linux-kernel - RE: [PATCH 5/5] compat: consolidate the compat

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Message-ID: <f69d570127db4f78a6b30e1775a020c4@AcuMS.aculab.com>
Date:   Tue, 11 Jan 2022 09:52:17 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Christoph Hellwig' <hch@....de>, Arnd Bergmann <arnd@...db.de>
CC:     Guo Ren <guoren@...nel.org>, "x86@...nel.org" <x86@...nel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>,
        "linux-parisc@...r.kernel.org" <linux-parisc@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>,
        "sparclinux@...r.kernel.org" <sparclinux@...r.kernel.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>
Subject: RE: [PATCH 5/5] compat: consolidate the compat_flock{,64} definition

From: Christoph Hellwig
> Sent: 11 January 2022 08:35
> 
> Provide a single common definition for the compat_flock and
> compat_flock64 structures using the same tricks as for the native
> variants.  Another extra define is added for the packing required on
> x86.
> 
...
>  /*
> - * IA32 uses 4 byte alignment for 64 bit quantities,
> - * so we need to pack this structure.
> + * IA32 uses 4 byte alignment for 64 bit quantities, so we need to pack the
> + * compat flock64 structure.
>   */
...
> +#define __ARCH_NEED_COMPAT_FLOCK64_PACKED

Maybe:
#define __ARCH_COMPAT_FLOCK64_ATTR (packed),(aligned(4)

...
Delete this bit:
> +#ifdef __ARCH_NEED_COMPAT_FLOCK64_PACKED
> +#define __ARCH_COMPAT_FLOCK64_PACK	__attribute__((packed))
> +#else
> +#define __ARCH_COMPAT_FLOCK64_PACK
> +#endif
...
> +struct compat_flock64 {
> +	short		l_type;
> +	short		l_whence;
> +	compat_loff_t	l_start;
> +	compat_loff_t	l_len;
> +	compat_pid_t	l_pid;
> +#ifdef __ARCH_COMPAT_FLOCK64_PAD
> +	__ARCH_COMPAT_FLOCK64_PAD
> +#endif
> +} __ARCH_COMPAT_FLOCK64_PACK;

then:
#ifdef __ARCH_COMPAT_FLOCK64_ATTR
} __attribute__(__ARCH_COMPAT_FLOCK64_ATTR);
#else
};
#endif

Makes it a bit more like the xxx_PAD bits.
Although the trailing ; does cause a bit of grief.

	David

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