f2fs: correct i_size change for atomic writes

f2fs: correct i_size change for atomic writes

[ Upstream commit 4d8d45df2252980f800c1b2fde941a103a18a70e ]

We need to make sure i_size doesn't change until atomic write commit is
successful and restore it when commit is failed.

Signed-off-by: Daeho Jeong <daehojeong@google.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Stable-dep-of: 0e8d040bfa4c ("f2fs: clear atomic_write_task in f2fs_abort_atomic_write()")
Signed-off-by: Sasha Levin <sashal@kernel.org>