From: Song Liu <songliubraving@fb.com>
Date: Mon, 23 Sep 2019 22:37:47 +0000 (-0700)
Subject: filemap: check compound_head(page)->mapping in pagecache_get_page()
X-Git-Tag: v5.15~5430^2~37
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=31895438e702f48e25b7aa6d88f9c97c795c79c7;p=platform%2Fkernel%2Flinux-starfive.git

filemap: check compound_head(page)->mapping in pagecache_get_page()

Similar to previous patch, pagecache_get_page() avoids race condition with
truncate by checking page->mapping == mapping.  This does not work for
compound pages.  This patch let it check compound_head(page)->mapping
instead.

Link: http://lkml.kernel.org/r/20190801184244.3169074-3-songliubraving@fb.com
Signed-off-by: Song Liu <songliubraving@fb.com>
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: William Kucharski <william.kucharski@oracle.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/mm/filemap.c b/mm/filemap.c
index fc7818b..0b30110 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1647,7 +1647,7 @@ repeat:
 		}
 
 		/* Has the page been truncated? */
-		if (unlikely(page->mapping != mapping)) {
+		if (unlikely(compound_head(page)->mapping != mapping)) {
 			unlock_page(page);
 			put_page(page);
 			goto repeat;