linux-kernel - [PATCH] ext4: disambiguate the return value of ext4_dio_write_end

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Message-ID: <20240815112746.18570-1-alexjlzheng@tencent.com>
Date: Thu, 15 Aug 2024 19:27:46 +0800
From: alexjlzheng@...il.com
To: tytso@....edu,
	adilger.kernel@...ger.ca
Cc: linux-ext4@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Jinliang Zheng <alexjlzheng@...cent.com>
Subject: [PATCH] ext4: disambiguate the return value of ext4_dio_write_end_io()

From: Jinliang Zheng <alexjlzheng@...cent.com>

The commit 91562895f803 ("ext4: properly sync file size update after O_SYNC
direct IO") causes confusion about the meaning of the return value of
ext4_dio_write_end_io().

Specifically, when the ext4_handle_inode_extension() operation succeeds,
ext4_dio_write_end_io() directly returns count instead of 0.

This does not cause a bug in the current kernel, but the semantics of the
return value of the ext4_dio_write_end_io() function are wrong, which is
likely to introduce bugs in the future code evolution.

Signed-off-by: Jinliang Zheng <alexjlzheng@...cent.com>
---
 fs/ext4/file.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index c89e434db6b7..6df5a92cec2b 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -392,8 +392,9 @@ static int ext4_dio_write_end_io(struct kiocb *iocb, ssize_t size,
 	 */
 	if (pos + size <= READ_ONCE(EXT4_I(inode)->i_disksize) &&
 	    pos + size <= i_size_read(inode))
-		return size;
-	return ext4_handle_inode_extension(inode, pos, size);
+		return 0;
+	error = ext4_handle_inode_extension(inode, pos, size);
+	return error < 0 ? error : 0;
 }

 static const struct iomap_dio_ops ext4_dio_write_ops = {
-- 
2.41.1