The patch titled
Subject: mm/thp: fix deadlock in collapse_file()
has been added to the -mm tree. Its filename is
mmthp-recheck-each-page-before-collapsing-file-thp-v4-fix.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mmthp-recheck-each-page-before-collapsing-file-thp-v4-fix.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mmthp-recheck-each-page-before-collapsing-file-thp-v4-fix.patch
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------------------------------------------------------
From: Song Liu <songliubraving@xxxxxx>
Subject: mm/thp: fix deadlock in collapse_file()
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.
Link: http://lkml.kernel.org/r/20191028221414.3685035-1-songliubraving@xxxxxx
Signed-off-by: Song Liu <songliubraving@xxxxxx>
Reported-by: syzbot+efb9e48b9fbdc49bb34a@xxxxxxxxxxxxxxxxxxxxxxxxx
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: William Kucharski <william.kucharski@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/khugepaged.c | 10 +---------
1 file changed, 1 insertion(+), 9 deletions(-)
--- a/mm/khugepaged.c~mmthp-recheck-each-page-before-collapsing-file-thp-v4-fix
+++ a/mm/khugepaged.c
@@ -1640,16 +1640,8 @@ static void collapse_file(struct mm_stru
/*
* 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;
}
_
Patches currently in -mm which might be from songliubraving@xxxxxx are
mmthp-recheck-each-page-before-collapsing-file-thp.patch
mmthp-recheck-each-page-before-collapsing-file-thp-v4.patch
mmthp-recheck-each-page-before-collapsing-file-thp-v4-fix.patch
