[PATCH 0/5] bitmap: align bitmap_find_next_zero_area_off() output with the rest of the API

[PATCH 0/5] bitmap: align bitmap_find_next_zero_area_off() output with the rest of the API

[Yury Norov]

Bitmap search functions return a value greater than or equal to nbits when
no suitable bits are found. bitmap_find_next_zero_area_off() is an
exception: it returns a value greater than nbits.

Align the function with the rest of the API and adjust the affected callers
accordingly.

Patches 1-4 are sent only to their respective maintainers and mailing
lists. Patch 5 and the cover letter are sent to all recipients.

On top of -next. I plan to carry the series with bitmap-for-next.

Yury Norov (5):
  ARM: dma-mapping: Treat bitmap size as allocation failure
  powerpc/msi: Treat bitmap size as allocation failure
  crypto: ccp: Treat bitmap size as allocation failure
  media: s5p-mfc: Treat bitmap size as allocation failure
  bitmap: Return size when no zero area is found

 arch/arm/mm/dma-mapping.c                            |  4 ++--
 arch/powerpc/sysdev/msi_bitmap.c                     |  2 +-
 drivers/crypto/ccp/ccp-dev-v3.c                      |  2 +-
 drivers/crypto/ccp/ccp-dev-v5.c                      |  6 +++---
 drivers/media/platform/samsung/s5p-mfc/s5p_mfc_opr.c |  2 +-
 include/linux/bitmap.h                               |  3 +++
 lib/bitmap.c                                         | 10 ++++------
 7 files changed, 15 insertions(+), 14 deletions(-)

-- 
2.53.0

[PATCH 2/5] powerpc/msi: Treat bitmap size as allocation failure

[Yury Norov]

bitmap_find_next_zero_area() uses an out-of-range return value to
indicate failure. Check for values greater than or equal to the bitmap
size so the caller does not depend on the exact failure sentinel.

Signed-off-by: Yury Norov <ynorov@nvidia.com>
---
 arch/powerpc/sysdev/msi_bitmap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/sysdev/msi_bitmap.c b/arch/powerpc/sysdev/msi_bitmap.c
index 456a4f64ae0a..2f38d4b41ad3 100644
--- a/arch/powerpc/sysdev/msi_bitmap.c
+++ b/arch/powerpc/sysdev/msi_bitmap.c
@@ -21,7 +21,7 @@ int msi_bitmap_alloc_hwirqs(struct msi_bitmap *bmp, int num)
 
 	offset = bitmap_find_next_zero_area(bmp->bitmap, bmp->irq_count, 0,
 					    num, (1 << order) - 1);
-	if (offset > bmp->irq_count)
+	if (offset >= bmp->irq_count)
 		goto err;
 
 	bitmap_set(bmp->bitmap, offset, num);
-- 
2.53.0

Re: [PATCH 2/5] powerpc/msi: Treat bitmap size as allocation failure

[Madhavan Srinivasan]

On 7/9/26 7:33 AM, Yury Norov wrote:
> bitmap_find_next_zero_area() uses an out-of-range return value to
> indicate failure. Check for values greater than or equal to the bitmap
> size so the caller does not depend on the exact failure sentinel.
Changes seems to fine.
Acked-by: Madhavan Srinivasan <maddy@linux.ibm.com>

When reviewing this, I did find the return value of 
bitmap_find_next_zero_area
to be unsigned long, but we are casting it to int. Not as concern at 
this point
this will be an issue when irq_count exceeds. May be a follow patch is 
needed
to fix this I guess.
Maddy

> Signed-off-by: Yury Norov <ynorov@nvidia.com>
> ---
>   arch/powerpc/sysdev/msi_bitmap.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/sysdev/msi_bitmap.c b/arch/powerpc/sysdev/msi_bitmap.c
> index 456a4f64ae0a..2f38d4b41ad3 100644
> --- a/arch/powerpc/sysdev/msi_bitmap.c
> +++ b/arch/powerpc/sysdev/msi_bitmap.c
> @@ -21,7 +21,7 @@ int msi_bitmap_alloc_hwirqs(struct msi_bitmap *bmp, int num)
>   
>   	offset = bitmap_find_next_zero_area(bmp->bitmap, bmp->irq_count, 0,
>   					    num, (1 << order) - 1);
> -	if (offset > bmp->irq_count)
> +	if (offset >= bmp->irq_count)
>   		goto err;
>   
>   	bitmap_set(bmp->bitmap, offset, num);

[PATCH 5/5] bitmap: Return size when no zero area is found

[Yury Norov]

Return the bitmap size, rather than size + 1, when
bitmap_find_next_zero_area_off() cannot find a suitable area. This
matches the conventional find_bit() failure sentinel and still lets
callers detect failure with an out-of-range check.

Document the public failure contract as a value greater than or equal
to the bitmap size, without requiring callers to depend on the exact
sentinel.

Signed-off-by: Yury Norov <ynorov@nvidia.com>
---
 include/linux/bitmap.h |  3 +++
 lib/bitmap.c           | 10 ++++------
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index 8854acf77869..33f175a30304 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -209,6 +209,9 @@ unsigned long bitmap_find_next_zero_area_off(unsigned long *map,
  * The @align_mask should be one less than a power of 2; the effect is that
  * the bit offset of all zero areas this function finds is multiples of that
  * power of 2. A @align_mask of 0 means no alignment is required.
+ *
+ * Return: The bit offset of the found area or a value >= @size
+ * if no area is found.
  */
 static __always_inline
 unsigned long bitmap_find_next_zero_area(unsigned long *map,
diff --git a/lib/bitmap.c b/lib/bitmap.c
index b464d843f4eb..ed685127a107 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -424,6 +424,9 @@ EXPORT_SYMBOL(__bitmap_clear);
  * The @align_mask should be one less than a power of 2; the effect is that
  * the bit offset of all zero areas this function finds plus @align_offset
  * is multiple of that power of 2.
+ *
+ * Return: The bit offset of the found area or a value greater than or equal
+ * to @size if no area is found.
  */
 unsigned long bitmap_find_next_zero_area_off(unsigned long *map,
 					     unsigned long size,
@@ -448,12 +451,7 @@ unsigned long bitmap_find_next_zero_area_off(unsigned long *map,
 		start = i;
 	}
 
-	/*
-	 * Here, returning size + 1 is to maintain consistency
-	 * with the old version, where the return value is always
-	 * greater than size when no zero areas are found.
-	 */
-	return size + 1;
+	return size;
 }
 EXPORT_SYMBOL(bitmap_find_next_zero_area_off);
 
-- 
2.53.0

Re: [PATCH 0/5] bitmap: align bitmap_find_next_zero_area_off() output with the rest of the API

[Yury Norov]

OK, adding in bitmap-for-next. Thanks everyone for review!

Thanks,
Yury

On Wed, Jul 08, 2026 at 10:03:06PM -0400, Yury Norov wrote:
> Bitmap search functions return a value greater than or equal to nbits when
> no suitable bits are found. bitmap_find_next_zero_area_off() is an
> exception: it returns a value greater than nbits.
> 
> Align the function with the rest of the API and adjust the affected callers
> accordingly.
> 
> Patches 1-4 are sent only to their respective maintainers and mailing
> lists. Patch 5 and the cover letter are sent to all recipients.
> 
> On top of -next. I plan to carry the series with bitmap-for-next.
> 
> Yury Norov (5):
>   ARM: dma-mapping: Treat bitmap size as allocation failure
>   powerpc/msi: Treat bitmap size as allocation failure
>   crypto: ccp: Treat bitmap size as allocation failure
>   media: s5p-mfc: Treat bitmap size as allocation failure
>   bitmap: Return size when no zero area is found
> 
>  arch/arm/mm/dma-mapping.c                            |  4 ++--
>  arch/powerpc/sysdev/msi_bitmap.c                     |  2 +-
>  drivers/crypto/ccp/ccp-dev-v3.c                      |  2 +-
>  drivers/crypto/ccp/ccp-dev-v5.c                      |  6 +++---
>  drivers/media/platform/samsung/s5p-mfc/s5p_mfc_opr.c |  2 +-
>  include/linux/bitmap.h                               |  3 +++
>  lib/bitmap.c                                         | 10 ++++------
>  7 files changed, 15 insertions(+), 14 deletions(-)
> 
> -- 
> 2.53.0