Subject: + mm-memoryc-use-entry-=-access_oncepte-in-handle_pte_fault.patch added to -mm tree
To: hughd@xxxxxxxxxx,kirill.shutemov@xxxxxxxxxxxxxxx,koct9i@xxxxxxxxx,sasha.levin@xxxxxxxxxx,torvalds@xxxxxxxxxxxxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Wed, 11 Jun 2014 16:10:50 -0700
The patch titled
Subject: mm/memory.c: use entry = ACCESS_ONCE(*pte) in handle_pte_fault()
has been added to the -mm tree. Its filename is
mm-memoryc-use-entry-=-access_oncepte-in-handle_pte_fault.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-memoryc-use-entry-=-access_oncepte-in-handle_pte_fault.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-memoryc-use-entry-=-access_oncepte-in-handle_pte_fault.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: mm/memory.c: use entry = ACCESS_ONCE(*pte) in handle_pte_fault()
Use ACCESS_ONCE() in handle_pte_fault() when getting the entry or orig_pte
upon which all subsequent decisions and pte_same() tests will be made.
I have no evidence that its lack is responsible for the mm/filemap.c:202
BUG_ON(page_mapped(page)) in __delete_from_page_cache() found by trinity,
and I am not optimistic that it will fix it. But I have found no other
explanation, and ACCESS_ONCE() here will surely not hurt.
If gcc does re-access the pte before passing it down, then that would be
disastrous for correct page fault handling, and certainly could explain
the page_mapped() BUGs seen (concurrent fault causing page to be mapped in
a second time on top of itself: mapcount 2 for a single pte).
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Sasha Levin <sasha.levin@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Konstantin Khlebnikov <koct9i@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff -puN mm/memory.c~mm-memoryc-use-entry-=-access_oncepte-in-handle_pte_fault mm/memory.c
--- a/mm/memory.c~mm-memoryc-use-entry-=-access_oncepte-in-handle_pte_fault
+++ a/mm/memory.c
@@ -3177,7 +3177,7 @@ static int handle_pte_fault(struct mm_st
pte_t entry;
spinlock_t *ptl;
- entry = *pte;
+ entry = ACCESS_ONCE(*pte);
if (!pte_present(entry)) {
if (pte_none(entry)) {
if (vma->vm_ops) {
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
origin.patch
mm-memoryc-use-entry-=-access_oncepte-in-handle_pte_fault.patch
list-use-argument-hlist_add_after-names-from-rcu-variant.patch
list-fix-order-of-arguments-for-hlist_add_after_rcu.patch
klist-use-same-naming-scheme-as-hlist-for-klist_add_after.patch
linux-next.patch
memcg-mm-introduce-lowlimit-reclaim.patch
memcg-mm-introduce-lowlimit-reclaim-fix.patch
memcg-mm-introduce-lowlimit-reclaim-fix2patch.patch
memcg-allow-setting-low_limit.patch
memcg-doc-clarify-global-vs-limit-reclaims.patch
memcg-doc-clarify-global-vs-limit-reclaims-fix.patch
memcg-document-memorylow_limit_in_bytes.patch
vmscan-memcg-check-whether-the-low-limit-should-be-ignored.patch
mm-replace-remap_file_pages-syscall-with-emulation-fix-3.patch
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
