From da86774e5a002acf2c8d779b805305bc193fc0a5 Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@suse.de>
Date: Tue, 6 Jun 2006 10:39:10 -0700
Subject: [PATCH 1/1] [PATCH] Add ioscheduler=x option to allow setting io
 scheduler

---
 README    |  1 +
 fio-ini.c | 10 ++++++++++
 fio.c     | 56 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 fio.h     |  4 ++++
 4 files changed, 71 insertions(+)

diff --git a/README b/README
index aec8207c..24bf5a00 100644
--- a/README
+++ b/README
@@ -113,6 +113,7 @@ The <jobs> format is as follows:
 	nice=x		Run job at given nice value.
 	exec_prerun=x	Run 'x' before job io is begun.
 	exec_postrun=x	Run 'x' after job io has finished.
+	ioscheduler=x	Use ioscheduler 'x' for this job.
 
 Examples using a job file
 -------------------------
diff --git a/fio-ini.c b/fio-ini.c
index 0c874085..d2122e3f 100644
--- a/fio-ini.c
+++ b/fio-ini.c
@@ -664,6 +664,12 @@ static int str_postrun_cb(struct thread_data *td, char *file)
 	return 0;
 }
 
+static int str_iosched_cb(struct thread_data *td, char *file)
+{
+	td->ioscheduler = strdup(file);
+	return 0;
+}
+
 int parse_jobs_ini(char *file)
 {
 	unsigned int prioclass, prio, cpu, global, il;
@@ -927,6 +933,10 @@ int parse_jobs_ini(char *file)
 				fgetpos(f, &off);
 				continue;
 			}
+			if (!check_str(p, "ioscheduler", str_iosched_cb, td)) {
+				fgetpos(f, &off);
+				continue;
+			}
 
 			printf("Client%d: bad option %s\n",td->thread_number,p);
 			return 1;
diff --git a/fio.c b/fio.c
index 79c11d5c..bd938979 100644
--- a/fio.c
+++ b/fio.c
@@ -1787,9 +1787,58 @@ static void init_disk_util(struct thread_data *td)
 		sprintf(foo, "%s", p);
 	}
 
+	td->sysfs_root = strdup(foo);
 	disk_util_add(dev, foo);
 }
 
+static int switch_ioscheduler(struct thread_data *td)
+{
+	char tmp[256], tmp2[128];
+	FILE *f;
+	int ret;
+
+	sprintf(tmp, "%s/queue/scheduler", td->sysfs_root);
+
+	f = fopen(tmp, "r+");
+	if (!f) {
+		td_verror(td, errno);
+		return 1;
+	}
+
+	/*
+	 * Set io scheduler.
+	 */
+	ret = fwrite(td->ioscheduler, strlen(td->ioscheduler), 1, f);
+	if (ferror(f) || ret != 1) {
+		td_verror(td, errno);
+		fclose(f);
+		return 1;
+	}
+
+	rewind(f);
+
+	/*
+	 * Read back and check that the selected scheduler is now the default.
+	 */
+	ret = fread(tmp, 1, sizeof(tmp), f);
+	if (ferror(f) || ret < 0) {
+		td_verror(td, errno);
+		fclose(f);
+		return 1;
+	}
+
+	sprintf(tmp2, "[%s]", td->ioscheduler);
+	if (!strstr(tmp, tmp2)) {
+		fprintf(stderr, "fio: io scheduler %s not found\n", td->ioscheduler);
+		td_verror(td, EINVAL);
+		fclose(f);
+		return 1;
+	}
+
+	fclose(f);
+	return 0;
+}
+
 static void disk_util_timer_arm(void)
 {
 	itimer.it_value.tv_sec = 0;
@@ -1869,6 +1918,9 @@ static void *thread_main(void *data)
 	if (init_random_state(td))
 		goto err;
 
+	if (td->ioscheduler && switch_ioscheduler(td))
+		goto err;
+
 	td_set_runstate(td, TD_INITIALIZED);
 	sem_post(&startup_sem);
 	sem_wait(&td->mutex);
@@ -1946,6 +1998,10 @@ err:
 		free(td->exec_prerun);
 	if (td->exec_postrun)
 		free(td->exec_postrun);
+	if (td->ioscheduler)
+		free(td->ioscheduler);
+	if (td->sysfs_root)
+		free(td->sysfs_root);
 	cleanup_io(td);
 	cleanup_io_u(td);
 	td_set_runstate(td, TD_EXITED);
diff --git a/fio.h b/fio.h
index d765ac6e..76a114f2 100644
--- a/fio.h
+++ b/fio.h
@@ -161,6 +161,10 @@ struct thread_data {
 	void *iolog_buf;
 	FILE *iolog_f;
 
+	char *sysfs_root;
+
+	char *ioscheduler;
+
 	struct drand48_data bsrange_state;
 	struct drand48_data verify_state;
 
-- 
2.25.1