fat: make discard a mount option

Currently shipping discard capable SSDs and arrays have rather sub-optimal
implementations of the command and can the use of it can cause massive
slowdowns.  Make issueing these commands option as it's already in btrfs
and gfs2.

Signed-off-by: Christoph Hellwig <hch@lst.de>
[hirofumi@mail.parknet.co.jp: tweaks, and add "discard" to fat_show_options]
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>

1 files changed, 2 insertions, 1 deletions

diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index 7db0979c6b72..e6efdfa0f6db 100644
--- a/fs/fat/fat.h
+++ b/fs/fat/fat.h
@@ -44,7 +44,8 @@ struct fat_mount_options {
                  nocase:1,        /* Does this need case conversion? 0=need case conversion*/
                  usefree:1,       /* Use free_clusters for FAT32 */
                  tz_utc:1,        /* Filesystem timestamps are in UTC */
-                 rodir:1;         /* allow ATTR_RO for directory */
+                 rodir:1,         /* allow ATTR_RO for directory */
+                 discard:1;       /* Issue discard requests on deletions */
 };
 
 #define FAT_HASH_BITS   8