From: Song Liu <songliubraving@xxxxxx> Subject: 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@xxxxxx Signed-off-by: Song Liu <songliubraving@xxxxxx> Suggested-by: Johannes Weiner <hannes@xxxxxxxxxxx> Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Hillf Danton <hdanton@xxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Rik van Riel <riel@xxxxxxxxxxx> Cc: William Kucharski <william.kucharski@xxxxxxxxxx> Cc: Oleg Nesterov <oleg@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/filemap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/mm/filemap.c~filemap-check-compound_headpage-mapping-in-pagecache_get_page +++ a/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; _
