mm: thp: Use more portable PMD clearing sequenece in zap_huge_pmd().
authorDavid Miller <davem@davemloft.net>
Mon, 8 Oct 2012 23:34:26 +0000 (16:34 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Tue, 9 Oct 2012 07:23:06 +0000 (16:23 +0900)
commitf5c8ad47284ca01dafc37da5a72bb9644174d387
tree9d05ff565ad5e3b90933cacad012ad9724a8a83e
parentb113da65785d5f3f9ff1451ec0fe43d6d76da25b
mm: thp: Use more portable PMD clearing sequenece in zap_huge_pmd().

Invalidation sequences are handled in various ways on various
architectures.

One way, which sparc64 uses, is to let the set_*_at() functions accumulate
pending flushes into a per-cpu array.  Then the flush_tlb_range() et al.
calls process the pending TLB flushes.

In this regime, the __tlb_remove_*tlb_entry() implementations are
essentially NOPs.

The canonical PTE zap in mm/memory.c is:

ptent = ptep_get_and_clear_full(mm, addr, pte,
tlb->fullmm);
tlb_remove_tlb_entry(tlb, pte, addr);

With a subsequent tlb_flush_mmu() if needed.

Mirror this in the THP PMD zapping using:

orig_pmd = pmdp_get_and_clear(tlb->mm, addr, pmd);
page = pmd_page(orig_pmd);
tlb_remove_pmd_tlb_entry(tlb, pmd, addr);

And we properly accomodate TLB flush mechanims like the one described
above.

Signed-off-by: David S. Miller <davem@davemloft.net>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/huge_memory.c