Merge branch 'for-linus' of git://git.kernel.dk/linux-block

Pull core block fix from Jens Axboe:
 "Jan reported a problem this morning with a crash in blk-mq, and after
  looking over the recent changes, it's obvious that the blk-mq-tag
  waitqueue handling change is buggy.  We could end up _not_ doing
  finish_wait() before switching to a new waitqueue, thus corrupting the
  wait task list"

* 'for-linus' of git://git.kernel.dk/linux-block:
  Revert "blk-mq: Micro-optimize bt_get()"

1 files changed, 3 insertions, 1 deletions

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);