From: Jinliang Zheng <alexjlzheng@tencent.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@tencent.com>
---
Changelog: Just RESEND

v1: https://lore.kernel.org/linux-ext4/20240815112746.18570-1-alexjlzheng@tencent.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

On Thu, 19 Sep 2024 16:25:39 +0800, alexjlzheng@gmail.com wrote:
> 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.
> 
> [...]

Applied, thanks!

[1/1] ext4: disambiguate the return value of ext4_dio_write_end_io()
      commit: e88d17afcf8364c353942e951f8e968f66bfcaa0

Best regards,
-- 
Theodore Ts'o <tytso@mit.edu>

On 2024/9/19 16:25, alexjlzheng@gmail.com wrote:
> From: Jinliang Zheng <alexjlzheng@tencent.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@tencent.com>

Make sense to me,

Reviewed-by: Zhang Yi <yi.zhang@huawei.com>

> ---
> Changelog: Just RESEND
> 
> v1: https://lore.kernel.org/linux-ext4/20240815112746.18570-1-alexjlzheng@tencent.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 = {