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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