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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 12E88EB64D0 for ; Tue, 13 Jun 2023 15:24:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242866AbjFMPYV (ORCPT ); Tue, 13 Jun 2023 11:24:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44776 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242789AbjFMPYO (ORCPT ); Tue, 13 Jun 2023 11:24:14 -0400 Received: from mx2.veeam.com (mx2.veeam.com [64.129.123.6]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F215E1BE7; Tue, 13 Jun 2023 08:24:00 -0700 (PDT) Received: from mail.veeam.com (prgmbx01.amust.local [172.24.128.102]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx2.veeam.com (Postfix) with ESMTPS id E534441C2D; Tue, 13 Jun 2023 11:23:57 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=veeam.com; s=mx2-2022; t=1686669838; bh=40s+nUN8R5Qgu61YlGIQxZXjwUmvIf+foe93wtMZLps=; h=Date:Subject:To:CC:References:From:In-Reply-To:From; b=kccezytyhEARm4Ht3h3sAzJiwHnocoTeyPml2SRgvpncfqGgta7s3s+qEVqw1g4UZ H+E5vne7MD40jhf568I1zCOrVj3KE000dpx1WRe20dqZYOBtW/ceykZWhQMov1QA1a 7EJJV1ADLISDrTHe5sAtfUbWQkkOfESPrqe015l5OT9cnijMYw30iK5A4XBnr5wwr+ n3/Mos+ot2gb7UdpKJ1OsdKKgB+Xp518iQf5mCZRCAqyqw89ff8AcQE07iXfoKYXZK EYx0OiVCWPX9nWTWc2clW2OMa805j5lStTV3MurApz/NVCdV0DT3F/z7hfpFt9911v F5GDfLPwSMEFA== Received: from [172.24.10.107] (172.24.10.107) by prgmbx01.amust.local (172.24.128.102) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1118.26; Tue, 13 Jun 2023 17:23:56 +0200 Message-ID: <5f6cdc55-ddbe-ab03-92bf-02ff0318985f@veeam.com> Date: Tue, 13 Jun 2023 17:23:50 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.11.2 Subject: Re: [PATCH v4 01/11] documentation: Block Device Filtering Mechanism Content-Language: en-US To: Randy Dunlap , , , , CC: , , , , , , , , , , , , "Bagas Sanjaya" References: <20230609115858.4737-1-sergei.shtepa@veeam.com> <004cc6b2-1941-5aed-6e09-3bd01dfbf8e4@infradead.org> From: Sergei Shtepa In-Reply-To: <004cc6b2-1941-5aed-6e09-3bd01dfbf8e4@infradead.org> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [172.24.10.107] X-ClientProxiedBy: prgmbx02.amust.local (172.24.128.103) To prgmbx01.amust.local (172.24.128.102) X-EsetResult: clean, is OK X-EsetId: 37303A29240315546D7161 X-Veeam-MMEX: True Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Thank you very much, Randy, for the work you've done. Sometimes I want to compile the documentation into bytecode, fix the warnings and debug it in the debugger. On 6/13/23 03:52, Randy Dunlap wrote: > Subject: > Re: [PATCH v4 01/11] documentation: Block Device Filtering Mechanism > From: > Randy Dunlap > Date: > 6/13/23, 03:52 > > To: > Sergei Shtepa , axboe@kernel.dk, hch@infradead.org, corbet@lwn.net, snitzer@kernel.org > CC: > viro@zeniv.linux.org.uk, brauner@kernel.org, willy@infradead.org, dlemoal@kernel.org, wsa@kernel.org, heikki.krogerus@linux.intel.com, ming.lei@redhat.com, gregkh@linuxfoundation.org, linux-block@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Bagas Sanjaya > > > Hi-- > > On 6/9/23 04:58, Sergei Shtepa wrote: >> The document contains: >> * Describes the purpose of the mechanism >> * A little historical background on the capabilities of handling I/O >> units of the Linux kernel >> * Brief description of the design >> * Reference to interface description >> >> Reviewed-by: Bagas Sanjaya >> Signed-off-by: Sergei Shtepa >> --- >> Documentation/block/blkfilter.rst | 64 +++++++++++++++++++++++++++++++ >> Documentation/block/index.rst | 1 + >> MAINTAINERS | 6 +++ >> 3 files changed, 71 insertions(+) >> create mode 100644 Documentation/block/blkfilter.rst >> >> diff --git a/Documentation/block/blkfilter.rst b/Documentation/block/blkfilter.rst >> new file mode 100644 >> index 000000000000..555625789244 >> --- /dev/null >> +++ b/Documentation/block/blkfilter.rst >> @@ -0,0 +1,64 @@ >> +.. SPDX-License-Identifier: GPL-2.0 >> + >> +================================ >> +Block Device Filtering Mechanism >> +================================ >> + >> +The block device filtering mechanism is an API that allows to attach block > that allows {what or who} to attach > > so who/what does the attach? Is it a driver or a user or admin or something else? > and attach them to what? > >> +device filters. Block device filters allow perform additional processing > allow performing ... > >> +for I/O units. >> + >> +Introduction >> +============ >> + >> +The idea of handling I/O units on block devices is not new. Back in the >> +2.6 kernel, there was an undocumented possibility of handling I/O units >> +by substituting the make_request_fn() function, which belonged to the >> +request_queue structure. But none of the in-tree kernel modules used this >> +feature, and it was eliminated in the 5.10 kernel. >> + >> +The block device filtering mechanism returns the ability to handle I/O units. >> +It is possible to safely attach filter to a block device "on the fly" without > attach a filter > or > attach filters > >> +changing the structure of block devices stack. > of the block device's stack. > >> + >> +It supports attaching one filter to one block device, because there is only >> +one filter implementation in the kernel yet. >> +See Documentation/block/blksnap.rst. >> + >> +Design >> +====== >> + >> +The block device filtering mechanism provides registration and unregistration >> +for filter operations. The struct blkfilter_operations contains a pointer to >> +the callback functions for the filter. After registering the filter operations, >> +filter can be managed using block device ioctl BLKFILTER_ATTACH, > a filter > or > the filter ioctls > >> +BLKFILTER_DETACH and BLKFILTER_CTL. >> + >> +When the filter is attached, the callback function is called for each I/O unit >> +for a block device, providing I/O unit filtering. Depending on the result of >> +filtering the I/O unit, it can either be passed for subsequent processing by >> +the block layer, or skipped. >> + >> +The filter can be implemented as a loadable module. In this case, the filter >> +module cannot be unloaded while the filter is attached to at least one of the >> +block devices. >> + >> +Interface description >> +===================== >> + >> +The ioctl BLKFILTER_ATTACH and BLKFILTER_DETACH use structure blkfilter_name. > ioctls > >> +It allows to attach a filter to a block device or detach it. > It allows a driver to attach a filter ... > ? > >> + >> +The ioctl BLKFILTER_CTL use structure blkfilter_ctl. It allows to send a > It allows a driver to send a > >> +filter-specific command. >> + >> +.. kernel-doc:: include/uapi/linux/blk-filter.h >> + >> +To register in the system, the filter creates its own account, which contains >> +callback functions, unique filter name and module owner. This filter account is >> +used by the registration functions. > I'm having a problem with this "account" thingy. Can you explain more about it? > Is there an alternate word that might be used here? > >> + >> +.. kernel-doc:: include/linux/blk-filter.h >> + >> +.. kernel-doc:: block/blk-filter.c >> + :export: > Thanks. > -- ~Randy > fix of the blkfilter.rst document and help in Kconfig for blksnap Reported-by: Randy Dunlap Signed-off-by: Sergei Shtepa --- Documentation/block/blkfilter.rst | 28 +++++++++++++++------------- drivers/block/blksnap/Kconfig | 2 +- 2 files changed, 16 insertions(+), 14 deletions(-) diff --git a/Documentation/block/blkfilter.rst b/Documentation/block/blkfilter.rst index 555625789244..b5160d1008fd 100644 --- a/Documentation/block/blkfilter.rst +++ b/Documentation/block/blkfilter.rst @@ -4,8 +4,8 @@ Block Device Filtering Mechanism ================================ -The block device filtering mechanism is an API that allows to attach block -device filters. Block device filters allow perform additional processing +The block device filtering mechanism provides the ability to attach block +device filters. Block device filters allow performing additional processing for I/O units. Introduction @@ -18,8 +18,8 @@ request_queue structure. But none of the in-tree kernel modules used this feature, and it was eliminated in the 5.10 kernel. The block device filtering mechanism returns the ability to handle I/O units. -It is possible to safely attach filter to a block device "on the fly" without -changing the structure of block devices stack. +It is possible to safely attach a filter to a block device "on the fly" without +changing the structure of the block device's stack. It supports attaching one filter to one block device, because there is only one filter implementation in the kernel yet. @@ -31,7 +31,7 @@ Design The block device filtering mechanism provides registration and unregistration for filter operations. The struct blkfilter_operations contains a pointer to the callback functions for the filter. After registering the filter operations, -filter can be managed using block device ioctl BLKFILTER_ATTACH, +the filter can be managed using block device ioctls BLKFILTER_ATTACH, BLKFILTER_DETACH and BLKFILTER_CTL. When the filter is attached, the callback function is called for each I/O unit @@ -46,17 +46,19 @@ block devices. Interface description ===================== -The ioctl BLKFILTER_ATTACH and BLKFILTER_DETACH use structure blkfilter_name. -It allows to attach a filter to a block device or detach it. - -The ioctl BLKFILTER_CTL use structure blkfilter_ctl. It allows to send a -filter-specific command. +The ioctl BLKFILTER_ATTACH allows user-space programs to attach a block device +filter to a block device. The ioctl BLKFILTER_DETACH allows user-space programs +to detach it. Both ioctls use structure blkfilter_name. The ioctl BLKFILTER_CTL +allows user-space programs to send a filter-specific command. It use structure +blkfilter_ctl. .. kernel-doc:: include/uapi/linux/blk-filter.h -To register in the system, the filter creates its own account, which contains -callback functions, unique filter name and module owner. This filter account is -used by the registration functions. +To register in the system, the filter uses the blkfilter_operations structure, +which contains callback functions, unique filter name and module owner. When +attaching a filter to a block device, the filter creates a blkfilter structure. +The pointer to the blkfilter structure allows the filter to determine for +which block device the callback functions are being called. .. kernel-doc:: include/linux/blk-filter.h diff --git a/drivers/block/blksnap/Kconfig b/drivers/block/blksnap/Kconfig index 14081359847b..11df0886489d 100644 --- a/drivers/block/blksnap/Kconfig +++ b/drivers/block/blksnap/Kconfig @@ -8,5 +8,5 @@ config BLKSNAP help Allow to create snapshots and track block changes for block devices. Designed for creating backups for simple block devices. Snapshots are - temporary and are released then backup is completed. Change block + temporary and are released when backup is completed. Change block tracking allows to create incremental or differential backups. -- 2.20.1