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 <[email protected]>
BugLink: https://bugzilla.linux-nfs.org/show_bug.cgi?id=314
Fixes: 5d252f90a800 ('svcrdma: Add class for RDMA backwards ... ')
Cc: [email protected] # v4.12
Signed-off-by: Chuck Lever <[email protected]>
Reviewed-by: Jeff Layton <[email protected]>
---
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.
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);
}
> On Oct 16, 2017, at 12:14 PM, Chuck Lever <[email protected]> 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 <[email protected]>
> BugLink: https://bugzilla.linux-nfs.org/show_bug.cgi?id=314
> Fixes: 5d252f90a800 ('svcrdma: Add class for RDMA backwards ... ')
> Cc: [email protected] # v4.12
> Signed-off-by: Chuck Lever <[email protected]>
> Reviewed-by: Jeff Layton <[email protected]>
> ---
> 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 [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
Chuck Lever
Thanks for the ping, apologies for the delay.
On Mon, Oct 16, 2017 at 12:14:33PM -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:
...
> It would be great if this could go into v4.14-rc, but I can live
> with v4.15.
OK, I'll be slightly lazy and queue this up for 4.15....
> 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.
If it's always a page then I guess the way to make it ridiculously
obvious would be to keep a pointer to the page instead and use
page_address() as necessary, but.... I'm guessing that's inconvenient
for other users.
So, no suggestions.
--b.
> 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);
> }
>