The patch titled
mm/ksm.c is doing an unneeded _notify in write_protect_page.
has been added to the -mm tree. Its filename is
mm-ksmc-is-doing-an-unneeded-_notify-in-write_protect_page.patch
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------------------------------------------------------
Subject: mm/ksm.c is doing an unneeded _notify in write_protect_page.
From: Robin Holt <holt@xxxxxxx>
ksm.c's write_protect_page implements a lockless means of verifying a page
does not have any users of the page which are not accounted for via other
kernel tracking means. It does this by removing the writable pte with TLB
flushes, checking the page_count against the total known users, and then
using set_pte_at_notify to make it a read-only entry.
An unneeded mmu_notifier callout is made in the case where the known users
does not match the page_count. In that event, we are inserting the
identical pte and there is no need for the set_pte_at_notify, but rather
the simpler set_pte_at suffices.
Signed-off-by: Robin Holt <holt@xxxxxxx>
Acked-by: Izik Eidus <ieidus@xxxxxxxxxx>
Acked-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Acked-by: Hugh Dickins <hugh.dickins@xxxxxxxxxxxxx>
Cc: Chris Wright <chrisw@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/ksm.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff -puN mm/ksm.c~mm-ksmc-is-doing-an-unneeded-_notify-in-write_protect_page mm/ksm.c
--- a/mm/ksm.c~mm-ksmc-is-doing-an-unneeded-_notify-in-write_protect_page
+++ a/mm/ksm.c
@@ -751,7 +751,7 @@ static int write_protect_page(struct vm_
* page
*/
if (page_mapcount(page) + 1 + swapped != page_count(page)) {
- set_pte_at_notify(mm, addr, ptep, entry);
+ set_pte_at(mm, addr, ptep, entry);
goto out_unlock;
}
entry = pte_wrprotect(entry);
_
Patches currently in -mm which might be from holt@xxxxxxx are
mm-ksmc-is-doing-an-unneeded-_notify-in-write_protect_page.patch
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