Return-Path: Received: from aserp1040.oracle.com ([141.146.126.69]:35338 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751335AbdJWSMO (ORCPT ); Mon, 23 Oct 2017 14:12:14 -0400 Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 9.3 \(3124\)) Subject: Re: [PATCH] svcrdma: Preserve CB send buffer across retransmits From: Chuck Lever In-Reply-To: <20171016161133.29152.48259.stgit@klimt.1015granger.net> Date: Mon, 23 Oct 2017 14:12:10 -0400 Cc: Linux NFS Mailing List Message-Id: References: <20171016161133.29152.48259.stgit@klimt.1015granger.net> To: Bruce Fields Sender: linux-nfs-owner@vger.kernel.org List-ID: > On Oct 16, 2017, at 12:14 PM, 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 > BugLink: https://bugzilla.linux-nfs.org/show_bug.cgi?id=314 > Fixes: 5d252f90a800 ('svcrdma: Add class for RDMA backwards ... ') > Cc: stable@vger.kernel.org # v4.12 > Signed-off-by: Chuck Lever > Reviewed-by: Jeff Layton > --- > net/sunrpc/xprtrdma/svc_rdma_backchannel.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > Hey Bruce- > > It would be great if this could go into v4.14-rc, but I can live > with v4.15. Ping! > Jeff's review suggested adding a comment documenting the requirement > that rqst->rq_buffer is backed by a single page. However, all of the > server-side transport mechanics are page-based, so I'm not sure this > wouldn't be a redundant comment. Suggestions welcome. > > > 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)); > 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); > } > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-nfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Chuck Lever