[PATCH] ext2: only flush DIRSYNC directories on every change

[Josef Bacik <josef@toxicpanda.com>]

Every change of an ext2 directory is written to disk before the system call
returns, whether the directory is DIRSYNC or not: its pages with
filemap_write_and_wait() and its inode with sync_inode_metadata().

Writes which reach the device for 2000 files, and 200 directories, in a
directory without DIRSYNC, with the flusher turned off:

            create   rename   unlink   mkdir
    before    4000     8000     4000     800
    after        0        0        0       0

In a directory with chattr +D the numbers are those of "before", before and
after.

commit bc943f4872a7 ("ext2: Don't flush page immediately for DIRSYNC
directories") moved the flush from ext2_commit_chunk() to the new
ext2_handle_dirsync().  The IS_DIRSYNC() check which was around it didn't
move along.

Fix by putting the check into ext2_handle_dirsync().

Fixes: bc943f4872a7 ("ext2: Don't flush page immediately for DIRSYNC directories")
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
I ran into this while testing an overlayfs series with ext2 as the upper
file system. Directory entries were always on disk after a crash, also
the ones nobody had synced.
---
 fs/ext2/dir.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/ext2/dir.c b/fs/ext2/dir.c
index e17bbc7598c1..5de32c221a83 100644
--- a/fs/ext2/dir.c
+++ b/fs/ext2/dir.c
@@ -442,6 +442,9 @@ static int ext2_handle_dirsync(struct inode *dir)
 {
 	int err;
 
+	if (!IS_DIRSYNC(dir))
+		return 0;
+
 	err = filemap_write_and_wait(dir->i_mapping);
 	if (!err)
 		err = sync_inode_metadata(dir, 1);

---
base-commit: c03c1a14507dfaf8b856c2608f9ac216021fc222
change-id: 20261027-b4-ext2-dirsync-86ca140154bc