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Fri, 9 Apr 2021 07:48:18 -0400 (EDT) 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, 9 Apr 2021 13:48:17 +0200 From: Sergei Shtepa To: Christoph Hellwig , Hannes Reinecke , Mike Snitzer , Alasdair Kergon , Alexander Viro , Jens Axboe , , , , Date: Fri, 9 Apr 2021 14:48:01 +0300 Message-ID: <1617968884-15149-2-git-send-email-sergei.shtepa@veeam.com> In-Reply-To: <1617968884-15149-1-git-send-email-sergei.shtepa@veeam.com> References: <1617968884-15149-1-git-send-email-sergei.shtepa@veeam.com> MIME-Version: 1.0 X-Originating-IP: [172.24.14.5] X-ClientProxiedBy: prgmbx01.amust.local (172.24.0.171) To prgmbx01.amust.local (172.24.0.171) X-EsetResult: clean, is OK X-EsetId: 37303A29D2A50B59657262 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 10.11.54.6 X-loop: dm-devel@redhat.com Cc: pavel.tide@veeam.com, sergei.shtepa@veeam.com Subject: [dm-devel] [PATCH v8 1/4] Adds blk_interposer. It allows to redirect bio requests to another block device. 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 2.84 on 10.5.11.22 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 Signed-off-by: Sergei Shtepa --- block/genhd.c | 51 +++++++++++++++++++++++++++++++++++++++ fs/block_dev.c | 3 +++ include/linux/blk_types.h | 6 +++++ include/linux/blkdev.h | 32 ++++++++++++++++++++++++ 4 files changed, 92 insertions(+) diff --git a/block/genhd.c b/block/genhd.c index 8c8f543572e6..533b33897187 100644 --- a/block/genhd.c +++ b/block/genhd.c @@ -1938,3 +1938,54 @@ static void disk_release_events(struct gendisk *disk) WARN_ON_ONCE(disk->ev && disk->ev->block != 1); kfree(disk->ev); } + +/** + * bdev_interposer_attach - Attach interposer block device to original + * @original: original block device + * @interposer: interposer block device + * + * Before attaching the interposer, it is necessary to lock the processing + * of bio requests of the original device by calling the bdev_interposer_lock(). + * + * The bdev_interposer_detach() function allows to detach the interposer + * from 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 the interposer, it is necessary to lock the processing + * of bio requests of the original device by calling the bdev_interposer_lock(). + * + * The interposer should be attached using function bdev_interposer_attach(). + */ +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..9e376ee34e19 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 interposer will not be locked. + * + * To unlock, use the function bdev_interposer_unlock(). + * + * This lock should be used to attach/detach 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 function bdev_interposer_lock(). + * + * This lock should be used to attach/detach 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 */