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| author | Vlastimil Babka <vbabka@suse.cz> | 2022-11-04 15:57:26 +0100 |
|---|---|---|
| committer | Vlastimil Babka <vbabka@suse.cz> | 2022-11-21 10:24:00 +0100 |
| commit | 8b8817630ae80032e80b2eaf334de756ac1ff6a3 (patch) | |
| tree | fab22d22b71a833fce49e3d74e5c6527076e6983 /mm/slab.c | |
| parent | mm/slub: perform free consistency checks before call_rcu (diff) | |
| download | linux-8b8817630ae80032e80b2eaf334de756ac1ff6a3.tar.xz linux-8b8817630ae80032e80b2eaf334de756ac1ff6a3.zip | |
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.c | 6 |
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; |