Re: NFS over RDMA crashing

J. Bruce Fields
2013-02-07T16:41:34Z

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;
}

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