mm, hwpoison: fix condition in free hugetlb page path

mainline inclusion
from mainline-v5.16-rc7
commit e37e7b0b
category: bugfix
bugzilla: https://e.gitee.com/open_euler/issues/list?issue=I4SJ2V
CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e37e7b0b3bd52ec4f8ab71b027bcec08f57f1b3b

--------------------------------

When a memory error hits a tail page of a free hugepage,
__page_handle_poison() is expected to be called to isolate the error in
4kB unit, but it's not called due to the outdated if-condition in
memory_failure_hugetlb().  This loses the chance to isolate the error in
the finer unit, so it's not optimal.  Drop the condition.

This "(p != head && TestSetPageHWPoison(head)" condition is based on the
old semantics of PageHWPoison on hugepage (where PG_hwpoison flag was
set on the subpage), so it's not necessray any more.  By getting to set
PG_hwpoison on head page for hugepages, concurrent error events on
different subpages in a single hugepage can be prevented by
TestSetPageHWPoison(head) at the beginning of memory_failure_hugetlb().
So dropping the condition should not reopen the race window originally
mentioned in commit b985194c ("hwpoison, hugetlb:
lock_page/unlock_page does not match for handling a free hugepage")

[naoya.horiguchi@linux.dev: fix "HardwareCorrupted" counter]
  Link: https://lkml.kernel.org/r/20211220084851.GA1460264@u2004

Link: https://lkml.kernel.org/r/20211210110208.879740-1-naoya.horiguchi@linux.devSigned-off-by: NNaoya Horiguchi <naoya.horiguchi@nec.com>
Reported-by: NFei Luo <luofei@unicloud.com>
Reviewed-by: NMike Kravetz <mike.kravetz@oracle.com>
Cc: <stable@vger.kernel.org>	[5.14+]
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NBin Wang <wangbin224@huawei.com>
Reviewed-by: Nluo chunsheng <luochunsheng@huawei.com>
Reviewed-by: NKefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

mm/memory-failure.c

@@ -1163,17 +1163,12 @@ static int memory_failure_hugetlb(unsigned long pfn, int flags)
 	num_poisoned_pages_inc();
 
 	if (!(flags & MF_COUNT_INCREASED) && !get_hwpoison_page(p)) {
-		/*
-		 * Check "filter hit" and "race with other subpage."
-		 */
 		lock_page(head);
-		if (PageHWPoison(head)) {
-			if ((hwpoison_filter(p) && TestClearPageHWPoison(p))
-			    || (p != head && TestSetPageHWPoison(head))) {
+		if (hwpoison_filter(p)) {
+			if (TestClearPageHWPoison(head))
 				num_poisoned_pages_dec();
-				unlock_page(head);
-				return 0;
-			}
+			unlock_page(head);
+			return 0;
 		}
 		unlock_page(head);
 		dissolve_free_huge_page(p);