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=-3.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 4BAC3C388F7 for ; Thu, 22 Oct 2020 18:35:17 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A92FF2417D for ; Thu, 22 Oct 2020 18:35:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A92FF2417D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 242F96B0062; Thu, 22 Oct 2020 14:35:16 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 21A526B006E; Thu, 22 Oct 2020 14:35:16 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 155956B0070; Thu, 22 Oct 2020 14:35:16 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0158.hostedemail.com [216.40.44.158]) by kanga.kvack.org (Postfix) with ESMTP id DD5B26B0062 for ; Thu, 22 Oct 2020 14:35:15 -0400 (EDT) Received: from smtpin17.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 7993F1EF1 for ; Thu, 22 Oct 2020 18:35:15 +0000 (UTC) X-FDA: 77400413790.17.shade56_43154ac27253 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin17.hostedemail.com (Postfix) with ESMTP id 58004180D0181 for ; Thu, 22 Oct 2020 18:35:15 +0000 (UTC) X-HE-Tag: shade56_43154ac27253 X-Filterd-Recvd-Size: 4095 Received: from mail-pf1-f195.google.com (mail-pf1-f195.google.com [209.85.210.195]) by imf07.hostedemail.com (Postfix) with ESMTP for ; Thu, 22 Oct 2020 18:35:14 +0000 (UTC) Received: by mail-pf1-f195.google.com with SMTP id 10so1687725pfp.5 for ; Thu, 22 Oct 2020 11:35:14 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=1XI2Q+0LJ+MrF6PTdb/vTI0hg1qM7/BgdBxfc/cQLFU=; b=bsnrvSkLvnr6/GbhYLDnzy39VTmUkHzmusV3ZCeKUigSoPKjXlYHbXF50ZZuJ3PthQ I+BO4Dllx7ohY7Ss68c5TC3sRJRqeZKByWK09E+lHbbQHNJLBsQx3fV5HRXAxRVdPnQK 7+Pc1g6MJqwHC4MpnjzL9Vr4OV1qK11TJyLq+jQuDIwAHCwXIxzrc8c9nH04JfGXIdHN GPnJm/oXlece8TkNeekgoEsHrrwn6aXbC58E5PUDPRXm4mtGmFBp0RPA4fg326+l/zJ9 FXtwSixtnheZP8nGHBJUw7W/mT6QP8rqwTs1PyBEp1kqW198OAk/EOpvW2oNTT4y2i5L T9Kg== X-Gm-Message-State: AOAM530UZuwAmHuJdwhuv7jfMfMj9CMOBVHCYNRSq5srhyV7irBEmKJ8 DA8a43olmcmK1x/kTax4OdHDmq8IAtgSFZnXwGk= X-Google-Smtp-Source: ABdhPJz36fkFyGr3qzw17+AgK9oYpIzBshcfChZVSHFTISPy8X4z6IdPGqE/7nwcLSyFF6/1DoPxCQ5X7a4DVfLIwnM= X-Received: by 2002:a63:a546:: with SMTP id r6mr3310324pgu.160.1603391713825; Thu, 22 Oct 2020 11:35:13 -0700 (PDT) MIME-Version: 1.0 References: <1603271049-20681-1-git-send-email-sergei.shtepa@veeam.com> In-Reply-To: <1603271049-20681-1-git-send-email-sergei.shtepa@veeam.com> From: Mike Snitzer Date: Thu, 22 Oct 2020 14:35:02 -0400 Message-ID: Subject: Re: [PATCH 0/2] block layer filter and block device snapshot module To: Sergei Shtepa Cc: Jens Axboe , Alexander Viro , Christoph Hellwig , "Darrick J. Wong" , linux-xfs@vger.kernel.org, linux-fsdevel , rjw@rjwysocki.net, len.brown@intel.com, Pavel Machek , Andrew Morton , johannes.thumshirn@wdc.com, Ming Lei , Jan Kara , Tejun Heo , gustavo@embeddedor.com, Bart Van Assche , osandov@fb.com, koct9i@gmail.com, Damien Le Moal , steve@sk2.org, linux-block , "linux-kernel@vger.kernel.org" , linux-pm@vger.kernel.org, linux-mm@kvack.org, device-mapper development Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Oct 21, 2020 at 5:04 AM Sergei Shtepa wrote: > > Hello everyone! Requesting for your comments and suggestions. > > # blk-filter > > Block layer filter allows to intercept BIO requests to a block device. > > Interception is performed at the very beginning of the BIO request > processing, and therefore does not affect the operation of the request > processing queue. This also makes it possible to intercept requests from > a specific block device, rather than from the entire disk. > > The logic of the submit_bio function has been changed - since the > function execution results are not processed anywhere (except for swap > and direct-io) the function won't return a value anymore. Your desire to switch to a void return comes exactly when I've noticed we need it. ->submit_bio's blk_qc_t return is the cookie assigned by blk-mq. Up to this point we haven't actually used it for bio-based devices but it seems clear we'll soon need for bio-based IO polling support. Just today, I've been auditing drivers/md/dm.c with an eye toward properly handling the blk_qc_t return (or lack thereof) from various DM methods. It could easily be that __submit_bio_noacct and __submit_bio_noacct_mq will be updated to do something meaningful with the returned cookie (or that DM will) to facilitate proper IO polling. Mike