linux-kernel - Re: compat_alloc_user_space removal, was Re: [PATCH 3/3] scsi: megaraid_sas: simplify compat

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Date:   Thu, 17 Sep 2020 16:55:49 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Kashyap Desai <kashyap.desai@...adcom.com>,
        Sumit Saxena <sumit.saxena@...adcom.com>,
        Shivasharan S <shivasharan.srikanteshwara@...adcom.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Anand Lodnoor <anand.lodnoor@...adcom.com>,
        Chandrakanth Patil <chandrakanth.patil@...adcom.com>,
        Hannes Reinecke <hare@...e.de>, megaraidlinux.pdl@...adcom.com,
        linux-scsi <linux-scsi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Al Viro <viro@...iv.linux.org.uk>
Subject: Re: compat_alloc_user_space removal, was Re: [PATCH 3/3] scsi:
 megaraid_sas: simplify compat_ioctl handling

On Sun, Sep 13, 2020 at 1:46 PM Arnd Bergmann <arnd@...db.de> wrote:
>
> On Sun, Sep 13, 2020 at 8:50 AM Christoph Hellwig <hch@...radead.org> wrote:
> >
> > On Sat, Sep 12, 2020 at 02:49:05PM +0200, Arnd Bergmann wrote:
> > > fs/quota/compat.c: dqblk = compat_alloc_user_space(sizeof(struct if_dqblk));
> > > fs/quota/compat.c: dqblk = compat_alloc_user_space(sizeof(struct if_dqblk));
> > > fs/quota/compat.c: fsqstat = compat_alloc_user_space(sizeof(struct
> > > fs_quota_stat));
> >
> > I sent this out a while ago, an Al has it in a branch, but not in
> > linux-next:
> >
> > https://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git/log/?h=work.quota-compat
>
> Nice! Aside from already being queued, your patch is also nicer than
> my version, and it makes it trivial to fix it for arm oabi as well by adding
>
> #ifdef CONFIG_OABI_COMPAT
> #define compat_need_64bit_alignment_fixup in_oabi_syscall
> #endif
>
> to arch/arm/include/asm/compat.h
>
> I had considered fixing that case for arch/arm as well but it ended up being
> harder to do in my version.

Unfortunately, the commit b902bfb3f0e "arm64: stop using <asm/compat.h>
directly" seems to introduce a circular header file inclusion between
linux/compat.h and asm/stat.h, breaking arm64 compilation.

Moving the compat_u64/compat_s64 definitions to include/asm-generic/compat.h
works fine though.

      Arnd