I've been using bcache on a Xen host (sitting on an LVM partition) for
many months without problems
Now that I added DRBD on top of bcache, bcache locks up within a few
hours, giving me this message:
Jul 5 04:06:43 dom0 kernel: [23043.136864] INFO: task
bcache_writebac:1342 blocked for more than 120 seconds.
Jul 5 04:06:43 dom0 kernel: [23043.136896] Not tainted
4.4.0-28-generic #47-Ubuntu
Jul 5 04:06:43 dom0 kernel: [23043.136916] "echo 0 >
/proc/sys/kernel/hung_task_timeout_secs" disables this message.
Jul 5 04:06:43 dom0 kernel: [23043.136946] bcache_writebac D
ffff880000983d18 0 1342 2 0x00000000
Jul 5 04:06:43 dom0 kernel: [23043.136952] ffff880000983d18
0000000000007ff0 ffffffff81e11500 ffff880035705780
Jul 5 04:06:43 dom0 kernel: [23043.136955] ffff880000984000
ffff880005080af0 ffff880005080ad8 ffffffff00000000
Jul 5 04:06:43 dom0 kernel: [23043.136958] ffffffff00000003
ffff880000983d30 ffffffff818235b5 ffff880035705780
Jul 5 04:06:43 dom0 kernel: [23043.136962] Call Trace:
Jul 5 04:06:43 dom0 kernel: [23043.136971] [<ffffffff818235b5>]
schedule+0x35/0x80
Jul 5 04:06:43 dom0 kernel: [23043.136974] [<ffffffff81826202>]
rwsem_down_write_failed+0x202/0x350
Jul 5 04:06:43 dom0 kernel: [23043.136990] [<ffffffffc015e6d0>] ?
read_dirty+0x370/0x370 [bcache]
Jul 5 04:06:43 dom0 kernel: [23043.136995] [<ffffffff813f9643>]
call_rwsem_down_write_failed+0x13/0x20
Jul 5 04:06:43 dom0 kernel: [23043.136999] [<ffffffff81825a3d>] ?
down_write+0x2d/0x40
Jul 5 04:06:43 dom0 kernel: [23043.137009] [<ffffffffc015e72b>]
bch_writeback_thread+0x5b/0x4c0 [bcache]
Jul 5 04:06:43 dom0 kernel: [23043.137020] [<ffffffffc015e6d0>] ?
read_dirty+0x370/0x370 [bcache]
Jul 5 04:06:43 dom0 kernel: [23043.137024] [<ffffffff810a0808>]
kthread+0xd8/0xf0
Jul 5 04:06:43 dom0 kernel: [23043.137027] [<ffffffff810a0730>] ?
kthread_create_on_node+0x1e0/0x1e0
Jul 5 04:06:43 dom0 kernel: [23043.137029] [<ffffffff81827a4f>]
ret_from_fork+0x3f/0x70
Jul 5 04:06:43 dom0 kernel: [23043.137032] [<ffffffff810a0730>] ?
kthread_create_on_node+0x1e0/0x1e0
Jul 5 04:06:43 dom0 kernel: [23043.137043] INFO: task
blkback.5.hda:3357 blocked for more than 120 seconds.
Jul 5 04:06:43 dom0 kernel: [23043.137069] Not tainted
4.4.0-28-generic #47-Ubuntu
Jul 5 04:06:43 dom0 kernel: [23043.137090] "echo 0 >
/proc/sys/kernel/hung_task_timeout_secs" disables this message.
Jul 5 04:06:43 dom0 kernel: [23043.137119] blkback.5.hda D
ffff88002341ba48 0 3357 2 0x00000000
Jul 5 04:06:43 dom0 kernel: [23043.137122] ffff88002341ba48
ffff88002341ba08 ffffffff81e11500 ffff880034189900
Jul 5 04:06:43 dom0 kernel: [23043.137124] ffff88002341c000
ffff880005080ad8 ffff880005080af0 ffff880023e08e60
Jul 5 04:06:43 dom0 kernel: [23043.137126] ffff880005080000
ffff88002341ba60 ffffffff818235b5 ffff880034189900
Jul 5 04:06:43 dom0 kernel: [23043.137128] Call Trace:
Jul 5 04:06:43 dom0 kernel: [23043.137131] [<ffffffff818235b5>]
schedule+0x35/0x80
Jul 5 04:06:43 dom0 kernel: [23043.137133] [<ffffffff81826430>]
rwsem_down_read_failed+0xe0/0x140
Jul 5 04:06:43 dom0 kernel: [23043.137136] [<ffffffff811903e5>] ?
mempool_alloc_slab+0x15/0x20
Jul 5 04:06:43 dom0 kernel: [23043.137138] [<ffffffff813f9614>]
call_rwsem_down_read_failed+0x14/0x30
Jul 5 04:06:43 dom0 kernel: [23043.137140] [<ffffffff81825a00>] ?
down_read+0x20/0x30
Jul 5 04:06:43 dom0 kernel: [23043.137148] [<ffffffffc01522a2>]
cached_dev_make_request+0x682/0xcc0 [bcache]
Jul 5 04:06:43 dom0 kernel: [23043.137151] [<ffffffff813bba52>]
generic_make_request+0xf2/0x1d0
Jul 5 04:06:43 dom0 kernel: [23043.137153] [<ffffffff813bbba6>]
submit_bio+0x76/0x170
Jul 5 04:06:43 dom0 kernel: [23043.137157] [<ffffffffc04ebbb7>]
dispatch_rw_block_io+0x7b7/0xab0 [xen_blkback]
Jul 5 04:06:43 dom0 kernel: [23043.137159] [<ffffffff8101d204>] ?
xen_load_sp0+0x84/0x180
Jul 5 04:06:43 dom0 kernel: [23043.137162] [<ffffffff810ca961>] ?
__raw_callee_save___pv_queued_spin_unlock+0x11/0x20
Jul 5 04:06:43 dom0 kernel: [23043.137165] [<ffffffffc04ec245>]
__do_block_io_op+0x395/0x710 [xen_blkback]
Jul 5 04:06:43 dom0 kernel: [23043.137167] [<ffffffff810ec8a8>] ?
del_timer_sync+0x48/0x50
Jul 5 04:06:43 dom0 kernel: [23043.137170] [<ffffffffc04eca7d>]
xen_blkif_schedule+0xdd/0x7b0 [xen_blkback]
Jul 5 04:06:43 dom0 kernel: [23043.137172] [<ffffffff810a975d>] ?
finish_task_switch+0x7d/0x220
Jul 5 04:06:43 dom0 kernel: [23043.137175] [<ffffffff810c3ca0>] ?
wake_atomic_t_function+0x60/0x60
Jul 5 04:06:43 dom0 kernel: [23043.137177] [<ffffffffc04ec9a0>] ?
xen_blkif_be_int+0x30/0x30 [xen_blkback]
Jul 5 04:06:43 dom0 kernel: [23043.137179] [<ffffffff810a0808>]
kthread+0xd8/0xf0
Jul 5 04:06:43 dom0 kernel: [23043.137181] [<ffffffff810a0730>] ?
kthread_create_on_node+0x1e0/0x1e0
Jul 5 04:06:43 dom0 kernel: [23043.137183] [<ffffffff81827a4f>]
ret_from_fork+0x3f/0x70
Jul 5 04:06:43 dom0 kernel: [23043.137185] [<ffffffff810a0730>] ?
kthread_create_on_node+0x1e0/0x1e0
At the same time (but always after bcache), Xen's blkback will also
give a similar message:
Jul 5 04:08:43 dom0 kernel: [23163.135027] INFO: task
bcache_writebac:1342 blocked for more than 120 seconds.
Jul 5 04:08:43 dom0 kernel: [23163.135056] Not tainted
4.4.0-28-generic #47-Ubuntu
Jul 5 04:08:43 dom0 kernel: [23163.135076] "echo 0 >
/proc/sys/kernel/hung_task_timeout_secs" disables this message.
Jul 5 04:08:43 dom0 kernel: [23163.135105] bcache_writebac D
ffff880000983d18 0 1342 2 0x00000000
Jul 5 04:08:43 dom0 kernel: [23163.135109] ffff880000983d18
0000000000007ff0 ffffffff81e11500 ffff880035705780
Jul 5 04:08:43 dom0 kernel: [23163.135112] ffff880000984000
ffff880005080af0 ffff880005080ad8 ffffffff00000000
Jul 5 04:08:43 dom0 kernel: [23163.135114] ffffffff00000003
ffff880000983d30 ffffffff818235b5 ffff880035705780
Jul 5 04:08:43 dom0 kernel: [23163.135116] Call Trace:
Jul 5 04:08:43 dom0 kernel: [23163.135124] [<ffffffff818235b5>]
schedule+0x35/0x80
Jul 5 04:08:43 dom0 kernel: [23163.135127] [<ffffffff81826202>]
rwsem_down_write_failed+0x202/0x350
Jul 5 04:08:43 dom0 kernel: [23163.135139] [<ffffffffc015e6d0>] ?
read_dirty+0x370/0x370 [bcache]
Jul 5 04:08:43 dom0 kernel: [23163.135143] [<ffffffff813f9643>]
call_rwsem_down_write_failed+0x13/0x20
Jul 5 04:08:43 dom0 kernel: [23163.135145] [<ffffffff81825a3d>] ?
down_write+0x2d/0x40
Jul 5 04:08:43 dom0 kernel: [23163.135153] [<ffffffffc015e72b>]
bch_writeback_thread+0x5b/0x4c0 [bcache]
Jul 5 04:08:43 dom0 kernel: [23163.135160] [<ffffffffc015e6d0>] ?
read_dirty+0x370/0x370 [bcache]
Jul 5 04:08:43 dom0 kernel: [23163.135162] [<ffffffff810a0808>]
kthread+0xd8/0xf0
Jul 5 04:08:43 dom0 kernel: [23163.135164] [<ffffffff810a0730>] ?
kthread_create_on_node+0x1e0/0x1e0
Jul 5 04:08:43 dom0 kernel: [23163.135166] [<ffffffff81827a4f>]
ret_from_fork+0x3f/0x70
Jul 5 04:08:43 dom0 kernel: [23163.135168] [<ffffffff810a0730>] ?
kthread_create_on_node+0x1e0/0x1e0
Jul 5 04:08:43 dom0 kernel: [23163.135178] INFO: task
blkback.5.hda:3357 blocked for more than 120 seconds.
Jul 5 04:08:43 dom0 kernel: [23163.135204] Not tainted
4.4.0-28-generic #47-Ubuntu
Jul 5 04:08:43 dom0 kernel: [23163.135224] "echo 0 >
/proc/sys/kernel/hung_task_timeout_secs" disables this message.
Jul 5 04:08:43 dom0 kernel: [23163.135286] blkback.5.hda D
ffff88002341ba48 0 3357 2 0x00000000
Jul 5 04:08:43 dom0 kernel: [23163.135289] ffff88002341ba48
ffff88002341ba08 ffffffff81e11500 ffff880034189900
Jul 5 04:08:43 dom0 kernel: [23163.135291] ffff88002341c000
ffff880005080ad8 ffff880005080af0 ffff880023e08e60
Jul 5 04:08:43 dom0 kernel: [23163.135293] ffff880005080000
ffff88002341ba60 ffffffff818235b5 ffff880034189900
Jul 5 04:08:43 dom0 kernel: [23163.135295] Call Trace:
Jul 5 04:08:43 dom0 kernel: [23163.135299] [<ffffffff818235b5>]
schedule+0x35/0x80
Jul 5 04:08:43 dom0 kernel: [23163.135301] [<ffffffff81826430>]
rwsem_down_read_failed+0xe0/0x140
Jul 5 04:08:43 dom0 kernel: [23163.135304] [<ffffffff811903e5>] ?
mempool_alloc_slab+0x15/0x20
Jul 5 04:08:43 dom0 kernel: [23163.135307] [<ffffffff813f9614>]
call_rwsem_down_read_failed+0x14/0x30
Jul 5 04:08:43 dom0 kernel: [23163.135309] [<ffffffff81825a00>] ?
down_read+0x20/0x30
Jul 5 04:08:43 dom0 kernel: [23163.135316] [<ffffffffc01522a2>]
cached_dev_make_request+0x682/0xcc0 [bcache]
Jul 5 04:08:43 dom0 kernel: [23163.135319] [<ffffffff813bba52>]
generic_make_request+0xf2/0x1d0
Jul 5 04:08:43 dom0 kernel: [23163.135321] [<ffffffff813bbba6>]
submit_bio+0x76/0x170
Jul 5 04:08:43 dom0 kernel: [23163.135326] [<ffffffffc04ebbb7>]
dispatch_rw_block_io+0x7b7/0xab0 [xen_blkback]
Jul 5 04:08:43 dom0 kernel: [23163.135328] [<ffffffff8101d204>] ?
xen_load_sp0+0x84/0x180
Jul 5 04:08:43 dom0 kernel: [23163.135331] [<ffffffff810ca961>] ?
__raw_callee_save___pv_queued_spin_unlock+0x11/0x20
Jul 5 04:08:43 dom0 kernel: [23163.135334] [<ffffffffc04ec245>]
__do_block_io_op+0x395/0x710 [xen_blkback]
Jul 5 04:08:43 dom0 kernel: [23163.135337] [<ffffffff810ec8a8>] ?
del_timer_sync+0x48/0x50
Jul 5 04:08:43 dom0 kernel: [23163.135340] [<ffffffffc04eca7d>]
xen_blkif_schedule+0xdd/0x7b0 [xen_blkback]
Jul 5 04:08:43 dom0 kernel: [23163.135343] [<ffffffff810a975d>] ?
finish_task_switch+0x7d/0x220
Jul 5 04:08:43 dom0 kernel: [23163.135346] [<ffffffff810c3ca0>] ?
wake_atomic_t_function+0x60/0x60
Jul 5 04:08:43 dom0 kernel: [23163.135348] [<ffffffffc04ec9a0>] ?
xen_blkif_be_int+0x30/0x30 [xen_blkback]
Jul 5 04:08:43 dom0 kernel: [23163.135350] [<ffffffff810a0808>]
kthread+0xd8/0xf0
Jul 5 04:08:43 dom0 kernel: [23163.135352] [<ffffffff810a0730>] ?
kthread_create_on_node+0x1e0/0x1e0
Jul 5 04:08:43 dom0 kernel: [23163.135354] [<ffffffff81827a4f>]
ret_from_fork+0x3f/0x70
Jul 5 04:08:43 dom0 kernel: [23163.135356] [<ffffffff810a0730>] ?
kthread_create_on_node+0x1e0/0x1e0
Access to the storage is no longer possible, then (it'll just appear to hang).
This is on the newest Ubuntu 16.04 LTS, with their 4.4.0-28 kernel.
# lsb_release -d
Description: Ubuntu 16.04 LTS
# uname -r
4.4.0-28-generic
bcache is set to writeback.
# cat /sys/block/bcache0/bcache/cache_mode
writethrough [writeback] writearound none
# cat /sys/block/bcache0/bcache/state
dirty
# cat /sys/block/bcache0/bcache/dirty_data
56.0k
The relevant disk stack looks like this:
# lsblk
sdd 8:48 0 232.9G 0 disk
`-sdd1 8:49 0 232.9G 0 part
`-md1 9:1 0 232.8G 0 raid1
`-ssd-bcache--back 252:4 0 30G 0 lvm
`-bcache0 251:0 0 2T 0 disk
`-storage-drback--test 252:6 0 200G 0 lvm
storage-drback--test is the backing device for DRBD.
This is reproducible, but I do not know what causes it, or how to
cause it on purpose. All I know is that once I put DRBD on top of
bcache, and produce minor load over time (I just have a single idle
Windows 2012R2 server on it as test - as Windows would always do
*something* ;-) it will lock up within 8 hours.
Do you have any clues as to what could be causing this?
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