[PATCH v2 0/2] Clean up svc scheduler

[PATCH v2 0/2] Clean up svc scheduler

[Chuck Lever]

Hi Bruce. I forgot that these two go together. Sorry about that.

"SUNRPC: Simplify the SVC dispatch code path" is unchanged from
its initial posting a few minutes ago.

---

Chuck Lever (2):
      SUNRPC: Simplify the SVC dispatch code path
      SUNRPC: De-duplicate .pc_release() call sites


 include/linux/sunrpc/svc.h |  5 +--
 net/sunrpc/svc.c           | 69 ++++----------------------------------
 2 files changed, 8 insertions(+), 66 deletions(-)

--
Chuck Lever

[PATCH v2 1/2] SUNRPC: Simplify the SVC dispatch code path

[Chuck Lever]

Micro-optimization: The last user of the generic SVC dispatch code
path has been removed, so svc_process_common() can be simplified.
This declutters the hot path so that the by-far most common case
(a dispatch function exists) is made the /only/ path.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 include/linux/sunrpc/svc.h |    5 +---
 net/sunrpc/svc.c           |   51 ++------------------------------------------
 2 files changed, 3 insertions(+), 53 deletions(-)

diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 6263410c948a..4205a6ef4770 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -443,10 +443,7 @@ struct svc_version {
 	/* Need xprt with congestion control */
 	bool			vs_need_cong_ctrl;
 
-	/* Override dispatch function (e.g. when caching replies).
-	 * A return value of 0 means drop the request. 
-	 * vs_dispatch == NULL means use default dispatcher.
-	 */
+	/* Dispatch function */
 	int			(*vs_dispatch)(struct svc_rqst *, __be32 *);
 };
 
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index 08ca797bb8a4..e0dd6e6a4602 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -1186,45 +1186,6 @@ void svc_printk(struct svc_rqst *rqstp, const char *fmt, ...)
 static __printf(2,3) void svc_printk(struct svc_rqst *rqstp, const char *fmt, ...) {}
 #endif
 
-static int
-svc_generic_dispatch(struct svc_rqst *rqstp, __be32 *statp)
-{
-	struct kvec *argv = &rqstp->rq_arg.head[0];
-	struct kvec *resv = &rqstp->rq_res.head[0];
-	const struct svc_procedure *procp = rqstp->rq_procinfo;
-
-	/*
-	 * Decode arguments
-	 * XXX: why do we ignore the return value?
-	 */
-	if (procp->pc_decode &&
-	    !procp->pc_decode(rqstp, argv->iov_base)) {
-		*statp = rpc_garbage_args;
-		return 1;
-	}
-
-	*statp = procp->pc_func(rqstp);
-
-	if (*statp == rpc_drop_reply ||
-	    test_bit(RQ_DROPME, &rqstp->rq_flags))
-		return 0;
-
-	if (rqstp->rq_auth_stat != rpc_auth_ok)
-		return 1;
-
-	if (*statp != rpc_success)
-		return 1;
-
-	/* Encode reply */
-	if (procp->pc_encode &&
-	    !procp->pc_encode(rqstp, resv->iov_base + resv->iov_len)) {
-		dprintk("svc: failed to encode reply\n");
-		/* serv->sv_stats->rpcsystemerr++; */
-		*statp = rpc_system_err;
-	}
-	return 1;
-}
-
 __be32
 svc_generic_init_request(struct svc_rqst *rqstp,
 		const struct svc_program *progp,
@@ -1392,16 +1353,8 @@ svc_process_common(struct svc_rqst *rqstp, struct kvec *argv, struct kvec *resv)
 		svc_reserve_auth(rqstp, procp->pc_xdrressize<<2);
 
 	/* Call the function that processes the request. */
-	if (!process.dispatch) {
-		if (!svc_generic_dispatch(rqstp, statp))
-			goto release_dropit;
-		if (*statp == rpc_garbage_args)
-			goto err_garbage;
-	} else {
-		dprintk("svc: calling dispatcher\n");
-		if (!process.dispatch(rqstp, statp))
-			goto release_dropit; /* Release reply info */
-	}
+	if (!process.dispatch(rqstp, statp))
+		goto release_dropit;
 
 	if (rqstp->rq_auth_stat != rpc_auth_ok)
 		goto err_release_bad_auth;

[PATCH v2 2/2] SUNRPC: De-duplicate .pc_release() call sites

[Chuck Lever]

There was some spaghetti in svc_process_common() that had evolved
over time such that there was still one case that needed a call
to .pc_release() but never made it. That issue was removed in
the previous patch.

As additional insurance against missing this important callout,
ensure that the .pc_release() method is always called, no matter
what the reply_stat is.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 net/sunrpc/svc.c |   22 +++++++---------------
 1 file changed, 7 insertions(+), 15 deletions(-)

diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index e0dd6e6a4602..4292278a9552 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -1252,7 +1252,7 @@ svc_process_common(struct svc_rqst *rqstp, struct kvec *argv, struct kvec *resv)
 	__be32			*statp;
 	u32			prog, vers;
 	__be32			rpc_stat;
-	int			auth_res;
+	int			auth_res, rc;
 	__be32			*reply_statp;
 
 	rpc_stat = rpc_success;
@@ -1353,20 +1353,18 @@ svc_process_common(struct svc_rqst *rqstp, struct kvec *argv, struct kvec *resv)
 		svc_reserve_auth(rqstp, procp->pc_xdrressize<<2);
 
 	/* Call the function that processes the request. */
-	if (!process.dispatch(rqstp, statp))
-		goto release_dropit;
-
+	rc = process.dispatch(rqstp, statp);
+	if (procp->pc_release)
+		procp->pc_release(rqstp);
+	if (!rc)
+		goto dropit;
 	if (rqstp->rq_auth_stat != rpc_auth_ok)
-		goto err_release_bad_auth;
+		goto err_bad_auth;
 
 	/* Check RPC status result */
 	if (*statp != rpc_success)
 		resv->iov_len = ((void*)statp)  - resv->iov_base + 4;
 
-	/* Release reply info */
-	if (procp->pc_release)
-		procp->pc_release(rqstp);
-
 	if (procp->pc_encode == NULL)
 		goto dropit;
 
@@ -1375,9 +1373,6 @@ svc_process_common(struct svc_rqst *rqstp, struct kvec *argv, struct kvec *resv)
 		goto close_xprt;
 	return 1;		/* Caller can now send it */
 
-release_dropit:
-	if (procp->pc_release)
-		procp->pc_release(rqstp);
  dropit:
 	svc_authorise(rqstp);	/* doesn't hurt to call this twice */
 	dprintk("svc: svc_process dropit\n");
@@ -1404,9 +1399,6 @@ svc_process_common(struct svc_rqst *rqstp, struct kvec *argv, struct kvec *resv)
 	svc_putnl(resv, 2);
 	goto sendit;
 
-err_release_bad_auth:
-	if (procp->pc_release)
-		procp->pc_release(rqstp);
 err_bad_auth:
 	dprintk("svc: authentication failed (%d)\n",
 		be32_to_cpu(rqstp->rq_auth_stat));

Re: [PATCH v2 0/2] Clean up svc scheduler

[J. Bruce Fields]

On Thu, Oct 07, 2021 at 04:17:17PM -0400, Chuck Lever wrote:
> Hi Bruce. I forgot that these two go together. Sorry about that.
> 
> "SUNRPC: Simplify the SVC dispatch code path" is unchanged from
> its initial posting a few minutes ago.

Looks good to me, thanks; applied.--b.

> 
> ---
> 
> Chuck Lever (2):
>       SUNRPC: Simplify the SVC dispatch code path
>       SUNRPC: De-duplicate .pc_release() call sites
> 
> 
>  include/linux/sunrpc/svc.h |  5 +--
>  net/sunrpc/svc.c           | 69 ++++----------------------------------
>  2 files changed, 8 insertions(+), 66 deletions(-)
> 
> --
> Chuck Lever