf.lf_comment = NULL;
if ((error = ufs_fiolfs(vp, &lf, 1)) != 0) {
release_backing_vnodes(&bfvpp, fiosnapp->backfilecount);
fiosnapp->error = FIOCOW_EWLOCK;
return (EINVAL);
}
/*
* File system must be fairly consistent to enable snapshots
*/
if (fs->fs_clean != FSACTIVE &&
fs->fs_clean != FSSTABLE &&
fs->fs_clean != FSCLEAN &&
fs->fs_clean != FSLOG) {
fiosnapp->error = FIOCOW_ECLEAN;
error = EINVAL;
goto unlockout;
}
/*
* Only one snapshot is allowed per file system, so error if
* a snapshot is already enabled.
*/
if (ufsvfsp->vfs_snapshot) {
fiosnapp->error = FIOCOW_EBUSY;
error = EBUSY;
goto unlockout;
}
/* Tell bio.c how to call our strategy routine. XXX ugly hack */
if (bio_snapshot_strategy == NULL)
bio_snapshot_strategy =
(void (*) (void *, buf_t *))fssnap_strategy;
/*
* use chunk size that is passed in, or the file system
* block size if it is zero. For most cases, the file system
* block size will be reasonably efficient. A larger
* chunksize uses less memory but may potentially induce more
* I/O copying the larger chunks aside.
*/
if (fiosnapp->chunksize != 0)
chunksize = fiosnapp->chunksize;
else
chunksize = fs->fs_bsize * 4;
/*
* compute the number of chunks in this whole file system. Since
* the UFS allocation bitmaps are in units of fragments, we first
* compute the number of fragments per chunk. Things work out
* nicer if the chunk size is a power-of-two multiple of the
* fragment size.
*/
if ((chunksize < fs->fs_fsize) || (chunksize % fs->fs_fsize != 0)) {
fiosnapp->error = FIOCOW_ECHUNKSZ;
error = EINVAL;
goto unlockout;
}
fragsperchunk = chunksize >> fs->fs_fshift;
nchunks = (fs->fs_size + fragsperchunk) / fragsperchunk;
/*
* Create and initialize snapshot state and allocate/initialize
* translation table. This does the real work of taking the snapshot.
*/
snapid = fssnap_create(nchunks, chunksize, fiosnapp->maxsize, vp,
fiosnapp->backfilecount, bfvpp, fiosnapp->backfilename,
fiosnapp->backfilesize);
if (snapid == NULL) {
fiosnapp->error = FIOCOW_ECREATE;
error = EINVAL;
goto unlockout;
}
error = ufs_snap_find_candidates(snapid, ufsvfsp, chunksize);
fiosnapp->snapshotnumber = fssnap_create_done(snapid);
if (error) {
cmn_err(CE_WARN, "ufs_snap_create: failed scanning bitmaps, "
"error = %d.", error);
fiosnapp->error = FIOCOW_EBITMAP;
goto unlockout;
}
ufsvfsp->vfs_snapshot = snapid;
unlockout:
/*
* Unlock the file system
*/
lf.lf_lock = LOCKFS_ULOCK;
lf.lf_flags = 0;
if ((ufs_fiolfs(vp, &lf, 1) != 0) && !error) {
fiosnapp->error = FIOCOW_ENOULOCK;
error = EINVAL;
} else {
fiosnapp->error = 0;
}
/* clean up the snapshot if an error occurred. */
if (error && snapid != NULL)
(void) fssnap_delete(&snapid);
else if (error && bfvpp != NULL)
release_backing_vnodes(&bfvpp, fiosnapp->backfilecount);
return (error);
}
static int
ufs_snap_init_backfile(int *filedesc, int count, vnode_t ***vppp,
struct ufsvfs *ufsvfsp)
{
file_t *fp;
vnode_t **vpp;
int i;
vpp = (vnode_t **)kmem_zalloc((count + 1) * sizeof (vnode_t *),
KM_SLEEP);
*vppp = vpp;
for (i = 0; i < count; i++) {
if ((fp = getf(*filedesc)) == NULL) {
release_backing_vnodes(vppp, count);
*vppp = NULL;
return (EBADF);
}
ASSERT(fp->f_vnode != NULL);
VN_HOLD(fp->f_vnode);
*vpp = fp->f_vnode;
releasef(*filedesc);
filedesc++;
/* make sure the backing file is on a different file system */
if ((*vpp)->v_vfsp == ufsvfsp->vfs_vfs) {
release_backing_vnodes(vppp, count);
*vppp = NULL;
return (EINVAL);
}
vpp++;
}
return (0);
}
static void
release_backing_vnodes(vnode_t ***bvppp, int count)
{
vnode_t **vpp;
vpp = *bvppp;
while (*vpp) {
VN_RELE(*vpp);
*vpp++ = NULL;
}
kmem_free(*bvppp, (count + 1) * sizeof (vnode_t *));
*bvppp = NULL;
}
static int
ufs_snap_find_candidates(void *snapid, struct ufsvfs *ufsvfsp, int chunksize)
{
struct fs *fs = ufsvfsp->vfs_fs;
struct buf *cgbp; /* cylinder group buffer */
struct cg *cgp; /* cylinder group data */
ulong_t cg;
ulong_t cgbase;
ulong_t chunk;
uchar_t *blksfree;
ulong_t curfrag;
int error = 0;
/*
* read through each ufs cylinder group and fetch the fragment
* allocation bitmap. UFS indicates a fragment is allocated by
* a zero bit (not a one bit) in the fragment offset.
*/
cgbase = 0LL;
for (cg = 0; cg < fs->fs_ncg; cg++) {
/* read the cylinder group in */
cgbp = BREAD(ufsvfsp->vfs_dev,
(daddr_t)fsbtodb(fs, cgtod(fs, cg)), (int)fs->fs_cgsize);
if ((error = geterror(cgbp)) != 0) {
brelse(cgbp);
goto errout;
}
cgp = cgbp->b_un.b_cg;
/* check the magic number */
if (cgp->cg_magic != CG_MAGIC) {
cmn_err(CE_WARN, "ufs_snap_find_candidates: cg %lu "
"magic number (0x%x) does not match expected "
"magic number (0x%x)", cg, cgp->cg_magic, CG_MAGIC);
error = EIO;
goto errout;
}
blksfree = cg_blksfree(cgp);
/*
* go through the allocation bitmap and set the
* corresponding bit in the candidate map.
*/
for (curfrag = 0; curfrag < cgp->cg_ndblk; curfrag++) {
if (isclr(blksfree, curfrag)) {
/*
* this assumes chunksize is a multiple of
* the fragment size
*/
chunk = (ulong_t)((cgbase + curfrag) /
(chunksize >> fs->fs_fshift));
fssnap_set_candidate(snapid, chunk);
/*
* no need to scan the rest of this chunk since
* it is already marked, so skip to the next
*/
curfrag += ((chunksize >> fs->fs_fshift) -
((cgbase + curfrag) %
(chunksize >> fs->fs_fshift))) - 1;
}
}
cgbase += cgp->cg_ndblk;
ASSERT(cgbase <= fs->fs_size);
brelse(cgbp);
} /* cylinder group loop */
ASSERT(cgbase == fs->fs_size);
errout:
return (error);
}
int
ufs_snap_delete(struct vnode *vp, struct fiosnapdelete *fiosnapp, cred_t *cr)
{
struct ufsvfs *ufsvfsp = VTOI(vp)->i_ufsvfs;
struct fs *fs = ufsvfsp->vfs_fs;
/*
* Initialize fields in the user's buffer
*/
fiosnapp->error = 0;
/*
* No snapshot exists, we're done.
*/
if (ufsvfsp->vfs_snapshot == NULL)
return (ENOENT);
/*
* must have sufficient privileges.
*/
if (secpolicy_fs_config(cr, ufsvfsp->vfs_vfs) != 0)
return (EPERM);
/*
* Readonly file system
*/
if (fs->fs_ronly) {
fiosnapp->error = FIOCOW_EREADONLY;
return (EROFS);
}
/* free the data structures and clear the vfs_snapshot field. */
fiosnapp->snapshotnumber = fssnap_delete(&ufsvfsp->vfs_snapshot);
if (fiosnapp->snapshotnumber == -1)
return (EINVAL);
return (0);
}