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, 2 insertions, 0 deletions

diff --git a/include/linux/nilfs2_fs.h b/include/linux/nilfs2_fs.h
index 72289d2bb341..3fe02cf8b65a 100644
--- a/include/linux/nilfs2_fs.h
+++ b/include/linux/nilfs2_fs.h
@@ -151,6 +151,8 @@ struct nilfs_super_root {
 #define NILFS_MOUNT_BARRIER             0x1000  /* Use block barriers */
 #define NILFS_MOUNT_STRICT_ORDER        0x2000  /* Apply strict in-order
                                                    semantics also for data */
+#define NILFS_MOUNT_NORECOVERY          0x4000  /* Disable write access during
+                                                   mount-time recovery */
 
 
 /**