linux-kernel - [PATCH v3] mm: slub: only warn once when allocating slab obj extensions fails

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Message-ID: <20250523165240.1477006-1-usamaarif642@gmail.com>
Date: Fri, 23 May 2025 17:52:40 +0100
From: Usama Arif <usamaarif642@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
	surenb@...gle.com
Cc: hannes@...xchg.org,
	shakeel.butt@...ux.dev,
	vlad.wing@...il.com,
	linux-mm@...ck.org,
	kent.overstreet@...ux.dev,
	cl@...two.org,
	rientjes@...gle.com,
	vbabka@...e.cz,
	roman.gushchin@...ux.dev,
	harry.yoo@...cle.com,
	linux-kernel@...r.kernel.org,
	kernel-team@...a.com,
	Usama Arif <usamaarif642@...il.com>
Subject: [PATCH v3] mm: slub: only warn once when allocating slab obj extensions fails

In memory bound systems, a large number of warnings for failing this
allocation repeatedly may mask any real issues in the system
during memory pressure being reported in dmesg. Change this to
warning only once.

Signed-off-by: Usama Arif <usamaarif642@...il.com>
Reported-by: Vlad Poenaru <vlad.wing@...il.com>
Closes: https://lore.kernel.org/all/17fab2d6-5a74-4573-bcc3-b75951508f0a@gmail.com/
---
v2 -> v3:
- Put warning back, but only warn once with pr_warn_once.
v1 -> v2:
- remove the warning completely. We will have a way in the
  future to indicate that the mem alloc profile is inaccurate.
---
 mm/slub.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index dc9e729e1d26..36d7c43a6f2a 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2102,10 +2102,12 @@ prepare_slab_obj_exts_hook(struct kmem_cache *s, gfp_t flags, void *p)
 
 	slab = virt_to_slab(p);
 	if (!slab_obj_exts(slab) &&
-	    WARN(alloc_slab_obj_exts(slab, s, flags, false),
-		 "%s, %s: Failed to create slab extension vector!\n",
-		 __func__, s->name))
+	    alloc_slab_obj_exts(slab, s, flags, false)) {
+		pr_warn_once("%s, %s: Failed to create slab extension vector!\n",
+			__func__, s->name);
 		return NULL;
+	}
+
 
 	return slab_obj_exts(slab) + obj_to_index(s, slab, p);
 }
-- 
2.47.1