linux-kernel - Re: [PATCH] x86/pat: Fix off-by-one bugs in interval tree search

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Message-ID: <20191201170115.molqadzebqo2sldu@linux-p48b>
Date:   Sun, 1 Dec 2019 09:01:15 -0800
From:   Davidlohr Bueso <dave@...olabs.net>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>, mceier@...il.com,
        kernel test robot <rong.a.chen@...el.com>,
        Davidlohr Bueso <dbueso@...e.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>,
        LKML <linux-kernel@...r.kernel.org>, lkp@...ts.01.org,
        "Kenneth R. Crudup" <kenny@...ix.com>
Subject: Re: [PATCH] x86/pat: Fix off-by-one bugs in interval tree search

On Sun, 01 Dec 2019, Ingo Molnar wrote:
>So the correct parameter to use in the interval tree searches is not
>'end' but 'end-1'.

Yes absolutely, I overlooked this in the final conversion. Going through some
older conversions, I had this end-1 at one point. Lookups need half-open intervals,
consistent with what memtype_interval_end() does.

[...]

>Patch is only lightly tested, so take care. (Patch is emphatically not
>signed off yet, because I spent most of the day on this and I don't yet
>trust my fix - all of the affected sites need to be reviewed more
>carefully.)

As a general note, this is rather consistent with how all interval-tree
users that need [a,b) nodes use the api.

Thanks,
Davidlohr