linux-kernel - Re: [PATCH 2/7] uprobes: kill dup_mmap()->uprobe_mmap(), simplify uprobe

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Message-ID: <20120813132042.GG31805@linux.vnet.ibm.com>
Date:	Mon, 13 Aug 2012 18:50:42 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Anton Arapov <anton@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/7] uprobes: kill dup_mmap()->uprobe_mmap(), simplify
 uprobe_mmap/munmap

* Oleg Nesterov <oleg@...hat.com> [2012-08-08 19:37:39]:

> 1. Kill dup_mmap()->uprobe_mmap(), it was only needed to calculate
>    new_mm->uprobes_state.count removed by the previous patch.
> 
>    If the forking process has a pending uprobe (int3) in vma, it will
>    be copied by copy_page_range(), note that it checks vma->anon_vma
>    so "Don't copy ptes" is not possible after install_breakpoint()
>    which does anon_vma_prepare().
> 
> 2. Remove is_swbp_at_addr() and "int count" in uprobe_mmap(). Again,
>    this was needed for uprobes_state.count.
> 
>    As a side effect this fixes the bug pointed out by Srikar,
>    this code lacked the necessary put_uprobe().
> 
> 3. uprobe_munmap() becomes a nop after the previous patch. Remove the
>    meaningless code but do not remove the helper, we will need it.

We could have removed uprobe_munmap() for now and reintroduced it. But
its fine to keep it this way for now.

> 
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>

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

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