[PATCH 4.20 46/50] Revert "ext4: use ext4_write_inode() when fsyncing w/o a journal"

Greg Kroah-Hartman
2019-02-13T18:48:11Z

From: Theodore Ts'o <tytso@mit.edu>

commit 8fdd60f2ae3682caf2a7258626abc21eb4711892 upstream.

This reverts commit ad211f3e94b314a910d4af03178a0b52a7d1ee0a.

As Jan Kara pointed out, this change was unsafe since it means we lose
the call to sync_mapping_buffers() in the nojournal case. The
original point of the commit was avoid taking the inode mutex (since
it causes a lockdep warning in generic/113); but we need the mutex in
order to call sync_mapping_buffers().

The real fix to this problem was discussed here:

https://lore.kernel.org/lkml/20181025150540.259281-4-bvanassche@acm.org

The proposed patch was to fix a syzbot complaint, but the problem can
also demonstrated via "kvm-xfstests -c nojournal generic/113".
Multiple solutions were discused in the e-mail thread, but none have
landed in the kernel as of this writing. Anyway, commit
ad211f3e94b314 is absolutely the wrong way to suppress the lockdep, so
revert it.

Fixes: ad211f3e94b314a910d4af03178a0b52a7d1ee0a ("ext4: use ext4_write_inode() when fsyncing w/o a journal")
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reported: Jan Kara <jack@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/ext4/fsync.c | 13 ++++---------
1 file changed, 4 insertions(+), 9 deletions(-)

--- a/fs/ext4/fsync.c
+++ b/fs/ext4/fsync.c
@@ -116,16 +116,8 @@ int ext4_sync_file(struct file *file, lo
goto out;
}

- ret = file_write_and_wait_range(file, start, end);
- if (ret)
- return ret;
-
if (!journal) {
- struct writeback_control wbc = {
- .sync_mode = WB_SYNC_ALL
- };
-
- ret = ext4_write_inode(inode, &wbc);
+ ret = __generic_file_fsync(file, start, end, datasync);
if (!ret)
ret = ext4_sync_parent(inode);
if (test_opt(inode->i_sb, BARRIER))
@@ -133,6 +125,9 @@ int ext4_sync_file(struct file *file, lo
goto out;
}

+ ret = file_write_and_wait_range(file, start, end);
+ if (ret)
+ return ret;
/*
* data=writeback,ordered:
* The caller's filemap_fdatawrite()/wait will sync the data.