btrfs: save the bio iter for checksum validation in common code

All callers of btrfs_submit_bio that want to validate checksums
currently have to store a copy of the iter in the btrfs_bio.  Move
the assignment into common code.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/bio.c

@@ -63,7 +63,6 @@ struct bio *btrfs_bio_clone_partial(struct bio *orig, u64 offset, u64 size,
 	btrfs_bio_init(bbio, inode, end_io, private);
 
 	bio_trim(bio, offset >> 9, size >> 9);
-	bbio->iter = bio->bi_iter;
 	return bio;
 }
 
@@ -254,6 +253,10 @@ void btrfs_submit_bio(struct btrfs_fs_info *fs_info, struct bio *bio, int mirror
 		BUG();
 	}
 
+	/* Save the iter for the end_io handler for data reads. */
+	if (bio_op(bio) == REQ_OP_READ && !(bio->bi_opf & REQ_META))
+		bbio->iter = bio->bi_iter;
+
 	if (!bioc) {
 		/* Single mirror read/write fast path */
 		bbio->mirror_num = mirror_num;

fs/btrfs/compression.c

@@ -789,10 +789,6 @@ void btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
 			submit = true;
 
 		if (submit) {
-			/* Save the original iter for read repair */
-			if (bio_op(comp_bio) == REQ_OP_READ)
-				btrfs_bio(comp_bio)->iter = comp_bio->bi_iter;
-
 			/*
 			 * Save the initial offset of this chunk, as there
 			 * is no direct correlation between compressed pages and

fs/btrfs/extent_io.c

@@ -756,7 +756,6 @@ int btrfs_repair_one_sector(struct btrfs_inode *inode, struct btrfs_bio *failed_
 	}
 
 	bio_add_page(repair_bio, page, failrec->len, pgoff);
-	repair_bbio->iter = repair_bio->bi_iter;
 
 	btrfs_debug(fs_info,
 		    "repair read error: submitting new read to mirror %d",

fs/btrfs/inode.c

@@ -2773,9 +2773,6 @@ void btrfs_submit_data_read_bio(struct btrfs_inode *inode, struct bio *bio,
 		return;
 	}
 
-	/* Save the original iter for read repair */
-	btrfs_bio(bio)->iter = bio->bi_iter;
-
 	/*
 	 * Lookup bio sums does extra checks around whether we need to csum or
 	 * not, which is why we ignore skip_sum here.
@@ -7988,10 +7985,6 @@ static void btrfs_submit_dio_bio(struct bio *bio, struct btrfs_inode *inode,
 	struct btrfs_fs_info *fs_info = inode->root->fs_info;
 	blk_status_t ret;
 
-	/* Save the original iter for read repair */
-	if (btrfs_op(bio) == BTRFS_MAP_READ)
-		btrfs_bio(bio)->iter = bio->bi_iter;
-
 	if (inode->flags & BTRFS_INODE_NODATASUM)
 		goto map;