mm/khugepaged.c: fix khugepaged's request size in collapse_file

collapse_file() in khugepaged passes PAGE_SIZE as the number of pages to
be read to page_cache_sync_readahead().  The intent was probably to read
a single page.  Fix it to use the number of pages to the end of the
window instead.

Fixes: 21abde3434f6 ("mm,thp: add read-only THP support for (non-shmem) FS")
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: Yang Shi <shy828301@gmail.com>
Acked-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Eric Biggers <ebiggers@google.com>
Link: https://lkml.kernel.org/r/20200903140844.14194-2-willy@infradead.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index e749e568e1eabc9367c8c731149dfd9473aeadf4..cfa0dba5fd3bc3b6b252acad3720d403b8ceea71 100644 (file)
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1709,7 +1709,7 @@ static void collapse_file(struct mm_struct *mm,
                                xas_unlock_irq(&xas);
                                page_cache_sync_readahead(mapping, &file->f_ra,
                                                          file, index,
-                                                         PAGE_SIZE);
+                                                         end - index);
                                /* drain pagevecs to help isolate_lru_page() */
                                lru_add_drain();
                                page = find_lock_page(mapping, index);