From patchwork Wed Dec 9 13:01:50 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sergei Shtepa X-Patchwork-Id: 11961301 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=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 28235C433FE for ; Wed, 9 Dec 2020 13:09:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EAD7023BCD for ; Wed, 9 Dec 2020 13:09:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731965AbgLINJP (ORCPT ); Wed, 9 Dec 2020 08:09:15 -0500 Received: from mx4.veeam.com ([104.41.138.86]:33956 "EHLO mx4.veeam.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729012AbgLINJE (ORCPT ); Wed, 9 Dec 2020 08:09:04 -0500 X-Greylist: delayed 391 seconds by postgrey-1.27 at vger.kernel.org; Wed, 09 Dec 2020 08:09:02 EST Received: from mail.veeam.com (prgmbx01.amust.local [172.24.0.171]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx4.veeam.com (Postfix) with ESMTPS id 6573FB9A6F; Wed, 9 Dec 2020 16:01:50 +0300 (MSK) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=veeam.com; s=mx4; t=1607518910; bh=/xuQD7v393TvlYTOY+wfRjPvoSZ5yMpkOEbp/g6NwMA=; h=From:To:CC:Subject:Date:In-Reply-To:References:From; b=X3k4xoB41/kSZCSYBbNYq0IjOh7AUDvFpa57zDh6VJM8fz49FqLwkWSiF2/8Ffj1x w4zoXXYLjWdUJ6WzKMsmuIzS3223+qBUihnc74i4++8lp5sv8qs0JQ7eShx9lvhqvh khVQbxOYyIKDq1iqbmDFwyBTnGSK0WB4bF7FcTw8= Received: from prgdevlinuxpatch01.amust.local (172.24.14.5) by prgmbx01.amust.local (172.24.0.171) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.721.2; Wed, 9 Dec 2020 14:01:48 +0100 From: Sergei Shtepa To: , , , , , , , , , CC: , Subject: [PATCH 2/3] block: blk_interposer - sample Date: Wed, 9 Dec 2020 16:01:50 +0300 Message-ID: <1607518911-30692-3-git-send-email-sergei.shtepa@veeam.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1607518911-30692-1-git-send-email-sergei.shtepa@veeam.com> References: <1607518911-30692-1-git-send-email-sergei.shtepa@veeam.com> MIME-Version: 1.0 X-Originating-IP: [172.24.14.5] X-ClientProxiedBy: prgmbx02.amust.local (172.24.0.172) To prgmbx01.amust.local (172.24.0.171) X-EsetResult: clean, is OK X-EsetId: 37303A29C604D26A627160 X-Veeam-MMEX: True Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org This sample demonstrates how to use blk_interposer. It show how to properly connect the interposer module to kernel, and perform the simplest monitoring of the number of bio. Signed-off-by: Sergei Shtepa Nacked-by: Mike Snitzer --- samples/blk_interposer/Makefile | 2 + samples/blk_interposer/blk-interposer.c | 276 ++++++++++++++++++++++++ 2 files changed, 278 insertions(+) create mode 100644 samples/blk_interposer/Makefile create mode 100644 samples/blk_interposer/blk-interposer.c diff --git a/samples/blk_interposer/Makefile b/samples/blk_interposer/Makefile new file mode 100644 index 000000000000..b11aefde2b1c --- /dev/null +++ b/samples/blk_interposer/Makefile @@ -0,0 +1,2 @@ +# SPDX-License-Identifier: GPL-2.0 +obj-$(CONFIG_SAMPLE_BLK_INTERPOSER) += blk-interposer.o diff --git a/samples/blk_interposer/blk-interposer.c b/samples/blk_interposer/blk-interposer.c new file mode 100644 index 000000000000..92b4c1fcf8f7 --- /dev/null +++ b/samples/blk_interposer/blk-interposer.c @@ -0,0 +1,276 @@ +// SPDX-License-Identifier: GPL-2.0 + +/* + * Block layer interposer allow to interpose bio requests from kernel module. + * This allows you to monitor requests, modify requests, add new request, + * or even redirect requests to another devices. + * + * This sample demonstrates how to use blk_interposer. + * It show how to properly connect the interposer module to kernel, + * and perform the simplest monitoring of the number of bio. + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include +#include +#include +#include +#include +#include + +int device_major = 8; +int device_minor; +int fmode = FMODE_READ | FMODE_WRITE; + +/* + * Each interposer must have a common part in the form of the blk_interposer structure, + * as well as its own unique data. + */ +struct my_interposer { + /* + * Common part of block device interposer. + */ + struct blk_interposer interposer; + /* + * Specific part for our interposer data. + */ + atomic_t counter; +}; + +struct my_interposer my_ip; + +/** + * blk_interposer_attach - Attach interposer to disk + * @disk: target disk + * @interposer: block device interposer + */ +static int blk_interposer_attach(struct gendisk *disk, struct blk_interposer *interposer) +{ + int ret = 0; + + /* + * Stop disks queue processing. + */ + blk_mq_freeze_queue(disk->queue); + blk_mq_quiesce_queue(disk->queue); + + /* + * Check if the interposer is already busy. + * The interposer will only connect if it is not busy. + */ + if (blk_has_interposer(disk)) { + pr_info("The interposer is already busy.\n"); + ret = -EBUSY; + goto out; + } + + /* + * Attach the interposer. + */ + disk->interposer = interposer; + /* + * And while the queue is stopped, we can do something specific for our module. + */ + pr_info("Block device interposer attached successfully.\n"); + +out: + /* + * Resume disks queue processing + */ + blk_mq_unquiesce_queue(disk->queue); + blk_mq_unfreeze_queue(disk->queue); + + return ret; +} + +/** + * blk_interposer_detach - Detach interposer from disk + * @disk: target disk + * @interposer: block device interposer + */ +static int blk_interposer_detach(struct gendisk *disk, struct blk_interposer *interposer) +{ + int ret = 0; + + if (WARN_ON(!disk)) + return -EINVAL; + + /* + * Stop disks queue processing. + */ + blk_mq_freeze_queue(disk->queue); + blk_mq_quiesce_queue(disk->queue); + + /* + * Check if the interposer is still available. + */ + if (!disk->interposer) { + pr_info("The interposer is not available.\n"); + return -ENOENT; + goto out; + } + /* + * Check if it is really our interposer. + */ + if (disk->interposer->ip_submit_bio != interposer->ip_submit_bio) { + pr_info("The interposer found is not ours.\n"); + return -EPERM; + goto out; + } + + /* + * Detach interposer. + */ + disk->interposer = NULL; + /* + * And while the queue is stopped, we can do something specific for our module. + */ + pr_info("Block device interposer detached successfully.\n"); + +out: + /* + * Resume disks queue processing. + */ + blk_mq_unquiesce_queue(disk->queue); + blk_mq_unfreeze_queue(disk->queue); + + return ret; +} + +/** + * blk_interposer_submit_bio - Interpose bio + * @interposer: block device interposer + * @bio: interposed bio + */ +static void blk_interposer_submit_bio(struct blk_interposer *interposer, struct bio *bio) +{ + struct my_interposer *ip = container_of(interposer, struct my_interposer, interposer); + + atomic_inc(&ip->counter); + if (atomic_read(&ip->counter) < 10) + pr_info("%s - %d", __func__, atomic_read(&ip->counter)); + else if (atomic_read(&ip->counter) == 10) + pr_info("%s the flooding of log has stopped", __func__); + + /* + * Here we can submit a new child bio requests before the original. + * If the new bio should not be interposed, set BIO_INTERPOSED flag. + */ + + /* + * We can resubmit the original bio or just add it to the current->bio_list. + * In the second case, we do not call submit_bio_checks() twice. + */ + bio_list_add(¤t->bio_list[0], bio); + + /* + * Here we can submit a new bio requests after the original, + * although I don't know how it might be useful. + */ + + /* + * All submitted bio will be just placed in the current->bio_list. + * We can't wait for the bio request to complete. + */ + + /* + * The function doesn't return anything, because it can only return BLK_QC_T_NONE. + */ +} + +static int __init blk_interposer_init(void) +{ + int ret = 0; + dev_t dev_id; + struct block_device *bdev; + + pr_info("Loading module\n"); + + pr_info("Tracking device: %d:%d\n", device_major, device_minor); + dev_id = MKDEV(device_major, device_minor); + + /* + * Open block device + */ + bdev = blkdev_get_by_dev(dev_id, fmode, &my_ip); + if (IS_ERR(bdev)) { + ret = PTR_ERR(bdev); + pr_err("Unable to open device [%d:%d]: blkdev_get_by_dev return %d\n", + MAJOR(dev_id), MINOR(dev_id), 0-ret); + return ret; + } + + /* + * Initialize block device interposer fields. + */ + my_ip.interposer.ip_submit_bio = blk_interposer_submit_bio; + + /* + * Initialize our interposer specific fields + */ + atomic_set(&my_ip.counter, 0); + + /* + * Attach interposer to disk + */ + ret = blk_interposer_attach(bdev->bd_disk, &my_ip.interposer); + if (ret) + pr_info("Failed to attach the block device interposer.\n"); + /* + * Close device + */ + blkdev_put(bdev, fmode); + + return ret; +} + +static void __exit blk_interposer_exit(void) +{ + int ret; + dev_t dev_id; + struct block_device *bdev; + + pr_info("Unloading module\n"); + + dev_id = MKDEV(device_major, device_minor); + + /* + * Open block device + */ + bdev = blkdev_get_by_dev(dev_id, fmode, &my_ip); + if (IS_ERR(bdev)) { + ret = PTR_ERR(bdev); + pr_err("Unable to open device [%d:%d]: blkdev_get_by_dev return %d\n", + MAJOR(dev_id), MINOR(dev_id), 0-ret); + return; + } + + /* + * Detach interposer from disk + */ + ret = blk_interposer_detach(bdev->bd_disk, &my_ip.interposer); + if (ret) + pr_info("Failed to detach the block device interposer.\n"); + /* + * Close device + */ + blkdev_put(bdev, fmode); + + /* + * The counter shows how much bio was interposed. + */ + pr_info("%d bio was interposed.\n", atomic_read(&my_ip.counter)); +} + +module_init(blk_interposer_init); +module_exit(blk_interposer_exit); + +MODULE_DESCRIPTION("Block Layer Interposer Sample kernel module"); +MODULE_AUTHOR("Veeam Software Group GmbH"); +MODULE_LICENSE("GPL"); + +module_param_named(device_major, device_major, int, 0644); +MODULE_PARM_DESC(device_major, "Tracking device major number"); +module_param_named(device_minor, device_minor, int, 0644); +MODULE_PARM_DESC(device_minor, "Tracking device minor number");