+ mm-slub-unify-cmpxchg_double_slab-and-__cmpxchg_double_slab.patch added to -mm tree

[akpm@linux-foundation.org]

The patch titled
     Subject: mm, slub: unify cmpxchg_double_slab() and __cmpxchg_double_slab()
has been added to the -mm tree.  Its filename is
     mm-slub-unify-cmpxchg_double_slab-and-__cmpxchg_double_slab.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-slub-unify-cmpxchg_double_slab-and-__cmpxchg_double_slab.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-slub-unify-cmpxchg_double_slab-and-__cmpxchg_double_slab.patch

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------------------------------------------------------
From: Vlastimil Babka <vbabka@suse.cz>
Subject: mm, slub: unify cmpxchg_double_slab() and __cmpxchg_double_slab()

These functions differ only in irq disabling in the slow path.  We can
create a common function with an extra bool parameter to control the irq
disabling.  As the functions are inline and the parameter compile-time
constant, there will be no runtime overhead due to this change.

Also change the DEBUG_VM based irqs disable assert to the more standard
lockdep_assert based one.

Link: https://lkml.kernel.org/r/20210805152000.12817-7-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/slub.c |   62 ++++++++++++++++++++--------------------------------
 1 file changed, 24 insertions(+), 38 deletions(-)

--- a/mm/slub.c~mm-slub-unify-cmpxchg_double_slab-and-__cmpxchg_double_slab
+++ a/mm/slub.c
@@ -371,13 +371,13 @@ static __always_inline void slab_unlock(
 	__bit_spin_unlock(PG_locked, &page->flags);
 }
 
-/* Interrupts must be disabled (for the fallback code to work right) */
-static inline bool __cmpxchg_double_slab(struct kmem_cache *s, struct page *page,
+static inline bool ___cmpxchg_double_slab(struct kmem_cache *s, struct page *page,
 		void *freelist_old, unsigned long counters_old,
 		void *freelist_new, unsigned long counters_new,
-		const char *n)
+		const char *n, bool disable_irqs)
 {
-	VM_BUG_ON(!irqs_disabled());
+	if (!disable_irqs)
+		lockdep_assert_irqs_disabled();
 #if defined(CONFIG_HAVE_CMPXCHG_DOUBLE) && \
     defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE)
 	if (s->flags & __CMPXCHG_DOUBLE) {
@@ -388,15 +388,23 @@ static inline bool __cmpxchg_double_slab
 	} else
 #endif
 	{
+		unsigned long flags;
+
+		if (disable_irqs)
+			local_irq_save(flags);
 		slab_lock(page);
 		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);
 			return true;
 		}
 		slab_unlock(page);
+		if (disable_irqs)
+			local_irq_restore(flags);
 	}
 
 	cpu_relax();
@@ -409,45 +417,23 @@ static inline bool __cmpxchg_double_slab
 	return false;
 }
 
-static inline bool cmpxchg_double_slab(struct kmem_cache *s, struct page *page,
+/* Interrupts must be disabled (for the fallback code to work right) */
+static inline bool __cmpxchg_double_slab(struct kmem_cache *s, struct page *page,
 		void *freelist_old, unsigned long counters_old,
 		void *freelist_new, unsigned long counters_new,
 		const char *n)
 {
-#if defined(CONFIG_HAVE_CMPXCHG_DOUBLE) && \
-    defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE)
-	if (s->flags & __CMPXCHG_DOUBLE) {
-		if (cmpxchg_double(&page->freelist, &page->counters,
-				   freelist_old, counters_old,
-				   freelist_new, counters_new))
-			return true;
-	} else
-#endif
-	{
-		unsigned long flags;
-
-		local_irq_save(flags);
-		slab_lock(page);
-		if (page->freelist == freelist_old &&
-					page->counters == counters_old) {
-			page->freelist = freelist_new;
-			page->counters = counters_new;
-			slab_unlock(page);
-			local_irq_restore(flags);
-			return true;
-		}
-		slab_unlock(page);
-		local_irq_restore(flags);
-	}
-
-	cpu_relax();
-	stat(s, CMPXCHG_DOUBLE_FAIL);
-
-#ifdef SLUB_DEBUG_CMPXCHG
-	pr_info("%s %s: cmpxchg double redo ", n, s->name);
-#endif
+	return ___cmpxchg_double_slab(s, page, freelist_old, counters_old,
+				      freelist_new, counters_new, n, false);
+}
 
-	return false;
+static inline bool cmpxchg_double_slab(struct kmem_cache *s, struct page *page,
+		void *freelist_old, unsigned long counters_old,
+		void *freelist_new, unsigned long counters_new,
+		const char *n)
+{
+	return ___cmpxchg_double_slab(s, page, freelist_old, counters_old,
+				      freelist_new, counters_new, n, true);
 }
 
 #ifdef CONFIG_SLUB_DEBUG
_

Patches currently in -mm which might be from vbabka@suse.cz are

mm-slub-fix-slub_debug-disablement-for-list-of-slabs.patch
mm-slub-dont-call-flush_all-from-slab_debug_trace_open.patch
mm-slub-allocate-private-object-map-for-debugfs-listings.patch
mm-slub-allocate-private-object-map-for-validate_slab_cache.patch
mm-slub-dont-disable-irq-for-debug_check_no_locks_freed.patch
mm-slub-remove-redundant-unfreeze_partials-from-put_cpu_partial.patch
mm-slub-unify-cmpxchg_double_slab-and-__cmpxchg_double_slab.patch
mm-slub-extract-get_partial-from-new_slab_objects.patch
mm-slub-dissolve-new_slab_objects-into-___slab_alloc.patch
mm-slub-return-slab-page-from-get_partial-and-set-c-page-afterwards.patch
mm-slub-restructure-new-page-checks-in-___slab_alloc.patch
mm-slub-simplify-kmem_cache_cpu-and-tid-setup.patch
mm-slub-move-disabling-enabling-irqs-to-___slab_alloc.patch
mm-slub-do-initial-checks-in-___slab_alloc-with-irqs-enabled.patch
mm-slub-move-disabling-irqs-closer-to-get_partial-in-___slab_alloc.patch
mm-slub-restore-irqs-around-calling-new_slab.patch
mm-slub-validate-slab-from-partial-list-or-page-allocator-before-making-it-cpu-slab.patch
mm-slub-check-new-pages-with-restored-irqs.patch
mm-slub-stop-disabling-irqs-around-get_partial.patch
mm-slub-move-reset-of-c-page-and-freelist-out-of-deactivate_slab.patch
mm-slub-make-locking-in-deactivate_slab-irq-safe.patch
mm-slub-call-deactivate_slab-without-disabling-irqs.patch
mm-slub-move-irq-control-into-unfreeze_partials.patch
mm-slub-discard-slabs-in-unfreeze_partials-without-irqs-disabled.patch
mm-slub-detach-whole-partial-list-at-once-in-unfreeze_partials.patch
mm-slub-separate-detaching-of-partial-list-in-unfreeze_partials-from-unfreezing.patch
mm-slub-only-disable-irq-with-spin_lock-in-__unfreeze_partials.patch
mm-slub-dont-disable-irqs-in-slub_cpu_dead.patch
mm-slab-make-flush_slab-possible-to-call-with-irqs-enabled.patch
mm-slub-optionally-save-restore-irqs-in-slab_lock.patch
mm-slub-make-slab_lock-disable-irqs-with-preempt_rt.patch
mm-slub-protect-put_cpu_partial-with-disabled-irqs-instead-of-cmpxchg.patch
mm-slub-use-migrate_disable-on-preempt_rt.patch
mm-slub-convert-kmem_cpu_slab-protection-to-local_lock.patch