ext4: make trim/discard optional (and off by default)

It is anticipated that when sb_issue_discard starts doing
real work on trim-capable devices, we may see issues.  Make
this mount-time optional, and default it to off until we know
that things are working out OK.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 8825515eedd..05ce38b981c 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -750,6 +750,7 @@ struct ext4_inode_info {
 #define EXT4_MOUNT_DELALLOC             0x8000000 /* Delalloc support */
 #define EXT4_MOUNT_DATA_ERR_ABORT       0x10000000 /* Abort on file data write */
 #define EXT4_MOUNT_BLOCK_VALIDITY       0x20000000 /* Block validity checking */
+#define EXT4_MOUNT_DISCARD              0x40000000 /* Issue DISCARD requests */
 
 #define clear_opt(o, opt)               o &= ~EXT4_MOUNT_##opt
 #define set_opt(o, opt)                 o |= EXT4_MOUNT_##opt