[Hirsute][PATCH 1/2] Revert "mm: filemap: check if THP has hwpoisoned subpage for PMD page fault"

[Kamal Mostafa]

BugLink: https://bugs.launchpad.net/bugs/1956984

This reverts commit 327aa2137d989f278ece7e8e31c218dfb3416c35.

This Ubuntu backport is bogus (hunk applied to routine finish_fault()
should have been applied to do_set_pmd()).  To be replaced by corrected
backport.

Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 include/linux/page-flags.h | 23 -----------------------
 mm/huge_memory.c           |  2 --
 mm/memory-failure.c        | 14 --------------
 mm/memory.c                |  9 ---------
 mm/page_alloc.c            |  4 +---
 5 files changed, 1 insertion(+), 51 deletions(-)

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 9b85f492bf56..ec5d0290e0ee 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -168,15 +168,6 @@ enum pageflags {
 	/* Compound pages. Stored in first tail page's flags */
 	PG_double_map = PG_workingset,
 
-#ifdef CONFIG_MEMORY_FAILURE
-	/*
-	 * Compound pages. Stored in first tail page's flags.
-	 * Indicates that at least one subpage is hwpoisoned in the
-	 * THP.
-	 */
-	PG_has_hwpoisoned = PG_mappedtodisk,
-#endif
-
 	/* non-lru isolated movable page */
 	PG_isolated = PG_reclaim,
 
@@ -709,20 +700,6 @@ PAGEFLAG_FALSE(DoubleMap)
 	TESTSCFLAG_FALSE(DoubleMap)
 #endif
 
-#if defined(CONFIG_MEMORY_FAILURE) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
-/*
- * PageHasHWPoisoned indicates that at least one subpage is hwpoisoned in the
- * compound page.
- *
- * This flag is set by hwpoison handler.  Cleared by THP split or free page.
- */
-PAGEFLAG(HasHWPoisoned, has_hwpoisoned, PF_SECOND)
-	TESTSCFLAG(HasHWPoisoned, has_hwpoisoned, PF_SECOND)
-#else
-PAGEFLAG_FALSE(HasHWPoisoned)
-	TESTSCFLAG_FALSE(HasHWPoisoned)
-#endif
-
 /*
  * For pages that are never mapped to userspace (and aren't PageSlab),
  * page_type may be used.  Because it is initialised to -1, we invert the
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index eab1ed3e9675..f735eb3755db 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2499,8 +2499,6 @@ static void __split_huge_page(struct page *page, struct list_head *list,
 	/* lock lru list/PageCompound, ref freezed by page_ref_freeze */
 	lruvec = lock_page_lruvec(head);
 
-	ClearPageHasHWPoisoned(head);
-
 	for (i = nr - 1; i >= 1; i--) {
 		__split_huge_page_tail(head, i, lruvec, list);
 		/* Some pages can be beyond i_size: drop them from page cache */
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 9890f822d692..5562b00db788 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1474,20 +1474,6 @@ int memory_failure(unsigned long pfn, int flags)
 	}
 
 	if (PageTransHuge(hpage)) {
-		/*
-		 * The flag must be set after the refcount is bumped
-		 * otherwise it may race with THP split.
-		 * And the flag can't be set in get_hwpoison_page() since
-		 * it is called by soft offline too and it is just called
-		 * for !MF_COUNT_INCREASE.  So here seems to be the best
-		 * place.
-		 *
-		 * Don't need care about the above error handling paths for
-		 * get_hwpoison_page() since they handle either free page
-		 * or unhandlable page.  The refcount is bumped iff the
-		 * page is a valid handlable page.
-		 */
-		SetPageHasHWPoisoned(hpage);
 		if (try_to_split_thp_page(p, "Memory Failure") < 0) {
 			action_result(pfn, MF_MSG_UNSPLIT_THP, MF_IGNORED);
 			res = -EBUSY;
diff --git a/mm/memory.c b/mm/memory.c
index c5c4edd74b5c..f7d2fc871423 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3923,15 +3923,6 @@ vm_fault_t finish_fault(struct vm_fault *vmf)
 	else
 		page = vmf->page;
 
-	/*
-	 * Just backoff if any subpage of a THP is corrupted otherwise
-	 * the corrupted page may mapped by PMD silently to escape the
-	 * check.  This kind of THP just can be PTE mapped.  Access to
-	 * the corrupted subpage should trigger SIGBUS as expected.
-	 */
-	if (unlikely(PageHasHWPoisoned(page)))
-		return ret;
-
 	/*
 	 * check even for read faults because we might have lost our CoWed
 	 * page
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index a65a76a7fb5a..132c85fa0913 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1236,10 +1236,8 @@ static __always_inline bool free_pages_prepare(struct page *page,
 
 		VM_BUG_ON_PAGE(compound && compound_order(page) != order, page);
 
-		if (compound) {
+		if (compound)
 			ClearPageDoubleMap(page);
-			ClearPageHasHWPoisoned(page);
-		}
 		for (i = 1; i < (1 << order); i++) {
 			if (compound)
 				bad += free_tail_pages_check(page, page + i);
-- 
2.17.1