[linux-lvm] LVM hangs up with snapshot merge initiated

[Jayaraman Thiruvady]

Hi all,

   I am using LVM 2.02.74 and my kernel is vanilla kernel 2.6.33 from
kernel.org. In lvm, there are 4 LVs created. I have one of LV to be
snapshot, which is of equal size LV. When i try to merge the snapshot
to the original LV, the lvm hangs up

And i get dmegs

[  278.551794] Buffer I/O error on device dm-6, logical block 0
[  278.551853] Buffer I/O error on device dm-6, logical block 0
[  278.551906] Buffer I/O error on device dm-6, logical block 0
[  278.551959] Buffer I/O error on device dm-6, logical block 0
[  278.552012] Buffer I/O error on device dm-6, logical block 0
[  278.552065] Buffer I/O error on device dm-6, logical block 0
[  278.552118] Buffer I/O error on device dm-6, logical block 0
[  278.552171] Buffer I/O error on device dm-6, logical block 0
[  278.552224] Buffer I/O error on device dm-6, logical block 0
[  278.552278] Buffer I/O error on device dm-6, logical block 7
and then
[  603.677690] INFO: task lvs:2657 blocked for more than 120 seconds.
[  603.677755] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
disables this message.
[  603.677837] lvs           D 0000000000000000     0  2657   1862 0x00000000
[  603.677840]  ffff880331a47bb8 0000000000000082 ffff880331a47b88
00000000af93d88f
[  603.677843]  000000000135d000 ffff8801b124efc0 0000000000000000
0000000000000282
[  603.677846]  ffff880331a47fd8 000000000000fb08 ffff8801b90bae00
ffff880330c61700
[  603.677849] Call Trace:
[  603.677851]  [<ffffffff8141c1c0>] ? dm_unplug_all+0x50/0x70
[  603.677854]  [<ffffffff815466c7>] io_schedule+0x47/0x70
[  603.677856]  [<ffffffff8116cece>] __blockdev_direct_IO+0x71e/0xc00
[  603.677859]  [<ffffffff815489ec>] ? _unlock_kernel+0x4c/0xa0
[  603.677862]  [<ffffffff8116ab3e>] blkdev_direct_IO+0x4e/0x50
[  603.677865]  [<ffffffff81169cf0>] ? blkdev_get_blocks+0x0/0xc0
[  603.677867]  [<ffffffff810edede>] generic_file_aio_read+0x61e/0x670
[  603.677870]  [<ffffffff8116b610>] ? blkdev_get+0x10/0x20
[  603.677872]  [<ffffffff8116b691>] ? blkdev_open+0x71/0xc0
[  603.677875]  [<ffffffff8113bd72>] do_sync_read+0xd2/0x110
[  603.677878]  [<ffffffff8116a0bc>] ? block_ioctl+0x3c/0x40
[  603.677880]  [<ffffffff8114b9bd>] ? vfs_ioctl+0x3d/0xd0
[  603.677883]  [<ffffffff8114bf28>] ? do_vfs_ioctl+0x88/0x570
[  603.677886]  [<ffffffff81244d86>] ? security_file_permission+0x16/0x20
[  603.677888]  [<ffffffff8113c5b5>] vfs_read+0xb5/0x1a0
[  603.677891]  [<ffffffff8113c6f1>] sys_read+0x51/0x80
[  603.677894]  [<ffffffff8100a072>] system_call_fastpath+0x16/0x1b

What could be problem?

Regards,
Jayaraman .T