f2fs/013: test to check potential corruption on atomic_write file

f2fs/013: test to check potential corruption on atomic_write file

This is a regression testcase to check whether we will handle database
inode dirty status correctly:
1. mount f2fs image w/ timeout fault injection option
2. create a regular file, and write data into the file
3. start transaction on the file (via F2FS_IOC_START_ATOMIC_WRITE)
4. write transaction data to the file
5. commit and end the transaction (via F2FS_IOC_COMMIT_ATOMIC_WRITE)
6. meanwhile loop call fsync in parallel
Before f098aeba04c9 ("f2fs: fix to avoid atomicity corruption of atomic
file"), database file may become corrupted after atomic write while
there is concurrent dirty inode flush in background.

Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Daeho Jeong <daehojeong@google.com>
Signed-off-by: Chao Yu <chao@kernel.org>
Reviewed-by: David Disseldorp <ddiss@suse.de>
Reviewed-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>