From: Hannes Reinecke <hare@suse.de>
To: Matteo Croce <mcroce@linux.microsoft.com>,
Matthew Wilcox <willy@infradead.org>
Cc: linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org,
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>,
"Damien Le Moal" <damien.lemoal@wdc.com>,
"Tejun Heo" <tj@kernel.org>,
"Javier González" <javier@javigon.com>,
"Niklas Cassel" <niklas.cassel@wdc.com>,
"Johannes Thumshirn" <johannes.thumshirn@wdc.com>
Subject: Re: [PATCH -next 1/5] block: add disk sequence number
Date: Fri, 26 Mar 2021 09:00:12 +0100 [thread overview]
Message-ID: <bf5478c7-e026-846c-3bb0-fd4c6c38372f@suse.de> (raw)
In-Reply-To: <CAFnufp3zKa+9K-hsV5vRkv-w8y-1nZioq_bFAnzaxs9RoP+sDA@mail.gmail.com>
On 3/25/21 6:29 PM, Matteo Croce wrote:
> On Mon, Mar 15, 2021 at 10:05 PM Matthew Wilcox <willy@infradead.org> wrote:
>>
>> On Mon, Mar 15, 2021 at 08:18:24PM +0000, Matthew Wilcox wrote:
>>> On Mon, Mar 15, 2021 at 09:02:38PM +0100, Matteo Croce wrote:
>>>> From: Matteo Croce <mcroce@microsoft.com>
>>>>
>>>> Add a sequence number to the disk devices. This number is put in the
>>>> uevent so userspace can correlate events when a driver reuses a device,
>>>> like the loop one.
>>>
>>> Should this be documented as monotonically increasing? I think this
>>> is actually a media identifier. Consider (if you will) a floppy disc.
>>> Back when such things were common, it was possible with personal computers
>>> of the era to have multiple floppy discs "in play" and be prompted to
>>> insert them as needed. So shouldn't it be possible to support something
>>> similar here -- you're really removing the media from the loop device.
>>> With a monotonically increasing number, you're always destroying the
>>> media when you remove it, but in principle, it should be possible to
>>> reinsert the same media and have the same media identifier number.
>>
>> So ... a lot of devices have UUIDs or similar. eg:
>>
>> $ cat /sys/block/nvme0n1/uuid
>> e8238fa6-bf53-0001-001b-448b49cec94f
>>
>> https://linux.die.net/man/8/scsi_id (for scsi)
>>
>
> Hi,
>
> I don't have uuid anywhere:
>
> matteo@saturno:~$ ll /dev/sd?
> brw-rw---- 1 root disk 8, 0 feb 16 13:24 /dev/sda
> brw-rw---- 1 root disk 8, 16 feb 16 13:24 /dev/sdb
> brw-rw---- 1 root disk 8, 32 feb 16 13:24 /dev/sdc
> brw-rw---- 1 root disk 8, 48 feb 16 13:24 /dev/sdd
> brw-rw---- 1 root disk 8, 64 mar 4 06:26 /dev/sde
> brw-rw---- 1 root disk 8, 80 feb 16 13:24 /dev/sdf
> matteo@saturno:~$ ll /sys/block/*/uuid
> ls: cannot access '/sys/block/*/uuid': No such file or directory
>
> mcroce@t490s:~$ ll /dev/nvme0n1
> brw-rw----. 1 root disk 259, 0 25 mar 14.22 /dev/nvme0n1
> mcroce@t490s:~$ ll /sys/block/*/uuid
> ls: cannot access '/sys/block/*/uuid': No such file or directory
>
> I find it only on a mdraid array:
>
> $ cat /sys/devices/virtual/block/md127/md/uuid
> 26117338-4f54-f14e-b5d4-93feb7fe825d
>
> I'm using a vanilla 5.11 kernel.
>
The 'uuid' is optional for NVMe devices, and indeed not even present for
other device types.
Use the 'wwid' attribute, which contains a unique identifier for all
nvme devices:
# cat /sys/block/nvme*/wwid
nvme.8086-4356504436343735303034323430304e474e-564f303430304b45464a42-00000001
nvme.8086-4356504436343735303034363430304e474e-564f303430304b45464a42-00000001
uuid.3c6500ee-a775-4c89-b223-e9551f5a9f7a
and for SCSI the wwid is part of the SCSI device:
# cat /sys/block/sd*/device/wwid
naa.600508b1001ce2e648a35b6ec14a3996
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@suse.de +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer
next prev parent reply other threads:[~2021-03-26 8:01 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-15 20:02 [PATCH -next 0/5] block: add a sequence number to disks Matteo Croce
2021-03-15 20:02 ` [PATCH -next 1/5] block: add disk sequence number Matteo Croce
2021-03-15 20:18 ` Matthew Wilcox
2021-03-15 21:04 ` Matthew Wilcox
2021-03-15 21:32 ` Lennart Poettering
2021-03-25 17:29 ` Matteo Croce
2021-03-26 8:00 ` Hannes Reinecke [this message]
2021-03-25 20:58 ` Lennart Poettering
2021-03-16 14:13 ` Christoph Hellwig
2021-04-20 20:12 ` Lennart Poettering
2021-03-25 20:52 ` Lennart Poettering
2021-03-16 1:44 ` JeffleXu
2021-03-23 17:43 ` Matteo Croce
2021-03-15 20:02 ` [PATCH -next 2/5] block: add ioctl to read the " Matteo Croce
2021-03-15 20:13 ` Matthew Wilcox
2021-03-15 20:17 ` Damien Le Moal
2021-03-15 20:34 ` Matteo Croce
2021-03-15 20:02 ` [PATCH -next 3/5] block: refactor sysfs code Matteo Croce
2021-03-15 20:02 ` [PATCH -next 4/5] block: export diskseq in sysfs Matteo Croce
2021-03-15 20:02 ` [PATCH -next 5/5] loop: increment sequence number Matteo Croce
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