f2fs: don't need to wait for node writes for atomic write

We have a node chain to serialize node block writes, so if any IOs for
node block writes are reordered, we'll get broken node chain. IOWs,
roll-forward recovery will see all or none node blocks given fsync
mark.

E.g.,
Node chain consists of:
 N1 -> N2 -> N3 -> NFSYNC -> N1' -> N2' -> N'FSYNC

Reordered to:
1) N1 -> N2 -> N3 -> N2' -> NFSYNC -> N'FSYNC -> power-cut
2) N1 -> N2 -> N3 -> N1' -> NFSYNC -> power-cut
3) N1 -> N2 -> NFSYNC -> N1' -> N'FSYNC -> N3 -> power-cut
4) N1 -> NFSYNC -> N1' -> N2' -> N'FSYNC -> N3 -> power-cut

Roll-forward recovery can proceed to:
1) N1 -> N2 -> N3 -> NFSYNC -> X
2) N1 -> N2 -> N3 -> NFSYNC -> N1' -> X
3) N1 -> N2 -> N3 -> FSYNC -> N1' -> X
4) N1 -> X

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index a0413c9514588f5b2dd308d2bd0c570af11b7b9e..0246d19d96c3cc93427b11e74a500900d248f9cc 100644 (file)
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -274,9 +274,19 @@ static int f2fs_do_sync_file(struct file *file, loff_t start, loff_t end,
                goto sync_nodes;
        }
 
-       ret = wait_on_node_pages_writeback(sbi, ino);
-       if (ret)
-               goto out;
+       /*
+        * If it's atomic_write, it's just fine to keep write ordering. So
+        * here we don't need to wait for node write completion, since we use
+        * node chain which serializes node blocks. If one of node writes are
+        * reordered, we can see simply broken chain, resulting in stopping
+        * roll-forward recovery. It means we'll recover all or none node blocks
+        * given fsync mark.
+        */
+       if (!atomic) {
+               ret = wait_on_node_pages_writeback(sbi, ino);
+               if (ret)
+                       goto out;
+       }
 
        /* once recovery info is written, don't need to tack this */
        remove_ino_entry(sbi, ino, APPEND_INO);