Documentation: update nfs option in filesystem/vfat.txt
Add descriptions about 'stale_rw' and 'nostale_ro' nfs options in
filesystem/vfat.txt
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Ravishankar N <ravi.n1@samsung.com>
Signed-off-by: Amit Sahrawat <a.sahrawat@samsung.com>
Acked-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Acked-by: Rob Landley <rob@landley.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/Documentation/filesystems/vfat.txt b/Documentation/filesystems/vfat.txt
index d230dd9..4a93e98 100644
--- a/Documentation/filesystems/vfat.txt
+++ b/Documentation/filesystems/vfat.txt
@@ -150,12 +150,28 @@
device when blocks are freed. This is useful for SSD devices
and sparse/thinly-provisoned LUNs.
-nfs -- This option maintains an index (cache) of directory
- inodes by i_logstart which is used by the nfs-related code to
- improve look-ups.
+nfs=stale_rw|nostale_ro
+ Enable this only if you want to export the FAT filesystem
+ over NFS.
- Enable this only if you want to export the FAT filesystem
- over NFS
+ stale_rw: This option maintains an index (cache) of directory
+ inodes by i_logstart which is used by the nfs-related code to
+ improve look-ups. Full file operations (read/write) over NFS is
+ supported but with cache eviction at NFS server, this could
+ result in ESTALE issues.
+
+ nostale_ro: This option bases the inode number and filehandle
+ on the on-disk location of a file in the MS-DOS directory entry.
+ This ensures that ESTALE will not be returned after a file is
+ evicted from the inode cache. However, it means that operations
+ such as rename, create and unlink could cause filehandles that
+ previously pointed at one file to point at a different file,
+ potentially causing data corruption. For this reason, this
+ option also mounts the filesystem readonly.
+
+ To maintain backward compatibility, '-o nfs' is also accepted,
+ defaulting to stale_rw
+
<bool>: 0,1,yes,no,true,false