nbd: fix io hung while disconnecting device

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2083917



commit 09dadb59
Author: Yu Kuai <yukuai3@huawei.com>
Date:   Sat May 21 15:37:47 2022 +0800

    nbd: fix io hung while disconnecting device

    In our tests, "qemu-nbd" triggers a io hung:

    INFO: task qemu-nbd:11445 blocked for more than 368 seconds.
          Not tainted 5.18.0-rc3-next-20220422-00003-g2176915513ca #884
    "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
    task:qemu-nbd        state:D stack:    0 pid:11445 ppid:     1 flags:0x00000000
    Call Trace:
     <TASK>
     __schedule+0x480/0x1050
     ? _raw_spin_lock_irqsave+0x3e/0xb0
     schedule+0x9c/0x1b0
     blk_mq_freeze_queue_wait+0x9d/0xf0
     ? ipi_rseq+0x70/0x70
     blk_mq_freeze_queue+0x2b/0x40
     nbd_add_socket+0x6b/0x270 [nbd]
     nbd_ioctl+0x383/0x510 [nbd]
     blkdev_ioctl+0x18e/0x3e0
     __x64_sys_ioctl+0xac/0x120
     do_syscall_64+0x35/0x80
     entry_SYSCALL_64_after_hwframe+0x44/0xae
    RIP: 0033:0x7fd8ff706577
    RSP: 002b:00007fd8fcdfebf8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
    RAX: ffffffffffffffda RBX: 0000000040000000 RCX: 00007fd8ff706577
    RDX: 000000000000000d RSI: 000000000000ab00 RDI: 000000000000000f
    RBP: 000000000000000f R08: 000000000000fbe8 R09: 000055fe497c62b0
    R10: 00000002aff20000 R11: 0000000000000246 R12: 000000000000006d
    R13: 0000000000000000 R14: 00007ffe82dc5e70 R15: 00007fd8fcdff9c0

    "qemu-ndb -d" will call ioctl 'NBD_DISCONNECT' first, however, following
    message was found:

    block nbd0: Send disconnect failed -32

    Which indicate that something is wrong with the server. Then,
    "qemu-nbd -d" will call ioctl 'NBD_CLEAR_SOCK', however ioctl can't clear
    requests after commit 2516ab15("nbd: only clear the queue on device
    teardown"). And in the meantime, request can't complete through timeout
    because nbd_xmit_timeout() will always return 'BLK_EH_RESET_TIMER', which
    means such request will never be completed in this situation.

    Now that the flag 'NBD_CMD_INFLIGHT' can make sure requests won't
    complete multiple times, switch back to call nbd_clear_sock() in
    nbd_clear_sock_ioctl(), so that inflight requests can be cleared.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
    Link: https://lore.kernel.org/r/20220521073749.3146892-5-yukuai3@huawei.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Signed-off-by: Ming Lei <ming.lei@redhat.com>