Conditionally use __blk_put_request() or blk_put_request() instead of
just blk_put_request() in multipath_release_clone().
Otherwise a deadlock will occur because scsi_end_request() will take the
clone request's queue_lock, around its call to blk_finish_request(), and
then the later blk_put_request() also tries to take it:
[12749.916332] queued_spin_lock_slowpath+0xb/0xf
[12749.916335] _raw_spin_lock_irqsave+0x37/0x40
[12749.916339] blk_put_request+0x39/0x60
[12749.916342] multipath_release_clone+0xe/0x10 [dm_multipath]
[12749.916350] dm_softirq_done+0x156/0x240 [dm_mod]
[12749.916353] __blk_mq_complete_request+0x90/0x140
[12749.916355] blk_mq_complete_request+0x16/0x20
[12749.916360] dm_complete_request+0x23/0x40 [dm_mod]
[12749.916365] end_clone_request+0x1d/0x20 [dm_mod]
[12749.916367] blk_finish_request+0x83/0x120
[12749.916370] scsi_end_request+0x12d/0x1d0
[12749.916371] scsi_io_completion+0x13c/0x630
[12749.916374] ? set_next_entity+0x7c/0x780
[12749.916376] scsi_finish_command+0xd9/0x120
[12749.916378] scsi_softirq_done+0x12a/0x150
[12749.916380] blk_done_softirq+0x9e/0xd0
[12749.916382] __do_softirq+0xc9/0x269
[12749.916384] run_ksoftirqd+0x29/0x50
[12749.916385] smpboot_thread_fn+0x110/0x160
[12749.916387] kthread+0x109/0x140
[12749.916389] ? sort_range+0x30/0x30
[12749.916390] ? kthread_park+0x60/0x60
[12749.916391] ret_from_fork+0x25/0x30
This "fix" is gross in that the long-term fitness of stacking blk-mq DM
multipath (dm-mq) ontop of old .request_fn devices is questionable. The
above stack trace shows just how ugly it is to have old .request_fn SCSI
code cascade into blk-mq code during DM multipath request completion.
Signed-off-by: Mike Snitzer <snit...@redhat.com>
---
drivers/md/dm-mpath.c | 16 ++++++++++++++--
drivers/md/dm-rq.c | 8 +++++---
drivers/md/dm-target.c | 4 ++--
include/linux/device-mapper.h | 3 ++-
4 files changed, 23 insertions(+), 8 deletions(-)
diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index 0e8ab5b..34cf7b6 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -520,9 +520,21 @@ static int multipath_clone_and_map(struct dm_target *ti,
struct request *rq,
return DM_MAPIO_REMAPPED;
}
-static void multipath_release_clone(struct request *clone)
+static void multipath_release_clone(struct dm_target *ti, struct request
*clone)
{
- blk_put_request(clone);
+ struct multipath *m = ti->private;
+ struct request_queue *q = clone->q;
+
+ if (!q->mq_ops && m->queue_mode == DM_TYPE_MQ_REQUEST_BASED) {
+ /*
+ * dm-mq on .request_fn already holds clone->q->queue_lock
+ * via blk_finish_request()...
+ * - true for .request_fn SCSI, but is it _always_ true?
+ */
+ lockdep_assert_held(q->queue_lock);
+ __blk_put_request(q, clone);
+ } else
+ blk_put_request(clone);
}
/*
diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index c6ebc5b..95bb44c 100644
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c
@@ -220,11 +220,12 @@ static void dm_end_request(struct request *clone,
blk_status_t error)
{
int rw = rq_data_dir(clone);
struct dm_rq_target_io *tio = clone->end_io_data;
+ struct dm_target *ti = tio->ti;
struct mapped_device *md = tio->md;
struct request *rq = tio->orig;
blk_rq_unprep_clone(clone);
- tio->ti->type->release_clone_rq(clone);
+ ti->type->release_clone_rq(ti, clone);
rq_end_stats(md, rq);
if (!rq->q->mq_ops)
@@ -267,6 +268,7 @@ static void dm_mq_delay_requeue_request(struct request *rq,
unsigned long msecs)
static void dm_requeue_original_request(struct dm_rq_target_io *tio, bool
delay_requeue)
{
+ struct dm_target *ti = tio->ti;
struct mapped_device *md = tio->md;
struct request *rq = tio->orig;
int rw = rq_data_dir(rq);
@@ -274,7 +276,7 @@ static void dm_requeue_original_request(struct
dm_rq_target_io *tio, bool delay_
rq_end_stats(md, rq);
if (tio->clone) {
blk_rq_unprep_clone(tio->clone);
- tio->ti->type->release_clone_rq(tio->clone);
+ ti->type->release_clone_rq(ti, tio->clone);
}
if (!rq->q->mq_ops)
@@ -488,7 +490,7 @@ static int map_request(struct dm_rq_target_io *tio)
case DM_MAPIO_REMAPPED:
if (setup_clone(clone, rq, tio, GFP_ATOMIC)) {
/* -ENOMEM */
- ti->type->release_clone_rq(clone);
+ ti->type->release_clone_rq(ti, clone);
return DM_MAPIO_REQUEUE;
}
diff --git a/drivers/md/dm-target.c b/drivers/md/dm-target.c
index c0d7e60..adbd17b 100644
--- a/drivers/md/dm-target.c
+++ b/drivers/md/dm-target.c
@@ -138,12 +138,12 @@ static int io_err_clone_and_map_rq(struct dm_target *ti,
struct request *rq,
return DM_MAPIO_KILL;
}
-static void io_err_release_clone_rq(struct request *clone)
+static void io_err_release_clone_rq(struct dm_target *ti, struct request
*clone)
{
}
static long io_err_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
- long nr_pages, void **kaddr, pfn_t *pfn)
+ long nr_pages, void **kaddr, pfn_t *pfn)
{
return -EIO;
}
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 0c1b50ad..f2ca0ab 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -61,7 +61,8 @@ typedef int (*dm_clone_and_map_request_fn) (struct dm_target
*ti,
struct request *rq,
union map_info *map_context,
struct request **clone);
-typedef void (*dm_release_clone_request_fn) (struct request *clone);
+typedef void (*dm_release_clone_request_fn) (struct dm_target *ti,
+ struct request *clone);
/*
* Returns:
--
2.10.1
