From: Dave Chinner <david@fromorbit.com>
To: Eric Sandeen <sandeen@sandeen.net>
Cc: Christoph Hellwig <hch@infradead.org>,
Eric Sandeen <sandeen@redhat.com>, xfs-oss <xfs@oss.sgi.com>
Subject: Re: [PATCH] xfs: clean up xfs_set_maxicount & use in growfs
Date: Thu, 27 Feb 2014 18:11:54 +1100 [thread overview]
Message-ID: <20140227071154.GK29907@dastard> (raw)
In-Reply-To: <530E3282.7000703@sandeen.net>
On Wed, Feb 26, 2014 at 12:29:22PM -0600, Eric Sandeen wrote:
> On 2/25/14, 8:11 PM, Christoph Hellwig wrote:
> > On Mon, Feb 24, 2014 at 11:27:35PM -0600, Eric Sandeen wrote:
> >> xfs_set_maxicount() overflowed fairly easily for large filesystems
> >> and large maxicount; we started out by multiplying dblocks by
> >> the percentage, *then* dividing by 100, and never checked for
> >> an overflow. The calculations were also, IMHO, a little hard
> >> to follow.
> >
> > Would be useful to get this test case into xfstests..
>
> Ok so I was going on Dave's assertion about that. ;)
>
> To overflow, we'd need dblocks * 100 to be > 2^64-1:
>
> so dblocks would need to be > (2^64-1)/100
>
> for 4k blocks that's 655 exabytes. Maybe not so possible after all ;)
Until the block count is corrupted by fsfuzzer? ;)
> Dave, maybe just removing the open-code is enough here.
Sure, but I still like the conversion to use mult_frac....
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
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next prev parent reply other threads:[~2014-02-27 7:12 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-25 5:27 [PATCH] xfs: clean up xfs_set_maxicount & use in growfs Eric Sandeen
2014-02-26 2:11 ` Christoph Hellwig
2014-02-26 2:18 ` Eric Sandeen
2014-02-26 18:29 ` Eric Sandeen
2014-02-27 7:11 ` Dave Chinner [this message]
2014-02-27 14:08 ` Eric Sandeen
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