Modify vdev_elevator_switch() to use elevator_change()

[zfs.git] / module / zfs / vdev_disk.c

diff --git a/module/zfs/vdev_disk.c b/module/zfs/vdev_disk.c
index ffb2980..c562256 100644 (file)
--- a/module/zfs/vdev_disk.c
+++ b/module/zfs/vdev_disk.c
@@ -111,19 +111,7 @@ vdev_disk_error(zio_t *zio)
  * elevator to do the maximum front/back merging allowed by the
  * physical device.  This yields the largest possible requests for
  * the device with the lowest total overhead.
- *
- * Unfortunately we cannot directly call the elevator_switch() function
- * because it is not exported from the block layer.  This means we have
- * to use the sysfs interface and a user space upcall.  Pools will be
- * automatically imported on module load so we must do this at device
- * open time from the kernel.
  */
-#define SET_SCHEDULER_CMD \
-       "exec 0</dev/null " \
-       "     1>/sys/block/%s/queue/scheduler " \
-       "     2>/dev/null; " \
-       "echo %s"
-
 static int
 vdev_elevator_switch(vdev_t *v, char *elevator)
 {
@@ -131,8 +119,6 @@ vdev_elevator_switch(vdev_t *v, char *elevator)
        struct block_device *bdev = vd->vd_bdev;
        struct request_queue *q = bdev_get_queue(bdev);
        char *device = bdev->bd_disk->disk_name;
-       char *argv[] = { "/bin/sh", "-c", NULL, NULL };
-       char *envp[] = { NULL };
        int error;
 
        /* Skip devices which are not whole disks (partitions) */
@@ -147,14 +133,33 @@ vdev_elevator_switch(vdev_t *v, char *elevator)
        if (!strncmp(elevator, "none", 4) && (strlen(elevator) == 4))
                return (0);
 
-       argv[2] = kmem_asprintf(SET_SCHEDULER_CMD, device, elevator);
-       error = call_usermodehelper(argv[0], argv, envp, 1);
+#ifdef HAVE_ELEVATOR_CHANGE
+       error = elevator_change(q, elevator);
+#else
+       /* For pre-2.6.36 kernels elevator_change() is not available.
+        * Therefore we fall back to using a usermodehelper to echo the
+        * elevator into sysfs;  This requires /bin/echo and sysfs to be
+        * mounted which may not be true early in the boot process.
+        */
+# define SET_SCHEDULER_CMD \
+       "exec 0</dev/null " \
+       "     1>/sys/block/%s/queue/scheduler " \
+       "     2>/dev/null; " \
+       "echo %s"
+
+       {
+               char *argv[] = { "/bin/sh", "-c", NULL, NULL };
+               char *envp[] = { NULL };
+
+               argv[2] = kmem_asprintf(SET_SCHEDULER_CMD, device, elevator);
+               error = call_usermodehelper(argv[0], argv, envp, 1);
+               strfree(argv[2]);
+       }
+#endif /* HAVE_ELEVATOR_CHANGE */
        if (error)
                printk("ZFS: Unable to set \"%s\" scheduler for %s (%s): %d\n",
                       elevator, v->vdev_path, device, error);
 
-       strfree(argv[2]);
-
        return (error);
 }