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Subject: Re: [PATCH v18 05/10] xbitmap: add more operations
From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
References: <201711301934.CDC21800.FSLtJFFOOVQHMO@I-love.SAKURA.ne.jp>
        <5A210C96.8050208@intel.com>
        <201712012202.BDE13557.MJFQLtOOHVOFSF@I-love.SAKURA.ne.jp>
        <286AC319A985734F985F78AFA26841F739376DA1@shsmsx102.ccr.corp.intel.com>
        <20171201172519.GA27192@bombadil.infradead.org>
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Matthew Wilcox wrote:
> On Fri, Dec 01, 2017 at 03:09:08PM +0000, Wang, Wei W wrote:
> > On Friday, December 1, 2017 9:02 PM, Tetsuo Handa wrote:
> > > If start == end is legal,
> > > 
> > >    for (; start < end; start = (start | (IDA_BITMAP_BITS - 1)) + 1) {
> > > 
> > > makes this loop do nothing because 10 < 10 is false.
> > 
> > How about "start <= end "?
> 
> Don't ask Tetsuo for his opinion, write some userspace code that uses it.
> 

Please be sure to prepare for "end == -1UL" case, for "start < end" will become
true when "start = (start | (IDA_BITMAP_BITS - 1)) + 1" made "start == 0" due to
overflow.