linux-kernel - [PATCH 7/9] mm, slub: introduce kmem_cache_debug

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Date:   Wed, 10 Jun 2020 18:31:33 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        kernel-team@...roid.com, vinmenon@...eaurora.org,
        Kees Cook <keescook@...omium.org>,
        Matthew Garrett <mjg59@...gle.com>,
        Roman Gushchin <guro@...com>, Vlastimil Babka <vbabka@...e.cz>,
        Jann Horn <jannh@...gle.com>,
        Vijayanand Jitta <vjitta@...eaurora.org>
Subject: [PATCH 7/9] mm, slub: introduce kmem_cache_debug_flags()

There are few places that call kmem_cache_debug(s) (which tests if any of debug
flags are enabled for a cache) immediatelly followed by a test for a specific
flag. The compiler can probably eliminate the extra check, but we can make the
code nicer by introducing kmem_cache_debug_flags() that works like
kmem_cache_debug() (including the static key check) but tests for specifig
flag(s). The next patches will add more users.

Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
 mm/slub.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 24d3e5f832aa..c8e8b4ae2451 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -122,18 +122,28 @@ DEFINE_STATIC_KEY_FALSE(slub_debug_enabled);
 #endif
 #endif
 
-static inline int kmem_cache_debug(struct kmem_cache *s)
+/*
+ * Returns true if any of the specified slub_debug flags is enabled for the
+ * cache. Use only for flags parsed by setup_slub_debug() as it also enables
+ * the static key.
+ */
+static inline int kmem_cache_debug_flags(struct kmem_cache *s, slab_flags_t flags)
 {
 #ifdef CONFIG_SLUB_DEBUG
 	if (static_branch_unlikely(&slub_debug_enabled))
-		return s->flags & SLAB_DEBUG_FLAGS;
+		return s->flags & flags;
 #endif
 	return 0;
 }
 
+static inline int kmem_cache_debug(struct kmem_cache *s)
+{
+	return kmem_cache_debug_flags(s, SLAB_DEBUG_FLAGS);
+}
+
 void *fixup_red_left(struct kmem_cache *s, void *p)
 {
-	if (kmem_cache_debug(s) && s->flags & SLAB_RED_ZONE)
+	if (kmem_cache_debug_flags(s, SLAB_RED_ZONE))
 		p += s->red_left_pad;
 
 	return p;
@@ -4076,7 +4086,7 @@ void __check_heap_object(const void *ptr, unsigned long n, struct page *page,
 	offset = (ptr - page_address(page)) % s->size;
 
 	/* Adjust for redzone and reject if within the redzone. */
-	if (kmem_cache_debug(s) && s->flags & SLAB_RED_ZONE) {
+	if (kmem_cache_debug_flags(s, SLAB_RED_ZONE)) {
 		if (offset < s->red_left_pad)
 			usercopy_abort("SLUB object in left red zone",
 				       s->name, to_user, offset, n);
-- 
2.26.2