From: Jianchao Wang <jianchao.w.wang@oracle.com>
To: axboe@kernel.dk
Cc: hch@lst.de, jthumshirn@suse.de, hare@suse.de,
josef@toxicpanda.com, bvanassche@acm.org, sagi@grimberg.me,
keith.busch@intel.com, jsmart2021@gmail.com,
linux-block@vger.kernel.org, linux-nvme@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: [PATCH V2 0/8]: blk-mq: use static_rqs to iterate busy tags
Date: Mon, 25 Mar 2019 13:38:30 +0800 [thread overview]
Message-ID: <1553492318-1810-1-git-send-email-jianchao.w.wang@oracle.com> (raw)
As we know, there is a risk of accesing stale requests when iterate
in-flight requests with tags->rqs[] and this has been talked in following
thread,
[1] https://marc.info/?l=linux-scsi&m=154511693912752&w=2
[2] https://marc.info/?l=linux-block&m=154526189023236&w=2
A typical sence could be
blk_mq_get_request blk_mq_queue_tag_busy_iter
-> blk_mq_get_tag
-> bt_for_each
-> bt_iter
-> rq = taags->rqs[]
-> rq->q
-> blk_mq_rq_ctx_init
-> data->hctx->tags->rqs[rq->tag] = rq;
The root cause is that there is a window between set bit on tag sbitmap
and set tags->rqs[].
This patch would fix this issue by iterating requests with tags->static_rqs[]
instead of tags->rqs[] which would be changed dynamically. Moreover,
we will try to get a non-zero q_usage_counter before access hctxs and tags and
thus could avoid the race with updating nr_hw_queues, switching io scheduler
and even queue clean up which are all under a frozen and drained queue.
The 1st patch get rid of the useless of synchronize_rcu in __blk_mq_update_nr_hw_queues
The 2nd patch modify the blk_mq_queue_tag_busy_iter to use tags->static_rqs[]
instead of tags->rqs[] to iterate the busy tags.
The 3rd ~ 7th patch change the blk_mq_tagset_busy_iter to blk_mq_queue_tag_busy_iter
which is safer
The 8th patch get rid of the blk_mq_tagset_busy_iter.
Change log
V1 -> V2:
- Add wrapper to hide "inflight" parameter to user based on Sagi's suggestion.
- Other misc changes on comment.
Jianchao Wang (8)
blk-mq: get rid of the synchronize_rcu in
blk-mq: use static_rqs instead of rqs to iterate tags
blk-mq: use blk_mq_queue_tag_inflight_iter in debugfs
mtip32xx: use blk_mq_queue_tag_inflight_iter
nbd: use blk_mq_queue_tag_inflight_iter
skd: use blk_mq_queue_tag_inflight_iter
nvme: use blk_mq_queue_tag_inflight_iter
blk-mq: remove blk_mq_tagset_busy_iter
diff stat
block/blk-mq-debugfs.c | 2 +-
block/blk-mq-tag.c | 193 ++++++++++++++------------------------
block/blk-mq-tag.h | 4 +-
block/blk-mq.c | 31 ++----
drivers/block/mtip32xx/mtip32xx.c | 6 +-
drivers/block/nbd.c | 2 +-
drivers/block/skd_main.c | 4 +-
drivers/nvme/host/core.c | 12 +++
drivers/nvme/host/fc.c | 10 +-
drivers/nvme/host/nvme.h | 2 +
drivers/nvme/host/pci.c | 5 +-
drivers/nvme/host/rdma.c | 4 +-
drivers/nvme/host/tcp.c | 5 +-
drivers/nvme/target/loop.c | 4 +-
include/linux/blk-mq.h | 7 +-
15 files changed, 119 insertions(+), 172 deletions(-)
Thanks
Jianchao
next reply other threads:[~2019-03-25 5:48 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-25 5:38 Jianchao Wang [this message]
2019-03-25 5:38 ` [PATCH V2 1/8] blk-mq: get rid of the synchronize_rcu in __blk_mq_update_nr_hw_queues Jianchao Wang
2019-03-25 5:38 ` [PATCH V2 2/8] blk-mq: use static_rqs instead of rqs to iterate tags Jianchao Wang
2019-03-25 7:12 ` Dongli Zhang
2019-03-25 7:14 ` jianchao.wang
2019-03-25 5:38 ` [PATCH V2 3/8] blk-mq: use blk_mq_queue_tag_inflight_iter in debugfs Jianchao Wang
2019-03-25 5:38 ` [PATCH V2 4/8] mtip32xx: use blk_mq_queue_tag_inflight_iter Jianchao Wang
2019-03-25 5:38 ` [PATCH V2 5/8] nbd: " Jianchao Wang
2019-03-25 5:38 ` [PATCH V2 6/8] skd: " Jianchao Wang
2019-03-25 5:38 ` [PATCH V2 7/8] nvme: " Jianchao Wang
2019-03-25 13:49 ` Keith Busch
2019-03-26 1:17 ` jianchao.wang
2019-03-26 2:41 ` Ming Lei
2019-03-26 3:05 ` jianchao.wang
2019-03-26 23:57 ` Keith Busch
2019-03-27 2:03 ` jianchao.wang
2019-03-27 2:15 ` Keith Busch
2019-03-27 2:27 ` jianchao.wang
2019-03-27 2:33 ` Keith Busch
2019-03-27 2:45 ` jianchao.wang
2019-03-27 6:51 ` Keith Busch
2019-03-27 7:18 ` jianchao.wang
2019-03-25 5:38 ` [PATCH V2 8/8] blk-mq: remove blk_mq_tagset_busy_iter Jianchao Wang
2019-03-25 7:18 ` Hannes Reinecke
2019-03-25 7:37 ` jianchao.wang
2019-03-25 8:25 ` Hannes Reinecke
2019-03-25 9:12 ` jianchao.wang
2019-03-26 14:17 ` Jens Axboe
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