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| author | Vlastimil Babka <vbabka@suse.cz> | 2020-04-26 09:06:17 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-05-02 17:24:16 +0200 |
| commit | 69e4bfba095a3a03015c35f6fbdfaafff5f8d26b (patch) | |
| tree | 06d9b9c9711482927a75632be2ac2125d6884ac5 /mm | |
| parent | bf2b525b1831cc8e73ed1a2f5e44919bb4a556c0 (diff) | |
| download | linux-rt-69e4bfba095a3a03015c35f6fbdfaafff5f8d26b.tar.gz | |
mm, slub: restore the original intention of prefetch_freepointer()
commit 0882ff9190e3bc51e2d78c3aadd7c690eeaa91d5 upstream.
In SLUB, prefetch_freepointer() is used when allocating an object from
cache's freelist, to make sure the next object in the list is cache-hot,
since it's probable it will be allocated soon.
Commit 2482ddec670f ("mm: add SLUB free list pointer obfuscation") has
unintentionally changed the prefetch in a way where the prefetch is
turned to a real fetch, and only the next->next pointer is prefetched.
In case there is not a stream of allocations that would benefit from
prefetching, the extra real fetch might add a useless cache miss to the
allocation. Restore the previous behavior.
Link: http://lkml.kernel.org/r/20180809085245.22448-1-vbabka@suse.cz
Fixes: 2482ddec670f ("mm: add SLUB free list pointer obfuscation")
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Daniel Micay <danielmicay@gmail.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthias Schiffer <mschiffer@universe-factory.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/slub.c | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/mm/slub.c b/mm/slub.c index 3c1a16f03b2b..481518c3f61a 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -269,8 +269,7 @@ static inline void *get_freepointer(struct kmem_cache *s, void *object) static void prefetch_freepointer(const struct kmem_cache *s, void *object) { - if (object) - prefetch(freelist_dereference(s, object + s->offset)); + prefetch(object + s->offset); } static inline void *get_freepointer_safe(struct kmem_cache *s, void *object) |