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Subject[RFC v2 06/34] mm, slub: unify cmpxchg_double_slab() and __cmpxchg_double_slab()
Date
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.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
mm/slub.c | 62 +++++++++++++++++++++----------------------------------
1 file changed, 24 insertions(+), 38 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index f740598696b4..76af5065baeb 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -365,13 +365,13 @@ static __always_inline void slab_unlock(struct page *page)
__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) {
@@ -382,15 +382,23 @@ static inline bool __cmpxchg_double_slab(struct kmem_cache *s, struct page *page
} 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();
@@ -403,45 +411,23 @@ static inline bool __cmpxchg_double_slab(struct kmem_cache *s, struct page *page
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
--
2.31.1
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