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[PATCH] Add some comments to slab.c

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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: Alok N Kataria <alok.kataria@calsoftinc.com>
Signed-off-by: Ravikiran Thirumalai <kiran@scalex86.org>
Signed-off-by: Shai 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: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Ravikiran G Thirumalai 2006-09-25 23:31:34 -07:00 • committed by Linus Torvalds
parent dfd54cbcc0
commit e5ac9c5aec
1 changed files with 27 additions and 2 deletions
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29
mm/slab.c
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@ -2206,8 +2206,17 @@ kmem_cache_create (const char *name, size_t size, size_t align,
cachep->gfpflags |= GFP_DMA; cachep->gfpflags |= GFP_DMA;
cachep->buffer_size = size; cachep->buffer_size = size;
if (flags & CFLGS_OFF_SLAB) if (flags & CFLGS_OFF_SLAB) {
cachep->slabp_cache = kmem_find_general_cachep(slab_size, 0u); 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->ctor = ctor;
cachep->dtor = dtor; cachep->dtor = dtor;
cachep->name = name; cachep->name = name;
@ -2441,7 +2450,17 @@ int kmem_cache_destroy(struct kmem_cache *cachep)
} }
EXPORT_SYMBOL(kmem_cache_destroy); 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, static struct slab *alloc_slabmgmt(struct kmem_cache *cachep, void *objp,
int colour_off, gfp_t local_flags, int colour_off, gfp_t local_flags,
int nodeid) int nodeid)
@ -3125,6 +3144,12 @@ static void free_block(struct kmem_cache *cachep, void **objpp, int nr_objects,
if (slabp->inuse == 0) { if (slabp->inuse == 0) {
if (l3->free_objects > l3->free_limit) { if (l3->free_objects > l3->free_limit) {
l3->free_objects -= cachep->num; 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); slab_destroy(cachep, slabp);
} else { } else {
list_add(&slabp->list, &l3->slabs_free); list_add(&slabp->list, &l3->slabs_free);