linux-kernel - Re: [patch] aio: Don't zero out the pages array inside struct dio

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Message-ID: <x49hbtgr2zw.fsf@segfault.boston.devel.redhat.com>
Date:	Fri, 30 Oct 2009 17:22:27 -0400
From:	Jeff Moyer <jmoyer@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, linux-aio@...ck.org,
	zach.brown@...cle.com
Subject: Re: [patch] aio: Don't zero out the pages array inside struct dio

Andrew Morton <akpm@...ux-foundation.org> writes:

> You forgot something:
>
> --- a/fs/direct-io.c~aio-dont-zero-out-the-pages-array-inside-struct-dio-fix
> +++ a/fs/direct-io.c
> @@ -130,6 +130,12 @@ struct dio {
>  	unsigned head;			/* next page to process */
>  	unsigned tail;			/* last valid page + 1 */
>  	int page_errors;		/* errno from get_user_pages() */
> +
> +	/*
> +	 * pages[] (and any fields placed after it) are not zeroed out at
> +	 * allocation time.  Don't add new fields after pages[] unless you
> +	 * wish that they not be zeroed.
> +	 */
>  	struct page *pages[DIO_PAGES];	/* page buffer */
>  };
>  

Yeah, that makes sense.  Thanks for adding it, Andrew.  Oh, and it looks
like I botched the subject line.  It should have read dio, not aio, but
I'm not sure that matters a whole lot.

Cheers,
Jeff
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