When stacking request-based dm device on non blk-mq device
and device-mapper target could not map the request
(error target is used, multipath target with all paths down, etc),
following warning will show up once:
WARNING: CPU: 7 PID: 0 at drivers/md/dm.c:1090 free_rq_clone+0x7a/0xf0
CPU: 7 PID: 0 Comm: swapper/7 Not tainted 4.1.0-rc5+ #1
..
Call Trace:
<IRQ> [<ffffffff81558095>] dump_stack+0x45/0x57
[<ffffffff8105ef3a>] warn_slowpath_common+0x8a/0xc0
[<ffffffff8105f02a>] warn_slowpath_null+0x1a/0x20
[<ffffffffa020bf3a>] free_rq_clone+0x7a/0xf0 [dm_mod]
[<ffffffffa020c7cc>] dm_softirq_done+0x13c/0x250 [dm_mod]
[<ffffffff812b87a0>] blk_done_softirq+0x80/0xa0
[<ffffffff81062f44>] __do_softirq+0xf4/0x2d0
[<ffffffff81063425>] irq_exit+0x125/0x130
[<ffffffff81037f05>] smp_call_function_single_interrupt+0x35/0x40
[<ffffffff8156027e>] call_function_single_interrupt+0x6e/0x80
<EOI> [<ffffffff8104b576>] ? native_safe_halt+0x6/0x10
[<ffffffff810b6348>] ? rcu_eqs_enter+0x68/0x90
[<ffffffff8100d6fe>] default_idle+0x1e/0xc0
[<ffffffff8100e1df>] arch_cpu_idle+0xf/0x20
[<ffffffff810a269c>] cpu_startup_entry+0x2fc/0x3a0
[<ffffffff81038892>] start_secondary+0x182/0x1b0
The warning was added by commit aa6df8dd28c0 ("dm: fix free_rq_clone()
NULL pointer when requeueing unmapped request").
But free_rq_clone() with clone->q == NULL is valid usage for non blk-mq
underlying device. Such a call can happen via dm_kill_unmapped_request().
Signed-off-by: Jun'ichi Nomura <j-nomura@xxxxxxxxxxxxx>
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 1badfb2..8ecd22b 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1087,14 +1087,13 @@ static void free_rq_clone(struct request *clone, bool must_be_mapped)
struct dm_rq_target_io *tio = clone->end_io_data;
struct mapped_device *md = tio->md;
- WARN_ON_ONCE(must_be_mapped && !clone->q);
-
blk_rq_unprep_clone(clone);
- if (md->type == DM_TYPE_MQ_REQUEST_BASED)
+ if (md->type == DM_TYPE_MQ_REQUEST_BASED) {
/* stacked on blk-mq queue(s) */
+ WARN_ON_ONCE(must_be_mapped && !clone->q);
tio->ti->type->release_clone_rq(clone);
- else if (!md->queue->mq_ops)
+ } else if (!md->queue->mq_ops)
/* request_fn queue stacked on request_fn queue(s) */
free_clone_request(md, clone);
/*
--
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