[PATCH] Undo mempolicy shared policy rbtree microoptimization

All mempolicy changes must be inside the spinlock and readding the rb_erase
prevents a crash while doing:

> echo "1" > /tmp/numatest
> numactl --length=0x4000 --shm /tmp/numatest --localalloc
> numactl --length=0x2000 --offset=0 --shm /tmp/numatest --membind=0
> numactl --length=0x2000 --offset=0x2000 --shm /tmp/numatest --membind=1
> ipcs
> ipcrm -M "the_key_value_of_this_shm_area"

Based on a patch by John Blackwood

Cc: <john.blackwood@ccur.com>
Cc: <andrea@suse.de>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index cb41c31..1694845 100644 (file)
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1138,11 +1138,11 @@ void mpol_free_shared_policy(struct shared_policy *p)
        while (next) {
                n = rb_entry(next, struct sp_node, nd);
                next = rb_next(&n->nd);
+               rb_erase(&n->nd, &p->root);
                mpol_free(n->policy);
                kmem_cache_free(sn_cache, n);
        }
        spin_unlock(&p->lock);
-       p->root = RB_ROOT;
 }
 
 /* assumes fs == KERNEL_DS */