linux-kernel - [PATCH 4/6] slab: move validate_slab_ptr() from alloc_consistency

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Message-Id: <20250911-slub-slab-validation-v1-4-8b67eb3b3dc5@suse.cz>
Date: Thu, 11 Sep 2025 19:02:37 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: "Matthew Wilcox (Oracle)" <willy@...radead.org>
Cc: Harry Yoo <harry.yoo@...cle.com>, Christoph Lameter <cl@...two.org>, 
 David Rientjes <rientjes@...gle.com>, 
 Roman Gushchin <roman.gushchin@...ux.dev>, 
 Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org, 
 linux-kernel@...r.kernel.org, Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH 4/6] slab: move validate_slab_ptr() from
 alloc_consistency_checks() to its caller

In alloc_debug_processing() we can call validate_slab_ptr() upfront and
then don't need to recheck when alloc_consistency_checks() fails for
other reasons.

Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
 mm/slub.c | 30 ++++++++++++++----------------
 1 file changed, 14 insertions(+), 16 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 94a089205a86f0667444484e158d307e72cd96e1..909c71372a2f542b6e0d67c12ea683133b246b66 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1633,11 +1633,6 @@ void setup_slab_debug(struct kmem_cache *s, struct slab *slab, void *addr)
 static inline int alloc_consistency_checks(struct kmem_cache *s,
 					struct slab *slab, void *object)
 {
-	if (!validate_slab_ptr(slab)) {
-		slab_err(s, slab, "Not a valid slab page");
-		return 0;
-	}
-
 	if (!check_slab(s, slab))
 		return 0;
 
@@ -1656,6 +1651,11 @@ static noinline bool alloc_debug_processing(struct kmem_cache *s,
 			struct slab *slab, void *object, int orig_size)
 {
 	if (s->flags & SLAB_CONSISTENCY_CHECKS) {
+		if (!validate_slab_ptr(slab)) {
+			slab_err(s, slab, "Not a valid slab page");
+			return false;
+		}
+
 		if (!alloc_consistency_checks(s, slab, object))
 			goto bad;
 	}
@@ -1667,17 +1667,15 @@ static noinline bool alloc_debug_processing(struct kmem_cache *s,
 	return true;
 
 bad:
-	if (validate_slab_ptr(slab)) {
-		/*
-		 * If this is a slab page then lets do the best we can
-		 * to avoid issues in the future. Marking all objects
-		 * as used avoids touching the remaining objects.
-		 */
-		slab_fix(s, "Marking all objects used");
-		slab->inuse = slab->objects;
-		slab->freelist = NULL;
-		slab->frozen = 1; /* mark consistency-failed slab as frozen */
-	}
+	/*
+	 * Let's do the best we can to avoid issues in the future. Marking all
+	 * objects as used avoids touching the remaining objects.
+	 */
+	slab_fix(s, "Marking all objects used");
+	slab->inuse = slab->objects;
+	slab->freelist = NULL;
+	slab->frozen = 1; /* mark consistency-failed slab as frozen */
+
 	return false;
 }
 

-- 
2.51.0