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Date: Mon, 10 Aug 2020 13:13:52 +0800
From: Rong Chen <rong.a.chen@...el.com>
To: Mike Snitzer <snitzer@...hat.com>,
kernel test robot <lkp@...el.com>
Cc: kbuild-all@...ts.01.org, linux-kernel@...r.kernel.org
Subject: Re: [kbuild-all] Re: drivers/md/dm-mpath.c:524
multipath_clone_and_map() error: double unlocked 'm->lock' (orig line 516)
On 8/8/20 10:35 PM, Mike Snitzer wrote:
> On Sat, Aug 08 2020 at 8:10am -0400,
> kernel test robot <lkp@...el.com> wrote:
>
>> tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
>> head: 449dc8c97089a6e09fb2dac4d92b1b7ac0eb7c1e
>> commit: 374117ad4736c5a4f8012cfe59fc07d9d58191d5 dm mpath: use double checked locking in fast path
>> date: 4 weeks ago
>> config: arm-randconfig-m031-20200808 (attached as .config)
>> compiler: arm-linux-gnueabi-gcc (GCC) 9.3.0
>>
>> If you fix the issue, kindly add following tag as appropriate
>> Reported-by: kernel test robot <lkp@...el.com>
> All 3 recent reports about smatch showing "double unlocked 'm->lock'"
> appear to be bogus. Think smatch is generating false positives (and
> given "Old smatch warnings" it seems it has been doing so for some
> time).
>
> In addition, does lkp@...el.com no longer test linux-next? The dm-mpath
> locking changes that were just merged into mainline have been in
> linux-next since July 13. Why were these tests only done against
> mainline?
Hi Mike,
kernel test robot still test linux-next, but the bisection worked on
linus/master and didn't check the fix in linux-next,
we'll optimize the bisection to avoid reporting this kind of problem.
Best Regards,
Rong Chen
>
> Mike
>
>
>
>> New smatch warnings:
>> drivers/md/dm-mpath.c:524 multipath_clone_and_map() error: double unlocked 'm->lock' (orig line 516)
>>
>> Old smatch warnings:
>> drivers/md/dm-mpath.c:446 choose_pgpath() error: double unlocked 'm->lock' (orig line 416)
>> drivers/md/dm-mpath.c:457 choose_pgpath() error: double unlocked 'm->lock' (orig line 403)
>> drivers/md/dm-mpath.c:525 multipath_clone_and_map() error: double unlocked 'm->lock' (orig line 516)
>> drivers/md/dm-mpath.c:526 multipath_clone_and_map() error: double unlocked 'm->lock' (orig line 524)
>> drivers/md/dm-mpath.c:626 __map_bio() error: double unlocked 'm->lock' (orig line 615)
>> drivers/md/dm-mpath.c:627 __map_bio() error: double unlocked 'm->lock' (orig line 615)
>> drivers/md/dm-mpath.c:628 __map_bio() error: double unlocked 'm->lock' (orig line 626)
>> drivers/md/dm-mpath.c:629 __map_bio() error: double unlocked 'm->lock' (orig line 628)
>> drivers/md/dm-mpath.c:1607 pg_init_done() error: double unlocked 'm->lock' (orig line 1560)
>> drivers/md/dm-mpath.c:1707 multipath_end_io_bio() error: double unlocked 'm->lock' (orig line 1704)
>> drivers/md/dm-mpath.c:1988 multipath_prepare_ioctl() error: double unlocked 'm->lock' (orig line 1984)
>> drivers/md/dm-mpath.c:2012 multipath_prepare_ioctl() error: double unlocked 'm->lock' (orig line 2001)
>>
>> vim +524 drivers/md/dm-mpath.c
>>
>> 498
>> 499 /*
>> 500 * Map cloned requests (request-based multipath)
>> 501 */
>> 502 static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
>> 503 union map_info *map_context,
>> 504 struct request **__clone)
>> 505 {
>> 506 struct multipath *m = ti->private;
>> 507 size_t nr_bytes = blk_rq_bytes(rq);
>> 508 struct pgpath *pgpath;
>> 509 struct block_device *bdev;
>> 510 struct dm_mpath_io *mpio = get_mpio(map_context);
>> 511 struct request_queue *q;
>> 512 struct request *clone;
>> 513
>> 514 /* Do we need to select a new pgpath? */
>> 515 pgpath = READ_ONCE(m->current_pgpath);
>> > 516 if (!pgpath || !mpath_double_check_test_bit(MPATHF_QUEUE_IO, m))
>> 517 pgpath = choose_pgpath(m, nr_bytes);
>> 518
>> 519 if (!pgpath) {
>> 520 if (must_push_back_rq(m))
>> 521 return DM_MAPIO_DELAY_REQUEUE;
>> 522 dm_report_EIO(m); /* Failed */
>> 523 return DM_MAPIO_KILL;
>> > 524 } else if (mpath_double_check_test_bit(MPATHF_QUEUE_IO, m) ||
>> 525 mpath_double_check_test_bit(MPATHF_PG_INIT_REQUIRED, m)) {
>> 526 pg_init_all_paths(m);
>> 527 return DM_MAPIO_DELAY_REQUEUE;
>> 528 }
>> 529
>> 530 mpio->pgpath = pgpath;
>> 531 mpio->nr_bytes = nr_bytes;
>> 532
>> 533 bdev = pgpath->path.dev->bdev;
>> 534 q = bdev_get_queue(bdev);
>> 535 clone = blk_get_request(q, rq->cmd_flags | REQ_NOMERGE,
>> 536 BLK_MQ_REQ_NOWAIT);
>> 537 if (IS_ERR(clone)) {
>> 538 /* EBUSY, ENODEV or EWOULDBLOCK: requeue */
>> 539 if (blk_queue_dying(q)) {
>> 540 atomic_inc(&m->pg_init_in_progress);
>> 541 activate_or_offline_path(pgpath);
>> 542 return DM_MAPIO_DELAY_REQUEUE;
>> 543 }
>> 544
>> 545 /*
>> 546 * blk-mq's SCHED_RESTART can cover this requeue, so we
>> 547 * needn't deal with it by DELAY_REQUEUE. More importantly,
>> 548 * we have to return DM_MAPIO_REQUEUE so that blk-mq can
>> 549 * get the queue busy feedback (via BLK_STS_RESOURCE),
>> 550 * otherwise I/O merging can suffer.
>> 551 */
>> 552 return DM_MAPIO_REQUEUE;
>> 553 }
>> 554 clone->bio = clone->biotail = NULL;
>> 555 clone->rq_disk = bdev->bd_disk;
>> 556 clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
>> 557 *__clone = clone;
>> 558
>> 559 if (pgpath->pg->ps.type->start_io)
>> 560 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
>> 561 &pgpath->path,
>> 562 nr_bytes);
>> 563 return DM_MAPIO_REMAPPED;
>> 564 }
>> 565
>>
>> ---
>> 0-DAY CI Kernel Test Service, Intel Corporation
>> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
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