linux-kernel - Re: [PATCH] generic debug pagealloc

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Date:	Tue, 03 Mar 2009 17:12:35 +0100
From:	Jiri Slaby <jirislaby@...il.com>
To:	Akinobu Mita <akinobu.mita@...il.com>
CC:	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	linux-mm@...ck.org, akpm@...ux-foundation.org
Subject: Re: [PATCH] generic debug pagealloc

On 3.3.2009 17:01, Akinobu Mita wrote:
...
> +static void dump_broken_mem(unsigned char *mem)
> +{
> +	int i;
> +	int start = 0;
> +	int end = PAGE_SIZE - 1;
> +
> +	for (i = 0; i<  PAGE_SIZE; i++) {
> +		if (mem[i] != PAGE_POISON) {
> +			start = i;
> +			break;
> +		}
> +	}
> +	for (i = PAGE_SIZE - 1; i>= start; i--) {
> +		if (mem[i] != PAGE_POISON) {
> +			end = i;
> +			break;
> +		}
> +	}
> +	printk(KERN_ERR "Page corruption: %p-%p\n", mem + start, mem + end);
> +	print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, mem + start,
> +			end - start + 1, 1);
> +}
> +
> +static void unpoison_page(struct page *page)
> +{
> +	unsigned char *mem;
> +	int i;
> +
> +	if (!page->poison)
> +		return;
> +
> +	mem = kmap_atomic(page, KM_USER0);
> +	for (i = 0; i<  PAGE_SIZE; i++) {
> +		if (mem[i] != PAGE_POISON) {
> +			dump_broken_mem(mem);

Just an optimisation: pass the i to the dump_broken_mem as a start index.

> +			break;
> +		}
> +	}
> +	kunmap_atomic(mem, KM_USER0);
> +	page->poison = false;
> +}
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