Eric Lee / linux-smarc-t335x-v3.2

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Commit ee6a6457886a80415db209e87033b63f2b06558c

Authored by Peter Zijlstra
Committed by Linus Torvalds
1 parent e88dd6c11c
Exists in master and in 4 other branches v3.2_AM335xPSP_04.06.00.11, v3.2_NEWT335xPSP_04.06.00.11, v3.2_SBC_SMARTMEN, v3.2_SMARCT335xPSP_04.06.00.11

[PATCH] mm: fixup do_wp_page() 

Wrt. the recent modifications in do_wp_page() Hugh Dickins pointed out:

  "I now realize it's right to the first order (normal case) and to the
   second order (ptrace poke), but not to the third order (ptrace poke
   anon page here to be COWed - perhaps can't occur without intervening
   mprotects)."

This patch restores the old COW behaviour for anonymous pages.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Showing 1 changed file with 13 additions and 6 deletions Side-by-side Diff

... ... @@ -1467,11 +1467,21 @@
1467 1467 goto gotten;
1468 1468  
1469 1469 /*
1470   - * Only catch write-faults on shared writable pages, read-only
1471   - * shared pages can get COWed by get_user_pages(.write=1, .force=1).
  1470 + * Take out anonymous pages first, anonymous shared vmas are
  1471 + * not dirty accountable.
1472 1472 */
1473   - if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
  1473 + if (PageAnon(old_page)) {
  1474 + if (!TestSetPageLocked(old_page)) {
  1475 + reuse = can_share_swap_page(old_page);
  1476 + unlock_page(old_page);
  1477 + }
  1478 + } else if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
1474 1479 (VM_WRITE|VM_SHARED))) {
  1480 + /*
  1481 + * Only catch write-faults on shared writable pages,
  1482 + * read-only shared pages can get COWed by
  1483 + * get_user_pages(.write=1, .force=1).
  1484 + */
1475 1485 if (vma->vm_ops && vma->vm_ops->page_mkwrite) {
1476 1486 /*
1477 1487 * Notify the address space that the page is about to
... ... @@ -1503,9 +1513,6 @@
1503 1513 dirty_page = old_page;
1504 1514 get_page(dirty_page);
1505 1515 reuse = 1;
1506   - } else if (PageAnon(old_page) && !TestSetPageLocked(old_page)) {
1507   - reuse = can_share_swap_page(old_page);
1508   - unlock_page(old_page);
1509 1516 }
1510 1517  
1511 1518 if (reuse) {