linux-kernel - Re: Page allocation failure on v3.8-rc5

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Message-Id: <20130131154331.09d157a3.akpm@linux-foundation.org>
Date:	Thu, 31 Jan 2013 15:43:31 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Ming Lei <ming.lei@...onical.com>
Cc:	balbi@...com, Linux USB Mailing List <linux-usb@...r.kernel.org>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Jens Axboe <axboe@...nel.dk>
Subject: Re: Page allocation failure on v3.8-rc5

On Wed, 30 Jan 2013 19:53:22 +0800
Ming Lei <ming.lei@...onical.com> wrote:

> The allocation failure is caused by the big sizeof(struct parsed_partitions),
> which is 64K in my 32bit box,

Geeze.

We could fix that nicely by making parsed_partitions.parts an array of
pointers to a single `struct parsed_partition' and allocating those
on-demand.

But given the short-lived nature of this storage and the infrequency of
check_partition(), that isn't necessary.

> could you test the blow patch to see
> if it can fix the allocation failure?

(The patch is wordwrapped)

> ...
>
> @@ -106,18 +107,43 @@ static int (*check_part[])(struct parsed_partitions *) = {
>  	NULL
>  };
> 
> +struct parsed_partitions *allocate_partitions(int nr)
> +{
> +	struct parsed_partitions *state;
> +
> +	state = kzalloc(sizeof(struct parsed_partitions), GFP_KERNEL);

I personally prefer sizefo(*state) here.  It means the reader doesn't
have to scroll back to check things.

> +	if (!state)
> +		return NULL;
> +
> +	state->parts = vzalloc(nr * sizeof(state->parts[0]));
> +	if (!state->parts) {
> +		kfree(state);
> +		return NULL;
> +	}

It doesn't really need to be this complex - we could just vmalloc the
entire `struct parsed_partitions'.  But I see that your change will
cause us to allcoate much less memory in many situations, which is
good.  It should be mentioned in the changelog!

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