[PATCH 1/1] x86/mm: fix spurious warning on __add_pages() failure

[PATCH 1/1] x86/mm: fix spurious warning on __add_pages() failure

[Lance Yang]

__add_pages() can fail if we run out of memory. The caller already
handles that, so we shouldn't WARN_ON_ONCE() just because an allocation
failed.

Let's return the error instead, and only update the end-of-memory
variables after __add_pages() succeeds.

Fixes: 10f22dde556d ("x86: arch/x86/mm/init_64.c printk fixes")
Reported-by: David Hildenbrand <david@kernel.org>
Link: https://lore.kernel.org/all/d4fac8af-fd71-47a2-bfe9-3c6559b92209@kernel.org/
Suggested-by: Muchun Song <muchun.song@linux.dev>
Link: https://lore.kernel.org/all/203892F4-B04A-4F69-A1B3-DC1619176C67@linux.dev/
Signed-off-by: Lance Yang <lance.yang@linux.dev>
---
 arch/x86/mm/init_64.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 70e682180291a..8b6d86fb5a42e 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -970,7 +970,8 @@ int add_pages(int nid, unsigned long start_pfn, unsigned long nr_pages,
 		return -ERANGE;
 
 	ret = __add_pages(nid, start_pfn, nr_pages, params);
-	WARN_ON_ONCE(ret);
+	if (ret)
+		return ret;
 
 	/*
 	 * Special case: add_pages() is called by memremap_pages() for adding device
-- 
2.49.0

Re: [PATCH 1/1] x86/mm: fix spurious warning on __add_pages() failure

[Muchun Song]

> On Oct 1, 2026, at 16:15, Lance Yang <lance.yang@linux.dev> wrote:
> 
> __add_pages() can fail if we run out of memory. The caller already
> handles that, so we shouldn't WARN_ON_ONCE() just because an allocation
> failed.
> 
> Let's return the error instead, and only update the end-of-memory
> variables after __add_pages() succeeds.
> 
> Fixes: 10f22dde556d ("x86: arch/x86/mm/init_64.c printk fixes")
> Reported-by: David Hildenbrand <david@kernel.org>
> Link: https://lore.kernel.org/all/d4fac8af-fd71-47a2-bfe9-3c6559b92209@kernel.org/
> Suggested-by: Muchun Song <muchun.song@linux.dev>
> Link: https://lore.kernel.org/all/203892F4-B04A-4F69-A1B3-DC1619176C67@linux.dev/
> Signed-off-by: Lance Yang <lance.yang@linux.dev>

I noticed that __add_pages() already reports invalid parameters where
appropriate, while errors such as -ENOMEM can legitimately occur and
are propagated to the caller. Therefore, the additional
WARN_ON_ONCE(ret) in add_pages() seems unnecessary to me.

The change looks reasonable.

Acked-by: Muchun Song <muchun.song@linux.dev>

Re: [PATCH 1/1] x86/mm: fix spurious warning on __add_pages() failure

[David Hildenbrand (Arm)]

On 10/1/26 10:15, Lance Yang wrote:
> __add_pages() can fail if we run out of memory. The caller already
> handles that, so we shouldn't WARN_ON_ONCE() just because an allocation
> failed.
> 
> Let's return the error instead, and only update the end-of-memory
> variables after __add_pages() succeeds.
> 
> Fixes: 10f22dde556d ("x86: arch/x86/mm/init_64.c printk fixes")
> Reported-by: David Hildenbrand <david@kernel.org>
> Link: https://lore.kernel.org/all/d4fac8af-fd71-47a2-bfe9-3c6559b92209@kernel.org/
> Suggested-by: Muchun Song <muchun.song@linux.dev>
> Link: https://lore.kernel.org/all/203892F4-B04A-4F69-A1B3-DC1619176C67@linux.dev/
> Signed-off-by: Lance Yang <lance.yang@linux.dev>
> ---
>  arch/x86/mm/init_64.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> index 70e682180291a..8b6d86fb5a42e 100644
> --- a/arch/x86/mm/init_64.c
> +++ b/arch/x86/mm/init_64.c
> @@ -970,7 +970,8 @@ int add_pages(int nid, unsigned long start_pfn, unsigned long nr_pages,
>  		return -ERANGE;
>  
>  	ret = __add_pages(nid, start_pfn, nr_pages, params);
> -	WARN_ON_ONCE(ret);
> +	if (ret)
> +		return ret;
>  
>  	/*
>  	 * Special case: add_pages() is called by memremap_pages() for adding device

Reviewed-by: David Hildenbrand (Arm) <david@kernel.org>

-- 
Cheers,

David

[tip: x86/mm] x86/mm: Fix spurious warning on __add_pages() failure

[tip-bot2 for Lance Yang]

The following commit has been merged into the x86/mm branch of tip:

Commit-ID:     d92b5ac5aeba1ffc734576e30a5bca882722de76
Gitweb:        https://git.kernel.org/tip/d92b5ac5aeba1ffc734576e30a5bca882722de76
Author:        Lance Yang <lance.yang@linux.dev>
AuthorDate:    Thu, 01 Oct 2026 16:15:55 +08:00
Committer:     Dave Hansen <dave.hansen@linux.intel.com>
CommitterDate: Thu, 01 Oct 2026 05:04:44 -07:00

x86/mm: Fix spurious warning on __add_pages() failure

__add_pages() can fail if we run out of memory. Callers already handle
that. Do not WARN_ON_ONCE() just because an allocation failed.

Return the error instead, and only update the end-of-memory variables
after __add_pages() succeeds.

[ dhansen: imperative voice changelog fixups ]

Fixes: 10f22dde556d ("x86: arch/x86/mm/init_64.c printk fixes")
Reported-by: David Hildenbrand <david@kernel.org>
Suggested-by: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Lance Yang <lance.yang@linux.dev>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: David Hildenbrand (Arm) <david@kernel.org>
Acked-by: Muchun Song <muchun.song@linux.dev>
Link: https://lore.kernel.org/all/d4fac8af-fd71-47a2-bfe9-3c6559b92209@kernel.org/
Link: https://lore.kernel.org/all/203892F4-B04A-4F69-A1B3-DC1619176C67@linux.dev/
Link: https://patch.msgid.link/20261001081555.35485-1-lance.yang@linux.dev
---
 arch/x86/mm/init_64.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 70e6821..8b6d86f 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -970,7 +970,8 @@ int add_pages(int nid, unsigned long start_pfn, unsigned long nr_pages,
 		return -ERANGE;
 
 	ret = __add_pages(nid, start_pfn, nr_pages, params);
-	WARN_ON_ONCE(ret);
+	if (ret)
+		return ret;
 
 	/*
 	 * Special case: add_pages() is called by memremap_pages() for adding device