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Date: Tue, 5 Jan 2016 16:35:01 +0100
From: Michal Hocko <mhocko@kernel.org>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Dave Chinner <david@fromorbit.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        Ming Lei <ming.lei@canonical.com>
Subject: Re: __vmalloc() vs. GFP_NOIO/GFP_NOFS
Message-ID: <20160105153501.GB15594@dhcp22.suse.cz>
References: <20160103071246.GK9938@ZenIV.linux.org.uk>
 <20160103201233.GC6682@dastard>
 <20160103203514.GN9938@ZenIV.linux.org.uk>
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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

From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <owner-linux-mm@kvack.org>
Date: Tue, 5 Jan 2016 16:35:01 +0100
From: Michal Hocko <mhocko@kernel.org>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Dave Chinner <david@fromorbit.com>, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	Ming Lei <ming.lei@canonical.com>
Subject: Re: __vmalloc() vs. GFP_NOIO/GFP_NOFS
Message-ID: <20160105153501.GB15594@dhcp22.suse.cz>
References: <20160103071246.GK9938@ZenIV.linux.org.uk>
 <20160103201233.GC6682@dastard>
 <20160103203514.GN9938@ZenIV.linux.org.uk>
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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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