Snapshot NBD breaks nbd #58
Description
When you click on "snapshot" VM that is on nbd, the nbd device breaks and it cannot recover even after stoping and starting VM again.
Also after that, when i did "move disk" from such nbd to moosefs file based share, it moved 100G in one second, deleted nbd disk and lost VM (but it was test VM anyways so cool)
`[107460.479236] nbd0: detected capacity change from 0 to 209715200
[107461.493755] tap603i0: entered promiscuous mode
[107461.544363] vmbr0: port 10(tap603i0) entered blocking state
[107461.544720] vmbr0: port 10(tap603i0) entered disabled state
[107461.544992] tap603i0: entered allmulticast mode
[107461.546009] vmbr0: port 10(tap603i0) entered blocking state
[107461.546724] vmbr0: port 10(tap603i0) entered forwarding state
[109062.177478] nbd1: detected capacity change from 0 to 1056
[109262.236652] block nbd0: NBD_DISCONNECT
[109262.238201] block nbd0: Unexpected reply (0) 00000000819febcb
[109262.238749] block nbd0: Disconnected due to user request.
[109262.239094] block nbd0: NBD_DISCONNECT
[109262.239499] block nbd0: Send disconnect failed -32
[109262.240827] I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
[109262.241294] Buffer I/O error on dev nbd0, logical block 0, async page read
[109262.241635] I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
[109262.242060] Buffer I/O error on dev nbd0, logical block 0, async page read
[109262.242360] I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
[109262.242633] Buffer I/O error on dev nbd0, logical block 0, async page read
[109262.242888] I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
[109262.243130] Buffer I/O error on dev nbd0, logical block 0, async page read
[109262.243350] ldm_validate_partition_table(): Disk read failed.
[109262.243561] I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
[109262.243799] Buffer I/O error on dev nbd0, logical block 0, async page read
[109262.244019] I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
[109262.244243] Buffer I/O error on dev nbd0, logical block 0, async page read
[109262.244462] I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
[109262.244688] Buffer I/O error on dev nbd0, logical block 0, async page read
[109262.244918] I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
[109262.245158] Buffer I/O error on dev nbd0, logical block 0, async page read
[109262.245423] Dev nbd0: unable to read RDB block 0
[109262.245619] I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
[109262.245835] Buffer I/O error on dev nbd0, logical block 0, async page read
[109262.246053] I/O error, dev nbd0, sector 24 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
[109262.246266] Buffer I/O error on dev nbd0, logical block 3, async page read
[109262.246484] nbd0: unable to read partition table
[109262.262291] ldm_validate_partition_table(): Disk read failed.
[109262.263401] Dev nbd0: unable to read RDB block 0
[109262.263729] nbd0: unable to read partition table
[109262.278420] ldm_validate_partition_table(): Disk read failed.
[109262.278987] Dev nbd0: unable to read RDB block 0
[109262.279249] nbd0: unable to read partition table
[109262.287990] ldm_validate_partition_table(): Disk read failed.
[109262.291336] Dev nbd0: unable to read RDB block 0
[109262.303220] nbd0: unable to read partition table
[109262.318589] ldm_validate_partition_table(): Disk read failed.
[109262.319285] Dev nbd0: unable to read RDB block 0
[109262.319568] nbd0: unable to read partition table
[109262.328389] ldm_validate_partition_table(): Disk read failed.
[109262.333244] Dev nbd0: unable to read RDB block 0
[109262.342717] nbd0: unable to read partition table
[109262.765285] nbd2: detected capacity change from 0 to 209715200
[109262.774093] ldm_validate_partition_table(): Disk read failed.
[109262.775295] Dev nbd0: unable to read RDB block 0
[109262.775590] nbd0: unable to read partition table
[109262.778191] ldm_validate_partition_table(): Disk read failed.
[109262.778982] Dev nbd0: unable to read RDB block 0
[109262.779309] nbd0: unable to read partition table
[109262.785419] ldm_validate_partition_table(): Disk read failed.
[109262.786411] Dev nbd0: unable to read RDB block 0
[109262.786845] nbd0: unable to read partition table
[109262.788131] ldm_validate_partition_table(): Disk read failed.
[109262.788539] Dev nbd0: unable to read RDB block 0
[109262.788785] nbd0: unable to read partition table
[109306.717405] block nbd2: NBD_DISCONNECT
[109306.717872] block nbd2: Unexpected reply (0) 0000000000000000
[109306.718641] block nbd2: Disconnected due to user request.
[109306.719182] block nbd2: NBD_DISCONNECT
[109306.719661] block nbd2: Send disconnect failed -32
[109306.767625] blk_print_req_error: 126 callbacks suppressed
[109306.767628] I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
[109306.768236] buffer_io_error: 102 callbacks suppressed
[109306.768238] Buffer I/O error on dev nbd0, logical block 0, async page read
[109306.768625] I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
[109306.768813] Buffer I/O error on dev nbd0, logical block 0, async page read
[109306.769004] I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
[109306.769187] Buffer I/O error on dev nbd0, logical block 0, async page read
[109306.769370] I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
[109306.769550] Buffer I/O error on dev nbd0, logical block 0, async page read
[109306.769729] ldm_validate_partition_table(): Disk read failed.
[109306.769910] I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
[109306.770103] Buffer I/O error on dev nbd0, logical block 0, async page read
[109306.770287] I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
[109306.770468] Buffer I/O error on dev nbd0, logical block 0, async page read
[109306.770652] I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
[109306.770833] Buffer I/O error on dev nbd0, logical block 0, async page read
[109306.771021] I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
[109306.771206] Buffer I/O error on dev nbd0, logical block 0, async page read
[109306.771390] Dev nbd0: unable to read RDB block 0
[109306.771580] I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
[109306.771770] Buffer I/O error on dev nbd0, logical block 0, async page read
[109306.771965] I/O error, dev nbd0, sector 24 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
[109306.772157] Buffer I/O error on dev nbd0, logical block 3, async page read
[109306.772356] nbd0: unable to read partition table
[109306.781053] ldm_validate_partition_table(): Disk read failed.
[109306.781840] Dev nbd0: unable to read RDB block 0
[109306.782123] nbd0: unable to read partition table
[109306.782515] ldm_validate_partition_table(): Disk read failed.
[109306.783258] Dev nbd0: unable to read RDB block 0
[109306.783591] nbd0: unable to read partition table
[109306.798387] ldm_validate_partition_table(): Disk read failed.
[109306.799756] Dev nbd0: unable to read RDB block 0
[109306.800177] nbd0: unable to read partition table
[109306.801527] ldm_validate_partition_table(): Disk read failed.
[109306.802121] Dev nbd0: unable to read RDB block 0
[109306.802472] nbd0: unable to read partition table
[109307.326150] nbd2: detected capacity change from 0 to 209715200
and then stopped and started or made that migration:
[109306.772356] nbd0: unable to read partition table
[109306.781053] ldm_validate_partition_table(): Disk read failed.
[109306.781840] Dev nbd0: unable to read RDB block 0
[109306.782123] nbd0: unable to read partition table
[109306.782515] ldm_validate_partition_table(): Disk read failed.
[109306.783258] Dev nbd0: unable to read RDB block 0
[109306.783591] nbd0: unable to read partition table
[109306.798387] ldm_validate_partition_table(): Disk read failed.
[109306.799756] Dev nbd0: unable to read RDB block 0
[109306.800177] nbd0: unable to read partition table
[109306.801527] ldm_validate_partition_table(): Disk read failed.
[109306.802121] Dev nbd0: unable to read RDB block 0
[109306.802472] nbd0: unable to read partition table
[109307.326150] nbd2: detected capacity change from 0 to 209715200
[109324.653274] tap603i0: left allmulticast mode
[109324.653671] vmbr0: port 10(tap603i0) entered disabled state
[109324.786882] block nbd2: NBD_DISCONNECT
[109324.787303] block nbd2: Unexpected reply (0) 0000000000000000
[109324.788203] block nbd2: Disconnected due to user request.
[109324.788642] block nbd2: NBD_DISCONNECT
[109324.789118] block nbd2: Send disconnect failed -32
`