[039/212] mm, slub: optionally save/restore irqs in slab_[un]lock()/

Commit Message

Andrew Morton Sept. 2, 2021, 9:52 p.m. UTC

From: Vlastimil Babka <[e-mail]>
Subject: mm, slub: optionally save/restore irqs in slab_[un]lock()/

For PREEMPT_RT we will need to disable irqs for this bit spinlock.  As a
preparation, add a flags parameter, and an internal version that takes
additional bool parameter to control irq saving/restoring (the flags
parameter is compile-time unused if the bool is a constant false).

Convert ___cmpxchg_double_slab(), which also comes with the same bool
parameter, to use the internal version.

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: Sebastian Andrzej Siewior <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/slub.c |   52 +++++++++++++++++++++++++++++++++-------------------
 1 file changed, 33 insertions(+), 19 deletions(-)

Patch

--- a/mm/slub.c~mm-slub-optionally-save-restore-irqs-in-slab_lock
+++ a/mm/slub.c
@@ -359,16 +359,33 @@  static inline unsigned int oo_objects(st
 /*
  * Per slab locking using the pagelock
  */
-static __always_inline void slab_lock(struct page *page)
+static __always_inline void
+__slab_lock(struct page *page, unsigned long *flags, bool disable_irqs)
 {
 	VM_BUG_ON_PAGE(PageTail(page), page);
+	if (disable_irqs)
+		local_irq_save(*flags);
 	bit_spin_lock(PG_locked, &page->flags);
 }
 
-static __always_inline void slab_unlock(struct page *page)
+static __always_inline void
+__slab_unlock(struct page *page, unsigned long *flags, bool disable_irqs)
 {
 	VM_BUG_ON_PAGE(PageTail(page), page);
 	__bit_spin_unlock(PG_locked, &page->flags);
+	if (disable_irqs)
+		local_irq_restore(*flags);
+}
+
+static __always_inline void
+slab_lock(struct page *page, unsigned long *flags)
+{
+	__slab_lock(page, flags, false);
+}
+
+static __always_inline void slab_unlock(struct page *page, unsigned long *flags)
+{
+	__slab_unlock(page, flags, false);
 }
 
 static inline bool ___cmpxchg_double_slab(struct kmem_cache *s, struct page *page,
@@ -388,23 +405,18 @@  static inline bool ___cmpxchg_double_sla
 	} else
 #endif
 	{
-		unsigned long flags;
+		/* init to 0 to prevent spurious warnings */
+		unsigned long flags = 0;
 
-		if (disable_irqs)
-			local_irq_save(flags);
-		slab_lock(page);
+		__slab_lock(page, &flags, disable_irqs);
 		if (page->freelist == freelist_old &&
 					page->counters == counters_old) {
 			page->freelist = freelist_new;
 			page->counters = counters_new;
-			slab_unlock(page);
-			if (disable_irqs)
-				local_irq_restore(flags);
+			__slab_unlock(page, &flags, disable_irqs);
 			return true;
 		}
-		slab_unlock(page);
-		if (disable_irqs)
-			local_irq_restore(flags);
+		__slab_unlock(page, &flags, disable_irqs);
 	}
 
 	cpu_relax();
@@ -1255,11 +1267,11 @@  static noinline int free_debug_processin
 	struct kmem_cache_node *n = get_node(s, page_to_nid(page));
 	void *object = head;
 	int cnt = 0;
-	unsigned long flags;
+	unsigned long flags, flags2;
 	int ret = 0;
 
 	spin_lock_irqsave(&n->list_lock, flags);
-	slab_lock(page);
+	slab_lock(page, &flags2);
 
 	if (s->flags & SLAB_CONSISTENCY_CHECKS) {
 		if (!check_slab(s, page))
@@ -1292,7 +1304,7 @@  out:
 		slab_err(s, page, "Bulk freelist count(%d) invalid(%d)\n",
 			 bulk_cnt, cnt);
 
-	slab_unlock(page);
+	slab_unlock(page, &flags2);
 	spin_unlock_irqrestore(&n->list_lock, flags);
 	if (!ret)
 		slab_fix(s, "Object at 0x%p not freed", object);
@@ -4070,9 +4082,10 @@  static void list_slab_objects(struct kme
 	void *addr = page_address(page);
 	unsigned long *map;
 	void *p;
+	unsigned long flags;
 
 	slab_err(s, page, text, s->name);
-	slab_lock(page);
+	slab_lock(page, &flags);
 
 	map = get_map(s, page);
 	for_each_object(p, s, addr, page->objects) {
@@ -4083,7 +4096,7 @@  static void list_slab_objects(struct kme
 		}
 	}
 	put_map(map);
-	slab_unlock(page);
+	slab_unlock(page, &flags);
 #endif
 }
 
@@ -4815,8 +4828,9 @@  static void validate_slab(struct kmem_ca
 {
 	void *p;
 	void *addr = page_address(page);
+	unsigned long flags;
 
-	slab_lock(page);
+	slab_lock(page, &flags);
 
 	if (!check_slab(s, page) || !on_freelist(s, page, NULL))
 		goto unlock;
@@ -4831,7 +4845,7 @@  static void validate_slab(struct kmem_ca
 			break;
 	}
 unlock:
-	slab_unlock(page);
+	slab_unlock(page, &flags);
 }
 
 static int validate_slab_node(struct kmem_cache *s,