int blkdev_fsync(struct file *filp, struct dentry *dentry, int datasync)
  {
-       struct block_device *bdev = I_BDEV(filp->f_mapping->host);
+       struct inode *bd_inode = filp->f_mapping->host;
+       struct block_device *bdev = I_BDEV(bd_inode);
        int error;
  
-       error = sync_blockdev(bdev);
-       if (error)
-               return error;
-       
-       error = blkdev_issue_flush(bdev, GFP_KERNEL, NULL,
-                               (BLKDEV_IFL_WAIT));
+       /*
+        * There is no need to serialise calls to blkdev_issue_flush with
+        * i_mutex and doing so causes performance issues with concurrent
+        * O_SYNC writers to a block device.
+        */
+       mutex_unlock(&bd_inode->i_mutex);
+ 
 -      error = blkdev_issue_flush(bdev, NULL);
++      error = blkdev_issue_flush(bdev, GFP_KERNEL, NULL, BLKDEV_IFL_WAIT);
        if (error == -EOPNOTSUPP)
                error = 0;
+ 
+       mutex_lock(&bd_inode->i_mutex);
+ 
        return error;
  }
  EXPORT_SYMBOL(blkdev_fsync);