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From:   Chuck Lever <chuck.lever@oracle.com>
To:     bfields@redhat.com
Cc:     linux-nfs@vger.kernel.org
Subject: [PATCH v2 1/2] SUNRPC: Simplify the SVC dispatch code path
Date:   Thu,  7 Oct 2021 16:17:24 -0400
Message-Id:  <163363784431.2295.7425775268719807693.stgit@bazille.1015granger.net>
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References:  <163363775944.2295.17512762002999927909.stgit@bazille.1015granger.net>
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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;