Re: [PATCH v3 02/16] iomap: cleanup the pending writeback tracking in iomap_writepage_map_blocks

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

On Mon, Jun 23, 2025 at 07:21:21PM -0700, Joanne Koong wrote:
> We don't care about the count of outstanding ioends, just if there is one.
> Replace the count variable passed to iomap_writepage_map_blocks with a
> boolean to make that more clear.
> 
> Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
> [hch: rename the variable, update the commit message]
> Signed-off-by: Christoph Hellwig <hch@lst.de>

/methinks this also fixes a theoretical logic bug if *count should
ever overflow back to zero so

Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> ---
>  fs/iomap/buffered-io.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index 71ad17bf827f..11a55da26a6f 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -1758,7 +1758,7 @@ static int iomap_add_to_ioend(struct iomap_writepage_ctx *wpc,
>  
>  static int iomap_writepage_map_blocks(struct iomap_writepage_ctx *wpc,
>  		struct folio *folio, u64 pos, u64 end_pos, unsigned dirty_len,
> -		unsigned *count)
> +		bool *wb_pending)
>  {
>  	int error;
>  
> @@ -1786,7 +1786,7 @@ static int iomap_writepage_map_blocks(struct iomap_writepage_ctx *wpc,
>  			error = iomap_add_to_ioend(wpc, folio, pos, end_pos,
>  					map_len);
>  			if (!error)
> -				(*count)++;
> +				*wb_pending = true;
>  			break;
>  		}
>  		dirty_len -= map_len;
> @@ -1873,7 +1873,7 @@ static int iomap_writepage_map(struct iomap_writepage_ctx *wpc,
>  	u64 pos = folio_pos(folio);
>  	u64 end_pos = pos + folio_size(folio);
>  	u64 end_aligned = 0;
> -	unsigned count = 0;
> +	bool wb_pending = false;
>  	int error = 0;
>  	u32 rlen;
>  
> @@ -1917,13 +1917,13 @@ static int iomap_writepage_map(struct iomap_writepage_ctx *wpc,
>  	end_aligned = round_up(end_pos, i_blocksize(inode));
>  	while ((rlen = iomap_find_dirty_range(folio, &pos, end_aligned))) {
>  		error = iomap_writepage_map_blocks(wpc, folio, pos, end_pos,
> -				rlen, &count);
> +				rlen, &wb_pending);
>  		if (error)
>  			break;
>  		pos += rlen;
>  	}
>  
> -	if (count)
> +	if (wb_pending)
>  		wpc->nr_folios++;
>  
>  	/*
> @@ -1945,7 +1945,7 @@ static int iomap_writepage_map(struct iomap_writepage_ctx *wpc,
>  		if (atomic_dec_and_test(&ifs->write_bytes_pending))
>  			folio_end_writeback(folio);
>  	} else {
> -		if (!count)
> +		if (!wb_pending)
>  			folio_end_writeback(folio);
>  	}
>  	mapping_set_error(inode->i_mapping, error);
> -- 
> 2.47.1
> 
>