Re: NFS over RDMA crashing

["J. Bruce Fields" <bfields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org>]

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.

--b.
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