blkdev_issue_discard() hangs forever if the underlying storage deviceis removed

[Bart Van Assche]

Apparently blkdev_issue_discard() never times out, not even if the
device has been removed. This is what appeared in the kernel log after
device removal (triggered by running mkfs.ext4 on an SRP SCSI device
node):

sd 15:0:0:0: [sdb] Attached SCSI disk
scsi host15: SRP abort called
scsi host15: SRP reset_device called
scsi host15: ib_srp: SRP reset_host called
scsi host15: ib_srp: connection closed
scsi host15: ib_srp: Got failed path rec status -110
scsi host15: ib_srp: Path record query failed
scsi host15: ib_srp: reconnect failed (-110), removing target port.
sd 15:0:0:0: Device offlined - not ready after error recovery
INFO: task mkfs.ext4:4304 blocked for more than 120 seconds.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
mkfs.ext4       D 0000000000000000     0  4304   3649 0x00000000
 ffff88006c313b98 0000000000000046 ffffffff813e3038 ffffffff81e6b580
 0000000000000082 000000010003cfdc ffff88006c313fd8 ffff880070fbcbc0
 00000000001d1f40 ffff88006c313fd8 ffff88006c312000 ffff88006c312000
Call Trace:
 [<ffffffff813e3038>] ? schedule+0x628/0x830
 [<ffffffff813e3835>] schedule_timeout+0x1d5/0x310
 [<ffffffff810805de>] ? put_lock_stats+0xe/0x40
 [<ffffffff81080e05>] ? lock_release_holdtime+0xb5/0x160
 [<ffffffff813e6ac0>] ? _raw_spin_unlock_irq+0x30/0x60
 [<ffffffff8103f7d9>] ? sub_preempt_count+0xa9/0xe0
 [<ffffffff813e28e0>] wait_for_common+0x110/0x160
 [<ffffffff810425f0>] ? try_to_wake_up+0x2c0/0x2c0
 [<ffffffff813e2a0d>] wait_for_completion+0x1d/0x20
 [<ffffffff811de93a>] blkdev_issue_discard+0x27a/0x2c0
 [<ffffffff813e2806>] ? wait_for_common+0x36/0x160
 [<ffffffff811df371>] blkdev_ioctl+0x701/0x760
 [<ffffffff8112b7bf>] ? kmem_cache_free+0x6f/0x160
 [<ffffffff811755b7>] block_ioctl+0x47/0x50
 [<ffffffff81151b78>] do_vfs_ioctl+0x98/0x570
 [<ffffffff813e76dc>] ? sysret_check+0x27/0x62
 [<ffffffff8115209f>] sys_ioctl+0x4f/0x80
 [<ffffffff813e76ab>] system_call_fastpath+0x16/0x1b
no locks held by mkfs.ext4/4304.

The above message kept repeating forever until system reboot.

Kernel version:
$ git show | head -n 1
commit ed8f37370d83e695c0a4fa5d5fc7a83ecb947526
$ git describe
v3.0-7216-ged8f373

I'm considering this as a bug because the state described above makes it
impossible to kill the mkfs process and also makes it impossible to remove the
kernel module ib_srp. That's why I also reported this as
https://bugzilla.kernel.org/show_bug.cgi?id=40472.

Any opinions ?

Thanks,

Bart.
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