This is a note to let you know that I've just added the patch titled swap: fix swapfile read/write offset to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: swap-fix-swapfile-read-write-offset.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From caf6912f3f4af7232340d500a4a2008f81b93f14 Mon Sep 17 00:00:00 2001 From: Jens Axboe <axboe@xxxxxxxxx> Date: Tue, 2 Mar 2021 14:53:21 -0700 Subject: swap: fix swapfile read/write offset From: Jens Axboe <axboe@xxxxxxxxx> 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@xxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx # 4.9 Signed-off-by: Anthony Iliopoulos <ailiop@xxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- mm/page_io.c | 11 +++-------- mm/swapfile.c | 2 +- 2 files changed, 4 insertions(+), 9 deletions(-) --- a/mm/page_io.c +++ b/mm/page_io.c @@ -32,7 +32,6 @@ static struct bio *get_swap_bio(gfp_t gf bio = bio_alloc(gfp_flags, 1); if (bio) { bio->bi_iter.bi_sector = map_swap_page(page, &bio->bi_bdev); - bio->bi_iter.bi_sector <<= PAGE_SHIFT - 9; bio->bi_end_io = end_io; bio_add_page(bio, page, PAGE_SIZE, 0); @@ -252,11 +251,6 @@ out: return ret; } -static sector_t swap_page_sector(struct page *page) -{ - return (sector_t)__page_file_index(page) << (PAGE_SHIFT - 9); -} - int __swap_writepage(struct page *page, struct writeback_control *wbc, bio_end_io_t end_write_func) { @@ -306,7 +300,8 @@ int __swap_writepage(struct page *page, 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_vm_event(PSWPOUT); return 0; @@ -357,7 +352,7 @@ int swap_readpage(struct page *page) 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); --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -1666,7 +1666,7 @@ sector_t map_swap_page(struct page *page { swp_entry_t entry; entry.val = page_private(page); - return map_swap_entry(entry, bdev); + return map_swap_entry(entry, bdev) << (PAGE_SHIFT - 9); } /* Patches currently in stable-queue which might be from axboe@xxxxxxxxx are queue-4.9/swap-fix-swapfile-read-write-offset.patch