The deadlock happens when the fsync thread waits on a inode page that has
been added to the f2fs' cached bio sbi->bio[NODE], and unfortunately,
no one else could be able to submit the cached bio to block layer for
writeback. This is because the fsync thread already hold a sbi->fs_lock and
the sbi->writepages lock, causing the bdi thread being blocked when attempt
to write data pages for the same inode. At the same time, f2fs_gc thread
does not notice the situation and could not help. Even the sync syscall
gets blocked.
To fix it, we could submit the cached bio first before waiting on a inode page
that is being written back.
Signed-off-by: Jin Xu <jinuxstyle@gmail.com>
[Jaegeuk Kim: add more cases to use f2fs_wait_on_page_writeback] Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>