linux-kernel - Re: [RFC/PATCH] Add preadv and pwritev system calls.

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Date:	Thu, 11 Dec 2008 18:49:08 -0500
From:	Christoph Hellwig <hch@...radead.org>
To:	Gerd Hoffmann <kraxel@...hat.com>
Cc:	lkml - Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC/PATCH] Add preadv and pwritev system calls.

On Fri, Dec 12, 2008 at 12:13:43AM +0100, Gerd Hoffmann wrote:
>   Hi,
> 
> The attached patch adds preadv and pwritev system calls.  These syscalls
> are a pretty straightforward combination of pread and readv (same for
> write).  They are quite useful for doing vectored I/O in threaded
> applications.  Using lseek+readv instead opens race windows you'll have
> to plug with locking.
> 
> Other systems have such system calls too, for example NetBSD, check
> here: http://www.daemon-systems.org/man/preadv.2.html
> 
> The patch sports the actual system call implementation and the windup in
> the x86 system call tables.  Other archs are TBD.
> 
> Comments?  Reviews?  Suggestions?  Flames?

Looks good, but you should Cc linux-arch so that arch maintainers get
a heads up to wire up the syscalls.

> +	if (ret > 0)
> +		add_rchar(current, ret);
> +	inc_syscr(current);
> +	return ret;

Could it be that these are missing for the compat case both for the existing
readv/writev and your new syscalls?

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