linux-kernel - Re: [PATCH] xen-blkfront: Use the bitmap API when applicable

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Date:   Thu, 2 Dec 2021 07:12:51 +0100
From:   Juergen Gross <jgross@...e.com>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        boris.ostrovsky@...cle.com, sstabellini@...nel.org,
        roger.pau@...rix.com, axboe@...nel.dk
Cc:     xen-devel@...ts.xenproject.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] xen-blkfront: Use the bitmap API when applicable

On 01.12.21 22:10, Christophe JAILLET wrote:
> Use 'bitmap_zalloc()' to simplify code, improve the semantic and avoid some
> open-coded arithmetic in allocator arguments.
> 
> Also change the corresponding 'kfree()' into 'bitmap_free()' to keep
> consistency.
> 
> Use 'bitmap_copy()' to avoid an explicit 'memcpy()'
> 
> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> ---
>   drivers/block/xen-blkfront.c | 8 +++-----
>   1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
> index 700c765a759a..fe4d69cf9469 100644
> --- a/drivers/block/xen-blkfront.c
> +++ b/drivers/block/xen-blkfront.c
> @@ -442,16 +442,14 @@ static int xlbd_reserve_minors(unsigned int minor, unsigned int nr)
>   	if (end > nr_minors) {
>   		unsigned long *bitmap, *old;
>   
> -		bitmap = kcalloc(BITS_TO_LONGS(end), sizeof(*bitmap),
> -				 GFP_KERNEL);
> +		bitmap = bitmap_zalloc(end, GFP_KERNEL);
>   		if (bitmap == NULL)
>   			return -ENOMEM;
>   
>   		spin_lock(&minor_lock);
>   		if (end > nr_minors) {
>   			old = minors;
> -			memcpy(bitmap, minors,
> -			       BITS_TO_LONGS(nr_minors) * sizeof(*bitmap));
> +			bitmap_copy(bitmap, minors, nr_minors);
>   			minors = bitmap;
>   			nr_minors = BITS_TO_LONGS(end) * BITS_PER_LONG;
>   		} else

Shouldn't you use bitmap_free(old) some lines down?

> @@ -2610,7 +2608,7 @@ static void __exit xlblk_exit(void)
>   
>   	xenbus_unregister_driver(&blkfront_driver);
>   	unregister_blkdev(XENVBD_MAJOR, DEV_NAME);
> -	kfree(minors);
> +	bitmap_free(minors);
>   }
>   module_exit(xlblk_exit);


Juergen


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