dm-integrity: align the outgoing bio in integrity_recheck

It is possible to set up dm-integrity with smaller sector size than
the logical sector size of the underlying device. In this situation,
dm-integrity guarantees that the outgoing bios have the same alignment as
incoming bios (so, if you create a filesystem with 4k block size,
dm-integrity would send 4k-aligned bios to the underlying device).

This guarantee was broken when integrity_recheck was implemented.
integrity_recheck sends bio that is aligned to ic->sectors_per_block. So
if we set up integrity with 512-byte sector size on a device with logical
block size 4k, we would be sending unaligned bio. This triggered a bug in
one of our internal tests.

This commit fixes it by determining the actual alignment of the
incoming bio and then makes sure that the outgoing bio in
integrity_recheck has the same alignment.

Fixes: c88f5e5 ("dm-integrity: recheck the integrity tag after a failure")
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

Author: Mikulas Patocka

drivers/md/dm-integrity.c

@@ -1699,7 +1699,6 @@ static noinline void integrity_recheck(struct dm_integrity_io *dio, char *checks
 	struct bio_vec bv;
 	sector_t sector, logical_sector, area, offset;
 	struct page *page;
-	void *buffer;
 
 	get_area_and_offset(ic, dio->range.logical_sector, &area, &offset);
 	dio->metadata_block = get_metadata_sector_and_offset(ic, area, offset,
@@ -1708,13 +1707,14 @@ static noinline void integrity_recheck(struct dm_integrity_io *dio, char *checks
 	logical_sector = dio->range.logical_sector;
 
 	page = mempool_alloc(&ic->recheck_pool, GFP_NOIO);
-	buffer = page_to_virt(page);
 
 	__bio_for_each_segment(bv, bio, iter, dio->bio_details.bi_iter) {
 		unsigned pos = 0;
 
 		do {
+			sector_t alignment;
 			char *mem;
+			char *buffer = page_to_virt(page);
 			int r;
 			struct dm_io_request io_req;
 			struct dm_io_region io_loc;
@@ -1727,6 +1727,14 @@ static noinline void integrity_recheck(struct dm_integrity_io *dio, char *checks
 			io_loc.sector = sector;
 			io_loc.count = ic->sectors_per_block;
 
+			/* Align the bio to logical block size */
+			alignment = dio->range.logical_sector | bio_sectors(bio) | (PAGE_SIZE >> SECTOR_SHIFT);
+			alignment &= -alignment;
+			io_loc.sector = round_down(io_loc.sector, alignment);
+			io_loc.count += sector - io_loc.sector;
+			buffer += (sector - io_loc.sector) << SECTOR_SHIFT;
+			io_loc.count = round_up(io_loc.count, alignment);
+
 			r = dm_io(&io_req, 1, &io_loc, NULL, IOPRIO_DEFAULT);
 			if (unlikely(r)) {
 				dio->bi_status = errno_to_blk_status(r);