!1400 [openEuler-1.0-LTS] block: Try to handle busy underlying device on discard

Merge Pull Request from: @zh-hhhhh 
 

If you run qemu-img convert -t none when iscsi back-end storage is used (mounted using multipath), an error message is displayed indicating Device or resource busy. The error message is resolved after patch is added

bugzilla: https://gitee.com/openeuler/kernel/issues/I7GDLI
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/fs/block_dev.c?h=v5.10.180&id=d44c9780ed40db88626c9354868eab72159c7a7f

     
 
Link:https://gitee.com/openeuler/kernel/pulls/1400 

Reviewed-by: Zhang Changzhong <zhangchangzhong@huawei.com> 
Reviewed-by: Yu Kuai <yukuai3@huawei.com> 
Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com> 

fs/block_dev.c

@@ -1149,12 +1149,21 @@ int truncate_bdev_range(struct block_device *bdev, fmode_t mode,
 		err = bd_prepare_to_claim(bdev, claimed_bdev,
 					  truncate_bdev_range);
 		if (err)
-			return err;
+			goto invalidate;
 	}
 	truncate_inode_pages_range(bdev->bd_inode->i_mapping, lstart, lend);
 	if (claimed_bdev)
 		bd_abort_claiming(bdev, claimed_bdev, truncate_bdev_range);
 	return 0;
+
+invalidate:
+	/*
+	 * Someone else has handle exclusively open. Try invalidating instead.
+	 * The 'end' argument is inclusive so the rounding is safe.
+	 */
+	return invalidate_inode_pages2_range(bdev->bd_inode->i_mapping,
+					     lstart >> PAGE_SHIFT,
+					     lend >> PAGE_SHIFT);
 }
 EXPORT_SYMBOL(truncate_bdev_range);