swap: fix swapfile read/write offset

commit caf6912f3f4af7232340d500a4a2008f81b93f14 upstream.

We're not factoring in the start of the file for where to write and
read the swapfile, which leads to very unfortunate side effects of
writing where we should not be...

[This issue only affects swapfiles on filesystems on top of blockdevs
that implement rw_page ops (brd, zram, btt, pmem), and not on top of any
other block devices, in contrast to the upstream commit fix.]

Fixes: dd6bd0d9c7db ("swap: use bdev_read_page() / bdev_write_page()")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Anthony Iliopoulos <ailiop@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/mm/page_io.c b/mm/page_io.c
index 5d882de3fbfd2bf0f94a35d004205ceddc87b817..253623dbbb64495e66599a710ea71f8d67fd1893 100644 (file)
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -38,7 +38,6 @@ static struct bio *get_swap_bio(gfp_t gfp_flags,
 
                bio->bi_iter.bi_sector = map_swap_page(page, &bdev);
                bio_set_dev(bio, bdev);
-               bio->bi_iter.bi_sector <<= PAGE_SHIFT - 9;
                bio->bi_end_io = end_io;
 
                for (i = 0; i < nr; i++)
@@ -261,11 +260,6 @@ int swap_writepage(struct page *page, struct writeback_control *wbc)
        return ret;
 }
 
-static sector_t swap_page_sector(struct page *page)
-{
-       return (sector_t)__page_file_index(page) << (PAGE_SHIFT - 9);
-}
-
 static inline void count_swpout_vm_event(struct page *page)
 {
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
@@ -324,7 +318,8 @@ int __swap_writepage(struct page *page, struct writeback_control *wbc,
                return ret;
        }
 
-       ret = bdev_write_page(sis->bdev, swap_page_sector(page), page, wbc);
+       ret = bdev_write_page(sis->bdev, map_swap_page(page, &sis->bdev),
+                             page, wbc);
        if (!ret) {
                count_swpout_vm_event(page);
                return 0;
@@ -374,7 +369,7 @@ int swap_readpage(struct page *page, bool do_poll)
                return ret;
        }
 
-       ret = bdev_read_page(sis->bdev, swap_page_sector(page), page);
+       ret = bdev_read_page(sis->bdev, map_swap_page(page, &sis->bdev), page);
        if (!ret) {
                if (trylock_page(page)) {
                        swap_slot_free_notify(page);

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 2aa7b59077b3c74b425739635a0a3aa0d421db42..f65d97fe2ef7e2c0340996300df4032e6cb7c014 100644 (file)
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2304,7 +2304,7 @@ sector_t map_swap_page(struct page *page, struct block_device **bdev)
 {
        swp_entry_t entry;
        entry.val = page_private(page);
-       return map_swap_entry(entry, bdev);
+       return map_swap_entry(entry, bdev) << (PAGE_SHIFT - 9);
 }
 
 /*