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dm: do not use waitqueue for request-based DM

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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: 3c94d83cb3 ("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>
This commit is contained in:
Ming Lei 2020-06-24 16:00:58 -04:00 committed by Mike Snitzer
parent dcb7fd82c7
commit 85067747cf
2 changed files with 39 additions and 29 deletions
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4
drivers/md/dm-rq.c
View File

@ -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
*/

64
drivers/md/dm.c
View File

@ -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
*/