[RFC PATCH 1/6] Fix khugepaged's request size in collapse_file() [ver #2]

[David Howells]

collapse_file() in khugepaged passes PAGE_SIZE as the number of pages to be
read ahead to page_cache_sync_readahead().  It seems this was expressed as a
number of bytes rather than a number of pages.

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 <dhowe...@redhat.com>
Acked-by: Song Liu <songliubrav...@fb.com>
Reviewed-by: Matthew Wilcox (Oracle) <wi...@infradead.org>
---

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

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 6d199c353281..f2d243077b74 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1706,7 +1706,7 @@ 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);