Re: [RFC][PATCH v2] mount.btrfs helper

[Goffredo Baroncelli <kreijack@inwind.it>]

On 12/05/2014 05:41 PM, David Sterba wrote:
> We're looking
> for good reasons to justify the existence of the helper, but this is
> still not enough IMHO. I can see the convenience to do it automatically,
> but this assumes no udev available which is probably rare these days.

I have the following reasons to support a mount.btrfs helper:
1) it is in a good point to check that everything is ok (see the thread
related LVM snapshot, due to a dev.uuid conflicts), 
2) it is in a good point to issue a good error explanation (missing 
device....)
3) it may handle case like "degraded" mode, where the filesystem is not
fully functional but even as degraded have "some" functionals..


On 12/05/2014 04:32 PM, Chris Mason wrote:
> I definitely agree that assembling the filesystem from userland is
> somewhat awkward, and people that don't want initrds end up needing
> to jump through hoops to get things done.
> 
> But, the tools we have to avoid the hoops are initrds and udev, and
> I'd much rather spend time fixing filesystem bugs than recreating
> those tools.  If people are having trouble with udev, or having
> trouble with tools in the initrd, lets contribute fixes to those
> projects instead.

Chris, I am bit confused by your answer: mount.btrfs helper is not 
a solution for the initrd-less system (whom I am not a fan 
anymore [*]). And I don't think that the awkward-ness of btrfs is due to
udev deficiencies.
Btrfs is new because acts both as filesystem and as dm/md layer. We 
know that there are very good reasons to do that. But also it
highlights new problems whom the old tools may be not a right solution.

See this from another point of view: md/dm have specific tools to
assemble the disks. So why btrfs wouldn't need a specific tool?

BR
G.Baroncelli


[*] I hope to not start another flame-war. I am not against to the 
initrd-less system; but if you want a multidevice filesystem (with 
or without md/dm) simply you cannot rely to the kernel only (IMHO).

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