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Date: Wed, 14 Jan 2015 20:07:06 +0530
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Subject: Re: [RFC][PATCH] procfs: Add /proc/<pid>/mapped_files
From: Siddhesh Poyarekar <siddhesh.poyarekar@gmail.com>
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Calvin Owens <calvinowens@fb.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Alexey Dobriyan <adobriyan@gmail.com>, Oleg Nesterov <oleg@redhat.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Peter Feiner <pfeiner@google.com>,
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On 14 January 2015 at 19:43, Rasmus Villemoes <linux@rasmusvillemoes.dk> wrote:
> Just thinking out loud: Could one simply mark a VMA as being used for
> stack during the clone call (is there room in vm_flags, or does
> VM_GROWSDOWN already tell the whole story?), and then write the TID into
> a new field in the VMA - I think one could make a union with vm_pgoff so
> as not to enlarge the structure.

vm_flags does not have space IIRC (that was my first approach at
implementing this) and VM_GROWSDOWN is not sufficient.  If we can make
a union with vm_pgoff like you say, we probably don't need a flag
value; a non-zero value could indicate that it is a thread stack.

One problem with caching the value on clone like this though is that
the stack could change due to a setcontext, but AFAICT we don't care
about that for the process stack either.

Siddhesh
-- 
http://siddhesh.in