[017/147] mm, slub: stop disabling irqs around get_partial()

Commit Message

Andrew Morton Sept. 8, 2021, 2:53 a.m. UTC

From: Vlastimil Babka <[e-mail]>
Subject: mm, slub: stop disabling irqs around get_partial()

The function get_partial() does not need to have irqs disabled as a whole.
It's sufficient to convert spin_lock operations to their irq
saving/restoring versions.

As a result, it's now possible to reach the page allocator from the slab
allocator without disabling and re-enabling interrupts on the way.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Vlastimil Babka <[e-mail]>
Cc: Christoph Lameter <[e-mail]>
Cc: David Rientjes <[e-mail]>
Cc: Jann Horn <[e-mail]>
Cc: Jesper Dangaard Brouer <[e-mail]>
Cc: Joonsoo Kim <[e-mail]>
Cc: Mel Gorman <[e-mail]>
Cc: Mike Galbraith <[e-mail]>
Cc: Pekka Enberg <[e-mail]>
Cc: Qian Cai <[e-mail]>
Cc: Sebastian Andrzej Siewior <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/slub.c |   22 ++++++++--------------
 1 file changed, 8 insertions(+), 14 deletions(-)

Patch

--- a/mm/slub.c~mm-slub-stop-disabling-irqs-around-get_partial
+++ a/mm/slub.c
@@ -2010,11 +2010,12 @@  static inline bool pfmemalloc_match(stru
  * Try to allocate a partial slab from a specific node.
  */
 static void *get_partial_node(struct kmem_cache *s, struct kmem_cache_node *n,
-			      struct page **ret_page, gfp_t flags)
+			      struct page **ret_page, gfp_t gfpflags)
 {
 	struct page *page, *page2;
 	void *object = NULL;
 	unsigned int available = 0;
+	unsigned long flags;
 	int objects;
 
 	/*
@@ -2026,11 +2027,11 @@  static void *get_partial_node(struct kme
 	if (!n || !n->nr_partial)
 		return NULL;
 
-	spin_lock(&n->list_lock);
+	spin_lock_irqsave(&n->list_lock, flags);
 	list_for_each_entry_safe(page, page2, &n->partial, slab_list) {
 		void *t;
 
-		if (!pfmemalloc_match(page, flags))
+		if (!pfmemalloc_match(page, gfpflags))
 			continue;
 
 		t = acquire_slab(s, n, page, object == NULL, &objects);
@@ -2051,7 +2052,7 @@  static void *get_partial_node(struct kme
 			break;
 
 	}
-	spin_unlock(&n->list_lock);
+	spin_unlock_irqrestore(&n->list_lock, flags);
 	return object;
 }
 
@@ -2779,8 +2780,10 @@  new_slab:
 			local_irq_restore(flags);
 			goto reread_page;
 		}
-		if (unlikely(!slub_percpu_partial(c)))
+		if (unlikely(!slub_percpu_partial(c))) {
+			local_irq_restore(flags);
 			goto new_objects; /* stolen by an IRQ handler */
+		}
 
 		page = c->page = slub_percpu_partial(c);
 		slub_set_percpu_partial(c, page);
@@ -2789,18 +2792,9 @@  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);
-	local_irq_restore(flags);
 	if (freelist)
 		goto check_new_page;