mm, slub: consider rest of partial list if acquire_slab() fails

stable inclusion
from stable-5.10.9
commit c8c01da728ef65ad20d26a338819639a2ee25a13
bugzilla: 47457

--------------------------------

commit 8ff60eb0 upstream.

acquire_slab() fails if there is contention on the freelist of the page
(probably because some other CPU is concurrently freeing an object from
the page).  In that case, it might make sense to look for a different page
(since there might be more remote frees to the page from other CPUs, and
we don't want contention on struct page).

However, the current code accidentally stops looking at the partial list
completely in that case.  Especially on kernels without CONFIG_NUMA set,
this means that get_partial() fails and new_slab_objects() falls back to
new_slab(), allocating new pages.  This could lead to an unnecessary
increase in memory fragmentation.

Link: https://lkml.kernel.org/r/20201228130853.1871516-1-jannh@google.com
Fixes: 7ced3719 ("slub: Acquire_slab() avoid loop")
Signed-off-by: NJann Horn <jannh@google.com>
Acked-by: NDavid Rientjes <rientjes@google.com>
Acked-by: NJoonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>

mm/slub.c

@@ -1971,7 +1971,7 @@ static void *get_partial_node(struct kmem_cache *s, struct kmem_cache_node *n,
 
 		t = acquire_slab(s, n, page, object == NULL, &objects);
 		if (!t)
-			break;
+			continue; /* cmpxchg raced */
 
 		available += objects;
 		if (!object) {