[PATCH v4 4/4] Documentation: update nfs option in filesystem/vfat.txt

[Namjae Jeon <linkinjeon@gmail.com>]

From: Namjae Jeon <namjae.jeon@samsung.com>

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>
---
 Documentation/filesystems/vfat.txt |   23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/Documentation/filesystems/vfat.txt b/Documentation/filesystems/vfat.txt
index de1e6c4..d62f8e6 100644
--- 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
-- 
1.7.9.5