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From:   Matteo Croce <mcroce@linux.microsoft.com>
Date:   Tue, 23 Feb 2021 16:46:51 +0100
Message-ID: <CAFnufp1zuXTVcNvSX9eE9hekZ6h455JVve0q2=Ht+xd007CVdQ@mail.gmail.com>
Subject: Re: [PATCH 0/5] block: add a sequence number to disks
To:     linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org,
        Lennart Poettering <lennart@poettering.net>,
        Luca Boccassi <bluca@debian.org>, Jens Axboe <axboe@kernel.dk>,
        Alexander Viro <viro@zeniv.linux.org.uk>
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On Sat, Feb 6, 2021 at 1:09 AM Matteo Croce <mcroce@linux.microsoft.com> wrote:
>
> From: Matteo Croce <mcroce@microsoft.com>
>
> 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(-)
>
> --
> 2.29.2
>

Hi,

Did anyone have a chance to look at this series?

Ideas or suggestions?

Regards,


--
per aspera ad upstream