linux-kernel - Re: [PATCH] fs: add the FIGETFROZEN ioctl call

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Date:	Sat, 23 Apr 2016 09:14:19 +1000
From:	Dave Chinner <david@...morbit.com>
To:	Florian Margaine <florian@...gaine.com>
Cc:	Eric Sandeen <sandeen@...deen.net>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Jeff Layton <jlayton@...chiereds.net>,
	"J. Bruce Fields" <bfields@...ldses.org>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fs: add the FIGETFROZEN ioctl call

On Fri, Apr 22, 2016 at 11:53:48PM +0200, Florian Margaine wrote:
> On Tue, Apr 19, 2016 at 1:06 AM, Dave Chinner <david@...morbit.com> wrote:
> >> A way to query freeze state might be nice, I think, but yeah, it's
> >> racy, so you can't depend on it - but it might be useful in the "huh,
> >> IO is failing, what's going on?  Oh, it's frozen, ok" scenario...
> >
> > So maybe we should just add the frozen state to /proc/self/mountinfo
> > or something similar, then people who think it matters can shoot
> > themselves in the foot all they want without us needing to care
> > about it.
> 
> Sorry if it's a basic question, but what is the difference between
> /proc/self/mountinfo and providing an ioctl call?

Simply this:

$ grep xfs /proc/self/mountinfo
22 0 9:0 / / rw,relatime - xfs /dev/block/9:0 rw,attr2,inode64,sunit=1024,swidth=2048,noquota

i.e. no need for a custom binary to query state in diagnostic
situations where it might matter. And it shows up in things like SOS
reports that distro's gather when users report issues.

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com