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

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Message-ID: <20140514112619.GA10637@mguzik.redhat.com>
Date:	Wed, 14 May 2014 13:26:21 +0200
From:	Mateusz Guzik <mguzik@...hat.com>
To:	Jan Kara <jack@...e.cz>
Cc:	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, 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.

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.

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.

-- 
Mateusz Guzik
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