nilfs2: disallow remount of snapshot from/to a regular mount
Snapshots and regular ro/rw mounts are essentially-different within
the meaning whether the checkpoint is static or not and is marked with
a snapshot flag or not.
The current implemenation, however, allows to remount a snapshot to a
regular rw-mount if the checkpoint number equals the latest one.
This transition is actually impossible since changing a checkpoint to
a snapshot makes another checkpoint, thus the condition is never
satisfied.
This fixes the weird state of affairs, and specifically separates
snapshots and regular rw/ro-mounts.
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
index c88e664..03b34b7 100644
--- a/fs/nilfs2/super.c
+++ b/fs/nilfs2/super.c
@@ -754,9 +754,7 @@
goto failed_sbi;
}
cno = sbi->s_snapshot_cno;
- } else
- /* Read-only mount */
- sbi->s_snapshot_cno = cno;
+ }
}
err = nilfs_attach_checkpoint(sbi, cno);
@@ -825,7 +823,7 @@
struct the_nilfs *nilfs = sbi->s_nilfs;
unsigned long old_sb_flags;
struct nilfs_mount_options old_opts;
- int err;
+ int was_snapshot, err;
lock_kernel();
@@ -833,6 +831,7 @@
old_sb_flags = sb->s_flags;
old_opts.mount_opt = sbi->s_mount_opt;
old_opts.snapshot_cno = sbi->s_snapshot_cno;
+ was_snapshot = nilfs_test_opt(sbi, SNAPSHOT);
if (!parse_options(data, sb)) {
err = -EINVAL;
@@ -840,20 +839,32 @@
}
sb->s_flags = (sb->s_flags & ~MS_POSIXACL);
- if ((*flags & MS_RDONLY) &&
- sbi->s_snapshot_cno != old_opts.snapshot_cno) {
- printk(KERN_WARNING "NILFS (device %s): couldn't "
- "remount to a different snapshot.\n",
- sb->s_id);
- err = -EINVAL;
- goto restore_opts;
+ err = -EINVAL;
+ if (was_snapshot) {
+ if (!(*flags & MS_RDONLY)) {
+ printk(KERN_ERR "NILFS (device %s): cannot remount "
+ "snapshot read/write.\n",
+ sb->s_id);
+ goto restore_opts;
+ } else if (sbi->s_snapshot_cno != old_opts.snapshot_cno) {
+ printk(KERN_ERR "NILFS (device %s): cannot "
+ "remount to a different snapshot.\n",
+ sb->s_id);
+ goto restore_opts;
+ }
+ } else {
+ if (nilfs_test_opt(sbi, SNAPSHOT)) {
+ printk(KERN_ERR "NILFS (device %s): cannot change "
+ "a regular mount to a snapshot.\n",
+ sb->s_id);
+ goto restore_opts;
+ }
}
if (!nilfs_valid_fs(nilfs)) {
printk(KERN_WARNING "NILFS (device %s): couldn't "
"remount because the filesystem is in an "
"incomplete recovery state.\n", sb->s_id);
- err = -EINVAL;
goto restore_opts;
}
@@ -864,9 +875,6 @@
nilfs_detach_segment_constructor(sbi);
sb->s_flags |= MS_RDONLY;
- sbi->s_snapshot_cno = nilfs_last_cno(nilfs);
- /* nilfs_set_opt(sbi, SNAPSHOT); */
-
/*
* Remounting a valid RW partition RDONLY, so set
* the RDONLY flag and then mark the partition as valid again.
@@ -885,24 +893,7 @@
* store the current valid flag. (It may have been changed
* by fsck since we originally mounted the partition.)
*/
- if (nilfs->ns_current && nilfs->ns_current != sbi) {
- printk(KERN_WARNING "NILFS (device %s): couldn't "
- "remount because an RW-mount exists.\n",
- sb->s_id);
- err = -EBUSY;
- goto restore_opts;
- }
- if (sbi->s_snapshot_cno != nilfs_last_cno(nilfs)) {
- printk(KERN_WARNING "NILFS (device %s): couldn't "
- "remount because the current RO-mount is not "
- "the latest one.\n",
- sb->s_id);
- err = -EINVAL;
- goto restore_opts;
- }
sb->s_flags &= ~MS_RDONLY;
- nilfs_clear_opt(sbi, SNAPSHOT);
- sbi->s_snapshot_cno = 0;
err = nilfs_attach_segment_constructor(sbi);
if (err)
@@ -911,8 +902,6 @@
down_write(&nilfs->ns_sem);
nilfs_setup_super(sbi);
up_write(&nilfs->ns_sem);
-
- nilfs->ns_current = sbi;
}
out:
up_write(&nilfs->ns_super_sem);