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authorJens Axboe <axboe@kernel.dk>2019-03-25 12:34:10 -0600
committerJens Axboe <axboe@kernel.dk>2019-03-25 13:05:47 -0600
commite861857545567adec8da3bdff728efdf7db12285 (patch)
tree71572b52d87ba2421159bf6ee70c85708878be44 /block
parent9e75ad5d8f399a21c86271571aa630dd080223e2 (diff)
downloadlinux-stericsson-e861857545567adec8da3bdff728efdf7db12285.tar.gz
blk-mq: fix sbitmap ws_active for shared tags
We now wrap sbitmap waitqueues in an active counter, so we can avoid iterating wakeups unless we have waiters there. This works as long as everyone that's manipulating the waitqueues use the proper helpers. For the tag wait case for shared tags, however, we add ourselves to the waitqueue without incrementing/decrementing the ->ws_active count. This means that wakeups can take a long time to happen. Fix this by manually doing the inc/dec as needed for the wait queue handling. Reported-by: Michael Leun <kbug@newton.leun.net> Tested-by: Michael Leun <kbug@newton.leun.net> Cc: stable@vger.kernel.org Reviewed-by: Omar Sandoval <osandov@fb.com> Fixes: 5d2ee7122c73 ("sbitmap: optimize wakeup check") Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block')
-rw-r--r--block/blk-mq.c13
1 files changed, 11 insertions, 2 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 28080b0235f0..3ff3d7b49969 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1072,7 +1072,13 @@ static int blk_mq_dispatch_wake(wait_queue_entry_t *wait, unsigned mode,
hctx = container_of(wait, struct blk_mq_hw_ctx, dispatch_wait);
spin_lock(&hctx->dispatch_wait_lock);
- list_del_init(&wait->entry);
+ if (!list_empty(&wait->entry)) {
+ struct sbitmap_queue *sbq;
+
+ list_del_init(&wait->entry);
+ sbq = &hctx->tags->bitmap_tags;
+ atomic_dec(&sbq->ws_active);
+ }
spin_unlock(&hctx->dispatch_wait_lock);
blk_mq_run_hw_queue(hctx, true);
@@ -1088,6 +1094,7 @@ static int blk_mq_dispatch_wake(wait_queue_entry_t *wait, unsigned mode,
static bool blk_mq_mark_tag_wait(struct blk_mq_hw_ctx *hctx,
struct request *rq)
{
+ struct sbitmap_queue *sbq = &hctx->tags->bitmap_tags;
struct wait_queue_head *wq;
wait_queue_entry_t *wait;
bool ret;
@@ -1110,7 +1117,7 @@ static bool blk_mq_mark_tag_wait(struct blk_mq_hw_ctx *hctx,
if (!list_empty_careful(&wait->entry))
return false;
- wq = &bt_wait_ptr(&hctx->tags->bitmap_tags, hctx)->wait;
+ wq = &bt_wait_ptr(sbq, hctx)->wait;
spin_lock_irq(&wq->lock);
spin_lock(&hctx->dispatch_wait_lock);
@@ -1120,6 +1127,7 @@ static bool blk_mq_mark_tag_wait(struct blk_mq_hw_ctx *hctx,
return false;
}
+ atomic_inc(&sbq->ws_active);
wait->flags &= ~WQ_FLAG_EXCLUSIVE;
__add_wait_queue(wq, wait);
@@ -1140,6 +1148,7 @@ static bool blk_mq_mark_tag_wait(struct blk_mq_hw_ctx *hctx,
* someone else gets the wakeup.
*/
list_del_init(&wait->entry);
+ atomic_dec(&sbq->ws_active);
spin_unlock(&hctx->dispatch_wait_lock);
spin_unlock_irq(&wq->lock);