iomap: do some small logical cleanup in buffered write

mainline inclusion
from mainline-v6.10-rc1
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I9DN5Z
CVE: NA

--------------------------------

Since iomap_write_end() can never return a partial write length, the
comparison between written, copied and bytes becomes useless, just
merge them with the unwritten branch.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Link: https://lore.kernel.org/r/20240320110548.2200662-10-yi.zhang@huaweicloud.com
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
(cherry picked from commit e1f453d)
Signed-off-by: Wentao Guan <guanwentao@uniontech.com>

Author: zhangyi089

fs/iomap/buffered-io.c

@@ -973,11 +973,6 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 
 		if (old_size < pos)
 			pagecache_isize_extended(iter->inode, old_size, pos);
-		if (written < bytes)
-			iomap_write_failed(iter->inode, pos + written,
-					   bytes - written);
-		if (unlikely(copied != written))
-			iov_iter_revert(i, copied - written);
 
 		cond_resched();
 		if (unlikely(written == 0)) {
@@ -987,6 +982,9 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 			 * halfway through, might be a race with munmap,
 			 * might be severe memory pressure.
 			 */
+			iomap_write_failed(iter->inode, pos, bytes);
+			iov_iter_revert(i, copied);
+
 			if (chunk > PAGE_SIZE)
 				chunk /= 2;
 			if (copied) {