This is a note to let you know that I've just added the patch titled
dm: do not use waitqueue for request-based DM
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
dm-do-not-use-waitqueue-for-request-based-dm.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 263a9a6fccc9efc92f056328c105472f60273782
Author: Ming Lei <ming.lei@xxxxxxxxxx>
Date: Wed Jun 24 16:00:58 2020 -0400
dm: do not use waitqueue for request-based DM
[ Upstream commit 85067747cf9888249fa11fa49ef75af5192d3988 ]
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@xxxxxxxxxx>
Depends-on: 3c94d83cb3526 ("blk-mq: change blk_mq_queue_busy() to blk_mq_queue_inflight()")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Stable-dep-of: 1e1fd567d32f ("dm suspend: return -ERESTARTSYS instead of -EINTR")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index 6bc61927d3205..3d6ac63ee85ae 100644
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c
@@ -143,10 +143,6 @@ 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 36d21a5d09ebf..f6f5b68a6950b 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -637,28 +637,6 @@ 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);
@@ -2428,15 +2406,29 @@ 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)) {
@@ -2453,6 +2445,28 @@ 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
*/
