Commit 2ed3a4ef authored by Christoph Lameter's avatar Christoph Lameter Committed by Linus Torvalds
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[PATCH] slab: do not panic when alloc_kmemlist fails and slab is up

It is fairly easy to get a system to oops by simply sizing a cache via
/proc in such a way that one of the chaches (shared is easiest) becomes
bigger than the maximum allowed slab allocation size.  This occurs because
enable_cpucache() fails if it cannot reallocate some caches.

However, enable_cpucache() is used for multiple purposes: resizing caches,
cache creation and bootstrap.

If the slab is already up then we already have working caches.  The resize
can fail without a problem.  We just need to return the proper error code.
F.e.  after this patch:

# echo "size-64 10000 50 1000" >/proc/slabinfo
-bash: echo: write error: Cannot allocate memory

notice no OOPS.

If we are doing a kmem_cache_create() then we also should not panic but
return -ENOMEM.

If on the other hand we do not have a fully bootstrapped slab allocator yet
then we should indeed panic since we are unable to bring up the slab to its
full functionality.

Signed-off-by: default avatarChristoph Lameter <>
Cc: Pekka Enberg <>
Cc: Manfred Spraul <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 117f6eb1
......@@ -313,7 +313,7 @@ static int drain_freelist(struct kmem_cache *cache,
struct kmem_list3 *l3, int tofree);
static void free_block(struct kmem_cache *cachep, void **objpp, int len,
int node);
static void enable_cpucache(struct kmem_cache *cachep);
static int enable_cpucache(struct kmem_cache *cachep);
static void cache_reap(void *unused);
......@@ -1490,7 +1490,8 @@ void __init kmem_cache_init(void)
struct kmem_cache *cachep;
list_for_each_entry(cachep, &cache_chain, next)
if (enable_cpucache(cachep))
......@@ -1924,12 +1925,11 @@ static size_t calculate_slab_order(struct kmem_cache *cachep,
return left_over;
static void setup_cpu_cache(struct kmem_cache *cachep)
static int setup_cpu_cache(struct kmem_cache *cachep)
if (g_cpucache_up == FULL) {
if (g_cpucache_up == FULL)
return enable_cpucache(cachep);
if (g_cpucache_up == NONE) {
* Note: the first kmem_cache_create must create the cache
......@@ -1976,6 +1976,7 @@ static void setup_cpu_cache(struct kmem_cache *cachep)
cpu_cache_get(cachep)->touched = 0;
cachep->batchcount = 1;
cachep->limit = BOOT_CPUCACHE_ENTRIES;
return 0;
......@@ -2242,8 +2243,11 @@ kmem_cache_create (const char *name, size_t size, size_t align,
cachep->dtor = dtor;
cachep->name = name;
if (setup_cpu_cache(cachep)) {
cachep = NULL;
goto oops;
/* cache setup completed, link it into the list */
list_add(&cachep->next, &cache_chain);
......@@ -3693,7 +3697,7 @@ static int do_tune_cpucache(struct kmem_cache *cachep, int limit,
int batchcount, int shared)
struct ccupdate_struct new;
int i, err;
int i;
memset(&, 0, sizeof(;
for_each_online_cpu(i) {
......@@ -3724,17 +3728,11 @@ static int do_tune_cpucache(struct kmem_cache *cachep, int limit,
err = alloc_kmemlist(cachep);
if (err) {
printk(KERN_ERR "alloc_kmemlist failed for %s, error %d.\n",
cachep->name, -err);
return 0;
return alloc_kmemlist(cachep);
/* Called with cache_chain_mutex held always */
static void enable_cpucache(struct kmem_cache *cachep)
static int enable_cpucache(struct kmem_cache *cachep)
int err;
int limit, shared;
......@@ -3786,6 +3784,7 @@ static void enable_cpucache(struct kmem_cache *cachep)
if (err)
printk(KERN_ERR "enable_cpucache failed for %s, error %d.\n",
cachep->name, -err);
return err;
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