Block devices without elevator (bio-based-dm/loop/etc) have "none"
for sysfs ioscheduler tunable, and write to this entry never fail
from the way elv_iosched_store() is implemented.
This commit checks if the entry is "none" type so as not to show
an irrelevant error message which assumes the entry has a list of
available I/O schedulers.
# cat /sys/block/dm-0/queue/scheduler
none
# echo deadline > /sys/block/dm-0/queue/scheduler ; echo $?
0
# cat /sys/block/dm-0/queue/scheduler
none
# echo aaa > /sys/block/dm-0/queue/scheduler ; echo $?
0
# cat /sys/block/dm-0/queue/scheduler
none
Signed-off-by: Tomohiro Kusumi <kusumi.tomohiro@xxxxxxxxx>
---
backend.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/backend.c b/backend.c
index 5872711..6bf5d67 100644
--- a/backend.c
+++ b/backend.c
@@ -1331,6 +1331,14 @@ static int switch_ioscheduler(struct thread_data *td)
*/
tmp[strlen(tmp) - 1] = '\0';
+ /*
+ * Write to "none" entry doesn't fail, so check the result here.
+ */
+ if (!strcmp(tmp, "none")) {
+ log_err("fio: io scheduler is not tunable\n");
+ fclose(f);
+ return 0;
+ }
sprintf(tmp2, "[%s]", td->o.ioscheduler);
if (!strstr(tmp, tmp2)) {
--
2.5.5
--
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