btrfs: add orig_logical to btrfs_bio for encryption

When checksumming the encrypted bio on writes we need to know which
logical address this checksum is for.  At the point where we get the
encrypted bio the bi_sector is the physical location on the target disk,
so we need to save the original logical offset in the btrfs_bio.  Then
we can use this when checksumming the bio instead of the
bio->iter.bi_sector.

Note: The patch was taken from v5 of fscrypt patchset
(https://lore.kernel.org/linux-btrfs/cover.1706116485.git.josef@toxicpanda.com/)
which was handled over time by various people: Omar Sandoval, Sweet Tea
Dorminy, Josef Bacik.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Daniel Vacek <neelx@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ add note ]
Signed-off-by: David Sterba <dsterba@suse.com>

Author: josefbacik

fs/btrfs/bio.c

@@ -94,6 +94,8 @@ static struct btrfs_bio *btrfs_split_bio(struct btrfs_fs_info *fs_info,
 	if (bbio_has_ordered_extent(bbio)) {
 		refcount_inc(&orig_bbio->ordered->refs);
 		bbio->ordered = orig_bbio->ordered;
+		bbio->orig_logical = orig_bbio->orig_logical;
+		orig_bbio->orig_logical += map_length;
 	}
 	bbio->csum_search_commit_root = orig_bbio->csum_search_commit_root;
 	atomic_inc(&orig_bbio->pending_ios);
@@ -765,6 +767,14 @@ static bool btrfs_submit_chunk(struct btrfs_bio *bbio, int mirror_num)
 		goto end_bbio;
 	}
 
+	/*
+	 * For fscrypt writes we will get the encrypted bio after we've
+	 * remapped our bio to the physical disk location, so we need to
+	 * save the original bytenr so we know what we're checksumming.
+	 */
+	if (bio_op(bio) == REQ_OP_WRITE && is_data_bbio(bbio))
+		bbio->orig_logical = logical;
+
 	map_length = min(map_length, length);
 	if (use_append)
 		map_length = btrfs_append_map_length(bbio, map_length);

fs/btrfs/bio.h

@@ -52,6 +52,7 @@ struct btrfs_bio {
 		 * - pointer to the checksums for this bio
 		 * - original physical address from the allocator
 		 *   (for zone append only)
+		 * - original logical address, used for checksumming fscrypt bios.
 		 */
 		struct {
 			struct btrfs_ordered_extent *ordered;
@@ -60,6 +61,7 @@ struct btrfs_bio {
 			struct completion csum_done;
 			struct bvec_iter csum_saved_iter;
 			u64 orig_physical;
+			u64 orig_logical;
 		};
 
 		/* For metadata reads: parentness verification. */

fs/btrfs/file-item.c

@@ -824,7 +824,7 @@ int btrfs_csum_one_bio(struct btrfs_bio *bbio, bool async)
 	if (!sums)
 		return -ENOMEM;
 
-	sums->logical = bio->bi_iter.bi_sector << SECTOR_SHIFT;
+	sums->logical = bbio->orig_logical;
 	sums->len = bio->bi_iter.bi_size;
 	INIT_LIST_HEAD(&sums->list);
 	bbio->sums = sums;