> On Oct 14, 2017, at 6:38 AM, Jeff Layton <jlayton@xxxxxxxxxx> wrote:
>
> On Sun, 2017-10-08 at 19:13 -0400, Chuck Lever wrote:
>> During each NFSv4 callback Call, an RDMA Send completion frees the
>> page that contains the RPC Call message. If the upper layer determines
>> that a retransmit is necessary, this is too soon.
>>
>> One possible symptom: after a GARBAGE_ARGS response an NFSv4.1
>> callback request, the following BUG fires on the NFS server:
>>
>> kernel: BUG: Bad page state in process kworker/0:2H pfn:7d3ce2
>> kernel: page:ffffea001f4f3880 count:-2 mapcount:0 mapping: (null) index:0x0
>> kernel: flags: 0x2fffff80000000()
>> kernel: raw: 002fffff80000000 0000000000000000 0000000000000000 fffffffeffffffff
>> kernel: raw: dead000000000100 dead000000000200 0000000000000000 0000000000000000
>> kernel: page dumped because: nonzero _refcount
>> kernel: Modules linked in: cts rpcsec_gss_krb5 ocfs2_dlmfs ocfs2_stack_o2cb ocfs2_dlm
>> ocfs2_nodemanager ocfs2_stackglue rpcrdm a ib_ipoib rdma_ucm ib_ucm ib_uverbs ib_umad
>> rdma_cm ib_cm iw_cm x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel
>> kvm irqbypass crct10dif_pc lmul crc32_pclmul ghash_clmulni_intel pcbc iTCO_wdt
>> iTCO_vendor_support aesni_intel crypto_simd glue_helper cryptd pcspkr lpc_ich i2c_i801
>> mei_me mf d_core mei raid0 sg wmi ioatdma ipmi_si ipmi_devintf ipmi_msghandler shpchp
>> acpi_power_meter acpi_pad nfsd nfs_acl lockd auth_rpcgss grace sunrpc ip_tables xfs
>> libcrc32c mlx4_en mlx4_ib mlx5_ib ib_core sd_mod sr_mod cdrom ast drm_kms_helper
>> syscopyarea sysfillrect sysimgblt fb_sys_fops ttm ahci crc32c_intel libahci drm
>> mlx5_core igb libata mlx4_core dca i2c_algo_bit i2c_core nvme
>> kernel: ptp nvme_core pps_core dm_mirror dm_region_hash dm_log dm_mod dax
>> kernel: CPU: 0 PID: 11495 Comm: kworker/0:2H Not tainted 4.14.0-rc3-00001-g577ce48 #811
>> kernel: Hardware name: Supermicro Super Server/X10SRL-F, BIOS 1.0c 09/09/2015
>> kernel: Workqueue: ib-comp-wq ib_cq_poll_work [ib_core]
>> kernel: Call Trace:
>> kernel: dump_stack+0x62/0x80
>> kernel: bad_page+0xfe/0x11a
>> kernel: free_pages_check_bad+0x76/0x78
>> kernel: free_pcppages_bulk+0x364/0x441
>> kernel: ? ttwu_do_activate.isra.61+0x71/0x78
>> kernel: free_hot_cold_page+0x1c5/0x202
>> kernel: __put_page+0x2c/0x36
>> kernel: svc_rdma_put_context+0xd9/0xe4 [rpcrdma]
>> kernel: svc_rdma_wc_send+0x50/0x98 [rpcrdma]
>>
>> This issue exists all the way back to v4.5, but refactoring and code
>> re-organization prevents this simple patch from applying to kernels
>> older than v4.12. The fix is the same, however, if someone needs to
>> backport it.
>>
>> Reported-by: Ben Coddington <bcodding@xxxxxxxxxx>
>> Fixes: 5d252f90a800 ('svcrdma: Add class for RDMA backwards ... ')
>> Cc: stable@xxxxxxxxxxxxxxx # v4.12
>> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
>> ---
>> net/sunrpc/xprtrdma/svc_rdma_backchannel.c | 6 +++++-
>> 1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> Hi Ben, Jeff-
>>
>> I was able to reproduce the problem here with a rigged Linux client.
>> This is my proposed fix. Fix also tested with a prototype Solaris
>> client similar to the one that exposed the problem.
>>
>>
>> diff --git a/net/sunrpc/xprtrdma/svc_rdma_backchannel.c b/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
>> index ec37ad8..1854db2 100644
>> --- a/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
>> +++ b/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
>> @@ -132,6 +132,10 @@ static int svc_rdma_bc_sendto(struct svcxprt_rdma *rdma,
>> if (ret)
>> goto out_err;
>>
>> + /* Bump page refcnt so Send completion doesn't release
>> + * the rq_buffer before all retransmits are complete.
>> + */
>> + get_page(virt_to_page(rqst->rq_buffer));
>
> Looks fairly reasonable, but is this enough? Could rq_buffer be larger
> than a page?
Not in the current implementation. See xprt_rdma_bc_allocate.
Thanks for the review!
>> ret = svc_rdma_post_send_wr(rdma, ctxt, 1, 0);
>> if (ret)
>> goto out_unmap;
>> @@ -164,7 +168,6 @@ static int svc_rdma_bc_sendto(struct svcxprt_rdma *rdma,
>> return -EINVAL;
>> }
>>
>> - /* svc_rdma_sendto releases this page */
>> page = alloc_page(RPCRDMA_DEF_GFP);
>> if (!page)
>> return -ENOMEM;
>> @@ -183,6 +186,7 @@ static int svc_rdma_bc_sendto(struct svcxprt_rdma *rdma,
>> {
>> struct rpc_rqst *rqst = task->tk_rqstp;
>>
>> + put_page(virt_to_page(rqst->rq_buffer));
>> kfree(rqst->rq_rbuffer);
>> }
>>
>>
>
> --
> Jeff Layton <jlayton@xxxxxxxxxx>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
Chuck Lever
--
To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
