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authorVlastimil Babka <vbabka@suse.cz>2022-11-04 17:57:26 +0300
committerVlastimil Babka <vbabka@suse.cz>2022-11-21 12:24:00 +0300
commit8b8817630ae80032e80b2eaf334de756ac1ff6a3 (patch)
treefab22d22b71a833fce49e3d74e5c6527076e6983 /mm/slab.c
parentbc29d5bd2ba977716e57572030290d6547ff3f6d (diff)
downloadlinux-8b8817630ae80032e80b2eaf334de756ac1ff6a3.tar.xz
mm/migrate: make isolate_movable_page() skip slab pages
In the next commit we want to rearrange struct slab fields to allow a larger rcu_head. Afterwards, the page->mapping field will overlap with SLUB's "struct list_head slab_list", where the value of prev pointer can become LIST_POISON2, which is 0x122 + POISON_POINTER_DELTA. Unfortunately the bit 1 being set can confuse PageMovable() to be a false positive and cause a GPF as reported by lkp [1]. To fix this, make isolate_movable_page() skip pages with the PageSlab flag set. This is a bit tricky as we need to add memory barriers to SLAB and SLUB's page allocation and freeing, and their counterparts to isolate_movable_page(). Based on my RFC from [2]. Added a comment update from Matthew's variant in [3] and, as done there, moved the PageSlab checks to happen before trying to take the page lock. [1] https://lore.kernel.org/all/208c1757-5edd-fd42-67d4-1940cc43b50f@intel.com/ [2] https://lore.kernel.org/all/aec59f53-0e53-1736-5932-25407125d4d4@suse.cz/ [3] https://lore.kernel.org/all/YzsVM8eToHUeTP75@casper.infradead.org/ Reported-by: kernel test robot <yujie.liu@intel.com> Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Diffstat (limited to 'mm/slab.c')
-rw-r--r--mm/slab.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/mm/slab.c b/mm/slab.c
index 59c8e28f7b6a..219beb48588e 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -1370,6 +1370,8 @@ static struct slab *kmem_getpages(struct kmem_cache *cachep, gfp_t flags,
account_slab(slab, cachep->gfporder, cachep, flags);
__folio_set_slab(folio);
+ /* Make the flag visible before any changes to folio->mapping */
+ smp_wmb();
/* Record if ALLOC_NO_WATERMARKS was set when allocating the slab */
if (sk_memalloc_socks() && page_is_pfmemalloc(folio_page(folio, 0)))
slab_set_pfmemalloc(slab);
@@ -1387,9 +1389,11 @@ static void kmem_freepages(struct kmem_cache *cachep, struct slab *slab)
BUG_ON(!folio_test_slab(folio));
__slab_clear_pfmemalloc(slab);
- __folio_clear_slab(folio);
page_mapcount_reset(folio_page(folio, 0));
folio->mapping = NULL;
+ /* Make the mapping reset visible before clearing the flag */
+ smp_wmb();
+ __folio_clear_slab(folio);
if (current->reclaim_state)
current->reclaim_state->reclaimed_slab += 1 << order;