Messages in this thread Patch in this message | | | From | Yu Kuai <> | Subject | [PATCH RFC -next 2/3] blk-mq: call 'bt_wait_ptr()' later in blk_mq_get_tag() | Date | Fri, 18 Mar 2022 16:25:04 +0800 |
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bt_wait_ptr() will increase 'wait_index', however, if blk_mq_get_tag() get a tag successfully after bt_wait_ptr() is called and before sbitmap_prepare_to_wait() is called, then the 'ws' is skipped. This behavior might cause 8 waitqueues to be unbalanced.
Move bt_wait_ptr() later should reduce the problem when the disk is under high io preesure.
Signed-off-by: Yu Kuai <yukuai3@huawei.com> --- block/blk-mq-tag.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c index 68ac23d0b640..a531351ab190 100644 --- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -131,7 +131,7 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data) { struct blk_mq_tags *tags = blk_mq_tags_from_data(data); struct sbitmap_queue *bt; - struct sbq_wait_state *ws; + struct sbq_wait_state *ws = NULL; DEFINE_SBQ_WAIT(wait); unsigned int tag_offset; int tag; @@ -155,7 +155,6 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data) if (data->flags & BLK_MQ_REQ_NOWAIT) return BLK_MQ_NO_TAG; - ws = bt_wait_ptr(bt, data->hctx); do { struct sbitmap_queue *bt_prev; @@ -173,7 +172,8 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data) tag = __blk_mq_get_tag(data, bt); if (tag != BLK_MQ_NO_TAG) break; - + if (!ws) + ws = bt_wait_ptr(bt, data->hctx); sbitmap_prepare_to_wait(bt, ws, &wait, TASK_UNINTERRUPTIBLE); tag = __blk_mq_get_tag(data, bt); -- 2.31.1
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