diff options
author | NeilBrown | 2011-04-11 14:13:10 +0200 |
---|---|---|
committer | Jens Axboe | 2011-04-11 14:13:10 +0200 |
commit | 109b81296c63228578d4760794d8dd46e02eddfb (patch) | |
tree | 2f723e1b69ab08e12528f677f04edbfc7473b7c5 /block | |
parent | 4263a2f1dad8c8e7ce2352a0cbc882c2b0c044a9 (diff) |
block: splice plug list to local context
If the request_fn ends up blocking, we could be re-entering
the plug flush. Since the list is protected by explicitly
not allowing schedule events, this isn't a terribly good idea.
Additionally, it can cause us to recurse. As request_fn called by
__blk_run_queue is allowed to 'schedule()' (after dropping the queue
lock of course), it is possible to get a recursive call:
schedule -> blk_flush_plug -> __blk_finish_plug -> flush_plug_list
-> __blk_run_queue -> request_fn -> schedule
We must make sure that the second schedule does not call into
blk_flush_plug again. So instead of leaving the list of requests on
blk_plug->list, move them to a separate list leaving blk_plug->list
empty.
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Diffstat (limited to 'block')
-rw-r--r-- | block/blk-core.c | 14 |
1 files changed, 9 insertions, 5 deletions
diff --git a/block/blk-core.c b/block/blk-core.c index 90f22cc30799..eeaca0998df5 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -2673,19 +2673,24 @@ static void flush_plug_list(struct blk_plug *plug) struct request_queue *q; unsigned long flags; struct request *rq; + LIST_HEAD(list); BUG_ON(plug->magic != PLUG_MAGIC); if (list_empty(&plug->list)) return; - if (plug->should_sort) - list_sort(NULL, &plug->list, plug_rq_cmp); + list_splice_init(&plug->list, &list); + + if (plug->should_sort) { + list_sort(NULL, &list, plug_rq_cmp); + plug->should_sort = 0; + } q = NULL; local_irq_save(flags); - while (!list_empty(&plug->list)) { - rq = list_entry_rq(plug->list.next); + while (!list_empty(&list)) { + rq = list_entry_rq(list.next); list_del_init(&rq->queuelist); BUG_ON(!(rq->cmd_flags & REQ_ON_PLUG)); BUG_ON(!rq->q); @@ -2713,7 +2718,6 @@ static void flush_plug_list(struct blk_plug *plug) spin_unlock(q->queue_lock); } - BUG_ON(!list_empty(&plug->list)); local_irq_restore(flags); } |