[PATCH 5.4 127/129] mm/khugepaged.c: fix khugepageds request size in collapse_file

[Greg Kroah-Hartman]

From: David Howells <dhowells@xxxxxxxxxx>

commit e5a59d308f52bb0052af5790c22173651b187465 upstream.

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: 99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shmem) FS")
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Reviewed-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Acked-by: Song Liu <songliubraving@xxxxxx>
Acked-by: Yang Shi <shy828301@xxxxxxxxx>
Acked-by: Pankaj Gupta <pankaj.gupta.linux@xxxxxxxxx>
Cc: Eric Biggers <ebiggers@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/20200903140844.14194-2-willy@xxxxxxxxxxxxx
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 mm/khugepaged.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1592,7 +1592,7 @@ static void collapse_file(struct mm_stru
 				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);