Commit message: mm: hwpoison: fix thp split handling in memory_failure()

When memory_failure() runs on a thp tail page after pmd is split, we
trigger the following VM_BUG_ON_PAGE():

   page:ffffd7cd819b0040 count:0 mapcount:0 mapping:         (null) index:0x1
   flags: 0x1fffc000400000(hwpoison)
   page dumped because: VM_BUG_ON_PAGE(!page_count(p))
   ------------[ cut here ]------------
   kernel BUG at /src/linux-dev/mm/memory-failure.c:1132!

memory_failure() passed refcount and page lock from tail page to head
page, which is not needed because we can pass any subpage to
split_huge_page().

Fixes: 61f5d698cc97 ("mm: re-enable THP")
Link: http://lkml.kernel.org/r/1477961577-7183-1-git-send-email-n-horiguchi@ah.jp.nec.com
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: <stable@vger.kernel.org>	[4.5+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
CVE: CVE-2019-10124
Vulnerability description: Rejected reason: DO NOT USE THIS CANDIDATE NUMBER. ConsultIDs: none. Reason: This candidate was withdrawn by its CNA. Further investigation showed that it was not a security issue. Notes: none

Project: linux
File: memory-failure.c

static void set_page_hwpoison_huge_page(struct page *hpage)
{
	int i;
	int nr_pages = 1 << compound_order(hpage);
	for (i = 0; i < nr_pages; i++)
		SetPageHWPoison(hpage + i);
}

Project: linux
File: memory-failure.c

static int soft_offline_in_use_page(struct page *page, int flags)
{
	int ret;
	struct page *hpage = compound_head(page);

	if (!PageHuge(page) && PageTransHuge(hpage)) {
		lock_page(hpage);
		if (!PageAnon(hpage) || unlikely(split_huge_page(hpage))) {
			unlock_page(hpage);
			if (!PageAnon(hpage))
				pr_info("soft offline: %#lx: non anonymous thp\n", page_to_pfn(page));
			else
				pr_info("soft offline: %#lx: thp split failed\n", page_to_pfn(page));
			put_hwpoison_page(hpage);
			return -EBUSY;
		}
		unlock_page(hpage);
		get_hwpoison_page(page);
		put_hwpoison_page(hpage);
	}

	if (PageHuge(page))
		ret = soft_offline_huge_page(page, flags);
	else
		ret = __soft_offline_page(page, flags);

	return ret;
}

Project: linux
File: memory-failure.c

static void clear_page_hwpoison_huge_page(struct page *hpage)
{
	int i;
	int nr_pages = 1 << compound_order(hpage);
	for (i = 0; i < nr_pages; i++)
		ClearPageHWPoison(hpage + i);
}

Project: linux
File: memory-failure.c

static int delete_from_lru_cache(struct page *p)
{
	if (!isolate_lru_page(p)) {
		/*
		 * Clear sensible page flags, so that the buddy system won't
		 * complain when the page is unpoison-and-freed.
		 */
		ClearPageActive(p);
		ClearPageUnevictable(p);
		/*
		 * drop the page count elevated by isolate_lru_page()
		 */
		put_page(p);
		return 0;
	}
	return -EIO;
}

Project: linux
File: memory-failure.c

static void soft_offline_free_page(struct page *page)
{
	if (PageHuge(page)) {
		struct page *hpage = compound_head(page);

		set_page_hwpoison_huge_page(hpage);
		if (!dequeue_hwpoisoned_huge_page(hpage))
			num_poisoned_pages_add(1 << compound_order(hpage));
	} else {
		if (!TestSetPageHWPoison(page))
			num_poisoned_pages_inc();
	}
}

Project: linux
File: memory-failure.c

static int page_action(struct page_state *ps, struct page *p,
			unsigned long pfn)
{
	int result;
	int count;

	result = ps->action(p, pfn);

	count = page_count(p) - 1;
	if (ps->action == me_swapcache_dirty && result == MF_DELAYED)
		count--;
	if (count != 0) {
		pr_err("Memory failure: %#lx: %s still referenced by %d users\n",
		       pfn, action_page_types[ps->type], count);
		result = MF_FAILED;
	}
	action_result(pfn, ps->type, result);

	/* Could do more checks here if page looks ok */
	/*
	 * Could adjust zone counters here to correct for the missing page.
	 */

	return (result == MF_RECOVERED || result == MF_DELAYED) ? 0 : -EBUSY;
}

Project: linux
File: memory-failure.c

static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
				  int trapno, int flags, struct page **hpagep)
{
	enum ttu_flags ttu = TTU_UNMAP | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
	struct address_space *mapping;
	LIST_HEAD(tokill);
	int ret;
	int kill = 1, forcekill;
	struct page *hpage = *hpagep;

	/*
	 * Here we are interested only in user-mapped pages, so skip any
	 * other types of pages.
	 */
	if (PageReserved(p) || PageSlab(p))
		return SWAP_SUCCESS;
	if (!(PageLRU(hpage) || PageHuge(p)))
		return SWAP_SUCCESS;

	/*
	 * This check implies we don't kill processes if their pages
	 * are in the swap cache early. Those are always late kills.
	 */
	if (!page_mapped(hpage))
		return SWAP_SUCCESS;

	if (PageKsm(p)) {
		pr_err("Memory failure: %#lx: can't handle KSM pages.\n", pfn);
		return SWAP_FAIL;
	}

	if (PageSwapCache(p)) {
		pr_err("Memory failure: %#lx: keeping poisoned page in swap cache\n",
			pfn);
		ttu |= TTU_IGNORE_HWPOISON;
	}

	/*
	 * Propagate the dirty bit from PTEs to struct page first, because we
	 * need this to decide if we should kill or just drop the page.
	 * XXX: the dirty test could be racy: set_page_dirty() may not always
	 * be called inside page lock (it's recommended but not enforced).
	 */
	mapping = page_mapping(hpage);
	if (!(flags & MF_MUST_KILL) && !PageDirty(hpage) && mapping &&
	    mapping_cap_writeback_dirty(mapping)) {
		if (page_mkclean(hpage)) {
			SetPageDirty(hpage);
		} else {
			kill = 0;
			ttu |= TTU_IGNORE_HWPOISON;
			pr_info("Memory failure: %#lx: corrupted page was clean: dropped without side effects\n",
				pfn);
		}
	}

	/*
	 * 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.
	 *
	 * Error handling: We ignore errors here because
	 * there's nothing that can be done.
	 */
	if (kill)
		collect_procs(hpage, &tokill, flags & MF_ACTION_REQUIRED);

	ret = try_to_unmap(hpage, ttu);
	if (ret != SWAP_SUCCESS)
		pr_err("Memory failure: %#lx: failed to unmap page (mapcount=%d)\n",
		       pfn, page_mapcount(hpage));

	/*
	 * Now that the dirty bit has been propagated to the
	 * struct page and all unmaps done we can decide if
	 * killing is needed or not.  Only kill when the page
	 * was dirty or the process is not restartable,
	 * otherwise the tokill list is merely
	 * freed.  When there was a problem unmapping earlier
	 * use a more force-full uncatchable kill to prevent
	 * any accesses to the poisoned memory.
	 */
	forcekill = PageDirty(hpage) || (flags & MF_MUST_KILL);
	kill_procs(&tokill, forcekill, trapno,
		      ret != SWAP_SUCCESS, p, pfn, flags);

	return ret;
}

Project: linux
File: memory-failure.c

static void add_to_kill(struct task_struct *tsk, struct page *p,
		       struct vm_area_struct *vma,
		       struct list_head *to_kill,
		       struct to_kill **tkc)
{
	struct to_kill *tk;

	if (*tkc) {
		tk = *tkc;
		*tkc = NULL;
	} else {
		tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC);
		if (!tk) {
			pr_err("Memory failure: Out of memory while machine check handling\n");
			return;
		}
	}
	tk->addr = page_address_in_vma(p, vma);
	tk->addr_valid = 1;

	/*
	 * In theory we don't have to kill when the page was
	 * munmaped. But it could be also a mremap. Since that's
	 * likely very rare kill anyways just out of paranoia, but use
	 * a SIGKILL because the error is not contained anymore.
	 */
	if (tk->addr == -EFAULT) {
		pr_info("Memory failure: Unable to find user space address %lx in %s\n",
			page_to_pfn(p), tsk->comm);
		tk->addr_valid = 0;
	}
	get_task_struct(tsk);
	tk->tsk = tsk;
	list_add_tail(&tk->nd, to_kill);
}

Project: linux
File: memory-failure.c

int unpoison_memory(unsigned long pfn)
{
	struct page *page;
	struct page *p;
	int freeit = 0;
	unsigned int nr_pages;
	static DEFINE_RATELIMIT_STATE(unpoison_rs, DEFAULT_RATELIMIT_INTERVAL,
					DEFAULT_RATELIMIT_BURST);

	if (!pfn_valid(pfn))
		return -ENXIO;

	p = pfn_to_page(pfn);
	page = compound_head(p);

	if (!PageHWPoison(p)) {
		unpoison_pr_info("Unpoison: Page was already unpoisoned %#lx\n",
				 pfn, &unpoison_rs);
		return 0;
	}

	if (page_count(page) > 1) {
		unpoison_pr_info("Unpoison: Someone grabs the hwpoison page %#lx\n",
				 pfn, &unpoison_rs);
		return 0;
	}

	if (page_mapped(page)) {
		unpoison_pr_info("Unpoison: Someone maps the hwpoison page %#lx\n",
				 pfn, &unpoison_rs);
		return 0;
	}

	if (page_mapping(page)) {
		unpoison_pr_info("Unpoison: the hwpoison page has non-NULL mapping %#lx\n",
				 pfn, &unpoison_rs);
		return 0;
	}

	/*
	 * unpoison_memory() can encounter thp only when the thp is being
	 * worked by memory_failure() and the page lock is not held yet.
	 * In such case, we yield to memory_failure() and make unpoison fail.
	 */
	if (!PageHuge(page) && PageTransHuge(page)) {
		unpoison_pr_info("Unpoison: Memory failure is now running on %#lx\n",
				 pfn, &unpoison_rs);
		return 0;
	}

	nr_pages = 1 << compound_order(page);

	if (!get_hwpoison_page(p)) {
		/*
		 * Since HWPoisoned hugepage should have non-zero refcount,
		 * race between memory failure and unpoison seems to happen.
		 * In such case unpoison fails and memory failure runs
		 * to the end.
		 */
		if (PageHuge(page)) {
			unpoison_pr_info("Unpoison: Memory failure is now running on free hugepage %#lx\n",
					 pfn, &unpoison_rs);
			return 0;
		}
		if (TestClearPageHWPoison(p))
			num_poisoned_pages_dec();
		unpoison_pr_info("Unpoison: Software-unpoisoned free page %#lx\n",
				 pfn, &unpoison_rs);
		return 0;
	}

	lock_page(page);
	/*
	 * This test is racy because PG_hwpoison is set outside of page lock.
	 * That's acceptable because that won't trigger kernel panic. Instead,
	 * the PG_hwpoison page will be caught and isolated on the entrance to
	 * the free buddy page pool.
	 */
	if (TestClearPageHWPoison(page)) {
		unpoison_pr_info("Unpoison: Software-unpoisoned page %#lx\n",
				 pfn, &unpoison_rs);
		num_poisoned_pages_sub(nr_pages);
		freeit = 1;
		if (PageHuge(page))
			clear_page_hwpoison_huge_page(page);
	}
	unlock_page(page);

	put_hwpoison_page(page);
	if (freeit && !(pfn == my_zero_pfn(0) && page_count(p) == 1))
		put_hwpoison_page(page);

	return 0;
}

Project: linux
File: memory-failure.c

static int get_any_page(struct page *page, unsigned long pfn, int flags)
{
	int ret = __get_any_page(page, pfn, flags);

	if (ret == 1 && !PageHuge(page) && !PageLRU(page)) {
		/*
		 * Try to free it.
		 */
		put_hwpoison_page(page);
		shake_page(page, 1);

		/*
		 * Did it turn free?
		 */
		ret = __get_any_page(page, pfn, 0);
		if (ret == 1 && !PageLRU(page)) {
			/* Drop page reference which is from __get_any_page() */
			put_hwpoison_page(page);
			pr_info("soft_offline: %#lx: unknown non LRU page type %lx\n",
				pfn, page->flags);
			return -EIO;
		}
	}
	return ret;
}

Project: linux
File: memory-failure.c

static int me_huge_page(struct page *p, unsigned long pfn)
{
	int res = 0;
	struct page *hpage = compound_head(p);

	if (!PageHuge(hpage))
		return MF_DELAYED;

	/*
	 * We can safely recover from error on free or reserved (i.e.
	 * not in-use) hugepage by dequeuing it from freelist.
	 * To check whether a hugepage is in-use or not, we can't use
	 * page->lru because it can be used in other hugepage operations,
	 * such as __unmap_hugepage_range() and gather_surplus_pages().
	 * So instead we use page_mapping() and PageAnon().
	 */
	if (!(page_mapping(hpage) || PageAnon(hpage))) {
		res = dequeue_hwpoisoned_huge_page(hpage);
		if (!res)
			return MF_RECOVERED;
	}
	return MF_DELAYED;
}

Project: linux
File: memory-failure.c

static void memory_failure_work_func(struct work_struct *work)
{
	struct memory_failure_cpu *mf_cpu;
	struct memory_failure_entry entry = { 0, };
	unsigned long proc_flags;
	int gotten;

	mf_cpu = this_cpu_ptr(&memory_failure_cpu);
	for (;;) {
		spin_lock_irqsave(&mf_cpu->lock, proc_flags);
		gotten = kfifo_get(&mf_cpu->fifo, &entry);
		spin_unlock_irqrestore(&mf_cpu->lock, proc_flags);
		if (!gotten)
			break;
		if (entry.flags & MF_SOFT_OFFLINE)
			soft_offline_page(pfn_to_page(entry.pfn), entry.flags);
		else
			memory_failure(entry.pfn, entry.trapno, entry.flags);
	}
}

Project: linux
File: memory-failure.c

void shake_page(struct page *p, int access)
{
	if (!PageSlab(p)) {
		lru_add_drain_all();
		if (PageLRU(p))
			return;
		drain_all_pages(page_zone(p));
		if (PageLRU(p) || is_free_buddy_page(p))
			return;
	}

	/*
	 * Only call shrink_node_slabs here (which would also shrink
	 * other caches) if access is not potentially fatal.
	 */
	if (access)
		drop_slab_node(page_to_nid(p));
}

Project: linux
File: memory-failure.c

static int me_pagecache_clean(struct page *p, unsigned long pfn)
{
	int err;
	int ret = MF_FAILED;
	struct address_space *mapping;

	delete_from_lru_cache(p);

	/*
	 * For anonymous pages we're done the only reference left
	 * should be the one m_f() holds.
	 */
	if (PageAnon(p))
		return MF_RECOVERED;

	/*
	 * Now truncate the page in the page cache. This is really
	 * more like a "temporary hole punch"
	 * Don't do this for block devices when someone else
	 * has a reference, because it could be file system metadata
	 * and that's not safe to truncate.
	 */
	mapping = page_mapping(p);
	if (!mapping) {
		/*
		 * Page has been teared down in the meanwhile
		 */
		return MF_FAILED;
	}

	/*
	 * Truncation is a bit tricky. Enable it per file system for now.
	 *
	 * Open: to take i_mutex or not for this? Right now we don't.
	 */
	if (mapping->a_ops->error_remove_page) {
		err = mapping->a_ops->error_remove_page(mapping, p);
		if (err != 0) {
			pr_info("Memory failure: %#lx: Failed to punch page: %d\n",
				pfn, err);
		} else if (page_has_private(p) &&
				!try_to_release_page(p, GFP_NOIO)) {
			pr_info("Memory failure: %#lx: failed to release buffers\n",
				pfn);
		} else {
			ret = MF_RECOVERED;
		}
	} else {
		/*
		 * If the file system doesn't support it just invalidate
		 * This fails on dirty or anything with private pages
		 */
		if (invalidate_inode_page(p))
			ret = MF_RECOVERED;
		else
			pr_info("Memory failure: %#lx: Failed to invalidate\n",
				pfn);
	}
	return ret;
}

Project: linux
File: memory-failure.c

static int me_pagecache_dirty(struct page *p, unsigned long pfn)
{
	struct address_space *mapping = page_mapping(p);

	SetPageError(p);
	/* TBD: print more information about the file. */
	if (mapping) {
		/*
		 * IO error will be reported by write(), fsync(), etc.
		 * who check the mapping.
		 * This way the application knows that something went
		 * wrong with its dirty file data.
		 *
		 * There's one open issue:
		 *
		 * The EIO will be only reported on the next IO
		 * operation and then cleared through the IO map.
		 * Normally Linux has two mechanisms to pass IO error
		 * first through the AS_EIO flag in the address space
		 * and then through the PageError flag in the page.
		 * Since we drop pages on memory failure handling the
		 * only mechanism open to use is through AS_AIO.
		 *
		 * This has the disadvantage that it gets cleared on
		 * the first operation that returns an error, while
		 * the PageError bit is more sticky and only cleared
		 * when the page is reread or dropped.  If an
		 * application assumes it will always get error on
		 * fsync, but does other operations on the fd before
		 * and the page is dropped between then the error
		 * will not be properly reported.
		 *
		 * This can already happen even without hwpoisoned
		 * pages: first on metadata IO errors (which only
		 * report through AS_EIO) or when the page is dropped
		 * at the wrong time.
		 *
		 * So right now we assume that the application DTRT on
		 * the first EIO, but we're not worse than other parts
		 * of the kernel.
		 */
		mapping_set_error(mapping, EIO);
	}

	return me_pagecache_clean(p, pfn);
}

Project: linux
File: memory-failure.c

static int soft_offline_huge_page(struct page *page, int flags)
{
	int ret;
	unsigned long pfn = page_to_pfn(page);
	struct page *hpage = compound_head(page);
	LIST_HEAD(pagelist);

	/*
	 * This double-check of PageHWPoison is to avoid the race with
	 * memory_failure(). See also comment in __soft_offline_page().
	 */
	lock_page(hpage);
	if (PageHWPoison(hpage)) {
		unlock_page(hpage);
		put_hwpoison_page(hpage);
		pr_info("soft offline: %#lx hugepage already poisoned\n", pfn);
		return -EBUSY;
	}
	unlock_page(hpage);

	ret = isolate_huge_page(hpage, &pagelist);
	/*
	 * get_any_page() and isolate_huge_page() takes a refcount each,
	 * so need to drop one here.
	 */
	put_hwpoison_page(hpage);
	if (!ret) {
		pr_info("soft offline: %#lx hugepage failed to isolate\n", pfn);
		return -EBUSY;
	}

	ret = migrate_pages(&pagelist, new_page, NULL, MPOL_MF_MOVE_ALL,
				MIGRATE_SYNC, MR_MEMORY_FAILURE);
	if (ret) {
		pr_info("soft offline: %#lx: migration failed %d, type %lx\n",
			pfn, ret, page->flags);
		/*
		 * We know that soft_offline_huge_page() tries to migrate
		 * only one hugepage pointed to by hpage, so we need not
		 * run through the pagelist here.
		 */
		putback_active_hugepage(hpage);
		if (ret > 0)
			ret = -EIO;
	} else {
		/* overcommit hugetlb page will be freed to buddy */
		if (PageHuge(page)) {
			set_page_hwpoison_huge_page(hpage);
			dequeue_hwpoisoned_huge_page(hpage);
			num_poisoned_pages_add(1 << compound_order(hpage));
		} else {
			SetPageHWPoison(page);
			num_poisoned_pages_inc();
		}
	}
	return ret;
}

Project: linux
File: memory-failure.c

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;

	if (!sysctl_memory_failure_recovery)
		panic("Memory failure from trap %d on page %lx", trapno, pfn);

	if (!pfn_valid(pfn)) {
		pr_err("Memory failure: %#lx: memory outside kernel control\n",
			pfn);
		return -ENXIO;
	}

	p = pfn_to_page(pfn);
	orig_head = hpage = compound_head(p);
	if (TestSetPageHWPoison(p)) {
		pr_err("Memory failure: %#lx: already hardware poisoned\n",
			pfn);
		return 0;
	}

	/*
	 * Currently errors on hugetlbfs pages are measured in hugepage units,
	 * so nr_pages should be 1 << compound_order.  OTOH when errors are on
	 * transparent hugepages, they are supposed to be split and error
	 * measurement is done in normal page units.  So nr_pages should be one
	 * in this case.
	 */
	if (PageHuge(p))
		nr_pages = 1 << compound_order(hpage);
	else /* normal page or thp */
		nr_pages = 1;
	num_poisoned_pages_add(nr_pages);

	/*
	 * We need/can do nothing about count=0 pages.
	 * 1) it's a free page, and therefore in safe hand:
	 *    prep_new_page() will be the gate keeper.
	 * 2) it's a free hugepage, which is also safe:
	 *    an affected hugepage will be dequeued from hugepage freelist,
	 *    so there's no concern about reusing it ever after.
	 * 3) it's part of a non-compound high order page.
	 *    Implies some kernel user: cannot stop them from
	 *    R/W the page; let's pray that the page has been
	 *    used and will be freed some time later.
	 * In fact it's dangerous to directly bump up page count from 0,
	 * that may make page_freeze_refs()/page_unfreeze_refs() mismatch.
	 */
	if (!(flags & MF_COUNT_INCREASED) && !get_hwpoison_page(p)) {
		if (is_free_buddy_page(p)) {
			action_result(pfn, MF_MSG_BUDDY, MF_DELAYED);
			return 0;
		} else if (PageHuge(hpage)) {
			/*
			 * Check "filter hit" and "race with other subpage."
			 */
			lock_page(hpage);
			if (PageHWPoison(hpage)) {
				if ((hwpoison_filter(p) && TestClearPageHWPoison(p))
				    || (p != hpage && TestSetPageHWPoison(hpage))) {
					num_poisoned_pages_sub(nr_pages);
					unlock_page(hpage);
					return 0;
				}
			}
			set_page_hwpoison_huge_page(hpage);
			res = dequeue_hwpoisoned_huge_page(hpage);
			action_result(pfn, MF_MSG_FREE_HUGE,
				      res ? MF_IGNORED : MF_DELAYED);
			unlock_page(hpage);
			return res;
		} else {
			action_result(pfn, MF_MSG_KERNEL_HIGH_ORDER, MF_IGNORED);
			return -EBUSY;
		}
	}

	if (!PageHuge(p) && PageTransHuge(hpage)) {
		lock_page(p);
		if (!PageAnon(p) || unlikely(split_huge_page(p))) {
			unlock_page(p);
			if (!PageAnon(p))
				pr_err("Memory failure: %#lx: non anonymous thp\n",
					pfn);
			else
				pr_err("Memory failure: %#lx: thp split failed\n",
					pfn);
			if (TestClearPageHWPoison(p))
				num_poisoned_pages_sub(nr_pages);
			put_hwpoison_page(p);
			return -EBUSY;
		}
		unlock_page(p);
		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
	 * - to avoid races with __SetPageLocked()
	 * - to avoid races with __SetPageSlab*() (and more non-atomic ops)
	 * The check (unnecessarily) ignores LRU pages being isolated and
	 * walked by the page reclaim code, however that's not a big loss.
	 */
	if (!PageHuge(p)) {
		if (!PageLRU(p))
			shake_page(p, 0);
		if (!PageLRU(p)) {
			/*
			 * shake_page could have turned it free.
			 */
			if (is_free_buddy_page(p)) {
				if (flags & MF_COUNT_INCREASED)
					action_result(pfn, MF_MSG_BUDDY, MF_DELAYED);
				else
					action_result(pfn, MF_MSG_BUDDY_2ND,
						      MF_DELAYED);
				return 0;
			}
		}
	}

	lock_page(hpage);

	/*
	 * The page could have changed compound pages during the locking.
	 * If this happens just bail out.
	 */
	if (PageCompound(p) && compound_head(p) != orig_head) {
		action_result(pfn, MF_MSG_DIFFERENT_COMPOUND, MF_IGNORED);
		res = -EBUSY;
		goto out;
	}

	/*
	 * We use page flags to determine what action should be taken, but
	 * the flags can be modified by the error containment action.  One
	 * example is an mlocked page, where PG_mlocked is cleared by
	 * page_remove_rmap() in try_to_unmap_one(). So to determine page status
	 * correctly, we save a copy of the page flags at this time.
	 */
	page_flags = p->flags;

	/*
	 * unpoison always clear PG_hwpoison inside page lock
	 */
	if (!PageHWPoison(p)) {
		pr_err("Memory failure: %#lx: just unpoisoned\n", pfn);
		num_poisoned_pages_sub(nr_pages);
		unlock_page(hpage);
		put_hwpoison_page(hpage);
		return 0;
	}
	if (hwpoison_filter(p)) {
		if (TestClearPageHWPoison(p))
			num_poisoned_pages_sub(nr_pages);
		unlock_page(hpage);
		put_hwpoison_page(hpage);
		return 0;
	}

	if (!PageHuge(p) && !PageTransTail(p) && !PageLRU(p))
		goto identify_page_state;

	/*
	 * For error on the tail page, we should set PG_hwpoison
	 * on the head page to show that the hugepage is hwpoisoned
	 */
	if (PageHuge(p) && PageTail(p) && TestSetPageHWPoison(hpage)) {
		action_result(pfn, MF_MSG_POISONED_HUGE, MF_IGNORED);
		unlock_page(hpage);
		put_hwpoison_page(hpage);
		return 0;
	}
	/*
	 * Set PG_hwpoison on all pages in an error hugepage,
	 * because containment is done in hugepage unit for now.
	 * Since we have done TestSetPageHWPoison() for the head page with
	 * page lock held, we can safely set PG_hwpoison bits on tail pages.
	 */
	if (PageHuge(p))
		set_page_hwpoison_huge_page(hpage);

	/*
	 * It's very difficult to mess with pages currently under IO
	 * and in many cases impossible, so we just avoid it here.
	 */
	wait_on_page_writeback(p);

	/*
	 * Now take care of user space mappings.
	 * Abort on fail: __delete_from_page_cache() assumes unmapped page.
	 *
	 * When the raw error page is thp tail page, hpage points to the raw
	 * page after thp split.
	 */
	if (hwpoison_user_mappings(p, pfn, trapno, flags, &hpage)
	    != SWAP_SUCCESS) {
		action_result(pfn, MF_MSG_UNMAP_FAILED, MF_IGNORED);
		res = -EBUSY;
		goto out;
	}

	/*
	 * Torn down by someone else?
	 */
	if (PageLRU(p) && !PageSwapCache(p) && p->mapping == NULL) {
		action_result(pfn, MF_MSG_TRUNCATED_LRU, MF_IGNORED);
		res = -EBUSY;
		goto out;
	}

identify_page_state:
	res = -EBUSY;
	/*
	 * The first check uses the current page flags which may not have any
	 * relevant information. The second check with the saved page flagss is
	 * carried out only if the first check can't determine the page status.
	 */
	for (ps = error_states;; ps++)
		if ((p->flags & ps->mask) == ps->res)
			break;

	page_flags |= (p->flags & (1UL << PG_dirty));

	if (!ps->mask)
		for (ps = error_states;; ps++)
			if ((page_flags & ps->mask) == ps->res)
				break;
	res = page_action(ps, p, pfn);
out:
	unlock_page(hpage);
	return res;
}

Project: linux
File: memory-failure.c

static int __soft_offline_page(struct page *page, int flags)
{
	int ret;
	unsigned long pfn = page_to_pfn(page);

	/*
	 * Check PageHWPoison again inside page lock because PageHWPoison
	 * is set by memory_failure() outside page lock. Note that
	 * memory_failure() also double-checks PageHWPoison inside page lock,
	 * so there's no race between soft_offline_page() and memory_failure().
	 */
	lock_page(page);
	wait_on_page_writeback(page);
	if (PageHWPoison(page)) {
		unlock_page(page);
		put_hwpoison_page(page);
		pr_info("soft offline: %#lx page already poisoned\n", pfn);
		return -EBUSY;
	}
	/*
	 * Try to invalidate first. This should work for
	 * non dirty unmapped page cache pages.
	 */
	ret = invalidate_inode_page(page);
	unlock_page(page);
	/*
	 * RED-PEN would be better to keep it isolated here, but we
	 * would need to fix isolation locking first.
	 */
	if (ret == 1) {
		put_hwpoison_page(page);
		pr_info("soft_offline: %#lx: invalidated\n", pfn);
		SetPageHWPoison(page);
		num_poisoned_pages_inc();
		return 0;
	}

	/*
	 * Simple invalidation didn't work.
	 * Try to migrate to a new page instead. migrate.c
	 * handles a large number of cases for us.
	 */
	ret = isolate_lru_page(page);
	/*
	 * Drop page reference which is came from get_any_page()
	 * successful isolate_lru_page() already took another one.
	 */
	put_hwpoison_page(page);
	if (!ret) {
		LIST_HEAD(pagelist);
		inc_node_page_state(page, NR_ISOLATED_ANON +
					page_is_file_cache(page));
		list_add(&page->lru, &pagelist);
		ret = migrate_pages(&pagelist, new_page, NULL, MPOL_MF_MOVE_ALL,
					MIGRATE_SYNC, MR_MEMORY_FAILURE);
		if (ret) {
			if (!list_empty(&pagelist)) {
				list_del(&page->lru);
				dec_node_page_state(page, NR_ISOLATED_ANON +
						page_is_file_cache(page));
				putback_lru_page(page);
			}

			pr_info("soft offline: %#lx: migration failed %d, type %lx\n",
				pfn, ret, page->flags);
			if (ret > 0)
				ret = -EIO;
		}
	} else {
		pr_info("soft offline: %#lx: isolation failed: %d, page count %d, type %lx\n",
			pfn, ret, page_count(page), page->flags);
	}
	return ret;
}

Project: linux
File: memory-failure.c

static struct page *new_page(struct page *p, unsigned long private, int **x)
{
	int nid = page_to_nid(p);
	if (PageHuge(p))
		return alloc_huge_page_node(page_hstate(compound_head(p)),
						   nid);
	else
		return __alloc_pages_node(nid, GFP_HIGHUSER_MOVABLE, 0);
}

Project: linux
File: memory-failure.c

void memory_failure_queue(unsigned long pfn, int trapno, int flags)
{
	struct memory_failure_cpu *mf_cpu;
	unsigned long proc_flags;
	struct memory_failure_entry entry = {
		.pfn =		pfn,
		.trapno =	trapno,
		.flags =	flags,
	};

	mf_cpu = &get_cpu_var(memory_failure_cpu);
	spin_lock_irqsave(&mf_cpu->lock, proc_flags);
	if (kfifo_put(&mf_cpu->fifo, entry))
		schedule_work_on(smp_processor_id(), &mf_cpu->work);
	else
		pr_err("Memory failure: buffer overflow when queuing memory failure at %#lx\n",
		       pfn);
	spin_unlock_irqrestore(&mf_cpu->lock, proc_flags);
	put_cpu_var(memory_failure_cpu);
}

Project: linux
File: memory-failure.c

static void kill_procs(struct list_head *to_kill, int forcekill, int trapno,
			  int fail, struct page *page, unsigned long pfn,
			  int flags)
{
	struct to_kill *tk, *next;

	list_for_each_entry_safe (tk, next, to_kill, nd) {
		if (forcekill) {
			/*
			 * In case something went wrong with munmapping
			 * make sure the process doesn't catch the
			 * signal and then access the memory. Just kill it.
			 */
			if (fail || tk->addr_valid == 0) {
				pr_err("Memory failure: %#lx: forcibly killing %s:%d because of failure to unmap corrupted page\n",
				       pfn, tk->tsk->comm, tk->tsk->pid);
				force_sig(SIGKILL, tk->tsk);
			}

			/*
			 * In theory the process could have mapped
			 * something else on the address in-between. We could
			 * check for that, but we need to tell the
			 * process anyways.
			 */
			else if (kill_proc(tk->tsk, tk->addr, trapno,
					      pfn, page, flags) < 0)
				pr_err("Memory failure: %#lx: Cannot send advisory machine check signal to %s:%d\n",
				       pfn, tk->tsk->comm, tk->tsk->pid);
		}
		put_task_struct(tk->tsk);
		kfree(tk);
	}
}

Project: linux
File: memory-failure.c

static int kill_proc(struct task_struct *t, unsigned long addr, int trapno,
			unsigned long pfn, struct page *page, int flags)
{
	struct siginfo si;
	int ret;

	pr_err("Memory failure: %#lx: Killing %s:%d due to hardware memory corruption\n",
		pfn, t->comm, t->pid);
	si.si_signo = SIGBUS;
	si.si_errno = 0;
	si.si_addr = (void *)addr;
#ifdef __ARCH_SI_TRAPNO
	si.si_trapno = trapno;
#endif
	si.si_addr_lsb = compound_order(compound_head(page)) + PAGE_SHIFT;

	if ((flags & MF_ACTION_REQUIRED) && t->mm == current->mm) {
		si.si_code = BUS_MCEERR_AR;
		ret = force_sig_info(SIGBUS, &si, current);
	} else {
		/*
		 * Don't use force here, it's convenient if the signal
		 * can be temporarily blocked.
		 * This could cause a loop when the user sets SIGBUS
		 * to SIG_IGN, but hopefully no one will do that?
		 */
		si.si_code = BUS_MCEERR_AO;
		ret = send_sig_info(SIGBUS, &si, t);  /* synchronous? */
	}
	if (ret < 0)
		pr_info("Memory failure: Error sending signal to %s:%d: %d\n",
			t->comm, t->pid, ret);
	return ret;
}

Project: linux
File: memory-failure.c

int soft_offline_page(struct page *page, int flags)
{
	int ret;
	unsigned long pfn = page_to_pfn(page);

	if (PageHWPoison(page)) {
		pr_info("soft offline: %#lx page already poisoned\n", pfn);
		if (flags & MF_COUNT_INCREASED)
			put_hwpoison_page(page);
		return -EBUSY;
	}

	get_online_mems();
	ret = get_any_page(page, pfn, flags);
	put_online_mems();

	if (ret > 0)
		ret = soft_offline_in_use_page(page, flags);
	else if (ret == 0)
		soft_offline_free_page(page);

	return ret;
}