[PATCH v4 21/35] mm, slub: call deactivate_slab() without disabling irqs
From: Vlastimil Babka <hidden>
Date: 2021-08-05 15:24:50
Also in:
lkml
Subsystem:
memory management, slab allocator, the rest · Maintainers:
Andrew Morton, Vlastimil Babka, Harry Yoo, Linus Torvalds
The function is now safe to be called with irqs enabled, so move the calls outside of irq disabled sections. When called from ___slab_alloc() -> flush_slab() we have irqs disabled, so to reenable them before deactivate_slab() we need to open-code flush_slab() in ___slab_alloc() and reenable irqs after modifying the kmem_cache_cpu fields. But that means a IRQ handler meanwhile might have assigned a new page to kmem_cache_cpu.page so we have to retry the whole check. The remaining callers of flush_slab() are the IPI handler which has disabled irqs anyway, and slub_cpu_dead() which will be dealt with in the following patch. Signed-off-by: Vlastimil Babka <redacted> --- mm/slub.c | 24 +++++++++++++++++++----- 1 file changed, 19 insertions(+), 5 deletions(-)
diff --git a/mm/slub.c b/mm/slub.c
index 27c98f4fb3f5..8de4ead2dbf3 100644
--- a/mm/slub.c
+++ b/mm/slub.c@@ -2749,8 +2749,8 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, freelist = c->freelist; c->page = NULL; c->freelist = NULL; - deactivate_slab(s, page, freelist); local_irq_restore(flags); + deactivate_slab(s, page, freelist); new_slab:
@@ -2818,18 +2818,32 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, */ goto return_single; +retry_load_page: + local_irq_save(flags); - if (unlikely(c->page)) - flush_slab(s, c); + if (unlikely(c->page)) { + void *flush_freelist = c->freelist; + struct page *flush_page = c->page; + + c->page = NULL; + c->freelist = NULL; + c->tid = next_tid(c->tid); + + local_irq_restore(flags); + + deactivate_slab(s, flush_page, flush_freelist); + + stat(s, CPUSLAB_FLUSH); + + goto retry_load_page; + } c->page = page; goto load_freelist; return_single: - local_irq_save(flags); deactivate_slab(s, page, get_freepointer(s, freelist)); - local_irq_restore(flags); return freelist; }
--
2.32.0