swapfile: change discard pgoff_t to sector_t

Change pgoff_t nr_blocks in discard_swap() and discard_swap_cluster() to
sector_t: given the constraints on swap offsets (in particular, the 5 bits
of swap type accommodated in the same unsigned long), pgoff_t was actually
safe as is, but it certainly looked worrying when shifted left.

[akpm@linux-foundation.org: fix shift overflow]
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: Joern Engel <joern@logfs.org>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Donjun Shin <djshin90@gmail.com>
Cc: Tejun Heo <teheo@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 763210732b5f..6a078557306a 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -96,7 +96,7 @@ static int discard_swap(struct swap_info_struct *si)
 
         list_for_each_entry(se, &si->extent_list, list) {
                 sector_t start_block = se->start_block << (PAGE_SHIFT - 9);
-                pgoff_t nr_blocks = se->nr_pages << (PAGE_SHIFT - 9);
+                sector_t nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9);
 
                 if (se->start_page == 0) {
                         /* Do not discard the swap header page! */
@@ -133,7 +133,7 @@ static void discard_swap_cluster(struct swap_info_struct *si,
                     start_page < se->start_page + se->nr_pages) {
                         pgoff_t offset = start_page - se->start_page;
                         sector_t start_block = se->start_block + offset;
-                        pgoff_t nr_blocks = se->nr_pages - offset;
+                        sector_t nr_blocks = se->nr_pages - offset;
 
                         if (nr_blocks > nr_pages)
                                 nr_blocks = nr_pages;