From: Song Liu <songliubraving@fb.com>
To: <linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>,
<akpm@linux-foundation.org>
Cc: <matthew.wilcox@oracle.com>, <kernel-team@fb.com>,
<william.kucharski@oracle.com>, <kirill.shutemov@linux.intel.com>,
Song Liu <songliubraving@fb.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Hugh Dickins <hughd@google.com>
Subject: [PATCH] mm/thp: fix deadlock in collapse_file()
Date: Mon, 28 Oct 2019 15:14:14 -0700 [thread overview]
Message-ID: <20191028221414.3685035-1-songliubraving@fb.com> (raw)
As syzbot reported, we cannot call filemap_flush() with the page locked.
Remove the filemap_flush() as it is not required. khugepaged would just
wait until the page is flushed naturally.
Reported-by: syzbot+efb9e48b9fbdc49bb34a@syzkaller.appspotmail.com
Fixes: 9d840e58caa0 ("mmthp-recheck-each-page-before-collapsing-file-thp-v4")
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: William Kucharski <william.kucharski@oracle.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Song Liu <songliubraving@fb.com>
---
mm/khugepaged.c | 10 +---------
1 file changed, 1 insertion(+), 9 deletions(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index cd480dce92c6..3ec5333ae94d 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1640,16 +1640,8 @@ static void collapse_file(struct mm_struct *mm,
/*
* khugepaged only works on read-only fd, so this
* page is dirty because it hasn't been flushed
- * since first write. There won't be new dirty
- * pages.
- *
- * Trigger async flush here and hope the writeback
- * is done when khugepaged revisits this page.
- *
- * This is a one-off situation. We are not forcing
- * writeback in loop.
+ * since first write.
*/
- filemap_flush(mapping);
result = SCAN_FAIL;
goto out_unlock;
}
--
2.17.1
reply other threads:[~2019-10-28 22:14 UTC|newest]
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