linux-kernel - Re: [PATCHv2 2/2] mm: add a field to store names for private anonymous memory

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Date:	Tue, 01 Oct 2013 20:37:04 -0400
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	ccross@...roid.com
CC:	linux-kernel@...r.kernel.org, penberg@...nel.org,
	dave.hansen@...el.com, peterz@...radead.org, mingo@...nel.org,
	oleg@...hat.com, ebiederm@...ssion.com, jan.glauber@...il.com,
	rob@...dley.net, akpm@...ux-foundation.org, gorcunov@...nvz.org,
	rientjes@...gle.com, dave@....org, keescook@...omium.org,
	xemul@...allels.com, liwanp@...ux.vnet.ibm.com, walken@...gle.com,
	mgorman@...e.de, riel@...hat.com, jiang.liu@...wei.com,
	khlebnikov@...nvz.org, paulmck@...ux.vnet.ibm.com,
	dhowells@...hat.com, arnd@...db.de, davej@...hat.com, holt@....com,
	rafael.j.wysocki@...el.com, shli@...ionio.com,
	sasha.levin@...cle.com, kosaki.motohiro@...fujitsu.com,
	hughd@...gle.com, hannes@...xchg.org, a.p.zijlstra@...llo.nl,
	linux-doc@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCHv2 2/2] mm: add a field to store names for private anonymous
 memory

> +static void seq_print_vma_name(struct seq_file *m, struct vm_area_struct *vma)
> +{
> +	const char __user *name = vma_get_anon_name(vma);
> +	struct mm_struct *mm = vma->vm_mm;
> +
> +	unsigned long page_start_vaddr;
> +	unsigned long page_offset;
> +	unsigned long num_pages;
> +	unsigned long max_len = NAME_MAX;
> +	int i;
> +
> +	page_start_vaddr = (unsigned long)name & PAGE_MASK;
> +	page_offset = (unsigned long)name - page_start_vaddr;
> +	num_pages = DIV_ROUND_UP(page_offset + max_len, PAGE_SIZE);
> +
> +	seq_puts(m, "[anon:");
> +
> +	for (i = 0; i < num_pages; i++) {
> +		int len;
> +		int write_len;
> +		const char *kaddr;
> +		long pages_pinned;
> +		struct page *page;
> +
> +		pages_pinned = get_user_pages(current, mm, page_start_vaddr,
> +				1, 0, 0, &page, NULL);
> +		if (pages_pinned < 1) {
> +			seq_puts(m, "<fault>]");
> +			return;
> +		}
> +
> +		kaddr = (const char *)kmap(page);
> +		len = min(max_len, PAGE_SIZE - page_offset);

You can't show the name if the name is placed in end of page.


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