BACKPORT: f2fs: correct i_size change for atomic writes

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

Bug: 298879042
Bug: 308706939
Change-Id: I0b54b9bcdda262d2ca7e89ae6c6e0e6324df7771
Signed-off-by: Daeho Jeong <daehojeong@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
(cherry picked from commit ec8ef4fe)
Signed-off-by: zhoudan8 <zhoudan8@xiaomi.com>