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slab: do ClearSlabPfmemalloc() for all pages of slab

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Right now, we call ClearSlabPfmemalloc() for first page of slab when we
clear SlabPfmemalloc flag.  This is fine for most swap-over-network use
cases as it is expected that order-0 pages are in use.  Unfortunately it
is possible that that __ac_put_obj() checks SlabPfmemalloc on a tail
page and while this is harmless, it is sloppy.  This patch ensures that
the head page is always used.

This problem was originally identified by Joonsoo Kim.

[js1304@gmail.com: Original implementation and problem identification]
Signed-off-by: Mel Gorman <mgorman@suse.de>
Cc: David Miller <davem@davemloft.net>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Mel Gorman 2012-09-17 14:09:03 -07:00 • committed by Linus Torvalds
parent fded4e090c
commit 30c29bea6a
1 changed files with 2 additions and 2 deletions
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4
mm/slab.c
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@ -1000,7 +1000,7 @@ static void *__ac_get_obj(struct kmem_cache *cachep, struct array_cache *ac,
l3 = cachep->nodelists[numa_mem_id()]; l3 = cachep->nodelists[numa_mem_id()];
if (!list_empty(&l3->slabs_free) && force_refill) { if (!list_empty(&l3->slabs_free) && force_refill) {
struct slab *slabp = virt_to_slab(objp); struct slab *slabp = virt_to_slab(objp);
ClearPageSlabPfmemalloc(virt_to_page(slabp->s_mem)); ClearPageSlabPfmemalloc(virt_to_head_page(slabp->s_mem));
clear_obj_pfmemalloc(&objp); clear_obj_pfmemalloc(&objp);
recheck_pfmemalloc_active(cachep, ac); recheck_pfmemalloc_active(cachep, ac);
return objp; return objp;
@ -1032,7 +1032,7 @@ static void *__ac_put_obj(struct kmem_cache *cachep, struct array_cache *ac,
{ {
if (unlikely(pfmemalloc_active)) { if (unlikely(pfmemalloc_active)) {
/* Some pfmemalloc slabs exist, check if this is one */ /* Some pfmemalloc slabs exist, check if this is one */
struct page *page = virt_to_page(objp); struct page *page = virt_to_head_page(objp);
if (PageSlabPfmemalloc(page)) if (PageSlabPfmemalloc(page))
set_obj_pfmemalloc(&objp); set_obj_pfmemalloc(&objp);
} }