linux-kernel - [PATCH RESEND] mm: Restructure kmem_cache_create() to move debug cache integrity checks into a new function

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Date:	Mon, 06 Aug 2012 09:14:56 -0600
From:	Shuah Khan <shuah.khan@...com>
To:	Pekka Enberg <penberg@...nel.org>
Cc:	cl@...ux.com, glommer@...allels.com, js1304@...il.com,
	linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>, shuahkhan@...il.com
Subject: [PATCH RESEND] mm: Restructure kmem_cache_create() to move debug
 cache integrity checks into a new function

kmem_cache_create() does cache integrity checks when CONFIG_DEBUG_VM
is defined. These checks interspersed with the regular code path has
lead to compile time warnings when compiled without CONFIG_DEBUG_VM
defined. Restructuring the code to move the integrity checks in to a new
function would eliminate the current compile warning problem and also
will allow for future changes to the debug only code to evolve without
introducing new warnings in the regular path. This restructuring work
is based on the discussion in the following thread:

https://lkml.org/lkml/2012/7/13/424

Signed-off-by: Shuah Khan <shuah.khan@...com>
---
 mm/slab_common.c |   74 ++++++++++++++++++++++++++++--------------------------
 1 file changed, 38 insertions(+), 36 deletions(-)

diff --git a/mm/slab_common.c b/mm/slab_common.c
index 12637ce..08bc2a4 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -23,6 +23,41 @@ enum slab_state slab_state;
 LIST_HEAD(slab_caches);
 DEFINE_MUTEX(slab_mutex);
 
+static int kmem_cache_sanity_check(const char *name, size_t size)
+{
+#ifdef CONFIG_DEBUG_VM
+	struct kmem_cache *s = NULL;
+
+	list_for_each_entry(s, &slab_caches, list) {
+		char tmp;
+		int res;
+
+		/*
+		 * This happens when the module gets unloaded and doesn't
+		 * destroy its slab cache and no-one else reuses the vmalloc
+		 * area of the module.  Print a warning.
+		 */
+		res = probe_kernel_address(s->name, tmp);
+		if (res) {
+			pr_err("Slab cache with size %d has lost its name\n",
+			       s->object_size);
+			continue;
+		}
+
+		if (!strcmp(s->name, name)) {
+			pr_err("%s (%s): Cache name already exists.\n",
+			       __func__, name);
+			dump_stack();
+			s = NULL;
+			return -EINVAL;
+		}
+	}
+
+	WARN_ON(strchr(name, ' '));	/* It confuses parsers */
+#endif
+	return 0;
+}
+
 /*
  * kmem_cache_create - Create a cache.
  * @name: A string which is used in /proc/slabinfo to identify this cache.
@@ -53,48 +88,17 @@ struct kmem_cache *kmem_cache_create(const char *name, size_t size, size_t align
 {
 	struct kmem_cache *s = NULL;
 
-#ifdef CONFIG_DEBUG_VM
 	if (!name || in_interrupt() || size < sizeof(void *) ||
 		size > KMALLOC_MAX_SIZE) {
-		printk(KERN_ERR "kmem_cache_create(%s) integrity check"
-			" failed\n", name);
+		pr_err("kmem_cache_create(%s) integrity check failed\n", name);
 		goto out;
 	}
-#endif
 
 	get_online_cpus();
 	mutex_lock(&slab_mutex);
 
-#ifdef CONFIG_DEBUG_VM
-	list_for_each_entry(s, &slab_caches, list) {
-		char tmp;
-		int res;
-
-		/*
-		 * This happens when the module gets unloaded and doesn't
-		 * destroy its slab cache and no-one else reuses the vmalloc
-		 * area of the module.  Print a warning.
-		 */
-		res = probe_kernel_address(s->name, tmp);
-		if (res) {
-			printk(KERN_ERR
-			       "Slab cache with size %d has lost its name\n",
-			       s->object_size);
-			continue;
-		}
-
-		if (!strcmp(s->name, name)) {
-			printk(KERN_ERR "kmem_cache_create(%s): Cache name"
-				" already exists.\n",
-				name);
-			dump_stack();
-			s = NULL;
-			goto oops;
-		}
-	}
-
-	WARN_ON(strchr(name, ' '));	/* It confuses parsers */
-#endif
+	if (kmem_cache_sanity_check(name, size))
+		goto oops;
 
 	s = __kmem_cache_create(name, size, align, flags, ctor);
 
@@ -102,9 +106,7 @@ oops:
 	mutex_unlock(&slab_mutex);
 	put_online_cpus();
 
-#ifdef CONFIG_DEBUG_VM
 out:
-#endif
 	if (!s && (flags & SLAB_PANIC))
 		panic("kmem_cache_create: Failed to create slab '%s'\n", name);
 
-- 
1.7.9.5



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