Fix set block scheduler warnings

[zfs] / module / zfs / vdev_disk.c

diff --git a/module/zfs/vdev_disk.c b/module/zfs/vdev_disk.c
index aba3c4ab57ef284df3641bb3661312eef8cb2419..69bc53b4b37328e1aef602ae43198a2356128f79 100644 (file)
--- a/module/zfs/vdev_disk.c
+++ b/module/zfs/vdev_disk.c
@@ -119,24 +119,42 @@ vdev_disk_error(zio_t *zio)
  * open time from the kernel.
  */
 static int
-vdev_elevator_switch(vdev_t *v, char *elevator, char *device)
+vdev_elevator_switch(vdev_t *v, char *elevator)
 {
+       vdev_disk_t *vd = v->vdev_tsd;
+       struct block_device *bdev = vd->vd_bdev;
+       struct request_queue *q = bdev_get_queue(bdev);
+       char *device = bdev->bd_disk->disk_name;
        char sh_path[] = "/bin/sh";
        char sh_cmd[128];
        char *argv[] = { sh_path, "-c", sh_cmd };
        char *envp[] = { NULL };
-       int error;
+       int count = 0, error;
+
+       /* Skip devices without schedulers (loop, ram, dm, etc) */
+       if (!q->elevator || !blk_queue_stackable(q))
+               return (0);
 
+       /* Leave existing scheduler when set to "none" */
        if (!strncmp(elevator, "none", 4) && (strlen(elevator) == 4))
                return (0);
 
+       /*
+        * Set the desired scheduler with a three attempt retry for
+        * -EFAULT which has been observed to occur spuriously.
+        */
        sprintf(sh_cmd, "%s \"%s\" >/sys/block/%s/queue/scheduler",
            "/bin/echo", elevator, device);
 
-       error = call_usermodehelper(sh_path, argv, envp, 1);
+       while (++count <= 3) {
+               error = call_usermodehelper(sh_path, argv, envp, 1);
+               if ((error == 0) || (error != -EFAULT))
+                      break;
+       }
+
        if (error)
                printk("ZFS: Unable to set \"%s\" scheduler for %s (%s): %d\n",
-                   elevator, v->vdev_path, device, error);
+                      elevator, v->vdev_path, device, error);
 
        return (error);
 }
@@ -207,8 +225,7 @@ vdev_disk_open(vdev_t *v, uint64_t *psize, uint64_t *ashift)
        *ashift = highbit(MAX(block_size, SPA_MINBLOCKSIZE)) - 1;
 
        /* Try to set the io scheduler elevator algorithm */
-       (void) vdev_elevator_switch(v, zfs_vdev_scheduler,
-           bdev->bd_disk->disk_name);
+       (void) vdev_elevator_switch(v, zfs_vdev_scheduler);
 
        return 0;
 }