Btrfs: don't commit the transaction in the async space flushing

We're triggering a huge number of commits from
btrfs_async_reclaim_metadata_space.  These aren't really requried,
because everyone calling the async reclaim code is going to end up
triggering a commit on their own.

Signed-off-by: Chris Mason <clm@fb.com>

1 files changed, 8 insertions, 6 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index ae8db3ba467c..3d4b3d680fea 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -4329,8 +4329,13 @@ out:
 static inline int need_do_async_reclaim(struct btrfs_space_info *space_info,
                                         struct btrfs_fs_info *fs_info, u64 used)
 {
-        return (used >= div_factor_fine(space_info->total_bytes, 98) &&
-                !btrfs_fs_closing(fs_info) &&
+        u64 thresh = div_factor_fine(space_info->total_bytes, 98);
+
+        /* If we're just plain full then async reclaim just slows us down. */
+        if (space_info->bytes_used >= thresh)
+                return 0;
+
+        return (used >= thresh && !btrfs_fs_closing(fs_info) &&
                 !test_bit(BTRFS_FS_STATE_REMOUNTING, &fs_info->fs_state));
 }
 
@@ -4385,10 +4390,7 @@ static void btrfs_async_reclaim_metadata_space(struct work_struct *work)
                 if (!btrfs_need_do_async_reclaim(space_info, fs_info,
                                                  flush_state))
                         return;
-        } while (flush_state <= COMMIT_TRANS);
-
-        if (btrfs_need_do_async_reclaim(space_info, fs_info, flush_state))
-                queue_work(system_unbound_wq, work);
+        } while (flush_state < COMMIT_TRANS);
 }
 
 void btrfs_init_async_reclaim_work(struct work_struct *work)