linux-kernel - Re: [PATCH 08/11] mm: convert vma_interval

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Date:   Fri, 4 Oct 2019 05:30:44 -0700
From:   Michel Lespinasse <walken@...gle.com>
To:     Davidlohr Bueso <dave@...olabs.net>,
        Matthew Wilcox <willy@...radead.org>
Cc:     akpm@...ux-foundation.org, peterz@...radead.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        dri-devel@...ts.freedesktop.org, linux-rdma@...r.kernel.org,
        Davidlohr Bueso <dbueso@...e.de>
Subject: Re: [PATCH 08/11] mm: convert vma_interval_tree to half closed
 intervals

On Thu, Oct 03, 2019 at 01:18:55PM -0700, Davidlohr Bueso wrote:
> The vma and anon vma interval tree really wants [a, b) intervals,
> not fully closed. As such convert it to use the new
> interval_tree_gen.h. Because of vma_last_pgoff(), the conversion
> is quite straightforward.

I am not certain if we need to worry about integer overflow here.
The problem case would be accessing the last block of a file that is
exactly 16TB long, on an arch where long (and thus pgoff_t) is 32-bit.
Maybe FS folks can tell us whether that case is currently supported,
or if we can just not worry about it ?

I would also want to rename the fields in struct zap_details into
start_index and end_index so we can verify we don't leave any
off-by-one uses.

-- 
Michel "Walken" Lespinasse
A program is never fully debugged until the last user dies.