linux-kernel - Re: [PATCH 2/5] uprobes: Change __copy_insn() to use copy_from

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Message-ID: <20130326120021.GD639@linux.vnet.ibm.com>
Date:	Tue, 26 Mar 2013 17:30:21 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Anton Arapov <anton@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Josh Stone <jistone@...hat.com>,
	Frank Eigler <fche@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	adrian.m.negreanu@...el.com, Torsten.Polle@....de
Subject: Re: [PATCH 2/5] uprobes: Change __copy_insn() to use
 copy_from_page()

* Oleg Nesterov <oleg@...hat.com> [2013-03-24 19:21:15]:

> Change __copy_insn() to use copy_from_page() and simplify the code.
> 
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>

Acked-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>

> ---
>  kernel/events/uprobes.c |   13 ++-----------
>  1 files changed, 2 insertions(+), 11 deletions(-)
> 
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index d6891cb..0a759c6 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -477,30 +477,21 @@ __copy_insn(struct address_space *mapping, struct file *filp, char *insn,
>  			unsigned long nbytes, loff_t offset)
>  {
>  	struct page *page;
> -	void *vaddr;
> -	unsigned long off;
> -	pgoff_t idx;
> 
>  	if (!filp)
>  		return -EINVAL;
> 
>  	if (!mapping->a_ops->readpage)
>  		return -EIO;
> -
> -	idx = offset >> PAGE_CACHE_SHIFT;
> -	off = offset & ~PAGE_MASK;
> -
>  	/*
>  	 * Ensure that the page that has the original instruction is
>  	 * populated and in page-cache.
>  	 */
> -	page = read_mapping_page(mapping, idx, filp);
> +	page = read_mapping_page(mapping, offset >> PAGE_CACHE_SHIFT, filp);
>  	if (IS_ERR(page))
>  		return PTR_ERR(page);
> 
> -	vaddr = kmap_atomic(page);
> -	memcpy(insn, vaddr + off, nbytes);
> -	kunmap_atomic(vaddr);
> +	copy_from_page(page, offset, insn, nbytes);
>  	page_cache_release(page);
> 
>  	return 0;
> -- 
> 1.5.5.1
> 

-- 
Thanks and Regards
Srikar Dronamraju

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