Merge branch 'akpm' (patches from Andrew)

Merge yet more updates from Andrew Morton:

 - the rest of MM

 - various misc fixes and tweaks

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (22 commits)
  mm: Change return type int to vm_fault_t for fault handlers
  lib/fonts: convert comments to utf-8
  s390: ebcdic: convert comments to UTF-8
  treewide: convert ISO_8859-1 text comments to utf-8
  drivers/gpu/drm/gma500/: change return type to vm_fault_t
  docs/core-api: mm-api: add section about GFP flags
  docs/mm: make GFP flags descriptions usable as kernel-doc
  docs/core-api: split memory management API to a separate file
  docs/core-api: move *{str,mem}dup* to "String Manipulation"
  docs/core-api: kill trailing whitespace in kernel-api.rst
  mm/util: add kernel-doc for kvfree
  mm/util: make strndup_user description a kernel-doc comment
  fs/proc/vmcore.c: hide vmcoredd_mmap_dumps() for nommu builds
  treewide: correct "differenciate" and "instanciate" typos
  fs/afs: use new return type vm_fault_t
  drivers/hwtracing/intel_th/msu.c: change return type to vm_fault_t
  mm: soft-offline: close the race against page allocation
  mm: fix race on soft-offlining free huge pages
  namei: allow restricted O_CREAT of FIFOs and regular files
  hfs: prevent crash on exit from failed search
  ...

1 files changed, 35 insertions, 9 deletions

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index c83a1746812f..192d0bbfc9ea 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -57,6 +57,7 @@
 #include <linux/mm_inline.h>
 #include <linux/kfifo.h>
 #include <linux/ratelimit.h>
+#include <linux/page-isolation.h>
 #include "internal.h"
 #include "ras/ras_event.h"
 
@@ -1598,8 +1599,18 @@ static int soft_offline_huge_page(struct page *page, int flags)
 		if (ret > 0)
 			ret = -EIO;
 	} else {
-		if (PageHuge(page))
-			dissolve_free_huge_page(page);
+		/*
+		 * We set PG_hwpoison only when the migration source hugepage
+		 * was successfully dissolved, because otherwise hwpoisoned
+		 * hugepage remains on free hugepage list, then userspace will
+		 * find it as SIGBUS by allocation failure. That's not expected
+		 * in soft-offlining.
+		 */
+		ret = dissolve_free_huge_page(page);
+		if (!ret) {
+			if (set_hwpoison_free_buddy_page(page))
+				num_poisoned_pages_inc();
+		}
 	}
 	return ret;
 }
@@ -1687,6 +1698,7 @@ static int __soft_offline_page(struct page *page, int flags)
 static int soft_offline_in_use_page(struct page *page, int flags)
 {
 	int ret;
+	int mt;
 	struct page *hpage = compound_head(page);
 
 	if (!PageHuge(page) && PageTransHuge(hpage)) {
@@ -1705,23 +1717,37 @@ static int soft_offline_in_use_page(struct page *page, int flags)
 		put_hwpoison_page(hpage);
 	}
 
+	/*
+	 * Setting MIGRATE_ISOLATE here ensures that the page will be linked
+	 * to free list immediately (not via pcplist) when released after
+	 * successful page migration. Otherwise we can't guarantee that the
+	 * page is really free after put_page() returns, so
+	 * set_hwpoison_free_buddy_page() highly likely fails.
+	 */
+	mt = get_pageblock_migratetype(page);
+	set_pageblock_migratetype(page, MIGRATE_ISOLATE);
 	if (PageHuge(page))
 		ret = soft_offline_huge_page(page, flags);
 	else
 		ret = __soft_offline_page(page, flags);
-
+	set_pageblock_migratetype(page, mt);
 	return ret;
 }
 
-static void soft_offline_free_page(struct page *page)
+static int soft_offline_free_page(struct page *page)
 {
+	int rc = 0;
 	struct page *head = compound_head(page);
 
-	if (!TestSetPageHWPoison(head)) {
-		num_poisoned_pages_inc();
-		if (PageHuge(head))
-			dissolve_free_huge_page(page);
+	if (PageHuge(head))
+		rc = dissolve_free_huge_page(page);
+	if (!rc) {
+		if (set_hwpoison_free_buddy_page(page))
+			num_poisoned_pages_inc();
+		else
+			rc = -EBUSY;
 	}
+	return rc;
 }
 
 /**
@@ -1765,7 +1791,7 @@ int soft_offline_page(struct page *page, int flags)
 	if (ret > 0)
 		ret = soft_offline_in_use_page(page, flags);
 	else if (ret == 0)
-		soft_offline_free_page(page);
+		ret = soft_offline_free_page(page);
 
 	return ret;
 }