Commit b6a245eb authored Jul 28, 2017 by Jaegeuk Kim

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>

parent dc6b2055

fs/f2fs/file.c

+13 −3

Original line number	Diff line number	Diff line
		@@ -274,9 +274,19 @@ sync_nodes:
		goto sync_nodes;
		}

		/*
		* 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);

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