Re: NFS over RDMA crashing

J. Bruce Fields
2013-02-11T18:13:39Z

On Mon, Feb 11, 2013 at 03:19:42PM +0000, Yan Burman wrote:
> > -----Original Message-----
> > From: J. Bruce Fields [mailto:bfields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org]
> > Sent: Thursday, February 07, 2013 18:42
> > To: Yan Burman
> > Cc: linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org; linux-
> > rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; Or Gerlitz
> > Subject: Re: NFS over RDMA crashing
> >
> > On Wed, Feb 06, 2013 at 05:24:35PM -0500, J. Bruce Fields wrote:
> > > On Wed, Feb 06, 2013 at 05:48:15PM +0200, Yan Burman wrote:
> > > > When killing mount command that got stuck:
> > > > -------------------------------------------
> > > >
> > > > BUG: unable to handle kernel paging request at ffff880324dc7ff8
> > > > IP: [<ffffffffa05f3dfb>] rdma_read_xdr+0x8bb/0xd40 [svcrdma] PGD
> > > > 1a0c063 PUD 32f82e063 PMD 32f2fd063 PTE 8000000324dc7161
> > > > Oops: 0003 [#1] PREEMPT SMP
> > > > Modules linked in: md5 ib_ipoib xprtrdma svcrdma rdma_cm ib_cm
> > iw_cm
> > > > ib_addr nfsd exportfs netconsole ip6table_filter ip6_tables
> > > > iptable_filter ip_tables ebtable_nat nfsv3 nfs_acl ebtables x_tables
> > > > nfsv4 auth_rpcgss nfs lockd autofs4 sunrpc target_core_iblock
> > > > target_core_file target_core_pscsi target_core_mod configfs 8021q
> > > > bridge stp llc ipv6 dm_mirror dm_region_hash dm_log vhost_net
> > > > macvtap macvlan tun uinput iTCO_wdt iTCO_vendor_support kvm_intel
> > > > kvm crc32c_intel microcode pcspkr joydev i2c_i801 lpc_ich mfd_core
> > > > ehci_pci ehci_hcd sg ioatdma ixgbe mdio mlx4_ib ib_sa ib_mad ib_core
> > > > mlx4_en mlx4_core igb hwmon dca ptp pps_core button dm_mod ext3
> > jbd
> > > > sd_mod ata_piix libata uhci_hcd megaraid_sas scsi_mod CPU 6
> > > > Pid: 4744, comm: nfsd Not tainted 3.8.0-rc5+ #4 Supermicro
> > > > X8DTH-i/6/iF/6F/X8DTH
> > > > RIP: 0010:[<ffffffffa05f3dfb>] [<ffffffffa05f3dfb>]
> > > > rdma_read_xdr+0x8bb/0xd40 [svcrdma]
> > > > RSP: 0018:ffff880324c3dbf8 EFLAGS: 00010297
> > > > RAX: ffff880324dc8000 RBX: 0000000000000001 RCX: ffff880324dd8428
> > > > RDX: ffff880324dc7ff8 RSI: ffff880324dd8428 RDI: ffffffff81149618
> > > > RBP: ffff880324c3dd78 R08: 000060f9c0000860 R09: 0000000000000001
> > > > R10: ffff880324dd8000 R11: 0000000000000001 R12: ffff8806299dcb10
> > > > R13: 0000000000000003 R14: 0000000000000001 R15: 0000000000000010
> > > > FS: 0000000000000000(0000) GS:ffff88063fc00000(0000)
> > > > knlGS:0000000000000000
> > > > CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> > > > CR2: ffff880324dc7ff8 CR3: 0000000001a0b000 CR4: 00000000000007e0
> > > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > > > DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> > > > Process nfsd (pid: 4744, threadinfo ffff880324c3c000, task
> > > > ffff880330550000)
> > > > Stack:
> > > > ffff880324c3dc78 ffff880324c3dcd8 0000000000000282 ffff880631cec000
> > > > ffff880324dd8000 ffff88062ed33040 0000000124c3dc48 ffff880324dd8000
> > > > ffff88062ed33058 ffff880630ce2b90 ffff8806299e8000 0000000000000003
> > > > Call Trace:
> > > > [<ffffffffa05f466e>] svc_rdma_recvfrom+0x3ee/0xd80 [svcrdma]
> > > > [<ffffffff81086540>] ? try_to_wake_up+0x2f0/0x2f0
> > > > [<ffffffffa045963f>] svc_recv+0x3ef/0x4b0 [sunrpc]
> > > > [<ffffffffa0571db0>] ? nfsd_svc+0x740/0x740 [nfsd]
> > > > [<ffffffffa0571e5d>] nfsd+0xad/0x130 [nfsd] [<ffffffffa0571db0>] ?
> > > > nfsd_svc+0x740/0x740 [nfsd] [<ffffffff81071df6>] kthread+0xd6/0xe0
> > > > [<ffffffff81071d20>] ? __init_kthread_worker+0x70/0x70
> > > > [<ffffffff814b462c>] ret_from_fork+0x7c/0xb0 [<ffffffff81071d20>] ?
> > > > __init_kthread_worker+0x70/0x70
> > > > Code: 63 c2 49 8d 8c c2 18 02 00 00 48 39 ce 77 e1 49 8b 82 40 0a 00
> > > > 00 48 39 c6 0f 84 92 f7 ff ff 90 48 8d 50 f8 49 89 92 40 0a 00 00
> > > > <48> c7 40 f8 00 00 00 00 49 8b 82 40 0a 00 00 49 3b 82 30 0a 00 RIP
> > > > [<ffffffffa05f3dfb>] rdma_read_xdr+0x8bb/0xd40 [svcrdma] RSP
> > > > <ffff880324c3dbf8>
> > > > CR2: ffff880324dc7ff8
> > > > ---[ end trace 06d0384754e9609a ]---
> > > >
> > > >
> > > > It seems that commit afc59400d6c65bad66d4ad0b2daf879cbff8e23e
> > > > "nfsd4: cleanup: replace rq_resused count by rq_next_page pointer"
> > > > is responsible for the crash (it seems to be crashing in
> > > > net/sunrpc/xprtrdma/svc_rdma_recvfrom.c:527)
> > > > It may be because I have CONFIG_DEBUG_SET_MODULE_RONX and
> > > > CONFIG_DEBUG_RODATA enabled. I did not try to disable them yet.
> > > >
> > > > When I moved to commit 79f77bf9a4e3dd5ead006b8f17e7c4ff07d8374e I
> > > > was no longer getting the server crashes, so the reset of my tests
> > > > were done using that point (it is somewhere in the middle of
> > > > 3.7.0-rc2).
> > >
> > > OK, so this part's clearly my fault--I'll work on a patch, but the
> > > rdma's use of the ->rq_pages array is pretty confusing.
> >
> > Does this help?
> >
> > They must have added this for some reason, but I'm not seeing how it could
> > have ever done anything....
> >
> > --b.
> >
> > diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
> > b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
> > index 0ce7552..e8f25ec 100644
> > --- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
> > +++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
> > @@ -520,13 +520,6 @@ next_sge:
> > for (ch_no = 0; &rqstp->rq_pages[ch_no] < rqstp->rq_respages;
> > ch_no++)
> > rqstp->rq_pages[ch_no] = NULL;
> >
> > - /*
> > - * Detach res pages. If svc_release sees any it will attempt to
> > - * put them.
> > - */
> > - while (rqstp->rq_next_page != rqstp->rq_respages)
> > - *(--rqstp->rq_next_page) = NULL;
> > -
> > return err;
> > }
> >
>
> I've been trying to reproduce the problem, but for some reason it does not happen anymore.
> The crash is not happening even without the patch now, but NFS over RDMA in 3.8.0-rc5 from net-next is not working.
> When running server and client in VM with SRIOV, it times out when trying to mount and oopses on the client when mount command is interrupted.
> When running two physical hosts, I get to mount the remote directory, but reading or writing fails with IO error.
>
> I am still doing some checks - I will post my findings when I will have more information.

OK, thanks for keeping us updated.

--b.