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Commit 415c64c1 authored by Naoya Horiguchi's avatar Naoya Horiguchi Committed by Linus Torvalds
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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: default avatarNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 95bbc0c7

mm/memory-failure.c

+25 −63
Original line number Diff line number Diff line
@@ -928,7 +928,6 @@ 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
@@ -977,59 +976,6 @@ 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,
@@ -1039,12 +985,12 @@ 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
@@ -1056,7 +1002,7 @@ 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);
@@ -1102,6 +1048,7 @@ 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;
@@ -1117,7 +1064,7 @@ 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;
@@ -1180,6 +1127,21 @@ int memory_failure(unsigned long pfn, int trapno, int flags) 
		}

	}



	if (!PageHuge(p) && PageTransHuge(hpage)) {

		if (!PageAnon(hpage)) {

			pr_err("MCE: %#lx: non anonymous thp\n", pfn);

			put_page(p);

			return -EBUSY;

		}

		if (unlikely(split_huge_page(hpage))) {

			pr_err("MCE: %#lx: thp split failed\n", 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
@@ -1189,9 +1151,9 @@ 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.

			 */
@@ -1212,7 +1174,7 @@ 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, MSG_DIFFERENT_COMPOUND, IGNORED);

		res = -EBUSY;

		goto out;