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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>
This commit is contained in:
Jaegeuk Kim 2017-07-28 02:29:12 -07:00
parent dc6b205510
commit b6a245eb34
1 changed files with 13 additions and 3 deletions
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16
fs/f2fs/file.c
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@ -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);