Slub: UP bandaid

Since the percpu allocator does not provide early allocation in UP mode (only
in SMP configurations) use __get_free_page() to improvise a compound page
allocation that can be later freed via kfree().

Compound pages will be released when the cpu caches are resized.

Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

1 files changed, 16 insertions, 0 deletions

diff --git a/mm/slub.c b/mm/slub.c
index 4c5a76f505e..05674aac929 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2103,8 +2103,24 @@ init_kmem_cache_node(struct kmem_cache_node *n, struct kmem_cache *s)
 
 static inline int alloc_kmem_cache_cpus(struct kmem_cache *s)
 {
+#ifdef CONFIG_SMP
+        /*
+         * Will use reserve that does not require slab operation during
+         * early boot.
+         */
         BUILD_BUG_ON(PERCPU_DYNAMIC_EARLY_SIZE <
                         SLUB_PAGE_SHIFT * sizeof(struct kmem_cache_cpu));
+#else
+        /*
+         * Special hack for UP mode. allocpercpu() falls back to kmalloc
+         * operations. So we cannot use that before the slab allocator is up
+         * Simply get the smallest possible compound page. The page will be
+         * released via kfree() when the cpu caches are resized later.
+         */
+        if (slab_state < UP)
+                s->cpu_slab = (__percpu void *)kmalloc_large(PAGE_SIZE << 1, GFP_NOWAIT);
+        else
+#endif
 
         s->cpu_slab = alloc_percpu(struct kmem_cache_cpu);