mm/slab_common: Improve error handling in kmem_cache_create

Instead of using s == NULL use an errorcode. This allows much more
detailed diagnostics as to what went wrong. As we add more functionality
from the slab allocators to the common kmem_cache_create() function we will
also add more error conditions.

Print the error code during the panic as well as in a warning if the module
can handle failure. The API for kmem_cache_create() currently does not allow
the returning of an error code. Return NULL but log the cause of the problem
in the syslog.

Reviewed-by: Glauber Costa <glommer@parallels.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

1 files changed, 24 insertions, 4 deletions

diff --git a/mm/slab_common.c b/mm/slab_common.c
index 8cf8b4962d6c..fe8dc943c285 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -98,16 +98,36 @@ struct kmem_cache *kmem_cache_create(const char *name, size_t size, size_t align
                 unsigned long flags, void (*ctor)(void *))
 {
         struct kmem_cache *s = NULL;
+        int err = 0;
 
         get_online_cpus();
         mutex_lock(&slab_mutex);
-        if (kmem_cache_sanity_check(name, size) == 0)
-                s = __kmem_cache_create(name, size, align, flags, ctor);
+
+        if (!kmem_cache_sanity_check(name, size) == 0)
+                goto out_locked;
+
+
+        s = __kmem_cache_create(name, size, align, flags, ctor);
+        if (!s)
+                err = -ENOSYS; /* Until __kmem_cache_create returns code */
+
+out_locked:
         mutex_unlock(&slab_mutex);
         put_online_cpus();
 
-        if (!s && (flags & SLAB_PANIC))
-                panic("kmem_cache_create: Failed to create slab '%s'\n", name);
+        if (err) {
+
+                if (flags & SLAB_PANIC)
+                        panic("kmem_cache_create: Failed to create slab '%s'. Error %d\n",
+                                name, err);
+                else {
+                        printk(KERN_WARNING "kmem_cache_create(%s) failed with error %d",
+                                name, err);
+                        dump_stack();
+                }
+
+                return NULL;
+        }
 
         return s;
 }