Re: [PATCH 0/3] btrfs-progs: remove full /dev scanning

[Eric Sandeen <sandeen@redhat.com>]

On 8/26/14, 5:55 AM, David Sterba wrote:
> On Thu, Aug 21, 2014 at 08:08:57PM +0200, Goffredo Baroncelli wrote:
>> Of course I (we) don't care cdrom and/or floppy, but this raises 
>> the question: are there other block devices which aren't showed in 
>> proc/partitions ? 
> 
> cdrom appears as /dev/sr0, floppy is /dev/fd0 if the respective modules
> are loaded, no breakage here.
> 
>> I am thinking to some less common hardware like
>> NON USB sd disk (I saw this kind of hardware, but now I don't have 
>> it in my hands....).
> 
> A block device whose driver calls register_blkdev should appear in
> proc/partitions, if not then I think it's a bug or a very non-standard
> interface.
> 
> I don't know about any other cases where full /dev scan would reveal
> something that /proc/partitions not, so I guess it's safe to remove it.

Yesterday, Chris did mention <something something mumble> about /dev/mapper/*

[12:57]  <cmason> I got inconsistent results from /proc/partitions
[12:57]  <cmason> this was 3 years ago now
[12:58]  <cmason> it didn't find everything for dm devices, yeah
[12:58]  <cmason> especially dm multipath got really confused

and I'll be honest, I didn't test with devicemapper devices, much
less dm multipath, so I suppose that's warranted prior to removal.

I'll see what I can do.

If there's a problem, I bet there's a solution that doesn't involve
scanning everything under /dev ...

-Eric