linux-kernel - Re: [PATCH] xfs: Use kmem_zalloc for bp->b

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Date:   Sat, 9 Mar 2019 09:32:30 -0800
From:   "Darrick J. Wong" <darrick.wong@...cle.com>
To:     Sean Fu <fxinrong@...il.com>
Cc:     linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] xfs: Use kmem_zalloc for bp->b_pages.

On Sat, Mar 09, 2019 at 11:36:36PM +0800, Sean Fu wrote:
> Change the allocation of bp->b_pages to use kmem_zalloc instead of
> kmem_alloc.
> Remove unnecessary memset for bp->b_pages.
> 
> This reduces text size by 42 bytes.
> Before:
>    text	   data	    bss	    dec	    hex	filename
>   23335	    588	      8	  23931	   5d7b	./fs/xfs/xfs_buf.o
> After:
>    text	   data	    bss	    dec	    hex	filename
>   23293	    588	      8	  23889	   5d51	./fs/xfs/xfs_buf.o
> 
> Signed-off-by: Sean Fu <fxinrong@...il.com>
> ---
>  fs/xfs/xfs_buf.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
> index 4f5f2ff3f70f..be4f740b97c1 100644
> --- a/fs/xfs/xfs_buf.c
> +++ b/fs/xfs/xfs_buf.c
> @@ -289,12 +289,11 @@ _xfs_buf_get_pages(
>  		if (page_count <= XB_PAGES) {
>  			bp->b_pages = bp->b_page_array;
>  		} else {
> -			bp->b_pages = kmem_alloc(sizeof(struct page *) *
> +			bp->b_pages = kmem_zalloc(sizeof(struct page *) *
>  						 page_count, KM_NOFS);
>  			if (bp->b_pages == NULL)
>  				return -ENOMEM;
>  		}
> -		memset(bp->b_pages, 0, sizeof(struct page *) * page_count);

Does this leave b_pages uninitialized in the page_count <= XB_PAGES
case?

--D

>  	}
>  	return 0;
>  }
> -- 
> 2.16.4
>