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block: add a sequence number to disks

Matteo Croce linux-block linux-fsdevel lkml 1 version In review

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  1. v1 Latest5 patches 2 repliesIn review

Patches in v1 No applies recorded yet

#Subject and filesSizeRepliesApplied
1/5block: add disk sequence numberblock/genhd.c include/linux/genhd.h+21 -00 replies
2/5block: add ioctl to read the disk sequence numberblock/ioctl.c include/uapi/linux/fs.h+3 -00 replies
3/5block: refactor sysfs codeblock/genhd.c+9 -40 replies
4/5block: export diskseq in sysfsDocumentation/ABI/testing/sysfs-block block/genhd.c+23 -00 replies
5/5loop: increment sequence numberdrivers/block/loop.c+3 -00 replies

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Cover letter [PATCH 0/5] block: add a sequence number to disks

From: Matteo Croce <[email protected]>

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(-)
Signature · 1 line
2.29.2

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