linux-kernel - Re: [PATCH V2 2/2] fs: print a message when freezing/unfreezing filesystems

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Message-ID: <20140514113945.GC5824@quack.suse.cz>
Date:	Wed, 14 May 2014 13:39:45 +0200
From:	Jan Kara <jack@...e.cz>
To:	Mateusz Guzik <mguzik@...hat.com>
Cc:	Jan Kara <jack@...e.cz>, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, Josef Bacik <jbacik@...com>,
	Al Viro <viro@...IV.linux.org.uk>,
	Eric Sandeen <esandeen@...hat.com>,
	Joe Perches <joe@...ches.com>
Subject: Re: [PATCH V2 2/2] fs: print a message when freezing/unfreezing
 filesystems

On Wed 14-05-14 13:26:21, Mateusz Guzik wrote:
> On Wed, May 14, 2014 at 01:14:49PM +0200, Jan Kara wrote:
> > On Wed 14-05-14 00:04:43, Mateusz Guzik wrote:
> > > This helps hang troubleshooting efforts when only dmesg is available.
> > > 
> > > While here remove code duplication with MS_RDONLY case and fix a
> > > whitespace nit.
> >   I'm somewhat undecided here I have to say. On one hand I don't like
> > printing to kernel log when everything is fine and kernel is operating
> > normally. On the other hand I've seen quite a few cases where people have
> > shot themselves in the foot with filesystem freezing so having some trace
> > of this in the log doesn't seem like a completely bad thing either. What do
> > other people think?
> > 
> 
> I would like to note that the kernel already prints messages when e.g.
> filesystems get mounted.
  Yeah, that's a fair point.

> And yes, situations where I/O is frozen and hung task detector comes into
> play happen more often than you may think. I can hide these behind a
> sysctl if this helps.
  No, I don't think hiding behind sysctl is really needed.

> Finally, somewhat related to the first mail, my preferred message format
> (which I was somewhat reluctant to propose earlier) would be:
> 
> VFS (%s): Filesystem frozen by %s:%d
> 
> with device, process and pid respectively.
  More common seems to be "%s (%d)" for process & pid but whatever. I like
the format change.

								Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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