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Subject: Re: [PATCH v4 07/30] xprtrdma: Fix ri_max_segs and the result of
 ro_maxpages
From:   Chuck Lever <chuck.lever@oracle.com>
In-Reply-To: <ca236b957f74998d0104d9865b2d65943850d5b4.camel@gmail.com>
Date:   Tue, 18 Dec 2018 14:39:24 -0500
Cc:     linux-rdma@vger.kernel.org,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>
Content-Transfer-Encoding: quoted-printable
Message-Id: <66C22632-967A-40C9-B30C-F407920E4DBA@oracle.com>
References: <20181217162406.24133.27356.stgit@manet.1015granger.net>
 <20181217163958.24133.16923.stgit@manet.1015granger.net>
 <ca236b957f74998d0104d9865b2d65943850d5b4.camel@gmail.com>
To:     Anna Schumaker <schumaker.anna@gmail.com>
Sender: linux-nfs-owner@vger.kernel.org
Precedence: bulk


> On Dec 18, 2018, at 2:35 PM, Anna Schumaker <schumaker.anna@gmail.com> =
wrote:
>=20
> Hi Chuck,
>=20
> On Mon, 2018-12-17 at 11:39 -0500, Chuck Lever wrote:
>> With certain combinations of krb5i/p, MR size, and r/wsize, I/O can
>> fail with EMSGSIZE. This is because the calculated value of
>> ri_max_segs (the max number of MRs per RPC) exceeded
>> RPCRDMA_MAX_HDR_SEGS, which caused Read or Write list encoding to
>> walk off the end of the transport header.
>>=20
>> Once that was addressed, the ro_maxpages result has to be corrected
>> to account for the number of MRs needed for Reply chunks, which is
>> 2 MRs smaller than a normal Read or Write chunk.
>>=20
>> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
>> ---
>> net/sunrpc/xprtrdma/fmr_ops.c   |    7 +++++--
>> net/sunrpc/xprtrdma/frwr_ops.c  |    7 +++++--
>> net/sunrpc/xprtrdma/transport.c |    6 ++++--
>> 3 files changed, 14 insertions(+), 6 deletions(-)
>>=20
>> diff --git a/net/sunrpc/xprtrdma/fmr_ops.c =
b/net/sunrpc/xprtrdma/fmr_ops.c
>> index 7f5632c..78a0224 100644
>> --- a/net/sunrpc/xprtrdma/fmr_ops.c
>> +++ b/net/sunrpc/xprtrdma/fmr_ops.c
>> @@ -176,7 +176,10 @@ enum {
>>=20
>> 	ia->ri_max_segs =3D max_t(unsigned int, 1, RPCRDMA_MAX_DATA_SEGS =
/
>> 				RPCRDMA_MAX_FMR_SGES);
>> -	ia->ri_max_segs +=3D 2;	/* segments for head and tail buffers */
>> +	/* Reply chunks require segments for head and tail buffers */
>> +	ia->ri_max_segs +=3D 2;
>> +	if (ia->ri_max_segs > RPCRDMA_MAX_HDR_SEGS)
>> +		ia->ri_max_segs =3D RPCRDMA_MAX_HDR_SEGS;
>> 	return 0;
>> }
>>=20
>> @@ -186,7 +189,7 @@ enum {
>> fmr_op_maxpages(struct rpcrdma_xprt *r_xprt)
>> {
>> 	return min_t(unsigned int, RPCRDMA_MAX_DATA_SEGS,
>> -		     RPCRDMA_MAX_HDR_SEGS * RPCRDMA_MAX_FMR_SGES);
>> +		     (ia->ri_max_segs - 2) * RPCRDMA_MAX_FMR_SGES);
>=20
> ia isn't defined in this function.  Should that be =
r_xprt->rx_ia.ri_max_segs
> instead?

Yeah. I compile-tested the tip of the branch, and so missed
this.

I'm going to have to send you a v5, so I'll fix this up in
the next post of this series.


> Thanks,
> Anna
>=20
>> }
>>=20
>> /* Use the ib_map_phys_fmr() verb to register a memory region
>> diff --git a/net/sunrpc/xprtrdma/frwr_ops.c =
b/net/sunrpc/xprtrdma/frwr_ops.c
>> index 27222c0..f587e44 100644
>> --- a/net/sunrpc/xprtrdma/frwr_ops.c
>> +++ b/net/sunrpc/xprtrdma/frwr_ops.c
>> @@ -244,7 +244,10 @@
>>=20
>> 	ia->ri_max_segs =3D max_t(unsigned int, 1, RPCRDMA_MAX_DATA_SEGS =
/
>> 				ia->ri_max_frwr_depth);
>> -	ia->ri_max_segs +=3D 2;	/* segments for head and tail buffers */
>> +	/* Reply chunks require segments for head and tail buffers */
>> +	ia->ri_max_segs +=3D 2;
>> +	if (ia->ri_max_segs > RPCRDMA_MAX_HDR_SEGS)
>> +		ia->ri_max_segs =3D RPCRDMA_MAX_HDR_SEGS;
>> 	return 0;
>> }
>>=20
>> @@ -257,7 +260,7 @@
>> 	struct rpcrdma_ia *ia =3D &r_xprt->rx_ia;
>>=20
>> 	return min_t(unsigned int, RPCRDMA_MAX_DATA_SEGS,
>> -		     RPCRDMA_MAX_HDR_SEGS * ia->ri_max_frwr_depth);
>> +		     (ia->ri_max_segs - 2) * ia->ri_max_frwr_depth);
>> }
>>=20
>> static void
>> diff --git a/net/sunrpc/xprtrdma/transport.c =
b/net/sunrpc/xprtrdma/transport.c
>> index a16296b..fbb14bf 100644
>> --- a/net/sunrpc/xprtrdma/transport.c
>> +++ b/net/sunrpc/xprtrdma/transport.c
>> @@ -704,8 +704,10 @@
>>  *	%-ENOTCONN if the caller should reconnect and call again
>>  *	%-EAGAIN if the caller should call again
>>  *	%-ENOBUFS if the caller should call again after a delay
>> - *	%-EIO if a permanent error occurred and the request was not
>> - *		sent. Do not try to send this message again.
>> + *	%-EMSGSIZE if encoding ran out of buffer space. The request
>> + *		was not sent. Do not try to send this message again.
>> + *	%-EIO if an I/O error occurred. The request was not sent.
>> + *		Do not try to send this message again.
>>  */
>> static int
>> xprt_rdma_send_request(struct rpc_rqst *rqst)

--
Chuck Lever