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Subject: Re: [PATCH v3 0/6] block: add a sequence number to disks
To:     Matteo Croce <mcroce@linux.microsoft.com>,
        linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        Jens Axboe <axboe@kernel.dk>
Cc:     linux-kernel@vger.kernel.org,
        Lennart Poettering <lennart@poettering.net>,
        Luca Boccassi <bluca@debian.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Damien Le Moal <damien.lemoal@wdc.com>,
        Tejun Heo <tj@kernel.org>,
        =?UTF-8?Q?Javier_Gonz=c3=a1lez?= <javier@javigon.com>,
        Niklas Cassel <niklas.cassel@wdc.com>,
        Johannes Thumshirn <johannes.thumshirn@wdc.com>,
        Matthew Wilcox <willy@infradead.org>,
        Christoph Hellwig <hch@infradead.org>,
        JeffleXu <jefflexu@linux.alibaba.com>
References: <20210623105858.6978-1-mcroce@linux.microsoft.com>
From:   Hannes Reinecke <hare@suse.de>
Message-ID: <bfdd6f56-ce2b-ef74-27b1-83b922e5f7d9@suse.de>
Date:   Wed, 23 Jun 2021 14:03:27 +0200
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On 6/23/21 12:58 PM, Matteo Croce 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.
> 
I'm failing to see the point here.
Apparently you are assuming that there is a userspace tool tracking 
events, and has a need to correlate events related to different 
instances of the disk.
But if you have an userspace application tracking events, why can't the 
same application track the 'add' and 'remove' events to track the 
lifetime of the devices, and implement its own numbering based on that?

Why do we need to burden the kernel with this?

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
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