linux-kernel - Re: [PATCH 1/7] mm: introduce simple_malloc()/simple

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Message-Id: <20081116231301.c6b0da95.akpm@linux-foundation.org>
Date:	Sun, 16 Nov 2008 23:13:01 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"KOSAKI Motohiro" <kosaki.motohiro@...fujitsu.com>
Cc:	"KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>,
	balbir@...ux.vnet.ibm.com, "Lai Jiangshan" <laijs@...fujitsu.com>,
	"Arjan van de Ven" <arjan@...radead.org>,
	"Dave Airlie" <airlied@...il.com>,
	"David Miller" <davem@...emloft.net>, menage@...gle.com,
	jens.axboe@...cle.com, jack@...e.cz, jes@....com,
	linux-kernel@...r.kernel.org, dada1@...mosbay.com,
	"Alexey Dobriyan" <adobriyan@...il.com>
Subject: Re: [PATCH 1/7] mm: introduce simple_malloc()/simple_free()

On Mon, 17 Nov 2008 15:43:59 +0900 "KOSAKI Motohiro" <kosaki.motohiro@...fujitsu.com> wrote:

> >> > (I'll rename simple_malloc/simple_free to kvmalloc/kvfree)
> >> >
> >>
> >> I would prefer to find a way to say that one cannot select gfp_mask with this API.
> >>
> > I think gfp_mask must be passed explicitly.
> 
> Agreed.

It would only make sense if __vmalloc() can be called in atomic contexts.

__vmalloc() cannot be called from irq contexts due to it taking
non-irq-safe spinlocks.

__vmalloc() kinda looks like it could be called from non-irq atomic
contexts with GFP_ATOMIC, but I think it lies.  For example,
pud_alloc_one/pmd_alloc_one/etc use hard-wired GFP_KERNEL.

In which case this new allocation function can only be called from
contexts where GFP_KERNEL can be used, hence we don't need to pass that
in - it would be misleading to do so.

In fact it's not immediately clear why __vmalloc() takes a gfp_t
argument either?
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