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Date: Tue, 12 May 2015 09:46:47 +0000
From: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
Andi Kleen <andi@...stfloor.org>
CC: Tony Luck <tony.luck@...el.com>,
"Kirill A. Shutemov" <kirill@...temov.name>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"Naoya Horiguchi" <nao.horiguchi@...il.com>
Subject: [PATCH 1/4] mm/memory-failure: split thp earlier in memory error
handling
memory_failure() doesn't handle thp itself at this time and need to split
it before doing isolation. Currently thp is split in the middle of
hwpoison_user_mappings(), but there're corner cases where memory_failure()
wrongly tries to handle thp without splitting.
1) "non anonymous" thp, which is not a normal operating mode of thp, but
a memory error could hit a thp before anon_vma is initialized. In such case,
split_huge_page() fails and me_huge_page() (intended for hugetlb) is called
for thp, which triggers BUG_ON in page_hstate().
2) !PageLRU case, where hwpoison_user_mappings() returns with SWAP_SUCCESS
and the result is the same as case 1.
memory_failure() can't avoid splitting, so let's split it more earlier, which
also reduces code which are prepared for both of normal page and thp.
Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
---
mm/memory-failure.c | 88 +++++++++++++++--------------------------------------
1 file changed, 25 insertions(+), 63 deletions(-)
diff --git v4.1-rc3.orig/mm/memory-failure.c v4.1-rc3/mm/memory-failure.c
index 9e9d04843d52..331c75b23ba2 100644
--- v4.1-rc3.orig/mm/memory-failure.c
+++ v4.1-rc3/mm/memory-failure.c
@@ -897,7 +897,6 @@ static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
int ret;
int kill = 1, forcekill;
struct page *hpage = *hpagep;
- struct page *ppage;
/*
* Here we are interested only in user-mapped pages, so skip any
@@ -947,59 +946,6 @@ static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
}
/*
- * ppage: poisoned page
- * if p is regular page(4k page)
- * ppage == real poisoned page;
- * else p is hugetlb or THP, ppage == head page.
- */
- ppage = hpage;
-
- if (PageTransHuge(hpage)) {
- /*
- * Verify that this isn't a hugetlbfs head page, the check for
- * PageAnon is just for avoid tripping a split_huge_page
- * internal debug check, as split_huge_page refuses to deal with
- * anything that isn't an anon page. PageAnon can't go away fro
- * under us because we hold a refcount on the hpage, without a
- * refcount on the hpage. split_huge_page can't be safely called
- * in the first place, having a refcount on the tail isn't
- * enough * to be safe.
- */
- if (!PageHuge(hpage) && PageAnon(hpage)) {
- if (unlikely(split_huge_page(hpage))) {
- /*
- * FIXME: if splitting THP is failed, it is
- * better to stop the following operation rather
- * than causing panic by unmapping. System might
- * survive if the page is freed later.
- */
- printk(KERN_INFO
- "MCE %#lx: failed to split THP\n", pfn);
-
- BUG_ON(!PageHWPoison(p));
- return SWAP_FAIL;
- }
- /*
- * We pinned the head page for hwpoison handling,
- * now we split the thp and we are interested in
- * the hwpoisoned raw page, so move the refcount
- * to it. Similarly, page lock is shifted.
- */
- if (hpage != p) {
- if (!(flags & MF_COUNT_INCREASED)) {
- put_page(hpage);
- get_page(p);
- }
- lock_page(p);
- unlock_page(hpage);
- *hpagep = p;
- }
- /* THP is split, so ppage should be the real poisoned page. */
- ppage = p;
- }
- }
-
- /*
* First collect all the processes that have the page
* mapped in dirty form. This has to be done before try_to_unmap,
* because ttu takes the rmap data structures down.
@@ -1008,12 +954,12 @@ static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
* there's nothing that can be done.
*/
if (kill)
- collect_procs(ppage, &tokill, flags & MF_ACTION_REQUIRED);
+ collect_procs(hpage, &tokill, flags & MF_ACTION_REQUIRED);
- ret = try_to_unmap(ppage, ttu);
+ ret = try_to_unmap(hpage, ttu);
if (ret != SWAP_SUCCESS)
printk(KERN_ERR "MCE %#lx: failed to unmap page (mapcount=%d)\n",
- pfn, page_mapcount(ppage));
+ pfn, page_mapcount(hpage));
/*
* Now that the dirty bit has been propagated to the
@@ -1025,7 +971,7 @@ static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
* use a more force-full uncatchable kill to prevent
* any accesses to the poisoned memory.
*/
- forcekill = PageDirty(ppage) || (flags & MF_MUST_KILL);
+ forcekill = PageDirty(hpage) || (flags & MF_MUST_KILL);
kill_procs(&tokill, forcekill, trapno,
ret != SWAP_SUCCESS, p, pfn, flags);
@@ -1071,6 +1017,7 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
struct page_state *ps;
struct page *p;
struct page *hpage;
+ struct page *orig_head;
int res;
unsigned int nr_pages;
unsigned long page_flags;
@@ -1086,7 +1033,7 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
}
p = pfn_to_page(pfn);
- hpage = compound_head(p);
+ orig_head = hpage = compound_head(p);
if (TestSetPageHWPoison(p)) {
printk(KERN_ERR "MCE %#lx: already hardware poisoned\n", pfn);
return 0;
@@ -1149,6 +1096,21 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
}
}
+ if (!PageHuge(p) && PageTransHuge(hpage)) {
+ if (!PageAnon(hpage)) {
+ pr_info("MCE: %#lx: non anonymous thp", pfn);
+ put_page(p);
+ return -EBUSY;
+ }
+ if (unlikely(split_huge_page(hpage))) {
+ pr_info("MCE: %#lx: thp split failed", pfn);
+ put_page(p);
+ return -EBUSY;
+ }
+ VM_BUG_ON_PAGE(!page_count(p), p);
+ hpage = compound_head(p);
+ }
+
/*
* We ignore non-LRU pages for good reasons.
* - PG_locked is only well defined for LRU pages and a few others
@@ -1158,9 +1120,9 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
* walked by the page reclaim code, however that's not a big loss.
*/
if (!PageHuge(p)) {
- if (!PageLRU(hpage))
- shake_page(hpage, 0);
- if (!PageLRU(hpage)) {
+ if (!PageLRU(p))
+ shake_page(p, 0);
+ if (!PageLRU(p)) {
/*
* shake_page could have turned it free.
*/
@@ -1181,7 +1143,7 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
* The page could have changed compound pages during the locking.
* If this happens just bail out.
*/
- if (compound_head(p) != hpage) {
+ if (PageCompound(p) && compound_head(p) != orig_head) {
action_result(pfn, MF_MSG_DIFFERENT_COMPOUND, MF_IGNORED);
res = -EBUSY;
goto out;
--
2.1.0
--
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