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Date: Thu, 15 Mar 2018 15:30:45 +0100
From: Oleg Nesterov <oleg@redhat.com>
To: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Cc: mhiramat@kernel.org, peterz@infradead.org, srikar@linux.vnet.ibm.com,
	acme@kernel.org, ananth@linux.vnet.ibm.com,
	akpm@linux-foundation.org, alexander.shishkin@linux.intel.com,
	alexis.berlemont@gmail.com, corbet@lwn.net,
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	yao.jin@linux.intel.com, fengguang.wu@intel.com
Subject: Re: [PATCH 5/8] trace_uprobe: Support SDT markers having reference
 count (semaphore)
Message-ID: <20180315143044.GA19643@redhat.com>
References: <20180313125603.19819-1-ravi.bangoria@linux.vnet.ibm.com>
 <20180313125603.19819-6-ravi.bangoria@linux.vnet.ibm.com>
 <20180315142120.GA19218@redhat.com>
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On 03/15, Oleg Nesterov wrote:
>
> > +static struct vm_area_struct *
> > +sdt_find_vma(struct mm_struct *mm, struct trace_uprobe *tu)
> > +{
> > +	struct vm_area_struct *tmp;
> > +
> > +	for (tmp = mm->mmap; tmp != NULL; tmp = tmp->vm_next)
> > +		if (sdt_valid_vma(tu, tmp))
> > +			return tmp;
> > +
> > +	return NULL;
>
> I can't understand the logic... Lets ignore sdt_valid_vma() for now.
> The caller has uprobe_map_info, why it can't simply do
> vma = find_vma(uprobe_map_info->vaddr)? and then check sdt_valid_vma().

Note to mention that sdt_find_vma() can return NULL but the callers do
vma_offset_to_vaddr(vma) without any check.

Oleg.