nilfs2: add norecovery mount option

This adds "norecovery" mount option which disables temporal write
access to read-only mounts or snapshots during mount/recovery.
Without this option, write access will be even performed for those
types of mounts; the temporal write access is needed to mount root
file system read-only after an unclean shutdown.

This option will be helpful when user wants to prevent any write
access to the device.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Cc: Eric Sandeen <sandeen@redhat.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/Documentation/filesystems/nilfs2.txt b/Documentation/filesystems/nilfs2.txt
index cbd877978c80..4949fcaa6b6a 100644
--- a/Documentation/filesystems/nilfs2.txt
+++ b/Documentation/filesystems/nilfs2.txt
@@ -70,6 +70,10 @@ order=strict		Apply strict in-order semantics that preserves sequence
                         blocks.  That means, it is guaranteed that no
                         overtaking of events occurs in the recovered file
                         system after a crash.
+norecovery              Disable recovery of the filesystem on mount.
+                        This disables every write access on the device for
+                        read-only mounts or snapshots.  This option will fail
+                        for r/w mounts on an unclean volume.
 
 NILFS2 usage
 ============