linux-kernel - Re: __vmalloc() vs. GFP_NOIO/GFP

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Message-ID: <20160105153501.GB15594@dhcp22.suse.cz>
Date:	Tue, 5 Jan 2016 16:35:01 +0100
From:	Michal Hocko <mhocko@...nel.org>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	Dave Chinner <david@...morbit.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	Ming Lei <ming.lei@...onical.com>
Subject: Re: __vmalloc() vs. GFP_NOIO/GFP_NOFS

On Sun 03-01-16 20:35:14, Al Viro wrote:
[...]
> BTW, far scarier one is not GFP_NOFS or GFP_IO - there's a weird
> caller passing GFP_ATOMIC to __vmalloc(), for no reason I can guess.
> 
> _That_ really couldn't be handled without passing gfp_t to page allocation
> primitives, but I very much doubt that it's needed there at all; it's in
> alloc_large_system_hash() and I really cannot imagine a situation when
> it would be used in e.g. a nonblocking context.

Yeah, this is an __init context. The original commit which has added it
doesn't explain GFP_ATOMIC at all. It just converted alloc_bootmem to
__vmalloc resp. __get_free_pages based on the size. So we can only guess
it wanted to (ab)use memory reserves.

-- 
Michal Hocko
SUSE Labs
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