Fix spurious -EFAULT when setting I/O scheduler

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

diff --git a/module/zfs/vdev_disk.c b/module/zfs/vdev_disk.c
index aba3c4a..5cb3fe2 100644 (file)
--- a/module/zfs/vdev_disk.c
+++ b/module/zfs/vdev_disk.c
@@ -118,25 +118,42 @@ vdev_disk_error(zio_t *zio)
  * 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, char *device)
+vdev_elevator_switch(vdev_t *v, char *elevator)
 {
-       char sh_path[] = "/bin/sh";
-       char sh_cmd[128];
-       char *argv[] = { sh_path, "-c", sh_cmd };
+       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 *argv[] = { "/bin/sh", "-c", NULL, NULL };
        char *envp[] = { NULL };
        int error;
 
-       if (!strncmp(elevator, "none", 4) && (strlen(elevator) == 4))
+       /* Skip devices which are not whole disks (partitions) */
+       if (!v->vdev_wholedisk)
+               return (0);
+
+       /* Skip devices without schedulers (loop, ram, dm, etc) */
+       if (!q->elevator || !blk_queue_stackable(q))
                return (0);
 
-       sprintf(sh_cmd, "%s \"%s\" >/sys/block/%s/queue/scheduler",
-           "/bin/echo", elevator, device);
+       /* Leave existing scheduler when set to "none" */
+       if (!strncmp(elevator, "none", 4) && (strlen(elevator) == 4))
+               return (0);
 
-       error = call_usermodehelper(sh_path, argv, envp, 1);
+       argv[2] = kmem_asprintf(SET_SCHEDULER_CMD, device, elevator);
+       error = call_usermodehelper(argv[0], argv, envp, 1);
        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);
+
+       strfree(argv[2]);
 
        return (error);
 }
@@ -207,8 +224,7 @@ 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;
 }