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Subject: Re: [PATCH v7 3.2-rc2 4/30] uprobes: Define hooks for mmap/munmap.
From: Peter Zijlstra <peterz@infradead.org>
Date: Wed, 23 Nov 2011 18:13:50 +0100
In-Reply-To: <20111118110723.10512.66282.sendpatchset@srdronam.in.ibm.com>
References: <20111118110631.10512.73274.sendpatchset@srdronam.in.ibm.com>
	 <20111118110723.10512.66282.sendpatchset@srdronam.in.ibm.com>
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To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>, Oleg Nesterov <oleg@redhat.com>, Andrew Morton <akpm@linux-foundation.org>, LKML <linux-kernel@vger.kernel.org>, Linux-mm <linux-mm@kvack.org>, Ingo Molnar <mingo@elte.hu>, Andi Kleen <andi@firstfloor.org>, Christoph Hellwig <hch@infradead.org>, Steven Rostedt <rostedt@goodmis.org>, Roland McGrath <roland@hack.frob.com>, Thomas Gleixner <tglx@linutronix.de>, Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>, Arnaldo Carvalho de Melo <acme@infradead.org>, Anton Arapov <anton@redhat.com>, Ananth N Mavinakayanahalli <ananth@in.ibm.com>, Jim Keniston <jkenisto@linux.vnet.ibm.com>, Stephen Wilson <wilsons@start.ca>

On Fri, 2011-11-18 at 16:37 +0530, Srikar Dronamraju wrote:
> +int mmap_uprobe(struct vm_area_struct *vma)
> +{
> +       struct list_head tmp_list;
> +       struct uprobe *uprobe, *u;
> +       struct inode *inode;
> +       int ret =3D 0, count =3D 0;
> +
> +       if (!atomic_read(&uprobe_events) || !valid_vma(vma, true))
> +               return ret;     /* Bail-out */
> +
> +       inode =3D igrab(vma->vm_file->f_mapping->host);
> +       if (!inode)
> +               return ret;=20

Since we hold mmap_sem, vma is pinned, which should pin the inode, why
take out another ref?

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