linux-kernel - Re: [PATCH] mm: get rid of __alloc_pages_high

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: <20151113101831.GF19677@suse.de>
Date:	Fri, 13 Nov 2015 10:18:31 +0000
From:	Mel Gorman <mgorman@...e.de>
To:	mhocko@...nel.org
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	LKML <linux-kernel@...r.kernel.org>,
	Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH] mm: get rid of __alloc_pages_high_priority

On Thu, Nov 12, 2015 at 04:53:38PM +0100, mhocko@...nel.org wrote:
> From: Michal Hocko <mhocko@...e.com>
> 
> __alloc_pages_high_priority doesn't do anything special other than it
> calls get_page_from_freelist and loops around GFP_NOFAIL allocation
> until it succeeds. It would be better if the first part was done in
> __alloc_pages_slowpath where we modify the zonelist because this would
> be easier to read and understand. And do the retry at the very same
> place because retrying without even attempting to do any reclaim is
> fragile because we are basically relying on somebody else to make the
> reclaim (be it the direct reclaim or OOM killer) for us. The caller
> might be holding resources (e.g. locks) which block other other
> reclaimers from making any progress for example.
> 
> Remove the helper and open code it into its only user. We have to be
> careful about __GFP_NOFAIL allocations from the PF_MEMALLOC context
> even though this is a very bad idea to begin with because no progress
> can be gurateed at all.  We shouldn't break the __GFP_NOFAIL semantic
> here though. It could be argued that this is essentially GFP_NOWAIT
> context which we do not support but PF_MEMALLOC is much harder to check
> for existing users because they might happen deep down the code path
> performed much later after setting the flag so we cannot really rule out
> there is no kernel path triggering this combination.
> 
> Signed-off-by: Michal Hocko <mhocko@...e.com>

Acked-by: Mel Gorman <mgorman@...e.de>

-- 
Mel Gorman
SUSE Labs
--
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/