mm, slab: split out the cpu offline variant of flush_slab()

flush_slab() is called either as part IPI handler on given live cpu, or as a
cleanup on behalf of another cpu that went offline. The first case needs to
protect updating the kmem_cache_cpu fields with disabled irqs. Currently the
whole call happens with irqs disabled by the IPI handler, but the following
patch will change from IPI to workqueue, and flush_slab() will have to disable
irqs (to be replaced with a local lock later) in the critical part.

To prepare for this change, replace the call to flush_slab() for the dead cpu
handling with an opencoded variant that will not disable irqs nor take a local
lock.

Suggested-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

diff --git a/mm/slub.c b/mm/slub.c
index c4a9b89..fa9a366 100644 (file)
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2511,9 +2511,17 @@ static inline void flush_slab(struct kmem_cache *s, struct kmem_cache_cpu *c)
 static inline void __flush_cpu_slab(struct kmem_cache *s, int cpu)
 {
        struct kmem_cache_cpu *c = per_cpu_ptr(s->cpu_slab, cpu);
+       void *freelist = c->freelist;
+       struct page *page = c->page;
 
-       if (c->page)
-               flush_slab(s, c);
+       c->page = NULL;
+       c->freelist = NULL;
+       c->tid = next_tid(c->tid);
+
+       if (page) {
+               deactivate_slab(s, page, freelist);
+               stat(s, CPUSLAB_FLUSH);
+       }
 
        unfreeze_partials_cpu(s, c);
 }