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[37.182.2.234]) by smtp.gmail.com with ESMTPSA id d3sm14566390wrp.79.2021.02.05.16.09.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 05 Feb 2021 16:09:06 -0800 (PST) From: Matteo Croce To: linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Lennart Poettering , Luca Boccassi , Jens Axboe , Alexander Viro Subject: [PATCH 0/5] block: add a sequence number to disks Date: Sat, 6 Feb 2021 01:08:58 +0100 Message-Id: <20210206000903.215028-1-mcroce@linux.microsoft.com> X-Mailer: git-send-email 2.29.2 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org From: Matteo Croce With this series a monotonically increasing number is added to disks, precisely in the genhd struct, and it's exported in sysfs and uevent. This helps the userspace correlate events for devices that reuse the same device, like loop. The first patch is the core one, the 2..4 expose the information in different ways, while the last one increase the sequence number for loop devices at every attach. # udevadm monitor -kp |grep -e ^DEVNAME -e ^DISKSEQ & [1] 523 # losetup -fP 3part [ 3698.615848] loop0: detected capacity change from 16384 to 0 DEVNAME=/dev/loop0 DISKSEQ=13 [ 3698.647189] loop0: p1 p2 p3 DEVNAME=/dev/loop0 DISKSEQ=13 DEVNAME=/dev/loop0p1 DISKSEQ=13 DEVNAME=/dev/loop0p2 DISKSEQ=13 DEVNAME=/dev/loop0p3 DISKSEQ=13 # losetup -fP 2part [ 3705.170766] loop1: detected capacity change from 40960 to 0 DEVNAME=/dev/loop1 DISKSEQ=14 [ 3705.247280] loop1: p1 p2 DEVNAME=/dev/loop1 DISKSEQ=14 DEVNAME=/dev/loop1p1 DISKSEQ=14 DEVNAME=/dev/loop1p2 DISKSEQ=14 # ./getdiskseq /dev/loop* /dev/loop0: 13 /dev/loop0p1: 13 /dev/loop0p2: 13 /dev/loop0p3: 13 /dev/loop1: 14 /dev/loop1p1: 14 /dev/loop1p2: 14 /dev/loop2: 5 /dev/loop3: 6 /dev/loop-control: Function not implemented # grep . /sys/class/block/*/diskseq /sys/class/block/loop0/diskseq:13 /sys/class/block/loop1/diskseq:14 /sys/class/block/loop2/diskseq:5 /sys/class/block/loop3/diskseq:6 /sys/class/block/ram0/diskseq:1 /sys/class/block/ram1/diskseq:2 /sys/class/block/vda/diskseq:7 If merged, this feature will immediately used by the userspace: https://github.com/systemd/systemd/issues/17469#issuecomment-762919781 Matteo Croce (5): block: add disk sequence number block: add ioctl to read the disk sequence number block: refactor sysfs code block: export diskseq in sysfs loop: increment sequence number Documentation/ABI/testing/sysfs-block | 12 ++++++++ block/genhd.c | 43 ++++++++++++++++++++++++--- block/ioctl.c | 2 ++ drivers/block/loop.c | 3 ++ include/linux/genhd.h | 2 ++ include/uapi/linux/fs.h | 1 + 6 files changed, 59 insertions(+), 4 deletions(-)