linux-kernel - Re: [PATCH 2/X] uprobes: write_opcode() needs put_page(new

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Message-ID: <20111018164739.GI11831@linux.vnet.ibm.com>
Date:	Tue, 18 Oct 2011 22:17:39 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	Steven Rostedt <rostedt@...dmis.org>,
	Linux-mm <linux-mm@...ck.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jonathan Corbet <corbet@....net>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Hugh Dickins <hughd@...gle.com>,
	Christoph Hellwig <hch@...radead.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andi Kleen <andi@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
	Roland McGrath <roland@...k.frob.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/X] uprobes: write_opcode() needs put_page(new_page)
 unconditionally

> Every write_opcode()->__replace_page() leaks the new page on success.
> 
> We have the reference after alloc_page_vma(), then __replace_page()
> does another get_page() for the new mapping, we need put_page(new_page)
> in any case.
> 
> Alternatively we could remove __replace_page()->get_page() but it is
> better to change write_opcode(). This way it is simpler to unify the
> code with ksm.c:replace_page() and we can simplify the error handling
> in write_opcode(), the patch simply adds a single page_cache_release()
> under "unlock_out" label.

I have folded this change and your other suggested changes into my patches.

-- 
Thanks and Regards
Srikar

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