From patchwork Wed Apr 21 16:45:42 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sergei Shtepa X-Patchwork-Id: 12216545 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=ham 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 AD333C433B4 for ; Wed, 21 Apr 2021 16:46:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 744D361454 for ; Wed, 21 Apr 2021 16:46:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244399AbhDUQqk (ORCPT ); Wed, 21 Apr 2021 12:46:40 -0400 Received: from mx2.veeam.com ([64.129.123.6]:41976 "EHLO mx2.veeam.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244370AbhDUQqj (ORCPT ); Wed, 21 Apr 2021 12:46:39 -0400 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 mx2.veeam.com (Postfix) with ESMTPS id 0FDFA424B9; Wed, 21 Apr 2021 12:45:59 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=veeam.com; s=mx2; t=1619023559; bh=wcm/Vxh/k3YGgzIVuZKWUD3Up5EwpdCaQtTu9lM71ME=; h=From:To:CC:Subject:Date:In-Reply-To:References:From; b=BeZlOsCg8/F2VPH67Yx74ffQ2+UWv8u0p4wizftzHlhZATcxysfMUNPo7NiOhkX8u u1QXrF+mCBCkkPqtF7JBZrRxW+WNAowTqn1GhS0KLrHentO+rIpQIKMrRnKGbi4IWq o3BTzAidCabs9TnH/Sh40sdEd/ERKYBiGTnDc684= 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 15.2.858.5; Wed, 21 Apr 2021 18:45:56 +0200 From: Sergei Shtepa To: Christoph Hellwig , Hannes Reinecke , Mike Snitzer , Alasdair Kergon , Alexander Viro , Jens Axboe , , , , CC: , Subject: [PATCH v9 1/4] Adds blk_interposer Date: Wed, 21 Apr 2021 19:45:42 +0300 Message-ID: <1619023545-23431-2-git-send-email-sergei.shtepa@veeam.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1619023545-23431-1-git-send-email-sergei.shtepa@veeam.com> References: <1619023545-23431-1-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: 37303A29D2A50B59677566 X-Veeam-MMEX: True Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Additional fields were added in the block_device structure: bd_interposer and bd_interposer_lock. The bd_interposer field contains a pointer to an interposer block device. bd_interposer_lock is a lock which allows to safely attach and detach the interposer device. New functions bdev_interposer_attach() and bdev_interposer_detach() allow to attach and detach an interposer device. But first it is required to lock the processing of bio requests by the block device with bdev_interposer_lock() function. The BIO_INTERPOSED flag means that the bio request has been already interposed. This flag avoids recursive bio request interception. Signed-off-by: Sergei Shtepa --- block/genhd.c | 52 +++++++++++++++++++++++++++++++++++++++ fs/block_dev.c | 3 +++ include/linux/blk_types.h | 6 +++++ include/linux/blkdev.h | 32 ++++++++++++++++++++++++ 4 files changed, 93 insertions(+) diff --git a/block/genhd.c b/block/genhd.c index 8c8f543572e6..3ec77947b3ba 100644 --- a/block/genhd.c +++ b/block/genhd.c @@ -1938,3 +1938,55 @@ static void disk_release_events(struct gendisk *disk) WARN_ON_ONCE(disk->ev && disk->ev->block != 1); kfree(disk->ev); } + +/** + * bdev_interposer_attach - Attach an interposer block device to original + * @original: original block device + * @interposer: interposer block device + * + * Before attaching an interposer, it is necessary to lock the processing + * of bio requests of the original device by calling bdev_interposer_lock(). + * + * The bdev_interposer_detach() function allows to detach the interposer + * from the original block device. + */ +int bdev_interposer_attach(struct block_device *original, + struct block_device *interposer) +{ + struct block_device *bdev; + + WARN_ON(!original); + if (original->bd_interposer) + return -EBUSY; + + bdev = bdgrab(interposer); + if (!bdev) + return -ENODEV; + + original->bd_interposer = bdev; + return 0; +} +EXPORT_SYMBOL_GPL(bdev_interposer_attach); + +/** + * bdev_interposer_detach - Detach interposer from block device + * @original: original block device + * + * Before detaching an interposer, it is necessary to lock the processing + * of bio requests of the original device by calling bdev_interposer_lock(). + * + * The interposer should be attached using the bdev_interposer_attach() + * function. + */ +void bdev_interposer_detach(struct block_device *original) +{ + if (WARN_ON(!original)) + return; + + if (!original->bd_interposer) + return; + + bdput(original->bd_interposer); + original->bd_interposer = NULL; +} +EXPORT_SYMBOL_GPL(bdev_interposer_detach); diff --git a/fs/block_dev.c b/fs/block_dev.c index 09d6f7229db9..a98a56cc634f 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -809,6 +809,7 @@ static void bdev_free_inode(struct inode *inode) { struct block_device *bdev = I_BDEV(inode); + percpu_free_rwsem(&bdev->bd_interposer_lock); free_percpu(bdev->bd_stats); kfree(bdev->bd_meta_info); @@ -909,6 +910,8 @@ struct block_device *bdev_alloc(struct gendisk *disk, u8 partno) iput(inode); return NULL; } + bdev->bd_interposer = NULL; + percpu_init_rwsem(&bdev->bd_interposer_lock); return bdev; } diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h index db026b6ec15a..8e4309eb3b18 100644 --- a/include/linux/blk_types.h +++ b/include/linux/blk_types.h @@ -46,6 +46,11 @@ struct block_device { spinlock_t bd_size_lock; /* for bd_inode->i_size updates */ struct gendisk * bd_disk; struct backing_dev_info *bd_bdi; + /* The interposer allows to redirect bio to another device */ + struct block_device *bd_interposer; + /* Lock the queue of block device to attach or detach interposer. + * Allows to safely suspend and flush interposer. */ + struct percpu_rw_semaphore bd_interposer_lock; /* The counter of freeze processes */ int bd_fsfreeze_count; @@ -304,6 +309,7 @@ enum { BIO_CGROUP_ACCT, /* has been accounted to a cgroup */ BIO_TRACKED, /* set if bio goes through the rq_qos path */ BIO_REMAPPED, + BIO_INTERPOSED, /* bio was reassigned to another block device */ BIO_FLAG_LAST }; diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 158aefae1030..3e38b0c40b9d 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -2029,4 +2029,36 @@ int fsync_bdev(struct block_device *bdev); int freeze_bdev(struct block_device *bdev); int thaw_bdev(struct block_device *bdev); +/** + * bdev_interposer_lock - Lock bio processing + * @bdev: locking block device + * + * Lock the bio processing in submit_bio_noacct() for the new requests in the + * original block device. Requests from the interposer will not be locked. + * + * To unlock, use the bdev_interposer_unlock() function. + * + * This lock should be used to attach/detach the interposer to the device. + */ +static inline void bdev_interposer_lock(struct block_device *bdev) +{ + percpu_down_write(&bdev->bd_interposer_lock); +} + +/** + * bdev_interposer_unlock - Unlock bio processing + * @bdev: locked block device + * + * Unlock the bio processing that was locked by bdev_interposer_lock() function. + * + * This lock should be used to attach/detach the interposer to the device. + */ +static inline void bdev_interposer_unlock(struct block_device *bdev) +{ + percpu_up_write(&bdev->bd_interposer_lock); +} + +int bdev_interposer_attach(struct block_device *original, + struct block_device *interposer); +void bdev_interposer_detach(struct block_device *original); #endif /* _LINUX_BLKDEV_H */