btrfs: btrfs_multi_bio replaced with btrfs_bio

btrfs_bio is a bio abstraction able to split and not complete after the last
bio has returned (like the old btrfs_multi_bio). Additionally, btrfs_bio
tracks the mirror_num used to read data which can be used for error
correction purposes.
Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>

fs/btrfs/extent-tree.c

@@ -1770,18 +1770,18 @@ static int btrfs_discard_extent(struct btrfs_root *root, u64 bytenr,
 {
 	int ret;
 	u64 discarded_bytes = 0;
-	struct btrfs_multi_bio *multi = NULL;
+	struct btrfs_bio *bbio = NULL;
 
 
 	/* Tell the block device(s) that the sectors can be discarded */
 	ret = btrfs_map_block(&root->fs_info->mapping_tree, REQ_DISCARD,
-			      bytenr, &num_bytes, &multi, 0);
+			      bytenr, &num_bytes, &bbio, 0);
 	if (!ret) {
-		struct btrfs_bio_stripe *stripe = multi->stripes;
+		struct btrfs_bio_stripe *stripe = bbio->stripes;
 		int i;
 
 
-		for (i = 0; i < multi->num_stripes; i++, stripe++) {
+		for (i = 0; i < bbio->num_stripes; i++, stripe++) {
 			if (!stripe->dev->can_discard)
 				continue;
 
@@ -1800,7 +1800,7 @@ static int btrfs_discard_extent(struct btrfs_root *root, u64 bytenr,
 			 */
 			ret = 0;
 		}
-		kfree(multi);
+		kfree(bbio);
 	}
 
 	if (actual_bytes)

fs/btrfs/scrub.c

@@ -572,7 +572,7 @@ static void scrub_fixup(struct scrub_bio *sbio, int ix)
 	struct scrub_dev *sdev = sbio->sdev;
 	struct btrfs_fs_info *fs_info = sdev->dev->dev_root->fs_info;
 	struct btrfs_mapping_tree *map_tree = &fs_info->mapping_tree;
-	struct btrfs_multi_bio *multi = NULL;
+	struct btrfs_bio *bbio = NULL;
 	struct scrub_fixup_nodatasum *fixup;
 	u64 logical = sbio->logical + ix * PAGE_SIZE;
 	u64 length;
@@ -610,8 +610,8 @@ static void scrub_fixup(struct scrub_bio *sbio, int ix)
 
 	length = PAGE_SIZE;
 	ret = btrfs_map_block(map_tree, REQ_WRITE, logical, &length,
-			      &multi, 0);
-	if (ret || !multi || length < PAGE_SIZE) {
+			      &bbio, 0);
+	if (ret || !bbio || length < PAGE_SIZE) {
 		printk(KERN_ERR
 		       "scrub_fixup: btrfs_map_block failed us for %llu\n",
 		       (unsigned long long)logical);
@@ -619,19 +619,19 @@ static void scrub_fixup(struct scrub_bio *sbio, int ix)
 		return;
 	}
 
-	if (multi->num_stripes == 1)
+	if (bbio->num_stripes == 1)
 		/* there aren't any replicas */
 		goto uncorrectable;
 
 	/*
 	 * first find a good copy
 	 */
-	for (i = 0; i < multi->num_stripes; ++i) {
+	for (i = 0; i < bbio->num_stripes; ++i) {
 		if (i + 1 == sbio->spag[ix].mirror_num)
 			continue;
 
-		if (scrub_fixup_io(READ, multi->stripes[i].dev->bdev,
-				   multi->stripes[i].physical >> 9,
+		if (scrub_fixup_io(READ, bbio->stripes[i].dev->bdev,
+				   bbio->stripes[i].physical >> 9,
 				   sbio->bio->bi_io_vec[ix].bv_page)) {
 			/* I/O-error, this is not a good copy */
 			continue;
@@ -640,7 +640,7 @@ static void scrub_fixup(struct scrub_bio *sbio, int ix)
 		if (scrub_fixup_check(sbio, ix) == 0)
 			break;
 	}
-	if (i == multi->num_stripes)
+	if (i == bbio->num_stripes)
 		goto uncorrectable;
 
 	if (!sdev->readonly) {
@@ -655,7 +655,7 @@ static void scrub_fixup(struct scrub_bio *sbio, int ix)
 		}
 	}
 
-	kfree(multi);
+	kfree(bbio);
 	spin_lock(&sdev->stat_lock);
 	++sdev->stat.corrected_errors;
 	spin_unlock(&sdev->stat_lock);
@@ -665,7 +665,7 @@ static void scrub_fixup(struct scrub_bio *sbio, int ix)
 	return;
 
 uncorrectable:
-	kfree(multi);
+	kfree(bbio);
 	spin_lock(&sdev->stat_lock);
 	++sdev->stat.uncorrectable_errors;
 	spin_unlock(&sdev->stat_lock);

fs/btrfs/volumes.h

@@ -136,7 +136,10 @@ struct btrfs_bio_stripe {
 	u64 length; /* only used for discard mappings */
 };
 
-struct btrfs_multi_bio {
+struct btrfs_bio;
+typedef void (btrfs_bio_end_io_t) (struct btrfs_bio *bio, int err);
+
+struct btrfs_bio {
 	atomic_t stripes_pending;
 	bio_end_io_t *end_io;
 	struct bio *orig_bio;
@@ -144,6 +147,7 @@ struct btrfs_multi_bio {
 	atomic_t error;
 	int max_errors;
 	int num_stripes;
+	int mirror_num;
 	struct btrfs_bio_stripe stripes[];
 };
 
@@ -171,7 +175,7 @@ struct map_lookup {
 int btrfs_account_dev_extents_size(struct btrfs_device *device, u64 start,
 				   u64 end, u64 *length);
 
-#define btrfs_multi_bio_size(n) (sizeof(struct btrfs_multi_bio) + \
+#define btrfs_bio_size(n) (sizeof(struct btrfs_bio) + \
 			    (sizeof(struct btrfs_bio_stripe) * (n)))
 
 int btrfs_alloc_dev_extent(struct btrfs_trans_handle *trans,
@@ -180,7 +184,7 @@ int btrfs_alloc_dev_extent(struct btrfs_trans_handle *trans,
 			   u64 chunk_offset, u64 start, u64 num_bytes);
 int btrfs_map_block(struct btrfs_mapping_tree *map_tree, int rw,
 		    u64 logical, u64 *length,
-		    struct btrfs_multi_bio **multi_ret, int mirror_num);
+		    struct btrfs_bio **bbio_ret, int mirror_num);
 int btrfs_rmap_block(struct btrfs_mapping_tree *map_tree,
 		     u64 chunk_start, u64 physical, u64 devid,
 		     u64 **logical, int *naddrs, int *stripe_len);