mm: adjust out-dated document of __GFP_NOFAIL

[Patch v2] mm: adjust out-dated document of __GFP_NOFAIL

Posted by Wei Yang 4 weeks ago

Commit ee040cbd6e48 ("mm/page_alloc: don't warn about large allocations
with __GFP_NOFAIL") remove a warning on allocating large folio with
__GFP_NOFAIL, which was placed there by commit 903edea6c53f ("mm: warn
about illegal __GFP_NOFAIL usage in a more appropriate location and
manner").

While in that commit, it also documented this behavior which is
out-dated now.

Adjust the document to align to current code, and adjust the comment
while at it.

Signed-off-by: Wei Yang <richard.weiyang@gmail.com>

---
v2:
  * s/is adjusted/was placed there/ in change log
  * instead of removing the document, say "is discouraged"

v1: https://lore.kernel.org/all/20260827030548.16631-1-richard.weiyang@gmail.com/T/#u
---
 include/linux/gfp_types.h | 2 +-
 mm/page_alloc.c           | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/gfp_types.h b/include/linux/gfp_types.h
index 190191411009..bfd4c43ed777 100644
--- a/include/linux/gfp_types.h
+++ b/include/linux/gfp_types.h
@@ -244,7 +244,7 @@ enum {
  * definitely preferable to use the flag rather than opencode endless
  * loop around allocator.
  * Allocating pages from the buddy with __GFP_NOFAIL and order > 1 is
- * not supported. Please consider using kvmalloc() instead.
+ * discouraged. Please consider using kvmalloc() instead if possible.
  */
 #define __GFP_IO	((__force gfp_t)___GFP_IO)
 #define __GFP_FS	((__force gfp_t)___GFP_FS)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ab385bc252cc..146f7e0a9462 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4804,7 +4804,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
 
 	if (unlikely(nofail)) {
 		/*
-		 * Also we don't support __GFP_NOFAIL without __GFP_DIRECT_RECLAIM,
+		 * We don't support __GFP_NOFAIL without __GFP_DIRECT_RECLAIM,
 		 * otherwise, we may result in lockup.
 		 */
 		WARN_ON_ONCE(!can_direct_reclaim);
-- 
2.34.1

Re: [Patch v2] mm: adjust out-dated document of __GFP_NOFAIL

Posted by Zi Yan 3 weeks, 5 days ago

On Fri Aug 28, 2026 at 10:58 PM EDT, Wei Yang wrote:
> Commit ee040cbd6e48 ("mm/page_alloc: don't warn about large allocations
> with __GFP_NOFAIL") remove a warning on allocating large folio with
> __GFP_NOFAIL, which was placed there by commit 903edea6c53f ("mm: warn
> about illegal __GFP_NOFAIL usage in a more appropriate location and
> manner").
>
> While in that commit, it also documented this behavior which is
> out-dated now.
>
> Adjust the document to align to current code, and adjust the comment
> while at it.
>
> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
>
> ---
> v2:
>   * s/is adjusted/was placed there/ in change log
>   * instead of removing the document, say "is discouraged"
>
> v1: https://lore.kernel.org/all/20260827030548.16631-1-richard.weiyang@gmail.com/T/#u
> ---
>  include/linux/gfp_types.h | 2 +-
>  mm/page_alloc.c           | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
>
LGTM.

Reviewed-by: Zi Yan <ziy@nvidia.com>


-- 
Best Regards,
Yan, Zi

Re: [Patch v2] mm: adjust out-dated document of __GFP_NOFAIL

Posted by Lorenzo Stoakes (ARM) 3 weeks, 5 days ago

On Sat, Aug 29, 2026 at 02:58:47AM +0000, Wei Yang wrote:
> Commit ee040cbd6e48 ("mm/page_alloc: don't warn about large allocations
> with __GFP_NOFAIL") remove a warning on allocating large folio with
> __GFP_NOFAIL, which was placed there by commit 903edea6c53f ("mm: warn
> about illegal __GFP_NOFAIL usage in a more appropriate location and
> manner").
>
> While in that commit, it also documented this behavior which is
> out-dated now.
>
> Adjust the document to align to current code, and adjust the comment
> while at it.
>
> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>

LGTM so:

Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>

>
> ---
> v2:
>   * s/is adjusted/was placed there/ in change log
>   * instead of removing the document, say "is discouraged"
>
> v1: https://lore.kernel.org/all/20260827030548.16631-1-richard.weiyang@gmail.com/T/#u
> ---
>  include/linux/gfp_types.h | 2 +-
>  mm/page_alloc.c           | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/gfp_types.h b/include/linux/gfp_types.h
> index 190191411009..bfd4c43ed777 100644
> --- a/include/linux/gfp_types.h
> +++ b/include/linux/gfp_types.h
> @@ -244,7 +244,7 @@ enum {
>   * definitely preferable to use the flag rather than opencode endless
>   * loop around allocator.
>   * Allocating pages from the buddy with __GFP_NOFAIL and order > 1 is
> - * not supported. Please consider using kvmalloc() instead.
> + * discouraged. Please consider using kvmalloc() instead if possible.
>   */
>  #define __GFP_IO	((__force gfp_t)___GFP_IO)
>  #define __GFP_FS	((__force gfp_t)___GFP_FS)
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index ab385bc252cc..146f7e0a9462 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -4804,7 +4804,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
>
>  	if (unlikely(nofail)) {
>  		/*
> -		 * Also we don't support __GFP_NOFAIL without __GFP_DIRECT_RECLAIM,
> +		 * We don't support __GFP_NOFAIL without __GFP_DIRECT_RECLAIM,
>  		 * otherwise, we may result in lockup.
>  		 */
>  		WARN_ON_ONCE(!can_direct_reclaim);
> --
> 2.34.1
>

--
Cheers, Lorenzo

Re: [Patch v2] mm: adjust out-dated document of __GFP_NOFAIL

Posted by Vlastimil Babka (SUSE) 3 weeks, 5 days ago

On 8/29/26 04:58, Wei Yang wrote:
> Commit ee040cbd6e48 ("mm/page_alloc: don't warn about large allocations
> with __GFP_NOFAIL") remove a warning on allocating large folio with
> __GFP_NOFAIL, which was placed there by commit 903edea6c53f ("mm: warn
> about illegal __GFP_NOFAIL usage in a more appropriate location and
> manner").
> 
> While in that commit, it also documented this behavior which is
> out-dated now.
> 
> Adjust the document to align to current code, and adjust the comment
> while at it.
> 
> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>

Reviewed-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>

> 
> ---
> v2:
>   * s/is adjusted/was placed there/ in change log
>   * instead of removing the document, say "is discouraged"
> 
> v1: https://lore.kernel.org/all/20260827030548.16631-1-richard.weiyang@gmail.com/T/#u
> ---
>  include/linux/gfp_types.h | 2 +-
>  mm/page_alloc.c           | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/gfp_types.h b/include/linux/gfp_types.h
> index 190191411009..bfd4c43ed777 100644
> --- a/include/linux/gfp_types.h
> +++ b/include/linux/gfp_types.h
> @@ -244,7 +244,7 @@ enum {
>   * definitely preferable to use the flag rather than opencode endless
>   * loop around allocator.
>   * Allocating pages from the buddy with __GFP_NOFAIL and order > 1 is
> - * not supported. Please consider using kvmalloc() instead.
> + * discouraged. Please consider using kvmalloc() instead if possible.
>   */
>  #define __GFP_IO	((__force gfp_t)___GFP_IO)
>  #define __GFP_FS	((__force gfp_t)___GFP_FS)
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index ab385bc252cc..146f7e0a9462 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -4804,7 +4804,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
>  
>  	if (unlikely(nofail)) {
>  		/*
> -		 * Also we don't support __GFP_NOFAIL without __GFP_DIRECT_RECLAIM,
> +		 * We don't support __GFP_NOFAIL without __GFP_DIRECT_RECLAIM,
>  		 * otherwise, we may result in lockup.
>  		 */
>  		WARN_ON_ONCE(!can_direct_reclaim);