[PATCH v2] xen-blkfront: Use the bitmap API when applicable

[PATCH v2] xen-blkfront: Use the bitmap API when applicable

[Christophe JAILLET]

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@wanadoo.fr>
---
v1 --> v2: change another kfree into bitmap_free
---
 drivers/block/xen-blkfront.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 700c765a759a..69cf13608ce0 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -442,22 +442,20 @@ 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
 			old = bitmap;
 		spin_unlock(&minor_lock);
-		kfree(old);
+		bitmap_free(old);
 	}
 
 	spin_lock(&minor_lock);
@@ -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);
 
-- 
2.30.2

Re: [PATCH v2] xen-blkfront: Use the bitmap API when applicable

[Roger Pau Monné]

On Thu, Dec 02, 2021 at 09:16:04PM +0100, 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@wanadoo.fr>

Acked-by: Roger Pau Monné <roger.pau@citrix.com>

Thanks, Roger.

Re: [PATCH v2] xen-blkfront: Use the bitmap API when applicable

[Roger Pau Monné]

On Tue, Dec 14, 2021 at 11:59:39AM +0100, Roger Pau Monné wrote:
> On Thu, Dec 02, 2021 at 09:16:04PM +0100, 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@wanadoo.fr>
> 
> Acked-by: Roger Pau Monné <roger.pau@citrix.com>

Oh, I see there's been further discussion on this to avoid relying
implicitly on the size of the bitmap being rounded to the size of an
unsigned long. I think a new version is expected then?

Thanks, Roger.

Re: [PATCH v2] xen-blkfront: Use the bitmap API when applicable

[Christophe JAILLET]

Le 14/12/2021 à 12:08, Roger Pau Monné a écrit :
> On Tue, Dec 14, 2021 at 11:59:39AM +0100, Roger Pau Monné wrote:
>> On Thu, Dec 02, 2021 at 09:16:04PM +0100, 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@wanadoo.fr>
>>
>> Acked-by: Roger Pau Monné <roger.pau@citrix.com>
> 
> Oh, I see there's been further discussion on this to avoid relying
> implicitly on the size of the bitmap being rounded to the size of an
> unsigned long. I think a new version is expected then?
> 
> Thanks, Roger.
> 

Yes, I'll send a patch in order to add a 'bitmap_size()'
I'll update this patch when/if it is merged.

You can drop it for now.

CJ