d/freebsd-dev
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Support accessing .zfs/snapshot via NFS

Browse Source 
This patch is based on the previous work done by @andrey-ve and
@yshui.  It triggers the automount by using kern_path() to traverse
to the known snapshout mount point.  Once the snapshot is mounted
NFS can access the contents of the snapshot.

Allowing NFS clients to access to the .zfs/snapshot directory would
normally mean that a root user on a client mounting an export with
'no_root_squash' would be able to use mkdir/rmdir/mv to manipulate
snapshots on the server.  To prevent configuration mistakes a
zfs_admin_snapshot module option was added which disables the
mkdir/rmdir/mv functionally.  System administators desiring this
functionally must explicitly enable it.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2797
Closes #1655
Closes #616
This commit is contained in:
Brian Behlendorf 2015-08-28 14:54:32 -07:00
parent aa9b27080b
commit 0500e835af
3 changed files with 141 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
man/man5/zfs-module-parameters.5
View File

@ -955,6 +955,21 @@ Seconds to expire .zfs/snapshot
Default value: \fB300\fR.
.RE
.sp
.ne 2
.na
\fBzfs_admin_snapshot\fR (int)
.ad
.RS 12n
Allow the creation, removal, or renaming of entries in the .zfs/snapshot
directory to cause the creation, destruction, or renaming of snapshots.
When enabled this functionality works both locally and over NFS exports
which have the 'no_root_squash' option set. This functionality is disabled
by default.
.sp
Use \fB1\fR for yes and \fB0\fR for no (default).
.RE
.sp
.ne 2
.na

124
module/zfs/zfs_ctldir.c
View File

@ -107,6 +107,7 @@ static kmutex_t zfs_snapshot_lock;
* Control Directory Tunables (.zfs)
*/
int zfs_expire_snapshot = ZFSCTL_EXPIRE_SNAPSHOT;
int zfs_admin_snapshot = 0;
/*
* Dedicated task queue for unmounting snapshots.
@ -585,7 +586,45 @@ zfsctl_root(znode_t *zp)
igrab(ZTOZSB(zp)->z_ctldir);
return (ZTOZSB(zp)->z_ctldir);
}
/*
* Generate a long fid which includes the root object and objset of a
* snapshot but not the generation number. For the root object the
* generation number is ignored when zero to avoid needing to open
* the dataset when generating fids for the snapshot names.
*/
static int
zfsctl_snapdir_fid(struct inode *ip, fid_t *fidp)
{
zfs_sb_t *zsb = ITOZSB(ip);
zfid_short_t *zfid = (zfid_short_t *)fidp;
zfid_long_t *zlfid = (zfid_long_t *)fidp;
uint32_t gen = 0;
uint64_t object;
uint64_t objsetid;
int i;
object = zsb->z_root;
objsetid = ZFSCTL_INO_SNAPDIRS - ip->i_ino;
zfid->zf_len = LONG_FID_LEN;
for (i = 0; i < sizeof (zfid->zf_object); i++)
zfid->zf_object[i] = (uint8_t)(object >> (8 * i));
for (i = 0; i < sizeof (zfid->zf_gen); i++)
zfid->zf_gen[i] = (uint8_t)(gen >> (8 * i));
for (i = 0; i < sizeof (zlfid->zf_setid); i++)
zlfid->zf_setid[i] = (uint8_t)(objsetid >> (8 * i));
for (i = 0; i < sizeof (zlfid->zf_setgen); i++)
zlfid->zf_setgen[i] = 0;
return (0);
}
/*
* Generate an appropriate fid for an entry in the .zfs directory.
*/
int
zfsctl_fid(struct inode *ip, fid_t *fidp)
{
@ -603,6 +642,11 @@ zfsctl_fid(struct inode *ip, fid_t *fidp)
return (SET_ERROR(ENOSPC));
}
if (zfsctl_is_snapdir(ip)) {
ZFS_EXIT(zsb);
return (zfsctl_snapdir_fid(ip, fidp));
}
zfid = (zfid_short_t *)fidp;
zfid->zf_len = SHORT_FID_LEN;
@ -671,6 +715,48 @@ zfsctl_snapshot_path(struct path *path, int len, char *full_path)
return (error);
}
/*
* Returns full path in full_path: "/pool/dataset/.zfs/snapshot/snap_name/"
*/
static int
zfsctl_snapshot_path_objset(zfs_sb_t *zsb, uint64_t objsetid,
int path_len, char *full_path)
{
objset_t *os = zsb->z_os;
fstrans_cookie_t cookie;
char *snapname;
boolean_t case_conflict;
uint64_t id, pos = 0;
int error = 0;
if (zsb->z_mntopts->z_mntpoint == NULL)
return (ENOENT);
cookie = spl_fstrans_mark();
snapname = kmem_alloc(MAXNAMELEN, KM_SLEEP);
while (error == 0) {
dsl_pool_config_enter(dmu_objset_pool(os), FTAG);
error = dmu_snapshot_list_next(zsb->z_os, MAXNAMELEN,
snapname, &id, &pos, &case_conflict);
dsl_pool_config_exit(dmu_objset_pool(os), FTAG);
if (error)
goto out;
if (id == objsetid)
break;
}
memset(full_path, 0, path_len);
snprintf(full_path, path_len - 1, "%s/.zfs/snapshot/%s",
zsb->z_mntopts->z_mntpoint, snapname);
out:
kmem_free(snapname, MAXNAMELEN);
spl_fstrans_unmark(cookie);
return (error);
}
/*
* Special case the handling of "..".
*/
@ -747,6 +833,9 @@ zfsctl_snapdir_rename(struct inode *sdip, char *snm,
char *to, *from, *real, *fsname;
int error;
if (!zfs_admin_snapshot)
return (EACCES);
ZFS_ENTER(zsb);
to = kmem_alloc(MAXNAMELEN, KM_SLEEP);
@ -819,6 +908,9 @@ zfsctl_snapdir_remove(struct inode *dip, char *name, cred_t *cr, int flags)
char *snapname, *real;
int error;
if (!zfs_admin_snapshot)
return (EACCES);
ZFS_ENTER(zsb);
snapname = kmem_alloc(MAXNAMELEN, KM_SLEEP);
@ -864,6 +956,9 @@ zfsctl_snapdir_mkdir(struct inode *dip, char *dirname, vattr_t *vap,
char *dsname;
int error;
if (!zfs_admin_snapshot)
return (EACCES);
dsname = kmem_alloc(MAXNAMELEN, KM_SLEEP);
if (zfs_component_namecheck(dirname, NULL, NULL) != 0) {
@ -1013,6 +1108,7 @@ zfsctl_snapshot_mount(struct path *path, int flags)
*/
zpl_follow_down_one(path);
snap_zsb = ITOZSB(path->dentry->d_inode);
snap_zsb->z_parent = zsb;
dentry = path->dentry;
path->mnt->mnt_flags |= MNT_SHRINKABLE;
zpl_follow_up(path);
@ -1060,6 +1156,31 @@ zfsctl_lookup_objset(struct super_block *sb, uint64_t objsetid, zfs_sb_t **zsbp)
}
mutex_exit(&zfs_snapshot_lock);
/*
* Automount the snapshot given the objset id by constructing the
* full mount point and performing a traversal.
*/
if (error == ENOENT) {
struct path path;
char *mnt;
mnt = kmem_alloc(MAXPATHLEN, KM_SLEEP);
error = zfsctl_snapshot_path_objset(sb->s_fs_info, objsetid,
MAXPATHLEN, mnt);
if (error) {
kmem_free(mnt, MAXPATHLEN);
return (SET_ERROR(error));
}
error = kern_path(mnt, LOOKUP_FOLLOW|LOOKUP_DIRECTORY, &path);
if (error == 0) {
*zsbp = ITOZSB(path.dentry->d_inode);
path_put(&path);
}
kmem_free(mnt, MAXPATHLEN);
}
return (error);
}
@ -1127,5 +1248,8 @@ zfsctl_fini(void)
mutex_destroy(&zfs_snapshot_lock);
}
module_param(zfs_admin_snapshot, int, 0644);
MODULE_PARM_DESC(zfs_admin_snapshot, "Enable mkdir/rmdir/mv in .zfs/snapshot");
module_param(zfs_expire_snapshot, int, 0644);
MODULE_PARM_DESC(zfs_expire_snapshot, "Seconds to expire .zfs/snapshot");

2
module/zfs/zfs_vfsops.c
View File

@ -1600,6 +1600,8 @@ zfs_vget(struct super_block *sb, struct inode **ipp, fid_t *fidp)
zp_gen = zp_gen & gen_mask;
if (zp_gen == 0)
zp_gen = 1;
if ((fid_gen == 0) && (zsb->z_root == object))
fid_gen = zp_gen;
if (zp->z_unlinked || zp_gen != fid_gen) {
dprintf("znode gen (%llu) != fid gen (%llu)\n", zp_gen,
fid_gen);