The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 85067747cf9888249fa11fa49ef75af5192d3988 Mon Sep 17 00:00:00 2001

From: Ming Lei ming.lei@redhat.com Date: Wed, 24 Jun 2020 16:00:58 -0400 Subject: [PATCH] dm: do not use waitqueue for request-based DM

Given request-based DM now uses blk-mq's blk_mq_queue_inflight() to determine if outstanding IO has completed (and DM has no control over the blk-mq state machine used to track outstanding IO) it is unsafe to wakeup waiter (dm_wait_for_completion) before blk-mq has cleared a request's state bits (e.g. MQ_RQ_IN_FLIGHT or MQ_RQ_COMPLETE). As such dm_wait_for_completion() could be left to wait indefinitely if no other requests complete.

Fix this by eliminating request-based DM's use of waitqueue to wait for blk-mq requests to complete in dm_wait_for_completion.

Signed-off-by: Ming Lei ming.lei@redhat.com Depends-on: 3c94d83cb3526 ("blk-mq: change blk_mq_queue_busy() to blk_mq_queue_inflight()") Cc: stable@vger.kernel.org Signed-off-by: Mike Snitzer snitzer@redhat.com

diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c index f60c02512121..85e0daabad49 100644 --- a/drivers/md/dm-rq.c +++ b/drivers/md/dm-rq.c @@ -146,10 +146,6 @@ static void rq_end_stats(struct mapped_device *md, struct request *orig) */ static void rq_completed(struct mapped_device *md) { - /* nudge anyone waiting on suspend queue */ - if (unlikely(wq_has_sleeper(&md->wait))) - wake_up(&md->wait); - /* * dm_put() must be at the end of this function. See the comment above */ diff --git a/drivers/md/dm.c b/drivers/md/dm.c index e6807792fec8..446aff589732 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -654,28 +654,6 @@ static void free_tio(struct dm_target_io *tio) bio_put(&tio->clone); }

-static bool md_in_flight_bios(struct mapped_device *md) -{ - int cpu; - struct hd_struct *part = &dm_disk(md)->part0; - long sum = 0; - - for_each_possible_cpu(cpu) { - sum += part_stat_local_read_cpu(part, in_flight[0], cpu); - sum += part_stat_local_read_cpu(part, in_flight[1], cpu); - } - - return sum != 0; -} - -static bool md_in_flight(struct mapped_device *md) -{ - if (queue_is_mq(md->queue)) - return blk_mq_queue_inflight(md->queue); - else - return md_in_flight_bios(md); -} - u64 dm_start_time_ns_from_clone(struct bio *bio) { struct dm_target_io *tio = container_of(bio, struct dm_target_io, clone); @@ -2470,15 +2448,29 @@ void dm_put(struct mapped_device *md) } EXPORT_SYMBOL_GPL(dm_put);

-static int dm_wait_for_completion(struct mapped_device *md, long task_state) +static bool md_in_flight_bios(struct mapped_device *md) +{ + int cpu; + struct hd_struct *part = &dm_disk(md)->part0; + long sum = 0; + + for_each_possible_cpu(cpu) { + sum += part_stat_local_read_cpu(part, in_flight[0], cpu); + sum += part_stat_local_read_cpu(part, in_flight[1], cpu); + } + + return sum != 0; +} + +static int dm_wait_for_bios_completion(struct mapped_device *md, long task_state) { int r = 0; DEFINE_WAIT(wait);

- while (1) { + while (true) { prepare_to_wait(&md->wait, &wait, task_state);

- if (!md_in_flight(md)) + if (!md_in_flight_bios(md)) break;

if (signal_pending_state(task_state, current)) { @@ -2493,6 +2485,28 @@ static int dm_wait_for_completion(struct mapped_device *md, long task_state) return r; }

+static int dm_wait_for_completion(struct mapped_device *md, long task_state) +{ + int r = 0; + + if (!queue_is_mq(md->queue)) + return dm_wait_for_bios_completion(md, task_state); + + while (true) { + if (!blk_mq_queue_inflight(md->queue)) + break; + + if (signal_pending_state(task_state, current)) { + r = -EINTR; + break; + } + + msleep(5); + } + + return r; +} + /* * Process the deferred bios */