lkml.org 
[lkml]   [2014]   [Apr]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH v5] mm,writeback: fix divide by zero in pos_ratio_polynom
    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 :)
    >
    > Masayoshi-san, does the bug still happen with this version, or does
    > this fix the problem?

    I assumed we wanted a reported-by in there.

    > Subject: mm,writeback: fix divide by zero in pos_ratio_polynom
    >
    > It is possible for "limit - setpoint + 1" to equal zero, after
    > getting truncated to a 32 bit variable, and resulting in a divide
    > by zero error.
    >
    > Using the fully 64 bit divide functions avoids this problem.

    This isn't the whole story, is it? I added stuff:

    : Using the fully 64 bit divide functions avoids this problem. It also will
    : cause pos_ratio_polynom() to return the correct value when (setpoint -
    : limit) exceeds 2^32.




    \
     
     \ /
      Last update: 2014-04-30 23:41    [W:2.308 / U:0.032 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site