[RFC PATCH 1/7] Fix khugepaged's request size in collapse_file()

David Howells
2020-09-01T16:28:45Z

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 <dhowells@redhat.com>
cc: Matthew Wilcox <willy@infradead.org>
cc: Song Liu <songliubraving@fb.com>
---

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);