linux-kernel - Re: [PATCH v5 3/4] iomap: make iomap_write_end() return the number of written length again

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Message-ID: <aNWRUyZhdhX7lzig@bfoster>
Date: Thu, 25 Sep 2025 15:00:35 -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 3/4] iomap: make iomap_write_end() return the number
 of written length again

On Tue, Sep 23, 2025 at 12:21:57PM +0800, alexjlzheng@...il.com wrote:
> From: Jinliang Zheng <alexjlzheng@...cent.com>
> 
> In the next patch, we allow iomap_write_end() to conditionally accept
> partial writes, so this patch makes iomap_write_end() return the number
> of accepted write bytes in preparation for the next patch.
> 
> Signed-off-by: Jinliang Zheng <alexjlzheng@...cent.com>
> ---
>  fs/iomap/buffered-io.c | 27 +++++++++++++--------------
>  1 file changed, 13 insertions(+), 14 deletions(-)
> 
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index e130db3b761e..6e516c7d9f04 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
...
> @@ -915,10 +915,10 @@ static void iomap_write_end_inline(const struct iomap_iter *iter,
>  }
>  
>  /*
> - * Returns true if all copied bytes have been written to the pagecache,
> - * otherwise return false.
> + * Returns number of copied bytes have been written to the pagecache,
> + * zero if block is partial update.
>   */
> -static bool iomap_write_end(struct iomap_iter *iter, size_t len, size_t copied,
> +static int iomap_write_end(struct iomap_iter *iter, size_t len, size_t copied,
>  		struct folio *folio)
>  {
>  	const struct iomap *srcmap = iomap_iter_srcmap(iter);
> @@ -926,7 +926,7 @@ static bool iomap_write_end(struct iomap_iter *iter, size_t len, size_t copied,
>  
>  	if (srcmap->type == IOMAP_INLINE) {
>  		iomap_write_end_inline(iter, folio, pos, copied);
> -		return true;
> +		return copied;
>  	}
>  
>  	if (srcmap->flags & IOMAP_F_BUFFER_HEAD) {
> @@ -934,7 +934,7 @@ static bool iomap_write_end(struct iomap_iter *iter, size_t len, size_t copied,
>  
>  		bh_written = block_write_end(pos, len, copied, folio);
>  		WARN_ON_ONCE(bh_written != copied && bh_written != 0);
> -		return bh_written == copied;
> +		return bh_written;

I notice block_write_end() actually returns an int. Not sure it's an
issue really, but perhaps we should just change the type of bh_written
here as well. Otherwise seems reasonable.

Brian

>  	}
>  
>  	return __iomap_write_end(iter->inode, pos, len, copied, folio);
> @@ -1000,8 +1000,7 @@ static int iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i,
>  			flush_dcache_folio(folio);
>  
>  		copied = copy_folio_from_iter_atomic(folio, offset, bytes, i);
> -		written = iomap_write_end(iter, bytes, copied, folio) ?
> -			  copied : 0;
> +		written = iomap_write_end(iter, bytes, copied, folio);
>  
>  		/*
>  		 * Update the in-memory inode size after copying the data into
> @@ -1315,7 +1314,7 @@ static int iomap_unshare_iter(struct iomap_iter *iter,
>  	do {
>  		struct folio *folio;
>  		size_t offset;
> -		bool ret;
> +		int ret;
>  
>  		bytes = min_t(u64, SIZE_MAX, bytes);
>  		status = iomap_write_begin(iter, write_ops, &folio, &offset,
> @@ -1327,7 +1326,7 @@ static int iomap_unshare_iter(struct iomap_iter *iter,
>  
>  		ret = iomap_write_end(iter, bytes, bytes, folio);
>  		__iomap_put_folio(iter, write_ops, bytes, folio);
> -		if (WARN_ON_ONCE(!ret))
> +		if (WARN_ON_ONCE(ret != bytes))
>  			return -EIO;
>  
>  		cond_resched();
> @@ -1388,7 +1387,7 @@ static int iomap_zero_iter(struct iomap_iter *iter, bool *did_zero,
>  	do {
>  		struct folio *folio;
>  		size_t offset;
> -		bool ret;
> +		int ret;
>  
>  		bytes = min_t(u64, SIZE_MAX, bytes);
>  		status = iomap_write_begin(iter, write_ops, &folio, &offset,
> @@ -1406,7 +1405,7 @@ static int iomap_zero_iter(struct iomap_iter *iter, bool *did_zero,
>  
>  		ret = iomap_write_end(iter, bytes, bytes, folio);
>  		__iomap_put_folio(iter, write_ops, bytes, folio);
> -		if (WARN_ON_ONCE(!ret))
> +		if (WARN_ON_ONCE(ret != bytes))
>  			return -EIO;
>  
>  		status = iomap_iter_advance(iter, &bytes);
> -- 
> 2.49.0
> 
>