mm, slub: move disabling irqs closer to get_partial() in ___slab_alloc()

Continue reducing the irq disabled scope. Check for per-cpu partial slabs with
first with irqs enabled and then recheck with irqs disabled before grabbing
the slab page. Mostly preparatory for the following patches.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

diff --git a/mm/slub.c b/mm/slub.c
index 6295695..4d1f3e4 100644 (file)
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2706,11 +2706,6 @@ reread_page:
                if (unlikely(node != NUMA_NO_NODE &&
                             !node_isset(node, slab_nodes)))
                        node = NUMA_NO_NODE;
-               local_irq_save(flags);
-               if (unlikely(c->page)) {
-                       local_irq_restore(flags);
-                       goto reread_page;
-               }
                goto new_slab;
        }
 redo:
@@ -2751,6 +2746,7 @@ redo:
 
        if (!freelist) {
                c->page = NULL;
+               local_irq_restore(flags);
                stat(s, DEACTIVATE_BYPASS);
                goto new_slab;
        }
@@ -2780,12 +2776,19 @@ deactivate_slab:
                goto reread_page;
        }
        deactivate_slab(s, page, c->freelist, c);
+       local_irq_restore(flags);
 
 new_slab:
 
-       lockdep_assert_irqs_disabled();
-
        if (slub_percpu_partial(c)) {
+               local_irq_save(flags);
+               if (unlikely(c->page)) {
+                       local_irq_restore(flags);
+                       goto reread_page;
+               }
+               if (unlikely(!slub_percpu_partial(c)))
+                       goto new_objects; /* stolen by an IRQ handler */
+
                page = c->page = slub_percpu_partial(c);
                slub_set_percpu_partial(c, page);
                local_irq_restore(flags);
@@ -2793,6 +2796,16 @@ new_slab:
                goto redo;
        }
 
+       local_irq_save(flags);
+       if (unlikely(c->page)) {
+               local_irq_restore(flags);
+               goto reread_page;
+       }
+
+new_objects:
+
+       lockdep_assert_irqs_disabled();
+
        freelist = get_partial(s, gfpflags, node, &page);
        if (freelist) {
                c->page = page;
@@ -2825,15 +2838,18 @@ new_slab:
 check_new_page:
 
        if (kmem_cache_debug(s)) {
-               if (!alloc_debug_processing(s, page, freelist, addr))
+               if (!alloc_debug_processing(s, page, freelist, addr)) {
                        /* Slab failed checks. Next slab needed */
+                       c->page = NULL;
+                       local_irq_restore(flags);
                        goto new_slab;
-               else
+               } else {
                        /*
                         * For debug case, we don't load freelist so that all
                         * allocations go through alloc_debug_processing()
                         */
                        goto return_single;
+               }
        }
 
        if (unlikely(!pfmemalloc_match(page, gfpflags)))