Btrfs: adjust btrfs_discard_extent() return errors and trimmed bytes

Callers of btrfs_discard_extent() should check if we are mounted with -o discard,
as we want to make fitrim to work even the fs is not mounted with -o discard.
Also we should use REQ_DISCARD to map the free extent to get a full mapping,
last we only return errors if
1. the error is not a EOPNOTSUPP
2. no device supports discard

Signed-off-by: Li Dongyang <lidongyang@novell.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 125639ddaffe..8ecc5419d8b6 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3054,7 +3054,10 @@ static int btrfs_destroy_pinned_extent(struct btrfs_root *root,
                         break;
 
                 /* opt_discard */
-                ret = btrfs_error_discard_extent(root, start, end + 1 - start);
+                if (btrfs_test_opt(root, DISCARD))
+                        ret = btrfs_error_discard_extent(root, start,
+                                                         end + 1 - start,
+                                                         NULL);
 
                 clear_extent_dirty(unpin, start, end, GFP_NOFS);
                 btrfs_error_unpin_extent_range(root, start, end);