mm, slub: make locking in deactivate_slab() irq-safe

dectivate_slab() now no longer touches the kmem_cache_cpu structure, so it will
be possible to call it with irqs enabled. Just convert the spin_lock calls to
their irq saving/restoring variants to make it irq-safe.

Note we now have to use cmpxchg_double_slab() for irq-safe slab_lock(), because
in some situations we don't take the list_lock, which would disable irqs.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

diff --git a/mm/slub.c b/mm/slub.c
index cea7a2a..6deb408 100644 (file)
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2223,6 +2223,7 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page,
        enum slab_modes l = M_NONE, m = M_NONE;
        void *nextfree, *freelist_iter, *freelist_tail;
        int tail = DEACTIVATE_TO_HEAD;
+       unsigned long flags = 0;
        struct page new;
        struct page old;
 
@@ -2298,7 +2299,7 @@ redo:
                         * that acquire_slab() will see a slab page that
                         * is frozen
                         */
-                       spin_lock(&n->list_lock);
+                       spin_lock_irqsave(&n->list_lock, flags);
                }
        } else {
                m = M_FULL;
@@ -2309,7 +2310,7 @@ redo:
                         * slabs from diagnostic functions will not see
                         * any frozen slabs.
                         */
-                       spin_lock(&n->list_lock);
+                       spin_lock_irqsave(&n->list_lock, flags);
                }
        }
 
@@ -2326,14 +2327,14 @@ redo:
        }
 
        l = m;
-       if (!__cmpxchg_double_slab(s, page,
+       if (!cmpxchg_double_slab(s, page,
                                old.freelist, old.counters,
                                new.freelist, new.counters,
                                "unfreezing slab"))
                goto redo;
 
        if (lock)
-               spin_unlock(&n->list_lock);
+               spin_unlock_irqrestore(&n->list_lock, flags);
 
        if (m == M_PARTIAL)
                stat(s, tail);