From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AEA2AC433DB for ; Sun, 14 Mar 2021 09:31:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7F3D064E6C for ; Sun, 14 Mar 2021 09:31:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235066AbhCNJbT (ORCPT ); Sun, 14 Mar 2021 05:31:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46430 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234926AbhCNJbL (ORCPT ); Sun, 14 Mar 2021 05:31:11 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B5710C061574; Sun, 14 Mar 2021 01:31:10 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=SykGWp4zjmnTjLde0zD0XJaXm2zUhar4dKi1VK326yQ=; b=ZZZ/k7tHndF4lrwDLu7QsF4LCY SiZr7u0v8HCIZqJXK7fEq48wHWj3Fwz2zBJ5ohvlluvs69SvUeBhIDjc92RYaJcO/vknHK3xj6ZrL kIlYFI9Xnxy+3PiCcR4IGGVBqZsPv75RBwAQDh0oG6Gv1kA3tD+RkEoWFgm7Li2xxJIamefvttM3l vHlDCt9WcNFb7v97qGxtuppZx7AMmct9BYvDtDuIMnOLUK5r1QSlhdAb24PDrKCobkw52WJIhP+jR 9u8hmOl4XU8Z0RgvKv96m7+ZZn25Y4RBz4OIz1xZC8sUhvkAKsCbPO1FenZSPOswBgTzAwD7H8dqb xAmendUQ==; Received: from hch by casper.infradead.org with local (Exim 4.94 #2 (Red Hat Linux)) id 1lLN54-00FqvD-M3; Sun, 14 Mar 2021 09:30:45 +0000 Date: Sun, 14 Mar 2021 09:30:38 +0000 From: Christoph Hellwig To: Sergei Shtepa Cc: Christoph Hellwig , Mike Snitzer , Alasdair Kergon , Hannes Reinecke , Jens Axboe , dm-devel@redhat.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, pavel.tide@veeam.com Subject: Re: [PATCH v7 3/3] dm: add DM_INTERPOSED_FLAG Message-ID: <20210314093038.GC3773360@infradead.org> References: <1615563895-28565-1-git-send-email-sergei.shtepa@veeam.com> <1615563895-28565-4-git-send-email-sergei.shtepa@veeam.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1615563895-28565-4-git-send-email-sergei.shtepa@veeam.com> X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Fri, Mar 12, 2021 at 06:44:55PM +0300, Sergei Shtepa wrote: > DM_INTERPOSED_FLAG allow to create DM targets on "the fly". > Underlying block device opens without a flag FMODE_EXCL. > DM target receives bio from the original device via > bdev_interposer. This is more of a philopical comment, but the idea of just letting the interposed reopen the device by itself seems like a bad idea. I think that is probably better hidden in the block layer interposer attachment function, which could do the extra blkdev_get_by_dev for the caller.