From: Jann Horn jannh@google.com
commit 8ff60eb052eeba95cfb3efe16b08c9199f8121cf 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: 7ced37197196 ("slub: Acquire_slab() avoid loop") Signed-off-by: Jann Horn jannh@google.com Acked-by: David Rientjes rientjes@google.com Acked-by: Joonsoo Kim iamjoonsoo.kim@lge.com Cc: Christoph Lameter cl@linux.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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- mm/slub.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/slub.c +++ b/mm/slub.c @@ -1682,7 +1682,7 @@ static void *get_partial_node(struct kme
t = acquire_slab(s, n, page, object == NULL, &objects); if (!t) - break; + continue; /* cmpxchg raced */
available += objects; if (!object) {