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Date:   Tue, 7 Jan 2020 00:16:43 +0000
From:   Chris Down <chris@chrisdown.name>
To:     Dave Chinner <david@fromorbit.com>
Cc:     linux-mm@kvack.org, Hugh Dickins <hughd@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Matthew Wilcox <willy@infradead.org>,
        Amir Goldstein <amir73il@gmail.com>,
        Jeff Layton <jlayton@kernel.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Tejun Heo <tj@kernel.org>, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH v5 2/2] tmpfs: Support 64-bit inums per-sb
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Dave Chinner writes:
>It took 15 years for us to be able to essentially deprecate
>inode32 (inode64 is the default behaviour), and we were very happy
>to get that albatross off our necks.  In reality, almost everything
>out there in the world handles 64 bit inodes correctly
>including 32 bit machines and 32bit binaries on 64 bit machines.
>And, IMNSHO, there no excuse these days for 32 bit binaries that
>don't using the *64() syscall variants directly and hence support
>64 bit inodes correctlyi out of the box on all platforms.
>
>I don't think we should be repeating past mistakes by trying to
>cater for broken 32 bit applications on 64 bit machines in this day
>and age.

I'm very glad to hear that. I strongly support moving to 64-bit inums in all 
cases if there is precedent that it's not a compatibility issue, but from the 
comments on my original[0] patch (especially that they strayed from the 
original patches' change to use ino_t directly into slab reuse), I'd been given 
the impression that it was known to be one.

 From my perspective I have no evidence that inode32 is needed other than the 
comment from Jeff above get_next_ino. If that turns out not to be a problem, I 
am more than happy to just wholesale migrate 64-bit inodes per-sb in tmpfs.

0: https://lore.kernel.org/patchwork/patch/1170963/