Re: [PATCH 02/10] xfs: use xfs_buf_alloc_pages for uncached buffers

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

On Thu, May 27, 2021 at 08:47:14AM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
> 
> Use the newly factored out page allocation code. This adds
> automatic buffer zeroing for non-read uncached buffers.
> 
> This also allows us to greatly simply the error handling in
> xfs_buf_get_uncached(). Because xfs_buf_alloc_pages() cleans up
> partial allocation failure, we can just call xfs_buf_free() in all
> error cases now to clean up after failures.
> 
> Signed-off-by: Dave Chinner <dchinner@redhat.com>

Nice cleanup!
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> ---
>  fs/xfs/libxfs/xfs_ag.c |  1 -
>  fs/xfs/xfs_buf.c       | 27 ++++++---------------------
>  2 files changed, 6 insertions(+), 22 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_ag.c b/fs/xfs/libxfs/xfs_ag.c
> index c68a36688474..be0087825ae0 100644
> --- a/fs/xfs/libxfs/xfs_ag.c
> +++ b/fs/xfs/libxfs/xfs_ag.c
> @@ -43,7 +43,6 @@ xfs_get_aghdr_buf(
>  	if (error)
>  		return error;
>  
> -	xfs_buf_zero(bp, 0, BBTOB(bp->b_length));
>  	bp->b_bn = blkno;
>  	bp->b_maps[0].bm_bn = blkno;
>  	bp->b_ops = ops;
> diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
> index 2e35d344a69b..b1610115d401 100644
> --- a/fs/xfs/xfs_buf.c
> +++ b/fs/xfs/xfs_buf.c
> @@ -973,7 +973,7 @@ xfs_buf_get_uncached(
>  	struct xfs_buf		**bpp)
>  {
>  	unsigned long		page_count;
> -	int			error, i;
> +	int			error;
>  	struct xfs_buf		*bp;
>  	DEFINE_SINGLE_BUF_MAP(map, XFS_BUF_DADDR_NULL, numblks);
>  
> @@ -982,41 +982,26 @@ xfs_buf_get_uncached(
>  	/* flags might contain irrelevant bits, pass only what we care about */
>  	error = _xfs_buf_alloc(target, &map, 1, flags & XBF_NO_IOACCT, &bp);
>  	if (error)
> -		goto fail;
> +		return error;
>  
>  	page_count = PAGE_ALIGN(numblks << BBSHIFT) >> PAGE_SHIFT;
> -	error = _xfs_buf_get_pages(bp, page_count);
> +	error = xfs_buf_alloc_pages(bp, page_count, flags);
>  	if (error)
>  		goto fail_free_buf;
>  
> -	for (i = 0; i < page_count; i++) {
> -		bp->b_pages[i] = alloc_page(xb_to_gfp(flags));
> -		if (!bp->b_pages[i]) {
> -			error = -ENOMEM;
> -			goto fail_free_mem;
> -		}
> -	}
> -	bp->b_flags |= _XBF_PAGES;
> -
>  	error = _xfs_buf_map_pages(bp, 0);
>  	if (unlikely(error)) {
>  		xfs_warn(target->bt_mount,
>  			"%s: failed to map pages", __func__);
> -		goto fail_free_mem;
> +		goto fail_free_buf;
>  	}
>  
>  	trace_xfs_buf_get_uncached(bp, _RET_IP_);
>  	*bpp = bp;
>  	return 0;
>  
> - fail_free_mem:
> -	while (--i >= 0)
> -		__free_page(bp->b_pages[i]);
> -	_xfs_buf_free_pages(bp);
> - fail_free_buf:
> -	xfs_buf_free_maps(bp);
> -	kmem_cache_free(xfs_buf_zone, bp);
> - fail:
> +fail_free_buf:
> +	xfs_buf_free(bp);
>  	return error;
>  }
>  
> -- 
> 2.31.1
>