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Fri, 12 Mar 2021 18:45:13 +0300 (MSK) 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; Fri, 12 Mar 2021 16:45:12 +0100 From: Sergei Shtepa To: Christoph Hellwig , Mike Snitzer , Alasdair Kergon , Hannes Reinecke , Jens Axboe , , , , Date: Fri, 12 Mar 2021 18:44:52 +0300 Message-ID: <1615563895-28565-1-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: 37303A29D2A50B58627366 X-Veeam-MMEX: True X-Mimecast-Impersonation-Protect: Policy=CLT - Impersonation Protection Definition; Similar Internal Domain=false; Similar Monitored External Domain=false; Custom External Domain=false; Mimecast External Domain=false; Newly Observed Domain=false; Internal User Name=false; Custom Display Name List=false; Reply-to Address Mismatch=false; Targeted Threat Dictionary=false; Mimecast Threat Dictionary=false; Custom Threat Dictionary=false X-Scanned-By: MIMEDefang 2.78 on 10.11.54.4 X-loop: dm-devel@redhat.com Cc: pavel.tide@veeam.com, sergei.shtepa@veeam.com Subject: [dm-devel] [PATCH v7 0/3] block device interposer X-BeenThere: dm-devel@redhat.com X-Mailman-Version: 2.1.12 Precedence: junk List-Id: device-mapper development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dm-devel-bounces@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Hi all. I'm joyful to suggest the block device interposer (bdev_interposer) v7. bdev_interposer allows to redirect bio requests to other block devices. In this series of patches I suggest a different implementation of the bio interception mechanism. Now the interposer is a different block device. Instead of an additional hook, the function fops->submit_bio() of the interposer device is used. This implementation greatly simplifies the application of this bdev_interposer in device-mapper. But there is one limitation - the size of the interposer device must be greater than or equal to the size of the original device. The first patch adds the function blk_mq_is_queue_frozen(). It allows to check a queue state. The second patch is dedicated to bdev_interposer itself, which provides the ability to redirect bio to the interposer device. The third one adds the DM_INTERPOSED_FLAG flag. When this flag is applied with the ioctl DM_TABLE_LOAD_CMD, the underlying devices are opened without the FMODE_EXCL flag and connected via bdev_interposer. Changes in this patchset v7: * the request interception mechanism. Now the interposer is a block device that receives requests instead of the original device; * code design fixes. History: v6 - https://patchwork.kernel.org/project/linux-block/cover/1614774618-22410-1-git-send-email-sergei.shtepa@veeam.com/ * designed for 5.12; * thanks to the new design of the bio structure in v5.12, it is possible to perform interception not for the entire disk, but for each block device; * instead of the new ioctl DM_DEV_REMAP_CMD and the 'noexcl' option, the DM_INTERPOSED_FLAG flag for the ioctl DM_TABLE_LOAD_CMD is applied. v5 - https://patchwork.kernel.org/project/linux-block/cover/1612881028-7878-1-git-send-email-sergei.shtepa@veeam.com/ * rebase for v5.11-rc7; * patch set organization; * fix defects in documentation; * add some comments; * change mutex names for better code readability; * remove calling bd_unlink_disk_holder() for targets with non-exclusive flag; * change type for struct dm_remap_param from uint8_t to __u8. v4 - https://patchwork.kernel.org/project/linux-block/cover/1612367638-3794-1-git-send-email-sergei.shtepa@veeam.com/ Mostly changes were made, due to Damien's comments: * on the design of the code; * by the patch set organization; * bug with passing a wrong parameter to dm_get_device(); * description of the 'noexcl' parameter in the linear.rst. Also added remap_and_filter.rst. v3 - https://patchwork.kernel.org/project/linux-block/cover/1611853955-32167-1-git-send-email-sergei.shtepa@veeam.com/ In this version, I already suggested blk_interposer to apply to dm-linear. Problems were solved: * Interception of bio requests from a specific device on the disk, not from the entire disk. To do this, we added the dm_interposed_dev structure and an interval tree to store these structures. * Implemented ioctl DM_DEV_REMAP_CMD. A patch with changes in the lvm2 project was sent to the team lvm-devel@redhat.com. * Added the 'noexcl' option for dm-linear, which allows you to open the underlying block-device without FMODE_EXCL mode. v2 - https://patchwork.kernel.org/project/linux-block/cover/1607518911-30692-1-git-send-email-sergei.shtepa@veeam.com/ I tried to suggest blk_interposer without using it in device mapper, but with the addition of a sample of its use. It was then that I learned about the maintainers' attitudes towards the samples directory :). v1 - https://lwn.net/ml/linux-block/20201119164924.74401-1-hare@suse.de/ This Hannes's patch can be considered as a starting point, since this is where the interception mechanism and the term blk_interposer itself appeared. It became clear that blk_interposer can be useful for device mapper. before v1 - https://patchwork.kernel.org/project/linux-block/cover/1603271049-20681-1-git-send-email-sergei.shtepa@veeam.com/ I tried to offer a rather cumbersome blk-filter and a monster-like blk-snap module for creating snapshots. Thank you to everyone who was able to take the time to review the previous versions. I hope that this time I achieved the required quality. Thanks, Sergei. Sergei Shtepa (3): block: add blk_mq_is_queue_frozen() block: add bdev_interposer dm: add DM_INTERPOSED_FLAG block/bio.c | 2 ++ block/blk-core.c | 57 ++++++++++++++++++++++++++++++++ block/blk-mq.c | 13 ++++++++ block/genhd.c | 54 +++++++++++++++++++++++++++++++ drivers/md/dm-core.h | 3 ++ drivers/md/dm-ioctl.c | 13 ++++++++ drivers/md/dm-table.c | 61 +++++++++++++++++++++++++++++------ drivers/md/dm.c | 38 +++++++++++++++------- include/linux/blk-mq.h | 1 + include/linux/blk_types.h | 3 ++ include/linux/blkdev.h | 9 ++++++ include/linux/device-mapper.h | 1 + include/uapi/linux/dm-ioctl.h | 6 ++++ 13 files changed, 240 insertions(+), 21 deletions(-)