Cleanup zvol initialization code

The following error will occur on some (possibly all) kernels
because blk_init_queue() will try to take the spinlock before
we initialize it.

  BUG: spinlock bad magic on CPU#0, zpool/4054
   lock: 0xffff88021a73de60, .magic: 00000000,
   .owner: <none>/-1, .owner_cpu: 0
  Pid: 4054, comm: zpool Not tainted 3.9.3 #11
  Call Trace:
   [<ffffffff81478ef8>] spin_dump+0x8c/0x91
   [<ffffffff81478f1e>] spin_bug+0x21/0x26
   [<ffffffff812da097>] do_raw_spin_lock+0x127/0x130
   [<ffffffff8147d851>] _raw_spin_lock_irq+0x21/0x30
   [<ffffffff812c2c1e>] cfq_init_queue+0x1fe/0x350
   [<ffffffff812aacb8>] elevator_init+0x78/0x140
   [<ffffffff812b2677>] blk_init_allocated_queue+0x87/0xb0
   [<ffffffff812b26d5>] blk_init_queue_node+0x35/0x70
   [<ffffffff812b271e>] blk_init_queue+0xe/0x10
   [<ffffffff8125211b>] __zvol_create_minor+0x24b/0x620
   [<ffffffff81253264>] zvol_create_minors_cb+0x24/0x30
   [<ffffffff811bd9ca>] dmu_objset_find_spa+0xea/0x510
   [<ffffffff811bda71>] dmu_objset_find_spa+0x191/0x510
   [<ffffffff81253ea2>] zvol_create_minors+0x92/0x180
   [<ffffffff811f8d80>] spa_open_common+0x250/0x380
   [<ffffffff811f8ece>] spa_open+0xe/0x10
   [<ffffffff8122817e>] pool_status_check.part.22+0x1e/0x80
   [<ffffffff81228a55>] zfsdev_ioctl+0x155/0x190
   [<ffffffff8116a695>] do_vfs_ioctl+0x325/0x5a0
   [<ffffffff8116a950>] sys_ioctl+0x40/0x80
   [<ffffffff814812c9>] ? do_page_fault+0x9/0x10
   [<ffffffff81483929>] system_call_fastpath+0x16/0x1b
   zd0: unknown partition table

We fix this by calling spin_lock_init before blk_init_queue.

The manner in which zvol_init() initializes structures is
suspectible to a race between initialization and a probe on
a zvol. We reorganize zvol_init() to prevent that.

Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

diff --git a/module/zfs/zvol.c b/module/zfs/zvol.c
index 43a7bb6..97b65c8 100644 (file)
--- a/module/zfs/zvol.c
+++ b/module/zfs/zvol.c
@@ -1215,6 +1215,9 @@ zvol_alloc(dev_t dev, const char *name)
 
        zv = kmem_zalloc(sizeof (zvol_state_t), KM_SLEEP);
 
+       spin_lock_init(&zv->zv_lock);
+       list_link_init(&zv->zv_next);
+
        zv->zv_queue = blk_init_queue(zvol_request, &zv->zv_lock);
        if (zv->zv_queue == NULL)
                goto out_kmem;
@@ -1248,9 +1251,6 @@ zvol_alloc(dev_t dev, const char *name)
            sizeof (rl_t), offsetof(rl_t, r_node));
        zv->zv_znode.z_is_zvol = TRUE;
 
-       spin_lock_init(&zv->zv_lock);
-       list_link_init(&zv->zv_next);
-
        zv->zv_disk->major = zvol_major;
        zv->zv_disk->first_minor = (dev & MINORMASK);
        zv->zv_disk->fops = &zvol_ops;
@@ -1561,30 +1561,38 @@ zvol_init(void)
 {
        int error;
 
+       list_create(&zvol_state_list, sizeof (zvol_state_t),
+                   offsetof(zvol_state_t, zv_next));
+       mutex_init(&zvol_state_lock, NULL, MUTEX_DEFAULT, NULL);
+
        zvol_taskq = taskq_create(ZVOL_DRIVER, zvol_threads, maxclsyspri,
                                  zvol_threads, INT_MAX, TASKQ_PREPOPULATE);
        if (zvol_taskq == NULL) {
                printk(KERN_INFO "ZFS: taskq_create() failed\n");
-               return (-ENOMEM);
+               error = -ENOMEM;
+               goto out1;
        }
 
        error = register_blkdev(zvol_major, ZVOL_DRIVER);
        if (error) {
                printk(KERN_INFO "ZFS: register_blkdev() failed %d\n", error);
-               taskq_destroy(zvol_taskq);
-               return (error);
+               goto out2;
        }
 
        blk_register_region(MKDEV(zvol_major, 0), 1UL << MINORBITS,
                            THIS_MODULE, zvol_probe, NULL, NULL);
 
-       mutex_init(&zvol_state_lock, NULL, MUTEX_DEFAULT, NULL);
-       list_create(&zvol_state_list, sizeof (zvol_state_t),
-                   offsetof(zvol_state_t, zv_next));
-
        (void) zvol_create_minors(NULL);
 
        return (0);
+
+out2:
+       taskq_destroy(zvol_taskq);
+out1:
+       mutex_destroy(&zvol_state_lock);
+       list_destroy(&zvol_state_list);
+
+       return (error);
 }
 
 void