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-rw-r--r--Documentation/filesystems/vfat.txt26
1 files changed, 21 insertions, 5 deletions
diff --git a/Documentation/filesystems/vfat.txt b/Documentation/filesystems/vfat.txt
index d230dd9c99b0..4a93e98b290a 100644
--- a/Documentation/filesystems/vfat.txt
+++ b/Documentation/filesystems/vfat.txt
@@ -150,12 +150,28 @@ 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.
+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
- Enable this only if you want to export the FAT filesystem
- over NFS
<bool>: 0,1,yes,no,true,false