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 <clameter@sgi.com>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 117f6eb1

mm/slab.c

+17 −18
Original line number Diff line number Diff line
@@ -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;

		mutex_lock(&cache_chain_mutex);

		list_for_each_entry(cachep, &cache_chain, next)

			enable_cpucache(cachep);

			if (enable_cpucache(cachep))

				BUG();

		mutex_unlock(&cache_chain_mutex);

	}
@@ -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) {

		enable_cpucache(cachep);

		return;

	}

	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;





	setup_cpu_cache(cachep);

	if (setup_cpu_cache(cachep)) {

		__kmem_cache_destroy(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(&new.new, 0, sizeof(new.new));

	for_each_online_cpu(i) {
@@ -3724,17 +3728,11 @@ static int do_tune_cpucache(struct kmem_cache *cachep, int limit, 
		kfree(ccold);

	}



	err = alloc_kmemlist(cachep);

	if (err) {

		printk(KERN_ERR "alloc_kmemlist failed for %s, error %d.\n",

		       cachep->name, -err);

		BUG();

	}

	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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