On Thu, Jul 26, 2018 at 1:55 AM Alex Gorbachev <ag@xxxxxxxxxxxxxxxxxxx> wrote: > > On Wed, Jul 25, 2018 at 7:07 PM, Alex Gorbachev <ag@xxxxxxxxxxxxxxxxxxx> wrote: > > On Wed, Jul 25, 2018 at 6:07 PM, Alex Gorbachev <ag@xxxxxxxxxxxxxxxxxxx> wrote: > >> On Wed, Jul 25, 2018 at 5:51 PM, Jason Dillaman <jdillama@xxxxxxxxxx> wrote: > >>> > >>> > >>> On Wed, Jul 25, 2018 at 5:41 PM Alex Gorbachev <ag@xxxxxxxxxxxxxxxxxxx> > >>> wrote: > >>>> > >>>> I am not sure this related to RBD, but in case it is, this would be an > >>>> important bug to fix. > >>>> > >>>> Running LVM on top of RBD, XFS filesystem on top of that, consumed in RHEL > >>>> 7.4. > >>>> > >>>> When running a large read operation and doing LVM snapshots during > >>>> that operation, the block being read winds up all zeroes in pagecache. > >>>> > >>>> Dropping the caches syncs up the block with what's on "disk" and > >>>> everything is fine. > >>>> > >>>> Working on steps to reproduce simply - ceph is Luminous 12.2.7, RHEL > >>>> client is Jewel 10.2.10-17.el7cp > >>> > >>> > >>> Is this krbd or QEMU+librbd? If the former, what kernel version are you > >>> running? > >> > >> It's krbd on RHEL. > >> > >> RHEL kernel: > >> > >> Linux dmg-cbcache01 3.10.0-862.el7.x86_64 #1 SMP Wed Mar 21 18:14:51 > >> EDT 2018 x86_64 x86_64 x86_64 GNU/Linux > > > > Not sure if this is exactly replicating the issue, but I was able to > > do this on two different systems: > > > > RHEL 7.4 kernel as above. > > > > Create a PVM PV on a mapped kRBD device > > > > example: pvcreate /dev/rbd/spin1/lvm1 > > > > Create a VG and LV, make an XFS FS > > > > vgcreate datavg /dev/rbd/spin1/lvm1 > > lvcreate -n data1 -L 5G datavg > > mkfs.xfs /dev/datavg/data1 > > <mount on something> > > > > Get some large file and copy it to some other file, same storage or > > different. All is well. > > > > Now snapshot the LV > > > > lvcreate -l8%ORIGIN -s -n snap_data1 /dev/datavg/data1 --addtag backup > > > > Now try to copy that file again. I get: > > > > NMI watchdog: BUG: soft lockup - CPU#2 stuck for 22s! [kworker/2:1:3470] > > > > And in dmesg (this is on Proxmox but I did the same on ESXi) > > > > [1397609.308673] sched: RT throttling activated > > [1397658.759259] NMI watchdog: BUG: soft lockup - CPU#0 stuck for 23s! > > [kworker/0:1:2648] > > [1397658.759354] Modules linked in: dm_snapshot dm_bufio rbd libceph > > rpcsec_gss_krb5 auth_rpcgss nfsv4 dns_resolver nfs lockd grace fscache > > sunrpc ppdev joydev pcspkr sg parport_pc virtio_balloon parport shpchp > > i2c_piix4 ip_tables xfs libcrc32c sd_mod sr_mod crc_t10dif > > crct10dif_generic cdrom crct10dif_common ata_generic pata_acpi > > virtio_scsi virtio_console virtio_net bochs_drm drm_kms_helper > > syscopyarea sysfillrect sysimgblt fb_sys_fops ttm drm ata_piix libata > > serio_raw virtio_pci i2c_core virtio_ring virtio floppy dm_mirror > > dm_region_hash dm_log dm_mod > > [1397658.759400] CPU: 0 PID: 2648 Comm: kworker/0:1 Kdump: loaded Not > > tainted 3.10.0-862.el7.x86_64 #1 > > [1397658.759402] Hardware name: QEMU Standard PC (i440FX + PIIX, > > 1996), BIOS rel-1.11.0-0-g63451fca13-prebuilt.qemu-project.org > > 04/01/2014 > > [1397658.759415] Workqueue: kcopyd do_work [dm_mod] > > [1397658.759418] task: ffff932df65d3f40 ti: ffff932fb138c000 task.ti: > > ffff932fb138c000 > > [1397658.759420] RIP: 0010:[<ffffffffc08535a0>] [<ffffffffc08535a0>] > > copy_callback+0x50/0x130 [dm_snapshot] > > [1397658.759426] RSP: 0018:ffff932fb138fd08 EFLAGS: 00000283 > > [1397658.759428] RAX: 000000000003e5e8 RBX: ffffebecc4943ec0 RCX: > > ffff932ff4704068 > > [1397658.759430] RDX: ffff932dc8050d00 RSI: ffff932fd6a0f9b8 RDI: > > 0000000000000000 > > [1397658.759431] RBP: ffff932fb138fd28 R08: ffff932dc7d2c0b0 R09: > > ffff932dc8050d20 > > [1397658.759433] R10: 00000000c7d2b301 R11: ffffebecc01f4a00 R12: > > 0000000000000000 > > [1397658.759435] R13: 0000000180090003 R14: 0000000000000000 R15: > > 00000000ffffff80 > > [1397658.759438] FS: 0000000000000000(0000) GS:ffff932fffc00000(0000) > > knlGS:0000000000000000 > > [1397658.759440] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b > > [1397658.759442] CR2: 00007f17bcd5e860 CR3: 0000000042c0e000 CR4: > > 00000000000006f0 > > [1397658.759447] Call Trace: > > [1397658.759452] [<ffffffffc0853550>] ? origin_resume+0x70/0x70 [dm_snapshot] > > [1397658.759459] [<ffffffffc0340eab>] run_complete_job+0x6b/0xc0 [dm_mod] > > [1397658.759466] [<ffffffffc0340f60>] process_jobs+0x60/0x100 [dm_mod] > > [1397658.759471] [<ffffffffc0340e40>] ? kcopyd_put_pages+0x50/0x50 [dm_mod] > > [1397658.759477] [<ffffffffc0341042>] do_work+0x42/0x90 [dm_mod] > > [1397658.759483] [<ffffffffa08b2dff>] process_one_work+0x17f/0x440 > > [1397658.759485] [<ffffffffa08b3bcc>] worker_thread+0x22c/0x3c0 > > [1397658.759489] [<ffffffffa08b39a0>] ? manage_workers.isra.24+0x2a0/0x2a0 > > [1397658.759494] [<ffffffffa08bae31>] kthread+0xd1/0xe0 > > [1397658.759497] [<ffffffffa08bad60>] ? insert_kthread_work+0x40/0x40 > > [1397658.759503] [<ffffffffa0f1f637>] ret_from_fork_nospec_begin+0x21/0x21 > > [1397658.759506] [<ffffffffa08bad60>] ? insert_kthread_work+0x40/0x40 > > > > > > > Tried same on Ubuntu kernel 4.14.39 - no issues I reproduced multiple soft lockups in copy_callback() on ceph-client testing branch (based on 4.18-rc7) and on 4.14.39 -- wanted to confirm it wasn't a regression. There is plenty of reports of kcopyd lockups in various places, here is one in copy_callback() on a disk array: https://www.mail-archive.com/dm-devel@xxxxxxxxxx/msg09077.html Why are you using dm-snapshot snapshots? The performance is not great, and they are pretty inflexible. Both lvm and device mapper folks steer people towards dm-thin instead, I believe. And of course, rbd supports native snapshots! Thanks, Ilya _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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