From c1f7510d80ae39992510589a31430ddd7b9f83ac Mon Sep 17 00:00:00 2001
From: Gleb Chesnokov <gleb.chesnokov@scst.dev>
Date: Fri, 7 Jul 2023 10:38:36 +0300
Subject: [PATCH] iscsi-scst: Improve 'write iop loop' in write_data()

This patch introduces several improvements to the 'write iop loop' in
the write_data() function:

1. Move iop-related variables under the scope of the 'write iop loop'.
2. Eliminate the 'retry' label, use 'continue' instead for simplicity.
3. Remove the redundant 'rest' variable, use just 'res' instead.

This patch doesn't change any functionality.
---
 iscsi-scst/kernel/nthread.c | 43 ++++++++++++++++++++-----------------
 1 file changed, 23 insertions(+), 20 deletions(-)

diff --git a/iscsi-scst/kernel/nthread.c b/iscsi-scst/kernel/nthread.c
index f0110729e..2806142ec 100644
--- a/iscsi-scst/kernel/nthread.c
+++ b/iscsi-scst/kernel/nthread.c
@@ -1095,8 +1095,6 @@ out:
 
 static int write_data(struct iscsi_conn *conn)
 {
-	struct file *file;
-	struct kvec *iop;
 	struct socket *sock;
 	ssize_t (*sock_sendpage)(struct socket *sock, struct page *page,
 				 int offset, size_t size, int flags);
@@ -1106,7 +1104,7 @@ static int write_data(struct iscsi_conn *conn)
 	struct scatterlist *sg;
 	size_t saved_size, size, sg_size;
 	size_t sendsize, length;
-	int offset, idx, flags, res = 0, count;
+	int offset, idx, flags, res = 0;
 	bool ref_cmd_to_parent;
 
 	TRACE_ENTRY();
@@ -1126,40 +1124,45 @@ static int write_data(struct iscsi_conn *conn)
 
 	req_add_to_write_timeout_list(parent_req);
 
-	file = conn->file;
-	size = conn->write_size;
-	saved_size = size;
-	iop = conn->write_iop;
-	count = conn->write_iop_used;
+	saved_size = size = conn->write_size;
+
+	if (conn->write_iop) {
+		struct file *file = conn->file;
+		struct kvec *iop = conn->write_iop;
+		int count = conn->write_iop_used;
+		loff_t off;
+
+		sBUG_ON(count > ARRAY_SIZE(conn->write_iov));
 
-	if (iop) {
 		while (true) {
-			loff_t off = 0;
-			int rest;
+			off = 0;
 
-			sBUG_ON(count > ARRAY_SIZE(conn->write_iov));
-retry:
 			res = scst_writev(file, iop, count, &off);
 			TRACE_WRITE("sid %#Lx, cid %u, res %d, iov_len %zd",
 				    (unsigned long long)conn->session->sid,
 				    conn->cid, res, iop->iov_len);
+
 			if (unlikely(res <= 0)) {
+				if (res == -EINTR)
+					continue;
+
 				if (res == -EAGAIN) {
 					conn->write_iop = iop;
 					conn->write_iop_used = count;
 					goto out_iov;
-				} else if (res == -EINTR)
-					goto retry;
+				}
+
 				goto out_err;
 			}
 
-			rest = res;
 			size -= res;
-			while ((typeof(rest))iop->iov_len <= rest && rest) {
-				rest -= iop->iov_len;
+
+			while ((typeof(res))iop->iov_len <= res && res) {
+				res -= iop->iov_len;
 				iop++;
 				count--;
 			}
+
 			if (count == 0) {
 				conn->write_iop = NULL;
 				conn->write_iop_used = 0;
@@ -1169,8 +1172,8 @@ retry:
 			}
 			sBUG_ON(iop >
 				conn->write_iov + ARRAY_SIZE(conn->write_iov));
-			iop->iov_base += rest;
-			iop->iov_len -= rest;
+			iop->iov_base += res;
+			iop->iov_len -= res;
 		}
 	}