linux-kernel - Re: [patch] mm: add comment about deprecation of __GFP

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Message-Id: <20100216102626.5f6f0e11.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Tue, 16 Feb 2010 10:26:26 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	Nick Piggin <npiggin@...e.de>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Lubos Lunak <l.lunak@...e.cz>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [patch] mm: add comment about deprecation of __GFP_NOFAIL

On Mon, 15 Feb 2010 17:13:57 -0800 (PST)
David Rientjes <rientjes@...gle.com> wrote:

> On Tue, 16 Feb 2010, KAMEZAWA Hiroyuki wrote:
> 
> > > As I already explained when you first brought this up, the possibility of 
> > > not invoking the oom killer is not unique to GFP_DMA, it is also possible 
> > > for GFP_NOFS.  Since __GFP_NOFAIL is deprecated and there are no current 
> > > users of GFP_DMA | __GFP_NOFAIL, that warning is completely unnecessary.  
> > > We're not adding any additional __GFP_NOFAIL allocations.
> > >
> > 
> > Please add documentation about that to gfp.h before doing this.
> > Doing this without writing any documenation is laziness.
> > (WARNING is a style of documentation.)
> > 
> 
> This is already documented in the page allocator, but I guess doing it in 
> include/linux/gfp.h as well doesn't hurt.
> 
I want warning when someone uses OBSOLETE interface but...

Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>

I hope no 3rd vendor (proprietary) driver uses __GFP_NOFAIL, they tend to
believe API is trustable and unchanged.

> 
> 
> mm: add comment about deprecation of __GFP_NOFAIL
> 
> __GFP_NOFAIL was deprecated in dab48dab, so add a comment that no new 
> users should be added.
> 
> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> Signed-off-by: David Rientjes <rientjes@...gle.com>
> ---
>  include/linux/gfp.h |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -30,7 +30,8 @@ struct vm_area_struct;
>   * _might_ fail.  This depends upon the particular VM implementation.
>   *
>   * __GFP_NOFAIL: The VM implementation _must_ retry infinitely: the caller
> - * cannot handle allocation failures.
> + * cannot handle allocation failures.  This modifier is deprecated and no new
> + * users should be added.
>   *
>   * __GFP_NORETRY: The VM implementation must not retry indefinitely.
>   *
> 
> --
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