linux-kernel - Re: [PATCH v5 2/4] iomap: move iter revert case out of the unwritten branch

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Message-ID: <aNWRKZJKePnNl2O3@bfoster>
Date: Thu, 25 Sep 2025 14:59:53 -0400
From: Brian Foster <bfoster@...hat.com>
To: alexjlzheng@...il.com
Cc: brauner@...nel.org, djwong@...nel.org, hch@...radead.org,
	kernel@...kajraghav.com, linux-xfs@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	yi.zhang@...wei.com, Jinliang Zheng <alexjlzheng@...cent.com>
Subject: Re: [PATCH v5 2/4] iomap: move iter revert case out of the unwritten
 branch

On Tue, Sep 23, 2025 at 12:21:56PM +0800, alexjlzheng@...il.com wrote:
> From: Jinliang Zheng <alexjlzheng@...cent.com>
> 
> The commit e1f453d4336d ("iomap: do some small logical cleanup in
> buffered write") merged iomap_write_failed() and iov_iter_revert()
> into the branch with written == 0. Because, at the time,
> iomap_write_end() could never return a partial write length.
> 
> In the subsequent patch, iomap_write_end() will be modified to allow
> to return block-aligned partial write length (partial write length
> here is relative to the folio-sized write), which violated the above
> patch's assumption.
> 
> This patch moves it back out to prepare for the subsequent patches.
> 
> Signed-off-by: Jinliang Zheng <alexjlzheng@...cent.com>
> ---

Reviewed-by: Brian Foster <bfoster@...hat.com>

>  fs/iomap/buffered-io.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index ee1b2cd8a4b4..e130db3b761e 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -1019,6 +1019,11 @@ static int 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)) {
> @@ -1028,9 +1033,6 @@ static int 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) {
> -- 
> 2.49.0
> 
>