btrfs: do not background blkdev_put()

At the end of unmount/dev-delete, if the device exclusive open is not
actually closed, then there might be a race with another program in
the userland who is trying to open the device in exclusive mode and
it may fail for eg:
      unmount /btrfs; fsck /dev/x
      btrfs dev del /dev/x /btrfs; fsck /dev/x
so here background blkdev_put() is not a choice

Signed-off-by: Anand Jain <Anand.Jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index e217035d63df419d29ebeaf4113ee210d67e9c4e..9a6f0dcb3e9c7602e31ddc339e06d04bbb38416f 100644 (file)
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -834,10 +834,6 @@ static void __free_device(struct work_struct *work)
        struct btrfs_device *device;
 
        device = container_of(work, struct btrfs_device, rcu_work);
-
-       if (device->bdev)
-               blkdev_put(device->bdev, device->mode);
-
        rcu_string_free(device->name);
        kfree(device);
 }
@@ -852,6 +848,17 @@ static void free_device(struct rcu_head *head)
        schedule_work(&device->rcu_work);
 }
 
+static void btrfs_close_bdev(struct btrfs_device *device)
+{
+       if (device->bdev && device->writeable) {
+               sync_blockdev(device->bdev);
+               invalidate_bdev(device->bdev);
+       }
+
+       if (device->bdev)
+               blkdev_put(device->bdev, device->mode);
+}
+
 static void btrfs_close_one_device(struct btrfs_device *device)
 {
        struct btrfs_fs_devices *fs_devices = device->fs_devices;
@@ -870,10 +877,7 @@ static void btrfs_close_one_device(struct btrfs_device *device)
        if (device->missing)
                fs_devices->missing_devices--;
 
-       if (device->bdev && device->writeable) {
-               sync_blockdev(device->bdev);
-               invalidate_bdev(device->bdev);
-       }
+       btrfs_close_bdev(device);
 
        new_device = btrfs_alloc_device(NULL, &device->devid,
                                        device->uuid);
@@ -1932,6 +1936,8 @@ int btrfs_rm_device(struct btrfs_root *root, char *device_path, u64 devid)
                btrfs_sysfs_rm_device_link(root->fs_info->fs_devices, device);
        }
 
+       btrfs_close_bdev(device);
+
        call_rcu(&device->rcu, free_device);
 
        num_devices = btrfs_super_num_devices(root->fs_info->super_copy) - 1;
@@ -2025,6 +2031,9 @@ void btrfs_rm_dev_replace_free_srcdev(struct btrfs_fs_info *fs_info,
                /* zero out the old super if it is writable */
                btrfs_scratch_superblocks(srcdev->bdev, srcdev->name->str);
        }
+
+       btrfs_close_bdev(srcdev);
+
        call_rcu(&srcdev->rcu, free_device);
 
        /*
@@ -2080,6 +2089,8 @@ void btrfs_destroy_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
         * the device_list_mutex lock.
         */
        btrfs_scratch_superblocks(tgtdev->bdev, tgtdev->name->str);
+
+       btrfs_close_bdev(tgtdev);
        call_rcu(&tgtdev->rcu, free_device);
 }