Commit e5ac9c5a authored by Ravikiran G Thirumalai's avatar Ravikiran G Thirumalai Committed by Linus Torvalds
Browse files

[PATCH] Add some comments to slab.c 



Also, checks if we get a valid slabp_cache for off slab slab-descriptors.
We should always get this.  If we don't, then in that case we, will have to
disable off-slab descriptors for this cache and do the calculations again.
This is a rare case, so add a BUG_ON, for now, just in case.

Signed-off-by: default avatarAlok N Kataria <alok.kataria@calsoftinc.com>
Signed-off-by: default avatarRavikiran Thirumalai <kiran@scalex86.org>
Signed-off-by: default avatarShai Fultheim <shai@scalex86.org>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Manfred Spraul <manfred@colorfullife.com>
Cc: Christoph Lameter <clameter@engr.sgi.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent dfd54cbc

mm/slab.c

+27 −2
Original line number Diff line number Diff line
@@ -2206,8 +2206,17 @@ kmem_cache_create (const char *name, size_t size, size_t align, 
		cachep->gfpflags |= GFP_DMA;

	cachep->buffer_size = size;



	if (flags & CFLGS_OFF_SLAB)

	if (flags & CFLGS_OFF_SLAB) {

		cachep->slabp_cache = kmem_find_general_cachep(slab_size, 0u);

		/*

		 * This is a possibility for one of the malloc_sizes caches.

		 * But since we go off slab only for object size greater than

		 * PAGE_SIZE/8, and malloc_sizes gets created in ascending order,

		 * this should not happen at all.

		 * But leave a BUG_ON for some lucky dude.

		 */

		BUG_ON(!cachep->slabp_cache);

	}

	cachep->ctor = ctor;

	cachep->dtor = dtor;

	cachep->name = name;
@@ -2441,7 +2450,17 @@ int kmem_cache_destroy(struct kmem_cache *cachep) 
}

EXPORT_SYMBOL(kmem_cache_destroy);



/* Get the memory for a slab management obj. */

/*

 * Get the memory for a slab management obj.

 * For a slab cache when the slab descriptor is off-slab, slab descriptors

 * always come from malloc_sizes caches.  The slab descriptor cannot

 * come from the same cache which is getting created because,

 * when we are searching for an appropriate cache for these

 * descriptors in kmem_cache_create, we search through the malloc_sizes array.

 * If we are creating a malloc_sizes cache here it would not be visible to

 * kmem_find_general_cachep till the initialization is complete.

 * Hence we cannot have slabp_cache same as the original cache.

 */

static struct slab *alloc_slabmgmt(struct kmem_cache *cachep, void *objp,

				   int colour_off, gfp_t local_flags,

				   int nodeid)
@@ -3125,6 +3144,12 @@ static void free_block(struct kmem_cache *cachep, void **objpp, int nr_objects, 
		if (slabp->inuse == 0) {

			if (l3->free_objects > l3->free_limit) {

				l3->free_objects -= cachep->num;

				/* No need to drop any previously held

				 * lock here, even if we have a off-slab slab

				 * descriptor it is guaranteed to come from

				 * a different cache, refer to comments before

				 * alloc_slabmgmt.

				 */

				slab_destroy(cachep, slabp);

			} else {

				list_add(&slabp->list, &l3->slabs_free);