Re: [syzbot] [nbd?] possible deadlock in nbd_queue_rq

From: Hillf Danton
Date: Sun Jul 06 2025 - 21:00:23 EST

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In reply to: syzbot: "[syzbot] [nbd?] possible deadlock in nbd_queue_rq"
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> Date: Sun, 06 Jul 2025 09:33:27 -0700
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 26ffb3d6f02c Add linux-next specific files for 20250704
> git tree: linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=154e6582580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=1e4f88512ae53408
> dashboard link: https://syzkaller.appspot.com/bug?extid=3dbc6142c85cc77eaf04
> compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/fd5569903143/disk-26ffb3d6.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/1b0c9505c543/vmlinux-26ffb3d6.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/9d864c72bed1/bzImage-26ffb3d6.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+3dbc6142c85cc77eaf04@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> ======================================================
> WARNING: possible circular locking dependency detected
> 6.16.0-rc4-next-20250704-syzkaller #0 Not tainted
> ------------------------------------------------------
> udevd/6083 is trying to acquire lock:
> ffff88807b837870 (&nsock->tx_lock){+.+.}-{4:4}, at: nbd_handle_cmd drivers/block/nbd.c:1140 [inline]
> ffff88807b837870 (&nsock->tx_lock){+.+.}-{4:4}, at: nbd_queue_rq+0x257/0xf10 drivers/block/nbd.c:1204
>
> but task is already holding lock:
> ffff8880597ee178 (&cmd->lock){+.+.}-{4:4}, at: nbd_queue_rq+0xc8/0xf10 drivers/block/nbd.c:1196
>
> which lock already depends on the new lock.
>
>
> the existing dependency chain (in reverse order) is:
>
> -> #6 (&cmd->lock){+.+.}-{4:4}:
> lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
> __mutex_lock_common kernel/locking/mutex.c:602 [inline]
> __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:747
> nbd_queue_rq+0xc8/0xf10 drivers/block/nbd.c:1196
> blk_mq_dispatch_rq_list+0x4c0/0x1900 block/blk-mq.c:2118
> __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline]
> blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline]
> __blk_mq_sched_dispatch_requests+0xda4/0x1570 block/blk-mq-sched.c:307
> blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329
> blk_mq_run_hw_queue+0x348/0x4f0 block/blk-mq.c:2356
> blk_mq_dispatch_list+0xd0c/0xe00 include/linux/spinlock.h:-1
> blk_mq_flush_plug_list+0x469/0x550 block/blk-mq.c:2965
> __blk_flush_plug+0x3d3/0x4b0 block/blk-core.c:1220
> blk_finish_plug block/blk-core.c:1247 [inline]
> __submit_bio+0x2d3/0x5a0 block/blk-core.c:649
> __submit_bio_noacct_mq block/blk-core.c:722 [inline]
> submit_bio_noacct_nocheck+0x4ab/0xb50 block/blk-core.c:751
> submit_bh fs/buffer.c:2829 [inline]
> block_read_full_folio+0x7b7/0x830 fs/buffer.c:2461
> filemap_read_folio+0x117/0x380 mm/filemap.c:2413
> do_read_cache_folio+0x350/0x590 mm/filemap.c:3957
> read_mapping_folio include/linux/pagemap.h:972 [inline]
> read_part_sector+0xb6/0x2b0 block/partitions/core.c:722
> adfspart_check_ICS+0xa4/0xa50 block/partitions/acorn.c:360
> check_partition block/partitions/core.c:141 [inline]
> blk_add_partitions block/partitions/core.c:589 [inline]
> bdev_disk_changed+0x75c/0x14b0 block/partitions/core.c:693
> blkdev_get_whole+0x380/0x510 block/bdev.c:748
> bdev_open+0x31e/0xd30 block/bdev.c:957
> blkdev_open+0x3a8/0x510 block/fops.c:676
> do_dentry_open+0xdf0/0x1970 fs/open.c:964
> vfs_open+0x3b/0x340 fs/open.c:1094
> do_open fs/namei.c:3887 [inline]
> path_openat+0x2ee5/0x3830 fs/namei.c:4046
> do_filp_open+0x1fa/0x410 fs/namei.c:4073
> do_sys_openat2+0x121/0x1c0 fs/open.c:1434
> do_sys_open fs/open.c:1449 [inline]
> __do_sys_openat fs/open.c:1465 [inline]
> __se_sys_openat fs/open.c:1460 [inline]
> __x64_sys_openat+0x138/0x170 fs/open.c:1460
> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> -> #5 (set->srcu){.+.+}-{0:0}:
> lock_sync+0xba/0x160 kernel/locking/lockdep.c:5919
> srcu_lock_sync include/linux/srcu.h:173 [inline]
> __synchronize_srcu+0x96/0x3a0 kernel/rcu/srcutree.c:1429
> elevator_switch+0x12b/0x5f0 block/elevator.c:587
> elevator_change+0x21b/0x320 block/elevator.c:679
> elevator_set_default+0x144/0x210 block/elevator.c:737
> blk_register_queue+0x35d/0x400 block/blk-sysfs.c:879
> __add_disk+0x677/0xd50 block/genhd.c:528
> add_disk_fwnode+0xfc/0x480 block/genhd.c:597
> add_disk include/linux/blkdev.h:765 [inline]
> nbd_dev_add+0x70e/0xb00 drivers/block/nbd.c:1963
> nbd_init+0x21a/0x2d0 drivers/block/nbd.c:2670

The first case of nbd_init in the lock chain,

> do_one_initcall+0x233/0x820 init/main.c:1269
> do_initcall_level+0x137/0x1f0 init/main.c:1331
> do_initcalls+0x69/0xd0 init/main.c:1347
> kernel_init_freeable+0x3d9/0x570 init/main.c:1579
> kernel_init+0x1d/0x1d0 init/main.c:1469
> ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
>
> -> #4 (&q->elevator_lock){+.+.}-{4:4}:
> lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
> __mutex_lock_common kernel/locking/mutex.c:602 [inline]
> __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:747
> elv_update_nr_hw_queues+0x87/0x2a0 block/elevator.c:699
> __blk_mq_update_nr_hw_queues block/blk-mq.c:5024 [inline]
> blk_mq_update_nr_hw_queues+0xd54/0x14c0 block/blk-mq.c:5045
> nbd_start_device+0x16c/0xac0 drivers/block/nbd.c:1476
> nbd_genl_connect+0x1250/0x1930 drivers/block/nbd.c:2201
> genl_family_rcv_msg_doit+0x212/0x300 net/netlink/genetlink.c:1115
> genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
> genl_rcv_msg+0x60e/0x790 net/netlink/genetlink.c:1210
> netlink_rcv_skb+0x208/0x470 net/netlink/af_netlink.c:2534
> genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
> netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline]
> netlink_unicast+0x75b/0x8d0 net/netlink/af_netlink.c:1339
> netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1883
> sock_sendmsg_nosec net/socket.c:714 [inline]
> __sock_sendmsg+0x219/0x270 net/socket.c:729
> ____sys_sendmsg+0x505/0x830 net/socket.c:2614
> ___sys_sendmsg+0x21f/0x2a0 net/socket.c:2668
> __sys_sendmsg net/socket.c:2700 [inline]
> __do_sys_sendmsg net/socket.c:2705 [inline]
> __se_sys_sendmsg net/socket.c:2703 [inline]
> __x64_sys_sendmsg+0x19b/0x260 net/socket.c:2703
> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> -> #3 (&q->q_usage_counter(io)#49){++++}-{0:0}:
> lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
> blk_alloc_queue+0x538/0x620 block/blk-core.c:461
> blk_mq_alloc_queue block/blk-mq.c:4398 [inline]
> __blk_mq_alloc_disk+0x162/0x340 block/blk-mq.c:4445
> nbd_dev_add+0x476/0xb00 drivers/block/nbd.c:1933
> nbd_init+0x21a/0x2d0 drivers/block/nbd.c:2670

and given the second one, the report is false positive.

> do_one_initcall+0x233/0x820 init/main.c:1269
> do_initcall_level+0x137/0x1f0 init/main.c:1331
> do_initcalls+0x69/0xd0 init/main.c:1347
> kernel_init_freeable+0x3d9/0x570 init/main.c:1579
> kernel_init+0x1d/0x1d0 init/main.c:1469
> ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
>
> -> #2 (fs_reclaim){+.+.}-{0:0}:
> lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
> __fs_reclaim_acquire mm/page_alloc.c:4231 [inline]
> fs_reclaim_acquire+0x72/0x100 mm/page_alloc.c:4245
> might_alloc include/linux/sched/mm.h:318 [inline]
> slab_pre_alloc_hook mm/slub.c:4131 [inline]
> slab_alloc_node mm/slub.c:4209 [inline]
> kmem_cache_alloc_node_noprof+0x47/0x3c0 mm/slub.c:4281
> __alloc_skb+0x112/0x2d0 net/core/skbuff.c:660
> alloc_skb_fclone include/linux/skbuff.h:1386 [inline]
> tcp_stream_alloc_skb+0x3d/0x340 net/ipv4/tcp.c:892
> tcp_sendmsg_locked+0x1f46/0x5630 net/ipv4/tcp.c:1198
> tcp_sendmsg+0x2f/0x50 net/ipv4/tcp.c:1394
> sock_sendmsg_nosec net/socket.c:714 [inline]
> __sock_sendmsg+0x19c/0x270 net/socket.c:729
> sock_write_iter+0x258/0x330 net/socket.c:1179
> new_sync_write fs/read_write.c:593 [inline]
> vfs_write+0x548/0xa90 fs/read_write.c:686
> ksys_write+0x145/0x250 fs/read_write.c:738
> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> -> #1 (sk_lock-AF_INET){+.+.}-{0:0}:
> lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
> lock_sock_nested+0x48/0x100 net/core/sock.c:3727
> lock_sock include/net/sock.h:1667 [inline]
> inet_shutdown+0x6a/0x390 net/ipv4/af_inet.c:905
> nbd_mark_nsock_dead+0x2e9/0x560 drivers/block/nbd.c:318
> recv_work+0x2138/0x24f0 drivers/block/nbd.c:1018
> process_one_work kernel/workqueue.c:3239 [inline]
> process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3322
> worker_thread+0x8a0/0xda0 kernel/workqueue.c:3403
> kthread+0x70e/0x8a0 kernel/kthread.c:463
> ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
>
> -> #0 (&nsock->tx_lock){+.+.}-{4:4}:
> check_prev_add kernel/locking/lockdep.c:3168 [inline]
> check_prevs_add kernel/locking/lockdep.c:3287 [inline]
> validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3911
> __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240
> lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
> __mutex_lock_common kernel/locking/mutex.c:602 [inline]
> __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:747
> nbd_handle_cmd drivers/block/nbd.c:1140 [inline]
> nbd_queue_rq+0x257/0xf10 drivers/block/nbd.c:1204
> blk_mq_dispatch_rq_list+0x4c0/0x1900 block/blk-mq.c:2118
> __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline]
> blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline]
> __blk_mq_sched_dispatch_requests+0xda4/0x1570 block/blk-mq-sched.c:307
> blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329
> blk_mq_run_hw_queue+0x348/0x4f0 block/blk-mq.c:2356
> blk_mq_dispatch_list+0xd0c/0xe00 include/linux/spinlock.h:-1
> blk_mq_flush_plug_list+0x469/0x550 block/blk-mq.c:2965
> __blk_flush_plug+0x3d3/0x4b0 block/blk-core.c:1220
> blk_finish_plug block/blk-core.c:1247 [inline]
> __submit_bio+0x2d3/0x5a0 block/blk-core.c:649
> __submit_bio_noacct_mq block/blk-core.c:722 [inline]
> submit_bio_noacct_nocheck+0x4ab/0xb50 block/blk-core.c:751
> submit_bh fs/buffer.c:2829 [inline]
> block_read_full_folio+0x7b7/0x830 fs/buffer.c:2461
> filemap_read_folio+0x117/0x380 mm/filemap.c:2413
> do_read_cache_folio+0x350/0x590 mm/filemap.c:3957
> read_mapping_folio include/linux/pagemap.h:972 [inline]
> read_part_sector+0xb6/0x2b0 block/partitions/core.c:722
> adfspart_check_ICS+0xa4/0xa50 block/partitions/acorn.c:360
> check_partition block/partitions/core.c:141 [inline]
> blk_add_partitions block/partitions/core.c:589 [inline]
> bdev_disk_changed+0x75c/0x14b0 block/partitions/core.c:693
> blkdev_get_whole+0x380/0x510 block/bdev.c:748
> bdev_open+0x31e/0xd30 block/bdev.c:957
> blkdev_open+0x3a8/0x510 block/fops.c:676
> do_dentry_open+0xdf0/0x1970 fs/open.c:964
> vfs_open+0x3b/0x340 fs/open.c:1094
> do_open fs/namei.c:3887 [inline]
> path_openat+0x2ee5/0x3830 fs/namei.c:4046
> do_filp_open+0x1fa/0x410 fs/namei.c:4073
> do_sys_openat2+0x121/0x1c0 fs/open.c:1434
> do_sys_open fs/open.c:1449 [inline]
> __do_sys_openat fs/open.c:1465 [inline]
> __se_sys_openat fs/open.c:1460 [inline]
> __x64_sys_openat+0x138/0x170 fs/open.c:1460
> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> other info that might help us debug this:
>
> Chain exists of:
> &nsock->tx_lock --> set->srcu --> &cmd->lock
>
> Possible unsafe locking scenario:
>
> CPU0 CPU1
> ---- ----
> lock(&cmd->lock);
> lock(set->srcu);
> lock(&cmd->lock);
> lock(&nsock->tx_lock);
>
> *** DEADLOCK ***
>
> 3 locks held by udevd/6083:
> #0: ffff888024ed8358 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_open+0xe0/0xd30 block/bdev.c:945
> #1: ffff888024d36f90 (set->srcu){.+.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:161 [inline]
> #1: ffff888024d36f90 (set->srcu){.+.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:253 [inline]
> #1: ffff888024d36f90 (set->srcu){.+.+}-{0:0}, at: blk_mq_run_hw_queue+0x31f/0x4f0 block/blk-mq.c:2356
> #2: ffff8880597ee178 (&cmd->lock){+.+.}-{4:4}, at: nbd_queue_rq+0xc8/0xf10 drivers/block/nbd.c:1196
>
> stack backtrace:
> CPU: 0 UID: 0 PID: 6083 Comm: udevd Not tainted 6.16.0-rc4-next-20250704-syzkaller #0 PREEMPT(full)
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
> Call Trace:
> <TASK>
> dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
> print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2046
> check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2178
> check_prev_add kernel/locking/lockdep.c:3168 [inline]
> check_prevs_add kernel/locking/lockdep.c:3287 [inline]
> validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3911
> __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240
> lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
> __mutex_lock_common kernel/locking/mutex.c:602 [inline]
> __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:747
> nbd_handle_cmd drivers/block/nbd.c:1140 [inline]
> nbd_queue_rq+0x257/0xf10 drivers/block/nbd.c:1204
> blk_mq_dispatch_rq_list+0x4c0/0x1900 block/blk-mq.c:2118
> __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline]
> blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline]
> __blk_mq_sched_dispatch_requests+0xda4/0x1570 block/blk-mq-sched.c:307
> blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329
> blk_mq_run_hw_queue+0x348/0x4f0 block/blk-mq.c:2356
> blk_mq_dispatch_list+0xd0c/0xe00 include/linux/spinlock.h:-1
> blk_mq_flush_plug_list+0x469/0x550 block/blk-mq.c:2965
> __blk_flush_plug+0x3d3/0x4b0 block/blk-core.c:1220
> blk_finish_plug block/blk-core.c:1247 [inline]
> __submit_bio+0x2d3/0x5a0 block/blk-core.c:649
> __submit_bio_noacct_mq block/blk-core.c:722 [inline]
> submit_bio_noacct_nocheck+0x4ab/0xb50 block/blk-core.c:751
> submit_bh fs/buffer.c:2829 [inline]
> block_read_full_folio+0x7b7/0x830 fs/buffer.c:2461
> filemap_read_folio+0x117/0x380 mm/filemap.c:2413
> do_read_cache_folio+0x350/0x590 mm/filemap.c:3957
> read_mapping_folio include/linux/pagemap.h:972 [inline]
> read_part_sector+0xb6/0x2b0 block/partitions/core.c:722
> adfspart_check_ICS+0xa4/0xa50 block/partitions/acorn.c:360
> check_partition block/partitions/core.c:141 [inline]
> blk_add_partitions block/partitions/core.c:589 [inline]
> bdev_disk_changed+0x75c/0x14b0 block/partitions/core.c:693
> blkdev_get_whole+0x380/0x510 block/bdev.c:748
> bdev_open+0x31e/0xd30 block/bdev.c:957
> blkdev_open+0x3a8/0x510 block/fops.c:676
> do_dentry_open+0xdf0/0x1970 fs/open.c:964
> vfs_open+0x3b/0x340 fs/open.c:1094
> do_open fs/namei.c:3887 [inline]
> path_openat+0x2ee5/0x3830 fs/namei.c:4046
> do_filp_open+0x1fa/0x410 fs/namei.c:4073
> do_sys_openat2+0x121/0x1c0 fs/open.c:1434
> do_sys_open fs/open.c:1449 [inline]
> __do_sys_openat fs/open.c:1465 [inline]
> __se_sys_openat fs/open.c:1460 [inline]
> __x64_sys_openat+0x138/0x170 fs/open.c:1460
> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f674caa7407
> Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
> RSP: 002b:00007fff79271070 EFLAGS: 00000202 ORIG_RAX: 0000000000000101
> RAX: ffffffffffffffda RBX: 00007f674d25e880 RCX: 00007f674caa7407
> RDX: 00000000000a0800 RSI: 000055ad17c52fe0 RDI: ffffffffffffff9c
> RBP: 000055ad17c52910 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000202 R12: 000055ad17c53000
> R13: 000055ad17c6a430 R14: 0000000000000000 R15: 000055ad17c53000
> </TASK>
> block nbd0: Dead connection, failed to find a fallback
> block nbd0: shutting down sockets
> I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0
> Buffer I/O error on dev nbd0, logical block 0, async page read
> I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0
> Buffer I/O error on dev nbd0, logical block 0, async page read
> I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0
> Buffer I/O error on dev nbd0, logical block 0, async page read
> I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0
> Buffer I/O error on dev nbd0, logical block 0, async page read
> I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0
> Buffer I/O error on dev nbd0, logical block 0, async page read
> I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0
> Buffer I/O error on dev nbd0, logical block 0, async page read
> I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0
> Buffer I/O error on dev nbd0, logical block 0, async page read
> I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0
> Buffer I/O error on dev nbd0, logical block 0, async page read
> ldm_validate_partition_table(): Disk read failed.
> I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0
> Buffer I/O error on dev nbd0, logical block 0, async page read
> I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0
> Buffer I/O error on dev nbd0, logical block 0, async page read
> Dev nbd0: unable to read RDB block 0
> nbd0: unable to read partition table
> ldm_validate_partition_table(): Disk read failed.
> Dev nbd0: unable to read RDB block 0
> nbd0: unable to read partition table
>
>
> ---
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