Messages in this thread | | | Date | Wed, 30 Apr 2014 17:21:27 -0400 | From | Rik van Riel <> | Subject | Re: [PATCH v5] mm,writeback: fix divide by zero in pos_ratio_polynom |
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On 04/30/2014 05:00 PM, Andrew Morton wrote: > On Wed, 30 Apr 2014 16:42:55 -0400 Rik van Riel <riel@redhat.com> wrote: > >> On Wed, 30 Apr 2014 13:13:53 -0700 >> Andrew Morton <akpm@linux-foundation.org> wrote: >> >>> This was a consequence of 64->32 truncation and it can't happen any >>> more, can it? >> >> Andrew, this is cleaner indeed :) > > I'm starting to get worried about 32-bit wraparound in the patch > version number ;) > >> Masayoshi-san, does the bug still happen with this version, or does >> this fix the problem? >> > > We could put something like > > if (WARN_ON_ONCE(setpoint == limit)) > setpoint--; > > in there if we're not sure. But it's better to be sure!
The more I look at the code, the more I am convinced that Michal is right, and we cannot actually hit the case that "limit - setpoint + 1 == 0".
Setpoint always seems to be some in-between point.
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