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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Mon, 13 Jan 2020 14:55:15 +0100
Message-ID: <CAK8P3a0eY6Vm5PNdzR8Min9MrwAqH8vnMZ3C+pxTQhiFVNPyWA@mail.gmail.com>
Subject: Re: [PATCH] xfs: Fix xfs_dir2_sf_entry_t size check
To:     Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc:     "Darrick J. Wong" <darrick.wong@oracle.com>,
        Eric Sandeen <sandeen@sandeen.net>,
        linux-xfs <linux-xfs@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Christoph Hellwig <hch@lst.de>
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On Thu, Jan 9, 2020 at 10:01 PM Vincenzo Frascino
<vincenzo.frascino@arm.com> wrote:
>
> Hi Darrick,
>
> On 09/01/2020 16:50, Darrick J. Wong wrote:
> > This sounds like gcc getting confused by the zero length array.  Though
> > it's odd that randconfig breaks, but defconfig doesn't?  This sounds
> > like one of the kernel gcc options causing problems.
> >
>
> This is what I started suspecting as well.

The important bit into the configuration is

# CONFIG_AEABI is not set

With ARM OABI (which you get when EABI is disabled), structures are padded
to multiples of 32 bits. See commits 8353a649f577 ("xfs: kill
xfs_dir2_sf_off_t")
and aa2dd0ad4d6d ("xfs: remove __arch_pack"). Those could be partially
reverted to fix it again, but it doesn't seem worth it as there is
probably nobody
running XFS on OABI machines (actually with the build failure we can
be fairly sure there isn't ;-).

I am testing randconfig builds with OABI and a few other things like ARCH_RPC
disabled because of random issues like this.

      Arnd