Re: [PATCH v3 7/9] iomap: use a new variable to handle the written bytes in iomap_write_iter()

["Darrick J. Wong" <djwong@kernel.org>]

On Tue, Mar 19, 2024 at 09:11:00AM +0800, Zhang Yi wrote:
> From: Zhang Yi <yi.zhang@huawei.com>
> 
> In iomap_write_iter(), the status variable used to receive the return
> value from iomap_write_end() is confusing, replace it with a new written
> variable to represent the written bytes in each cycle, no logic changes.
> 
> Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>

Looks good,
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> ---
>  fs/iomap/buffered-io.c | 33 +++++++++++++++++----------------
>  1 file changed, 17 insertions(+), 16 deletions(-)
> 
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index e9112dc78d15..291648c61a32 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -851,7 +851,7 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
>  	loff_t length = iomap_length(iter);
>  	size_t chunk = PAGE_SIZE << MAX_PAGECACHE_ORDER;
>  	loff_t pos = iter->pos;
> -	ssize_t written = 0;
> +	ssize_t total_written = 0;
>  	long status = 0;
>  	struct address_space *mapping = iter->inode->i_mapping;
>  	unsigned int bdp_flags = (iter->flags & IOMAP_NOWAIT) ? BDP_ASYNC : 0;
> @@ -862,6 +862,7 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
>  		size_t offset;		/* Offset into folio */
>  		size_t bytes;		/* Bytes to write to folio */
>  		size_t copied;		/* Bytes copied from user */
> +		size_t written;		/* Bytes have been written */
>  
>  		bytes = iov_iter_count(i);
>  retry:
> @@ -906,7 +907,7 @@ static loff_t 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);
> -		status = iomap_write_end(iter, pos, bytes, copied, folio);
> +		written = iomap_write_end(iter, pos, bytes, copied, folio);
>  
>  		/*
>  		 * Update the in-memory inode size after copying the data into
> @@ -916,22 +917,22 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
>  		 * unlock and release the folio.
>  		 */
>  		old_size = iter->inode->i_size;
> -		if (pos + status > old_size) {
> -			i_size_write(iter->inode, pos + status);
> +		if (pos + written > old_size) {
> +			i_size_write(iter->inode, pos + written);
>  			iter->iomap.flags |= IOMAP_F_SIZE_CHANGED;
>  		}
> -		__iomap_put_folio(iter, pos, status, folio);
> +		__iomap_put_folio(iter, pos, written, folio);
>  
>  		if (old_size < pos)
>  			pagecache_isize_extended(iter->inode, old_size, pos);
> -		if (status < bytes)
> -			iomap_write_failed(iter->inode, pos + status,
> -					   bytes - status);
> -		if (unlikely(copied != status))
> -			iov_iter_revert(i, copied - status);
> +		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(status == 0)) {
> +		if (unlikely(written == 0)) {
>  			/*
>  			 * A short copy made iomap_write_end() reject the
>  			 * thing entirely.  Might be memory poisoning
> @@ -945,17 +946,17 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
>  				goto retry;
>  			}
>  		} else {
> -			pos += status;
> -			written += status;
> -			length -= status;
> +			pos += written;
> +			total_written += written;
> +			length -= written;
>  		}
>  	} while (iov_iter_count(i) && length);
>  
>  	if (status == -EAGAIN) {
> -		iov_iter_revert(i, written);
> +		iov_iter_revert(i, total_written);
>  		return -EAGAIN;
>  	}
> -	return written ? written : status;
> +	return total_written ? total_written : status;
>  }
>  
>  ssize_t
> -- 
> 2.39.2
> 
>