From 35d37c66356eed46700e0d5db87211844d43a241 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Mon, 15 Dec 2014 08:30:26 -0700 Subject: [PATCH] Revert "blk-mq: Micro-optimize bt_get()" This reverts commit 52f7eb945f2ba62b324bb9ae16d945326a961dcf. The optimization is only really safe for a single queue, otherwise 'bs' and 'bt' can indeed change, and if we don't do a finish_wait() for each loop, we'll potentially change the wait structure and corrupt task wait list. Reported-by: Jan Kara --- block/blk-mq-tag.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c index e3d4e4043b49..32e8dbb9ad1c 100644 --- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -248,8 +248,8 @@ static int bt_get(struct blk_mq_alloc_data *data, if (!(data->gfp & __GFP_WAIT)) return -1; + bs = bt_wait_ptr(bt, hctx); do { - bs = bt_wait_ptr(bt, hctx); prepare_to_wait(&bs->wait, &wait, TASK_UNINTERRUPTIBLE); tag = __bt_get(hctx, bt, last_tag); @@ -285,6 +285,8 @@ static int bt_get(struct blk_mq_alloc_data *data, hctx = data->hctx; bt = &hctx->tags->bitmap_tags; } + finish_wait(&bs->wait, &wait); + bs = bt_wait_ptr(bt, hctx); } while (1); finish_wait(&bs->wait, &wait); -- 2.30.2