linux-kernel - Re: [GIT PULL] aio: changes for 3.19

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Message-ID: <20141214230809.GK2672@kvack.org>
Date:	Sun, 14 Dec 2014 18:08:09 -0500
From:	Benjamin LaHaise <bcrl@...ck.org>
To:	"Kirill A. Shutemov" <kirill@...temov.name>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-aio@...ck.org, Linux Kernel <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>,
	Pavel Emelyanov <xemul@...allels.com>,
	Dmitry Monakhov <dmonakhov@...nvz.org>
Subject: Re: [GIT PULL] aio: changes for 3.19

On Mon, Dec 15, 2014 at 01:02:08AM +0200, Kirill A. Shutemov wrote:
> But it seems the problem is bigger than what the patch fixes. To me we are
> too permisive on what vma can be remapped.
> 
> How can we know that it's okay to move vma around for random driver which
> provide .mmap? Or I miss something obvious?

Most drivers do not care if a vma is moved within the virtual address space 
of a process.  The aio ring buffer is special in that it gets unmapped when 
userspace does an io_destroy(), and io_destroy() has to know what the address 
is moved to in order to perform the unmap.  Normal drivers don't perform the 
unmap themselves.

		-ben
-- 
"Thought is the essence of where you are now."
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