From: Shaohua Li <shaohua.li@intel.com>
Date: Wed, 25 May 2011 00:11:20 +0000 (-0700)
Subject: mmap: avoid merging cloned VMAs
X-Git-Tag: v3.0-rc1~295
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=965f55dea0e331152fa53941a51e4e16f9f06fae;p=pandora-kernel.git

mmap: avoid merging cloned VMAs

Avoid merging a VMA with another VMA which is cloned from the parent process.

The cloned VMA shares the anon_vma lock with the parent process's VMA.  If
we do the merge, more vmas (even the new range is only for current
process) use the perent process's anon_vma lock.  This introduces
scalability issues.  find_mergeable_anon_vma() already considers this
case.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

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