linux-kernel - Re: [PATCH 1/3] f2fs: avoid using __GFP

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Message-ID: <20171106162303.syinckwdtdlwmeeg@dhcp22.suse.cz>
Date:   Mon, 6 Nov 2017 17:23:03 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Chao Yu <chao@...nel.org>
Cc:     jaegeuk@...nel.org, linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, Chao Yu <yuchao0@...wei.com>
Subject: Re: [PATCH 1/3] f2fs: avoid using __GFP_NOFAIL

On Tue 07-11-17 00:08:25, Chao Yu wrote:
[...]
> BTW, I notice the comments of __GFP_NOFAIL, what does this mean?
>  *   Using this flag for costly allocations is _highly_ discouraged.

This means that using __GFP_NOFAIL for high order allocations
(especially those with order > PAGE_ALLOC_COSTLY_ORDER) are highly
discouraged because we those are quite hard to get and looping inside
the allocator basically for ever is not a wise thing to do. That being
said replacing __GFP_NOFAIL by an open coded retry loop might make sense
for those e.g. to check signals or other termination conditions.
-- 
Michal Hocko
SUSE Labs