linux-kernel - Re: [PATCH trivial] block: GFP_ATOMIC is __GFP

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20080629043827.135f39d7@linux360.ro>
Date:	Sun, 29 Jun 2008 04:38:27 +0300
From:	Eduard - Gabriel Munteanu <eduard.munteanu@...ux360.ro>
To:	Hugh Dickins <hugh@...itas.com>
Cc:	Jens Axboe <jens.axboe@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH trivial] block: GFP_ATOMIC is __GFP_HIGH

On Sun, 29 Jun 2008 00:54:27 +0100 (BST)
Hugh Dickins <hugh@...itas.com> wrote:

> GFP_ATOMIC is __GFP_HIGH: no need for alloc_io_context() to add that.
> 
> Signed-off-by: Hugh Dickins <hugh@...itas.com>
> ---
> 
>  block/blk-ioc.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> --- linux-next/block/blk-ioc.c	2008-05-12 02:01:05.000000000
> +0100 +++ linux/block/blk-ioc.c	2008-06-27 14:08:00.000000000
> +0100 @@ -98,7 +98,7 @@ struct io_context *alloc_io_context(gfp_
>  		ret->last_waited = jiffies; /* doesn't matter... */
>  		ret->nr_batch_requests = 0; /* because this is 0 */
>  		ret->aic = NULL;
> -		INIT_RADIX_TREE(&ret->radix_root, GFP_ATOMIC |
> __GFP_HIGH);
> +		INIT_RADIX_TREE(&ret->radix_root, GFP_ATOMIC);
>  		INIT_HLIST_HEAD(&ret->cic_list);
>  		ret->ioc_data = NULL;
>  	}

Hi,

I'm not sure this is a good idea: GFP_ATOMIC and __GFP_HIGH are
semantically different, even though they are equivalent at the moment.
Have you seen GFP_NOWAIT's definition?
/* This equals 0, but use constants in case they ever change */
#define GFP_NOWAIT      (GFP_ATOMIC & ~__GFP_HIGH)

I think it's best to look at what that code intends to do, not at what
it does at the moment. Definitions for gfp flags might change in the
future.

If the code does not _semantically_ need __GFP_HIGH, then your commit
message should indicate so, rather than comparing it with GFP_ATOMIC.


	Cheers,
	Eduard
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/