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mm: softdirty: make freshly remapped file pages being softdirty unconditionally 

Hugh reported:

 | I noticed your soft_dirty work in install_file_pte(): which looked
 | good at first, until I realized that it's propagating the soft_dirty
 | of a pte it's about to zap completely, to the unrelated entry it's
 | about to insert in its place.  Which seems very odd to me.

Indeed this code ends up being nop in result -- pte_file_mksoft_dirty()
operates with pte_t argument and returns new pte_t which were never used
after.  After looking more I think what we need is to soft-dirtify all
newely remapped file pages because it should look like a new mapping for
memory tracker.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Reported-by: Hugh Dickins <hughd@google.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Cyrill Gorcunov 2014-06-04 16:06:41 -07:00 committed by Linus Torvalds
parent 52383431b3
commit 0bf073315c
1 changed files with 2 additions and 5 deletions
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7
mm/fremap.c
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@ -82,13 +82,10 @@ static int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma,
ptfile = pgoff_to_pte(pgoff);
if (!pte_none(*pte)) {
if (pte_present(*pte) && pte_soft_dirty(*pte))
pte_file_mksoft_dirty(ptfile);
if (!pte_none(*pte))
zap_pte(mm, vma, addr, pte);
}
set_pte_at(mm, addr, pte, ptfile);
set_pte_at(mm, addr, pte, pte_file_mksoft_dirty(ptfile));
/*
* We don't need to run update_mmu_cache() here because the "file pte"
* being installed by install_file_pte() is not a real pte - it's a