mm: rmap: make try_to_unmap() void function

Currently try_to_unmap() return bool value by checking page_mapcount(),
however this may return false positive since page_mapcount() doesn't check
all subpages of compound page.  The total_mapcount() could be used
instead, but its cost is higher since it traverses all subpages.

Actually the most callers of try_to_unmap() don't care about the return
value at all.  So just need check if page is still mapped by page_mapped()
when necessary.  And page_mapped() does bail out early when it finds
mapped subpage.

Link: https://lkml.kernel.org/r/bb27e3fe-6036-b637-5086-272befbfe3da@google.com
Suggested-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Yang Shi <shy828301@gmail.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jue Wang <juew@google.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Wang Yugui <wangyugui@e16-tech.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 7 insertions, 8 deletions

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 9d2d31ffe8a4..419d92b3225d 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1269,7 +1269,7 @@ static bool hwpoison_user_mappings(struct page *p, unsigned long pfn,
 	enum ttu_flags ttu = TTU_IGNORE_MLOCK;
 	struct address_space *mapping;
 	LIST_HEAD(tokill);
-	bool unmap_success = true;
+	bool unmap_success;
 	int kill = 1, forcekill;
 	struct page *hpage = *hpagep;
 	bool mlocked = PageMlocked(hpage);
@@ -1332,7 +1332,7 @@ static bool hwpoison_user_mappings(struct page *p, unsigned long pfn,
 		collect_procs(hpage, &tokill, flags & MF_ACTION_REQUIRED);
 
 	if (!PageHuge(hpage)) {
-		unmap_success = try_to_unmap(hpage, ttu);
+		try_to_unmap(hpage, ttu);
 	} else {
 		if (!PageAnon(hpage)) {
 			/*
@@ -1344,17 +1344,16 @@ static bool hwpoison_user_mappings(struct page *p, unsigned long pfn,
 			 */
 			mapping = hugetlb_page_mapping_lock_write(hpage);
 			if (mapping) {
-				unmap_success = try_to_unmap(hpage,
-						     ttu|TTU_RMAP_LOCKED);
+				try_to_unmap(hpage, ttu|TTU_RMAP_LOCKED);
 				i_mmap_unlock_write(mapping);
-			} else {
+			} else
 				pr_info("Memory failure: %#lx: could not lock mapping for mapped huge page\n", pfn);
-				unmap_success = false;
-			}
 		} else {
-			unmap_success = try_to_unmap(hpage, ttu);
+			try_to_unmap(hpage, ttu);
 		}
 	}
+
+	unmap_success = !page_mapped(hpage);
 	if (!unmap_success)
 		pr_err("Memory failure: %#lx: failed to unmap page (mapcount=%d)\n",
 		       pfn, page_mapcount(hpage));