diff options
authorJens Axboe2006-06-08 01:49:06 -0500
committerLinus Torvalds2006-06-08 17:14:23 -0500
commitbc1c116974a5c3f498112a6f175d3e4a8cd5bdbc (patch)
tree69ea68db91fb871cd24a0a5c5045abbe9c77bd3a /block/noop-iosched.c
parent26e780e8ef1cc3ef581a07aafe2346bb5a07b4f9 (diff)
[PATCH] elevator switching race
There's a race between shutting down one io scheduler and firing up the next, in which a new io could enter and cause the io scheduler to be invoked with bad or NULL data. To fix this, we need to maintain the queue lock for a bit longer. Unfortunately we cannot do that, since the elevator init requires to be run without the lock held. This isn't easily fixable, without also changing the mempool API. So split the initialization into two parts, and alloc-init operation and an attach operation. Then we can preallocate the io scheduler and related structures, and run the attach inside the lock after we detach the old one. This patch has survived 30 minutes of 1 second io scheduler switching with a very busy io load. Signed-off-by: Jens Axboe <axboe@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'block/noop-iosched.c')
1 files changed, 3 insertions, 4 deletions
diff --git a/block/noop-iosched.c b/block/noop-iosched.c
index f370e4a7fe6..56a7c620574 100644
--- a/block/noop-iosched.c
+++ b/block/noop-iosched.c
@@ -65,16 +65,15 @@ noop_latter_request(request_queue_t *q, struct request *rq)
65 return list_entry(rq->queuelist.next, struct request, queuelist); 65 return list_entry(rq->queuelist.next, struct request, queuelist);
66} 66}
67 67
68static int noop_init_queue(request_queue_t *q, elevator_t *e) 68static void *noop_init_queue(request_queue_t *q, elevator_t *e)
69{ 69{
70 struct noop_data *nd; 70 struct noop_data *nd;
71 71
72 nd = kmalloc(sizeof(*nd), GFP_KERNEL); 72 nd = kmalloc(sizeof(*nd), GFP_KERNEL);
73 if (!nd) 73 if (!nd)
74 return -ENOMEM; 74 return NULL;
75 INIT_LIST_HEAD(&nd->queue); 75 INIT_LIST_HEAD(&nd->queue);
76 e->elevator_data = nd; 76 return nd;
77 return 0;
78} 77}
79 78
80static void noop_exit_queue(elevator_t *e) 79static void noop_exit_queue(elevator_t *e)