linux-kernel - [PATCH v10 1/7] filemap: check compound_head(page)->mapping in filemap

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Message-ID: <20190801184244.3169074-2-songliubraving@fb.com>
Date:   Thu, 1 Aug 2019 11:42:38 -0700
From:   Song Liu <songliubraving@...com>
To:     <linux-mm@...ck.org>, <linux-fsdevel@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
CC:     <matthew.wilcox@...cle.com>, <kirill.shutemov@...ux.intel.com>,
        <kernel-team@...com>, <william.kucharski@...cle.com>,
        <akpm@...ux-foundation.org>, <hdanton@...a.com>,
        Song Liu <songliubraving@...com>
Subject: [PATCH v10 1/7] filemap: check compound_head(page)->mapping in filemap_fault()

Currently, filemap_fault() 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.

Acked-by: Rik van Riel <riel@...riel.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Acked-by: Johannes Weiner <hannes@...xchg.org>
Signed-off-by: Song Liu <songliubraving@...com>
---
 mm/filemap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 7161fb937e78..d0bd9e585c2f 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2537,7 +2537,7 @@ vm_fault_t filemap_fault(struct vm_fault *vmf)
 		goto out_retry;
 
 	/* Did it get truncated? */
-	if (unlikely(page->mapping != mapping)) {
+	if (unlikely(compound_head(page)->mapping != mapping)) {
 		unlock_page(page);
 		put_page(page);
 		goto retry_find;
-- 
2.17.1