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From:   Amir Goldstein <amir73il@gmail.com>
Date:   Tue, 7 Jan 2020 12:12:00 +0200
Message-ID: <CAOQ4uxiMQ3Oz4M0wKo5FA_uamkMpM1zg7ydD8FXv+sR9AH_eFA@mail.gmail.com>
Subject: Re: [PATCH v5 2/2] tmpfs: Support 64-bit inums per-sb
To:     Hugh Dickins <hughd@google.com>
Cc:     Dave Chinner <david@fromorbit.com>,
        Chris Down <chris@chrisdown.name>,
        Linux MM <linux-mm@kvack.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Matthew Wilcox <willy@infradead.org>,
        Jeff Layton <jlayton@kernel.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Tejun Heo <tj@kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>, kernel-team@fb.com
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On Tue, Jan 7, 2020 at 10:36 AM Hugh Dickins <hughd@google.com> wrote:
>
> On Tue, 7 Jan 2020, Amir Goldstein wrote:
> > On Tue, Jan 7, 2020 at 2:40 AM Dave Chinner <david@fromorbit.com> wrote:
> > > On Tue, Jan 07, 2020 at 12:16:43AM +0000, Chris Down wrote:
> > > > 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.
>
> Interesting take on it.  I'd all along imagined we would have to resort
> to a mount option for safety, but Dave is right that I was too focused on
> avoiding tmpfs regressions, without properly realizing that people were
> very unlikely to have written such tools for tmpfs in particular, but
> written them for all filesystems, and already encountered and fixed
> such EOVERFLOWs for other filesystems.
>
> Hmm, though how readily does XFS actually reach the high inos on
> ordinary users' systems?
>

Define 'ordinary'
I my calculations are correct, with default mkfs.xfs any inode allocated
from logical offset > 2TB on a volume has high ino bits set.
Besides, a deployment with more than 4G inodes shouldn't be hard to find.

Thanks,
Amir.