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

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Date:   Thu, 2 Dec 2021 19:12:01 +0100
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     Juergen Gross <jgross@...e.com>, 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

Le 02/12/2021 à 07:12, Juergen Gross a écrit :
> 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?

Obvious.
I'll send a V2, Thx for the review.

CJ

> 
>> @@ -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
>