Re: [PATCH 04/34] fs: remove the buffer_unwritten check in page_seek_hole_data

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Wed, May 23, 2018 at 04:43:27PM +0200, Christoph Hellwig wrote:
> We only call into this function through the iomap iterators, so we already
> know the buffer is unwritten.  In addition to that we always require the
> uptodate flag that is ORed with the result anyway.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Looks ok, though it took me a while to dig through all the twisty
bits...

Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

--D

> ---
>  fs/iomap.c | 13 ++++---------
>  1 file changed, 4 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/iomap.c b/fs/iomap.c
> index 4a01d2f4e8e9..bef5e91d40bf 100644
> --- a/fs/iomap.c
> +++ b/fs/iomap.c
> @@ -611,14 +611,9 @@ page_seek_hole_data(struct page *page, loff_t lastoff, int whence)
>  			continue;
>  
>  		/*
> -		 * Unwritten extents that have data in the page cache covering
> -		 * them can be identified by the BH_Unwritten state flag.
> -		 * Pages with multiple buffers might have a mix of holes, data
> -		 * and unwritten extents - any buffer with valid data in it
> -		 * should have BH_Uptodate flag set on it.
> +		 * Any buffer with valid data in it should have BH_Uptodate set.
>  		 */
> -
> -		if ((buffer_unwritten(bh) || buffer_uptodate(bh)) == seek_data)
> +		if (buffer_uptodate(bh) == seek_data)
>  			return lastoff;
>  
>  		lastoff = offset;
> @@ -630,8 +625,8 @@ page_seek_hole_data(struct page *page, loff_t lastoff, int whence)
>   * Seek for SEEK_DATA / SEEK_HOLE in the page cache.
>   *
>   * Within unwritten extents, the page cache determines which parts are holes
> - * and which are data: unwritten and uptodate buffer heads count as data;
> - * everything else counts as a hole.
> + * and which are data: uptodate buffer heads count as data; everything else
> + * counts as a hole.
>   *
>   * Returns the resulting offset on successs, and -ENOENT otherwise.
>   */
> -- 
> 2.17.0
> 
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