[PATCH V2] svcrdma: Advertise the correct max payload

[PATCH V2] svcrdma: Advertise the correct max payload

[Steve Wise]

Svcrdma currently advertises 1MB, which is too large.  The correct value
is the minimum of RPCSVC_MAXPAYLOAD and 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          |    4 ++++
 2 files changed, 5 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..a9cf5c3 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -392,4 +392,8 @@ 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 \
+	(RPCSVC_MAXPAYLOAD < (RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT) ? \
+	 RPCSVC_MAXPAYLOAD : (RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT))
+
 #endif				/* _LINUX_SUNRPC_XPRT_RDMA_H */

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RE: [PATCH V2] svcrdma: Advertise the correct max payload

[Steve Wise]

> > diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
> > index c419498..a9cf5c3 100644
> > --- a/net/sunrpc/xprtrdma/xprt_rdma.h
> > +++ b/net/sunrpc/xprtrdma/xprt_rdma.h
> > @@ -392,4 +392,8 @@ 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 \
> > +	(RPCSVC_MAXPAYLOAD < (RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT) ? \
> > +	 RPCSVC_MAXPAYLOAD : (RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT))
> > +
> 
> Couldn't you use:
> 
> #if RPCSVC_MAXPAYLOAD < (RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT)
> #define RPCSVC_MAXPAYLOAD_RDMA RPC_MAXPAYLOAD
> #else
> #define RPCSVC_MAXPAYLOAD_RDMA (RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT)
> #endif
> 
> That seems more idiomatic.

Sure.  That makes it easier to read in my opinion too.

I'll send out V3 with this change.

Thanks,

Steve.

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Re: [PATCH V2] svcrdma: Advertise the correct max payload

['J. Bruce Fields']

On Tue, Sep 23, 2014 at 02:42:34PM -0500, Steve Wise wrote:
> 
> > > diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
> > > index c419498..a9cf5c3 100644
> > > --- a/net/sunrpc/xprtrdma/xprt_rdma.h
> > > +++ b/net/sunrpc/xprtrdma/xprt_rdma.h
> > > @@ -392,4 +392,8 @@ 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 \
> > > +	(RPCSVC_MAXPAYLOAD < (RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT) ? \
> > > +	 RPCSVC_MAXPAYLOAD : (RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT))
> > > +
> > 
> > Couldn't you use:
> > 
> > #if RPCSVC_MAXPAYLOAD < (RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT)
> > #define RPCSVC_MAXPAYLOAD_RDMA RPC_MAXPAYLOAD
> > #else
> > #define RPCSVC_MAXPAYLOAD_RDMA (RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT)
> > #endif
> > 
> > That seems more idiomatic.
> 
> Sure.  That makes it easier to read in my opinion too.
> 
> I'll send out V3 with this change.

While we're bikeshedding, why not use min()?

--b.
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RE: [PATCH V2] svcrdma: Advertise the correct max payload

[Steve Wise]

> -----Original Message-----
> From: 'J. Bruce Fields' [mailto:bfields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org]
> Sent: Tuesday, September 23, 2014 2:48 PM
> To: Steve Wise
> Cc: 'Chuck Lever'; linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> Subject: Re: [PATCH V2] svcrdma: Advertise the correct max payload
> 
> On Tue, Sep 23, 2014 at 02:42:34PM -0500, Steve Wise wrote:
> >
> > > > diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
> > > > index c419498..a9cf5c3 100644
> > > > --- a/net/sunrpc/xprtrdma/xprt_rdma.h
> > > > +++ b/net/sunrpc/xprtrdma/xprt_rdma.h
> > > > @@ -392,4 +392,8 @@ 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 \
> > > > +	(RPCSVC_MAXPAYLOAD < (RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT) ? \
> > > > +	 RPCSVC_MAXPAYLOAD : (RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT))
> > > > +
> > >
> > > Couldn't you use:
> > >
> > > #if RPCSVC_MAXPAYLOAD < (RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT)
> > > #define RPCSVC_MAXPAYLOAD_RDMA RPC_MAXPAYLOAD
> > > #else
> > > #define RPCSVC_MAXPAYLOAD_RDMA (RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT)
> > > #endif
> > >
> > > That seems more idiomatic.
> >
> > Sure.  That makes it easier to read in my opinion too.
> >
> > I'll send out V3 with this change.
> 
> While we're bikeshedding, why not use min()?
> 
> --b.

I tried that initially.  But min() and min_t() don't work because of the way we use the #define.  With it defined thusly:

#define RPCSVC_MAXPAYLOAD_RDMA min(RPC_MAXPAYLOAD, RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT)

I see this error:

  CC [M]  net/sunrpc/xprtrdma/svc_rdma_transport.o
net/sunrpc/xprtrdma/svc_rdma_transport.c:94: error: braced-group within expression allowed only inside a function
make[3]: *** [net/sunrpc/xprtrdma/svc_rdma_transport.o] Error 1
make[2]: *** [net/sunrpc/xprtrdma] Error 2
make[1]: *** [net/sunrpc] Error 2
make: *** [net] Error 2

min() looks like this:

#define min(x, y) ({                            \
        typeof(x) _min1 = (x);                  \
        typeof(y) _min2 = (y);                  \
        (void) (&_min1 == &_min2);              \
        _min1 < _min2 ? _min1 : _min2; })

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Re: [PATCH V2] svcrdma: Advertise the correct max payload

['J. Bruce Fields']

On Tue, Sep 23, 2014 at 02:53:28PM -0500, Steve Wise wrote:
> 
> 
> > -----Original Message-----
> > From: 'J. Bruce Fields' [mailto:bfields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org]
> > Sent: Tuesday, September 23, 2014 2:48 PM
> > To: Steve Wise
> > Cc: 'Chuck Lever'; linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> > Subject: Re: [PATCH V2] svcrdma: Advertise the correct max payload
> > 
> > On Tue, Sep 23, 2014 at 02:42:34PM -0500, Steve Wise wrote:
> > >
> > > > > diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
> > > > > index c419498..a9cf5c3 100644
> > > > > --- a/net/sunrpc/xprtrdma/xprt_rdma.h
> > > > > +++ b/net/sunrpc/xprtrdma/xprt_rdma.h
> > > > > @@ -392,4 +392,8 @@ 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 \
> > > > > +	(RPCSVC_MAXPAYLOAD < (RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT) ? \
> > > > > +	 RPCSVC_MAXPAYLOAD : (RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT))
> > > > > +
> > > >
> > > > Couldn't you use:
> > > >
> > > > #if RPCSVC_MAXPAYLOAD < (RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT)
> > > > #define RPCSVC_MAXPAYLOAD_RDMA RPC_MAXPAYLOAD
> > > > #else
> > > > #define RPCSVC_MAXPAYLOAD_RDMA (RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT)
> > > > #endif
> > > >
> > > > That seems more idiomatic.
> > >
> > > Sure.  That makes it easier to read in my opinion too.
> > >
> > > I'll send out V3 with this change.
> > 
> > While we're bikeshedding, why not use min()?
> > 
> > --b.
> 
> I tried that initially.  But min() and min_t() don't work because of the way we use the #define.  With it defined thusly:

OK, OK.  Whatever works.--b.

> 
> #define RPCSVC_MAXPAYLOAD_RDMA min(RPC_MAXPAYLOAD, RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT)
> 
> I see this error:
> 
>   CC [M]  net/sunrpc/xprtrdma/svc_rdma_transport.o
> net/sunrpc/xprtrdma/svc_rdma_transport.c:94: error: braced-group within expression allowed only inside a function
> make[3]: *** [net/sunrpc/xprtrdma/svc_rdma_transport.o] Error 1
> make[2]: *** [net/sunrpc/xprtrdma] Error 2
> make[1]: *** [net/sunrpc] Error 2
> make: *** [net] Error 2
> 
> min() looks like this:
> 
> #define min(x, y) ({                            \
>         typeof(x) _min1 = (x);                  \
>         typeof(y) _min2 = (y);                  \
>         (void) (&_min1 == &_min2);              \
>         _min1 < _min2 ? _min1 : _min2; })
> 
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