Documentation: update nfs option in filesystem/vfat.txt

Update nfs option 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>
Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/Documentation/filesystems/vfat.txt b/Documentation/filesystems/vfat.txt
index de1e6c4dccff047766f1bfc1801319ef28cdf0d1..d62f8e6967dc5c0e631feb0567acccbdc9b2181e 100644 (file)
--- a/Documentation/filesystems/vfat.txt
+++ b/Documentation/filesystems/vfat.txt
@@ -141,13 +141,26 @@ discard       -- If set, issues discard/TRIM commands to the block
                 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.
-
-                Enable this only if you want to export the FAT filesystem
+nfs= stale_rw|nostale_ro
+             -- 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
 
 TODO