File 0001-iscsid-set-host-workqueue-priority-correct... of Package open-iscsi

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File 0001-iscsid-set-host-workqueue-priority-correctly.patch of Package open-iscsi (Revision 35880d772e4e6ad819a24a2b944232b1)

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From d5f55a50b377af4082ae4c51c5f6e391c740b8eb Mon Sep 17 00:00:00 2001
From: Lee Duncan <lduncan@suse.com>
Date: Fri, 23 Feb 2024 12:44:56 -0800
Subject: [PATCH 1/2] iscsid: set host workqueue priority correctly

The code was scanning through /proc for processes with the
workqueue name (iscsi_q_HOSTNUM) in the process name, and that
didn't always work in newer kernels, where only the current
workqueue being used is part of the kernel worker thread name.
In addition, this method was slow. This often failed, printing
a message like "Could not set sessionN priority. ..." in the
system journal.

Instead, write the the sysfs workqueue "nice" attribute, using
the same value that we used when previously calling setpriority().
Also, add some debugging that can be enabled.
---
 usr/initiator.c | 113 ++++++++++++++++++++----------------------------
 1 file changed, 46 insertions(+), 67 deletions(-)

diff --git a/usr/initiator.c b/usr/initiator.c
index 9c48dd506e17..ea0770f541ff 100644
--- a/usr/initiator.c
+++ b/usr/initiator.c
@@ -1389,85 +1389,64 @@ static void session_conn_recv_pdu(void *data)
 
 static void session_increase_wq_priority(struct iscsi_session *session)
 {
-	DIR *proc_dir;
-	struct dirent *proc_dent;
+	char nice_pathname[PATH_SIZE];
 	struct stat statb;
-	char stat_file[PATH_SIZE];
-	char sbuf[1024];	/* got this from ps */
-	int pid, stat_fd, num_read;
-	char *proc_name, *proc_name_end;
-	uint32_t host_no;
+	int nice_fd;
+	char nice_value_buf[10];	/* large enough for "-20" */
+	int buflen;
+
+	log_debug(5, "Trying to increase workqueue priority: sid %u host no %u",
+		  session->id, session->hostno);
 
 	/* drivers like bnx2i and qla4xxx do not have a write wq */
-	if (session->t->caps & CAP_DATA_PATH_OFFLOAD)
+	if (session->t->caps & CAP_DATA_PATH_OFFLOAD) {
+		log_debug(5, "Offload host detected: no workqueue");
 		return;
+	}
 
-	proc_dir = opendir(PROC_DIR);
-	if (!proc_dir)
-		goto fail;
-
-	while ((proc_dent = readdir(proc_dir))) {
-		if (!strcmp(proc_dent->d_name, ".") ||
-		    !strcmp(proc_dent->d_name, ".."))
-			continue;
-		if (sscanf(proc_dent->d_name, "%d", &pid) != 1)
-			continue;
-
-		memset(stat_file, 0, sizeof(stat_file));
-		sprintf(stat_file, PROC_DIR"/%d/stat", pid);
-		if (stat(stat_file, &statb))
-			continue;
-
-		if (!S_ISREG( statb.st_mode))
-			continue;
-
-		stat_fd = open(stat_file, O_RDONLY);
-		if (stat_fd == -1)
-			continue;
+	snprintf(nice_pathname, sizeof(nice_pathname),
+		 "/sys/bus/workqueue/devices/iscsi_q_%u/nice",
+		 session->hostno);
 
-		memset(sbuf, 0, sizeof(sbuf));
-		num_read = read(stat_fd, sbuf, sizeof(sbuf));
-		close(stat_fd);
-		if (num_read == -1)
-			continue;
-		if (num_read == sizeof(sbuf))
-			sbuf[num_read - 1] = '\0';
-		else
-			sbuf[num_read] = '\0';
+	if (stat(nice_pathname, &statb)) {
+		log_debug(5, "Cannot stat %s: %s", nice_pathname,
+			  strerror(errno));
+		goto fail;
+	}
 
-		/*
-		 * Finally match proc name to iscsi thread name.
-		 * In newer kernels the name is iscsi_wq_%HOST_NO.
-		 * In older kernels before 2.6.30, it was scsi_wq_%HOST_NO.
-		 *
-		 * We only support newer kernels.
-		 */
-		proc_name = strchr(sbuf, '(') + 1;
-		if (!proc_name)
-			continue;
+	if ((statb.st_mode & S_IWUSR) == 0) {
+		log_debug(5, "Cannot write to %s: Invalid permissions",
+			  nice_pathname);
+		goto fail;
+	}
 
-		proc_name_end = strchr(proc_name, ')');
-		if (!proc_name_end)
-			continue;
+	if (!S_ISREG(statb.st_mode)) {
+		log_debug(5, "Not a regular file: %s", nice_pathname);
+		goto fail;
+	}
 
-		*proc_name_end = '\0';
+	nice_fd = open(nice_pathname, O_RDWR);
+	if (nice_fd < 0) {
+		log_debug(5, "Cannot open: %s: %s", nice_pathname,
+			  strerror(errno));
+		goto fail;
+	}
 
-		if (sscanf(proc_name, "iscsi_q_%u\n", &host_no) == 1) {
-			if (host_no == session->hostno) {
-				if (!setpriority(PRIO_PROCESS, pid,
-					session->nrec.session.xmit_thread_priority)) {
-					closedir(proc_dir);
-					return;
-				} else
-					break;
-			}
-		}
+	buflen = snprintf(nice_value_buf, sizeof(nice_value_buf), "%d",
+			  session->nrec.session.xmit_thread_priority);
+	if (write(nice_fd, nice_value_buf, buflen) < 0) {
+		log_debug(5, "Cannot write \"%s\" to %s: %s", nice_value_buf,
+			  nice_pathname, strerror(errno));
+		close(nice_fd);
+		goto fail;
 	}
-	closedir(proc_dir);
+	close(nice_fd);
+	return;
+
 fail:
-	log_error("Could not set session%d priority. "
-		  "READ/WRITE throughout and latency could be "
-		  "affected.", session->id);
+	log_error("Could not set session%u priority host %u. "
+		  "READ/WRITE throughout and latency could be effected.",
+		  session->id, session->hostno);
 }
 
 static int session_ipc_create(struct iscsi_session *session)
-- 
2.35.3

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File 0001-iscsid-set-host-workqueue-priority-correctly.patch of Package open-iscsi (Revision 35880d772e4e6ad819a24a2b944232b1)

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