Support accessing .zfs/snapshot via NFS
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
parent
aa9b27080b
commit
0500e835af
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@ -955,6 +955,21 @@ Seconds to expire .zfs/snapshot
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Default value: \fB300\fR.
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.RE
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.sp
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.ne 2
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.na
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\fBzfs_admin_snapshot\fR (int)
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.ad
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.RS 12n
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Allow the creation, removal, or renaming of entries in the .zfs/snapshot
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directory to cause the creation, destruction, or renaming of snapshots.
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When enabled this functionality works both locally and over NFS exports
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which have the 'no_root_squash' option set. This functionality is disabled
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by default.
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.sp
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Use \fB1\fR for yes and \fB0\fR for no (default).
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.RE
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.sp
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.ne 2
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.na
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@ -107,6 +107,7 @@ static kmutex_t zfs_snapshot_lock;
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* Control Directory Tunables (.zfs)
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*/
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int zfs_expire_snapshot = ZFSCTL_EXPIRE_SNAPSHOT;
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int zfs_admin_snapshot = 0;
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/*
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* Dedicated task queue for unmounting snapshots.
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@ -585,7 +586,45 @@ zfsctl_root(znode_t *zp)
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igrab(ZTOZSB(zp)->z_ctldir);
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return (ZTOZSB(zp)->z_ctldir);
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}
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/*
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* Generate a long fid which includes the root object and objset of a
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* snapshot but not the generation number. For the root object the
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* generation number is ignored when zero to avoid needing to open
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* the dataset when generating fids for the snapshot names.
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*/
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static int
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zfsctl_snapdir_fid(struct inode *ip, fid_t *fidp)
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{
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zfs_sb_t *zsb = ITOZSB(ip);
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zfid_short_t *zfid = (zfid_short_t *)fidp;
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zfid_long_t *zlfid = (zfid_long_t *)fidp;
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uint32_t gen = 0;
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uint64_t object;
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uint64_t objsetid;
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int i;
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object = zsb->z_root;
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objsetid = ZFSCTL_INO_SNAPDIRS - ip->i_ino;
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zfid->zf_len = LONG_FID_LEN;
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for (i = 0; i < sizeof (zfid->zf_object); i++)
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zfid->zf_object[i] = (uint8_t)(object >> (8 * i));
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for (i = 0; i < sizeof (zfid->zf_gen); i++)
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zfid->zf_gen[i] = (uint8_t)(gen >> (8 * i));
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for (i = 0; i < sizeof (zlfid->zf_setid); i++)
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zlfid->zf_setid[i] = (uint8_t)(objsetid >> (8 * i));
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for (i = 0; i < sizeof (zlfid->zf_setgen); i++)
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zlfid->zf_setgen[i] = 0;
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return (0);
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}
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/*
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* Generate an appropriate fid for an entry in the .zfs directory.
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*/
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int
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zfsctl_fid(struct inode *ip, fid_t *fidp)
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{
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@ -603,6 +642,11 @@ zfsctl_fid(struct inode *ip, fid_t *fidp)
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return (SET_ERROR(ENOSPC));
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}
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if (zfsctl_is_snapdir(ip)) {
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ZFS_EXIT(zsb);
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return (zfsctl_snapdir_fid(ip, fidp));
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}
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zfid = (zfid_short_t *)fidp;
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zfid->zf_len = SHORT_FID_LEN;
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@ -671,6 +715,48 @@ out:
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return (error);
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}
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/*
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* Returns full path in full_path: "/pool/dataset/.zfs/snapshot/snap_name/"
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*/
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static int
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zfsctl_snapshot_path_objset(zfs_sb_t *zsb, uint64_t objsetid,
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int path_len, char *full_path)
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{
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objset_t *os = zsb->z_os;
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fstrans_cookie_t cookie;
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char *snapname;
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boolean_t case_conflict;
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uint64_t id, pos = 0;
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int error = 0;
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if (zsb->z_mntopts->z_mntpoint == NULL)
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return (ENOENT);
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cookie = spl_fstrans_mark();
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snapname = kmem_alloc(MAXNAMELEN, KM_SLEEP);
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while (error == 0) {
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dsl_pool_config_enter(dmu_objset_pool(os), FTAG);
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error = dmu_snapshot_list_next(zsb->z_os, MAXNAMELEN,
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snapname, &id, &pos, &case_conflict);
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dsl_pool_config_exit(dmu_objset_pool(os), FTAG);
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if (error)
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goto out;
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if (id == objsetid)
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break;
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}
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memset(full_path, 0, path_len);
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snprintf(full_path, path_len - 1, "%s/.zfs/snapshot/%s",
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zsb->z_mntopts->z_mntpoint, snapname);
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out:
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kmem_free(snapname, MAXNAMELEN);
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spl_fstrans_unmark(cookie);
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return (error);
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}
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/*
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* Special case the handling of "..".
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*/
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@ -747,6 +833,9 @@ zfsctl_snapdir_rename(struct inode *sdip, char *snm,
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char *to, *from, *real, *fsname;
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int error;
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if (!zfs_admin_snapshot)
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return (EACCES);
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ZFS_ENTER(zsb);
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to = kmem_alloc(MAXNAMELEN, KM_SLEEP);
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@ -819,6 +908,9 @@ zfsctl_snapdir_remove(struct inode *dip, char *name, cred_t *cr, int flags)
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char *snapname, *real;
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int error;
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if (!zfs_admin_snapshot)
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return (EACCES);
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ZFS_ENTER(zsb);
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snapname = kmem_alloc(MAXNAMELEN, KM_SLEEP);
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@ -864,6 +956,9 @@ zfsctl_snapdir_mkdir(struct inode *dip, char *dirname, vattr_t *vap,
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char *dsname;
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int error;
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if (!zfs_admin_snapshot)
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return (EACCES);
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dsname = kmem_alloc(MAXNAMELEN, KM_SLEEP);
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if (zfs_component_namecheck(dirname, NULL, NULL) != 0) {
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@ -1013,6 +1108,7 @@ zfsctl_snapshot_mount(struct path *path, int flags)
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*/
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zpl_follow_down_one(path);
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snap_zsb = ITOZSB(path->dentry->d_inode);
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snap_zsb->z_parent = zsb;
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dentry = path->dentry;
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path->mnt->mnt_flags |= MNT_SHRINKABLE;
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zpl_follow_up(path);
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@ -1060,6 +1156,31 @@ zfsctl_lookup_objset(struct super_block *sb, uint64_t objsetid, zfs_sb_t **zsbp)
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}
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mutex_exit(&zfs_snapshot_lock);
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/*
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* Automount the snapshot given the objset id by constructing the
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* full mount point and performing a traversal.
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*/
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if (error == ENOENT) {
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struct path path;
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char *mnt;
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mnt = kmem_alloc(MAXPATHLEN, KM_SLEEP);
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error = zfsctl_snapshot_path_objset(sb->s_fs_info, objsetid,
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MAXPATHLEN, mnt);
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if (error) {
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kmem_free(mnt, MAXPATHLEN);
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return (SET_ERROR(error));
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}
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error = kern_path(mnt, LOOKUP_FOLLOW|LOOKUP_DIRECTORY, &path);
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if (error == 0) {
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*zsbp = ITOZSB(path.dentry->d_inode);
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path_put(&path);
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}
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kmem_free(mnt, MAXPATHLEN);
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}
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return (error);
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}
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@ -1127,5 +1248,8 @@ zfsctl_fini(void)
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mutex_destroy(&zfs_snapshot_lock);
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}
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module_param(zfs_admin_snapshot, int, 0644);
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MODULE_PARM_DESC(zfs_admin_snapshot, "Enable mkdir/rmdir/mv in .zfs/snapshot");
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module_param(zfs_expire_snapshot, int, 0644);
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MODULE_PARM_DESC(zfs_expire_snapshot, "Seconds to expire .zfs/snapshot");
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@ -1600,6 +1600,8 @@ zfs_vget(struct super_block *sb, struct inode **ipp, fid_t *fidp)
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zp_gen = zp_gen & gen_mask;
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if (zp_gen == 0)
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zp_gen = 1;
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if ((fid_gen == 0) && (zsb->z_root == object))
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fid_gen = zp_gen;
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if (zp->z_unlinked || zp_gen != fid_gen) {
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dprintf("znode gen (%llu) != fid gen (%llu)\n", zp_gen,
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fid_gen);
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