[PATCH] svcrdma: Advertise the correct max payload

[PATCH] svcrdma: Advertise the correct max payload

[Steve Wise]

Svcrdma currently advertises 1MB, which is too large.  The correct value
is the max scatter-gather allowed in an NFSRDMA IO chunk * the host page
size. This bug is usually benign because the Linux X64 NFSRDMA client
correctly limits the payload size to the correct value (64*4096 = 256KB).
But if the Linux client is PPC64 with a 64KB page size, then the client
will indeed use a payload size that will overflow the server.

Signed-off-by: Steve Wise <swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>
---

 net/sunrpc/xprtrdma/svc_rdma_transport.c |    2 +-
 net/sunrpc/xprtrdma/xprt_rdma.h          |    2 ++
 2 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c
index 374feb4..4e61880 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_transport.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c
@@ -91,7 +91,7 @@ struct svc_xprt_class svc_rdma_class = {
 	.xcl_name = "rdma",
 	.xcl_owner = THIS_MODULE,
 	.xcl_ops = &svc_rdma_ops,
-	.xcl_max_payload = RPCSVC_MAXPAYLOAD_TCP,
+	.xcl_max_payload = RPCSVC_MAXPAYLOAD_RDMA,
 	.xcl_ident = XPRT_TRANSPORT_RDMA,
 };
 
diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
index c419498..467a77c 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -392,4 +392,6 @@ extern struct kmem_cache *svc_rdma_ctxt_cachep;
 /* Workqueue created in svc_rdma.c */
 extern struct workqueue_struct *svc_rdma_wq;
 
+#define RPCSVC_MAXPAYLOAD_RDMA	(RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT)
+
 #endif				/* _LINUX_SUNRPC_XPRT_RDMA_H */

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Re: [PATCH] svcrdma: Advertise the correct max payload

[J. Bruce Fields]

On Mon, Sep 22, 2014 at 01:36:53PM -0500, Steve Wise wrote:
> Svcrdma currently advertises 1MB, which is too large.  The correct value
> is the max scatter-gather allowed in an NFSRDMA IO chunk * the host page
> size. This bug is usually benign because the Linux X64 NFSRDMA client
> correctly limits the payload size to the correct value (64*4096 = 256KB).
> But if the Linux client is PPC64 with a 64KB page size, then the client
> will indeed use a payload size that will overflow the server.
> 
> Signed-off-by: Steve Wise <swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>
> ---
> 
>  net/sunrpc/xprtrdma/svc_rdma_transport.c |    2 +-
>  net/sunrpc/xprtrdma/xprt_rdma.h          |    2 ++
>  2 files changed, 3 insertions(+), 1 deletions(-)
> 
> diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c
> index 374feb4..4e61880 100644
> --- a/net/sunrpc/xprtrdma/svc_rdma_transport.c
> +++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c
> @@ -91,7 +91,7 @@ struct svc_xprt_class svc_rdma_class = {
>  	.xcl_name = "rdma",
>  	.xcl_owner = THIS_MODULE,
>  	.xcl_ops = &svc_rdma_ops,
> -	.xcl_max_payload = RPCSVC_MAXPAYLOAD_TCP,
> +	.xcl_max_payload = RPCSVC_MAXPAYLOAD_RDMA,
>  	.xcl_ident = XPRT_TRANSPORT_RDMA,
>  };
>  
> diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
> index c419498..467a77c 100644
> --- a/net/sunrpc/xprtrdma/xprt_rdma.h
> +++ b/net/sunrpc/xprtrdma/xprt_rdma.h
> @@ -392,4 +392,6 @@ extern struct kmem_cache *svc_rdma_ctxt_cachep;
>  /* Workqueue created in svc_rdma.c */
>  extern struct workqueue_struct *svc_rdma_wq;
>  
> +#define RPCSVC_MAXPAYLOAD_RDMA	(RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT)

Do you want to define this as the minimum of this and
RPCSVC_MAXPAYLOAD_TCP, in case RPCRDMA_MAX_DATA_SEGS gets increased some
day?

--b.

> +
>  #endif				/* _LINUX_SUNRPC_XPRT_RDMA_H */
> 
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Re: [PATCH] svcrdma: Advertise the correct max payload

[Steve Wise]

On 9/22/2014 1:39 PM, J. Bruce Fields wrote:
> On Mon, Sep 22, 2014 at 01:36:53PM -0500, Steve Wise wrote:
>> Svcrdma currently advertises 1MB, which is too large.  The correct value
>> is the max scatter-gather allowed in an NFSRDMA IO chunk * the host page
>> size. This bug is usually benign because the Linux X64 NFSRDMA client
>> correctly limits the payload size to the correct value (64*4096 = 256KB).
>> But if the Linux client is PPC64 with a 64KB page size, then the client
>> will indeed use a payload size that will overflow the server.
>>
>> Signed-off-by: Steve Wise <swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>
>> ---
>>
>>   net/sunrpc/xprtrdma/svc_rdma_transport.c |    2 +-
>>   net/sunrpc/xprtrdma/xprt_rdma.h          |    2 ++
>>   2 files changed, 3 insertions(+), 1 deletions(-)
>>
>> diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c
>> index 374feb4..4e61880 100644
>> --- a/net/sunrpc/xprtrdma/svc_rdma_transport.c
>> +++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c
>> @@ -91,7 +91,7 @@ struct svc_xprt_class svc_rdma_class = {
>>   	.xcl_name = "rdma",
>>   	.xcl_owner = THIS_MODULE,
>>   	.xcl_ops = &svc_rdma_ops,
>> -	.xcl_max_payload = RPCSVC_MAXPAYLOAD_TCP,
>> +	.xcl_max_payload = RPCSVC_MAXPAYLOAD_RDMA,
>>   	.xcl_ident = XPRT_TRANSPORT_RDMA,
>>   };
>>   
>> diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
>> index c419498..467a77c 100644
>> --- a/net/sunrpc/xprtrdma/xprt_rdma.h
>> +++ b/net/sunrpc/xprtrdma/xprt_rdma.h
>> @@ -392,4 +392,6 @@ extern struct kmem_cache *svc_rdma_ctxt_cachep;
>>   /* Workqueue created in svc_rdma.c */
>>   extern struct workqueue_struct *svc_rdma_wq;
>>   
>> +#define RPCSVC_MAXPAYLOAD_RDMA	(RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT)
> Do you want to define this as the minimum of this and
> RPCSVC_MAXPAYLOAD_TCP, in case RPCRDMA_MAX_DATA_SEGS gets increased some
> day?

Why would it need to be limited by MAXPAYLOAD_TCP?

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Re: [PATCH] svcrdma: Advertise the correct max payload

[Chuck Lever]

On Sep 22, 2014, at 11:39 AM, J. Bruce Fields <bfields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org> wrote:

> On Mon, Sep 22, 2014 at 01:36:53PM -0500, Steve Wise wrote:
>> Svcrdma currently advertises 1MB, which is too large.  The correct value
>> is the max scatter-gather allowed in an NFSRDMA IO chunk * the host page
>> size. This bug is usually benign because the Linux X64 NFSRDMA client
>> correctly limits the payload size to the correct value (64*4096 = 256KB).
>> But if the Linux client is PPC64 with a 64KB page size, then the client
>> will indeed use a payload size that will overflow the server.
>> 
>> Signed-off-by: Steve Wise <swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>
>> ---
>> 
>> net/sunrpc/xprtrdma/svc_rdma_transport.c |    2 +-
>> net/sunrpc/xprtrdma/xprt_rdma.h          |    2 ++
>> 2 files changed, 3 insertions(+), 1 deletions(-)
>> 
>> diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c
>> index 374feb4..4e61880 100644
>> --- a/net/sunrpc/xprtrdma/svc_rdma_transport.c
>> +++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c
>> @@ -91,7 +91,7 @@ struct svc_xprt_class svc_rdma_class = {
>> 	.xcl_name = "rdma",
>> 	.xcl_owner = THIS_MODULE,
>> 	.xcl_ops = &svc_rdma_ops,
>> -	.xcl_max_payload = RPCSVC_MAXPAYLOAD_TCP,
>> +	.xcl_max_payload = RPCSVC_MAXPAYLOAD_RDMA,
>> 	.xcl_ident = XPRT_TRANSPORT_RDMA,
>> };
>> 
>> diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
>> index c419498..467a77c 100644
>> --- a/net/sunrpc/xprtrdma/xprt_rdma.h
>> +++ b/net/sunrpc/xprtrdma/xprt_rdma.h
>> @@ -392,4 +392,6 @@ extern struct kmem_cache *svc_rdma_ctxt_cachep;
>> /* Workqueue created in svc_rdma.c */
>> extern struct workqueue_struct *svc_rdma_wq;
>> 
>> +#define RPCSVC_MAXPAYLOAD_RDMA	(RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT)
> 
> Do you want to define this as the minimum of this and
> RPCSVC_MAXPAYLOAD_TCP, in case RPCRDMA_MAX_DATA_SEGS gets increased some
> day?

Hey Bruce-

I don’t see the _TCP and _RDMA settings are related.

> --b.
> 
>> +
>> #endif				/* _LINUX_SUNRPC_XPRT_RDMA_H */
>> 
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--
Chuck Lever
chuck[dot]lever[at]oracle[dot]com



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Re: [PATCH] svcrdma: Advertise the correct max payload

[J. Bruce Fields]

On Mon, Sep 22, 2014 at 01:42:07PM -0500, Steve Wise wrote:
> On 9/22/2014 1:39 PM, J. Bruce Fields wrote:
> >On Mon, Sep 22, 2014 at 01:36:53PM -0500, Steve Wise wrote:
> >>Svcrdma currently advertises 1MB, which is too large.  The correct value
> >>is the max scatter-gather allowed in an NFSRDMA IO chunk * the host page
> >>size. This bug is usually benign because the Linux X64 NFSRDMA client
> >>correctly limits the payload size to the correct value (64*4096 = 256KB).
> >>But if the Linux client is PPC64 with a 64KB page size, then the client
> >>will indeed use a payload size that will overflow the server.
> >>
> >>Signed-off-by: Steve Wise <swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>
> >>---
> >>
> >>  net/sunrpc/xprtrdma/svc_rdma_transport.c |    2 +-
> >>  net/sunrpc/xprtrdma/xprt_rdma.h          |    2 ++
> >>  2 files changed, 3 insertions(+), 1 deletions(-)
> >>
> >>diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c
> >>index 374feb4..4e61880 100644
> >>--- a/net/sunrpc/xprtrdma/svc_rdma_transport.c
> >>+++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c
> >>@@ -91,7 +91,7 @@ struct svc_xprt_class svc_rdma_class = {
> >>  	.xcl_name = "rdma",
> >>  	.xcl_owner = THIS_MODULE,
> >>  	.xcl_ops = &svc_rdma_ops,
> >>-	.xcl_max_payload = RPCSVC_MAXPAYLOAD_TCP,
> >>+	.xcl_max_payload = RPCSVC_MAXPAYLOAD_RDMA,
> >>  	.xcl_ident = XPRT_TRANSPORT_RDMA,
> >>  };
> >>diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
> >>index c419498..467a77c 100644
> >>--- a/net/sunrpc/xprtrdma/xprt_rdma.h
> >>+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
> >>@@ -392,4 +392,6 @@ extern struct kmem_cache *svc_rdma_ctxt_cachep;
> >>  /* Workqueue created in svc_rdma.c */
> >>  extern struct workqueue_struct *svc_rdma_wq;
> >>+#define RPCSVC_MAXPAYLOAD_RDMA	(RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT)
> >Do you want to define this as the minimum of this and
> >RPCSVC_MAXPAYLOAD_TCP, in case RPCRDMA_MAX_DATA_SEGS gets increased some
> >day?
> 
> Why would it need to be limited by MAXPAYLOAD_TCP?

Because you're also limited by the size of the rq_pages array, which is
determined by RPCSVC_MAXPAGES, calculated from RPCSVC_MAXPAYLOAD.

(Actually you probably want RPCSVC_MAXPAYLOAD, not MAXPAYLOAD_TCP.)

--b.
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Re: [PATCH] svcrdma: Advertise the correct max payload

[Steve Wise]

On 9/22/2014 1:55 PM, J. Bruce Fields wrote:
> On Mon, Sep 22, 2014 at 01:42:07PM -0500, Steve Wise wrote:
>> On 9/22/2014 1:39 PM, J. Bruce Fields wrote:
>>> On Mon, Sep 22, 2014 at 01:36:53PM -0500, Steve Wise wrote:
>>>> Svcrdma currently advertises 1MB, which is too large.  The correct value
>>>> is the max scatter-gather allowed in an NFSRDMA IO chunk * the host page
>>>> size. This bug is usually benign because the Linux X64 NFSRDMA client
>>>> correctly limits the payload size to the correct value (64*4096 = 256KB).
>>>> But if the Linux client is PPC64 with a 64KB page size, then the client
>>>> will indeed use a payload size that will overflow the server.
>>>>
>>>> Signed-off-by: Steve Wise <swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>
>>>> ---
>>>>
>>>>   net/sunrpc/xprtrdma/svc_rdma_transport.c |    2 +-
>>>>   net/sunrpc/xprtrdma/xprt_rdma.h          |    2 ++
>>>>   2 files changed, 3 insertions(+), 1 deletions(-)
>>>>
>>>> diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c
>>>> index 374feb4..4e61880 100644
>>>> --- a/net/sunrpc/xprtrdma/svc_rdma_transport.c
>>>> +++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c
>>>> @@ -91,7 +91,7 @@ struct svc_xprt_class svc_rdma_class = {
>>>>   	.xcl_name = "rdma",
>>>>   	.xcl_owner = THIS_MODULE,
>>>>   	.xcl_ops = &svc_rdma_ops,
>>>> -	.xcl_max_payload = RPCSVC_MAXPAYLOAD_TCP,
>>>> +	.xcl_max_payload = RPCSVC_MAXPAYLOAD_RDMA,
>>>>   	.xcl_ident = XPRT_TRANSPORT_RDMA,
>>>>   };
>>>> diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
>>>> index c419498..467a77c 100644
>>>> --- a/net/sunrpc/xprtrdma/xprt_rdma.h
>>>> +++ b/net/sunrpc/xprtrdma/xprt_rdma.h
>>>> @@ -392,4 +392,6 @@ extern struct kmem_cache *svc_rdma_ctxt_cachep;
>>>>   /* Workqueue created in svc_rdma.c */
>>>>   extern struct workqueue_struct *svc_rdma_wq;
>>>> +#define RPCSVC_MAXPAYLOAD_RDMA	(RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT)
>>> Do you want to define this as the minimum of this and
>>> RPCSVC_MAXPAYLOAD_TCP, in case RPCRDMA_MAX_DATA_SEGS gets increased some
>>> day?
>> Why would it need to be limited by MAXPAYLOAD_TCP?
> Because you're also limited by the size of the rq_pages array, which is
> determined by RPCSVC_MAXPAGES, calculated from RPCSVC_MAXPAYLOAD.
>
> (Actually you probably want RPCSVC_MAXPAYLOAD, not MAXPAYLOAD_TCP.)
>
>

I see.  I agree.

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Re: [PATCH] svcrdma: Advertise the correct max payload

[Chuck Lever]

On Sep 22, 2014, at 11:55 AM, J. Bruce Fields <bfields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org> wrote:

> On Mon, Sep 22, 2014 at 01:42:07PM -0500, Steve Wise wrote:
>> On 9/22/2014 1:39 PM, J. Bruce Fields wrote:
>>> On Mon, Sep 22, 2014 at 01:36:53PM -0500, Steve Wise wrote:
>>>> Svcrdma currently advertises 1MB, which is too large.  The correct value
>>>> is the max scatter-gather allowed in an NFSRDMA IO chunk * the host page
>>>> size. This bug is usually benign because the Linux X64 NFSRDMA client
>>>> correctly limits the payload size to the correct value (64*4096 = 256KB).
>>>> But if the Linux client is PPC64 with a 64KB page size, then the client
>>>> will indeed use a payload size that will overflow the server.
>>>> 
>>>> Signed-off-by: Steve Wise <swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>
>>>> ---
>>>> 
>>>> net/sunrpc/xprtrdma/svc_rdma_transport.c |    2 +-
>>>> net/sunrpc/xprtrdma/xprt_rdma.h          |    2 ++
>>>> 2 files changed, 3 insertions(+), 1 deletions(-)
>>>> 
>>>> diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c
>>>> index 374feb4..4e61880 100644
>>>> --- a/net/sunrpc/xprtrdma/svc_rdma_transport.c
>>>> +++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c
>>>> @@ -91,7 +91,7 @@ struct svc_xprt_class svc_rdma_class = {
>>>> 	.xcl_name = "rdma",
>>>> 	.xcl_owner = THIS_MODULE,
>>>> 	.xcl_ops = &svc_rdma_ops,
>>>> -	.xcl_max_payload = RPCSVC_MAXPAYLOAD_TCP,
>>>> +	.xcl_max_payload = RPCSVC_MAXPAYLOAD_RDMA,
>>>> 	.xcl_ident = XPRT_TRANSPORT_RDMA,
>>>> };
>>>> diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
>>>> index c419498..467a77c 100644
>>>> --- a/net/sunrpc/xprtrdma/xprt_rdma.h
>>>> +++ b/net/sunrpc/xprtrdma/xprt_rdma.h
>>>> @@ -392,4 +392,6 @@ extern struct kmem_cache *svc_rdma_ctxt_cachep;
>>>> /* Workqueue created in svc_rdma.c */
>>>> extern struct workqueue_struct *svc_rdma_wq;
>>>> +#define RPCSVC_MAXPAYLOAD_RDMA	(RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT)
>>> Do you want to define this as the minimum of this and
>>> RPCSVC_MAXPAYLOAD_TCP, in case RPCRDMA_MAX_DATA_SEGS gets increased some
>>> day?
>> 
>> Why would it need to be limited by MAXPAYLOAD_TCP?
> 
> Because you're also limited by the size of the rq_pages array, which is
> determined by RPCSVC_MAXPAGES, calculated from RPCSVC_MAXPAYLOAD.
> 
> (Actually you probably want RPCSVC_MAXPAYLOAD, not MAXPAYLOAD_TCP.)

Agree with this last bit.

--
Chuck Lever
chuck[dot]lever[at]oracle[dot]com



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