linux-kernel - Re: [patch v2 1/5] mm: add nofail variants of kmalloc kcalloc and kzalloc

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Message-ID: <4C7F5951.6040809@gmail.com>
Date:	Thu, 02 Sep 2010 09:59:13 +0200
From:	Jiri Slaby <jirislaby@...il.com>
To:	David Rientjes <rientjes@...gle.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Neil Brown <neilb@...e.de>, Alasdair G Kergon <agk@...hat.com>,
	Chris Mason <chris.mason@...cle.com>,
	Steven Whitehouse <swhiteho@...hat.com>,
	Jens Axboe <jaxboe@...ionio.com>, Jan Kara <jack@...e.cz>,
	Frederic Weisbecker <fweisbec@...il.com>,
	linux-raid@...r.kernel.org, linux-btrfs@...r.kernel.org,
	cluster-devel@...hat.com, linux-ext4@...r.kernel.org,
	reiserfs-devel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [patch v2 1/5] mm: add nofail variants of kmalloc kcalloc and
 kzalloc

On 09/02/2010 03:02 AM, David Rientjes wrote:
> --- a/include/linux/slab.h
> +++ b/include/linux/slab.h
> @@ -334,6 +334,57 @@ static inline void *kzalloc_node(size_t size, gfp_t flags, int node)
>  	return kmalloc_node(size, flags | __GFP_ZERO, node);
>  }
>  
> +/**
> + * kmalloc_nofail - infinitely loop until kmalloc() succeeds.
> + * @size: how many bytes of memory are required.
> + * @flags: the type of memory to allocate (see kmalloc).
> + *
> + * NOTE: no new callers of this function should be implemented!
> + * All memory allocations should be failable whenever possible.
> + */
> +static inline void *kmalloc_nofail(size_t size, gfp_t flags)
> +{
> +	void *ret;
> +
> +	for (;;) {
> +		ret = kmalloc(size, flags);
> +		if (ret)
> +			return ret;
> +		WARN_ON_ONCE(get_order(size) > PAGE_ALLOC_COSTLY_ORDER);

This doesn't work as you expect. kmalloc will warn every time it fails.
__GFP_NOFAIL used to disable the warning. Actually what's wrong with
__GFP_NOFAIL? I cannot find a reason in the changelogs why the patches
are needed.

> +	}



-- 
js
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