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 <>
Signed-off-by: default avatarRavikiran Thirumalai <>
Signed-off-by: default avatarShai Fultheim <>
Cc: Pekka Enberg <>
Cc: Manfred Spraul <>
Cc: Christoph Lameter <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent dfd54cbc
......@@ -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.
cachep->ctor = ctor;
cachep->dtor = dtor;
cachep->name = name;
......@@ -2441,7 +2450,17 @@ int kmem_cache_destroy(struct kmem_cache *cachep)
/* 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);
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