[PATCH RFC v2 6/8] btrfs: add code to read raid extent

[Johannes Thumshirn <johannes.thumshirn@wdc.com>]

Add boilerplate code to lookup the physical address from the
raid-stripe-tree when a read on an RAID volume formatted with the
raid-stripe-tree was attempted.

Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
---
 fs/btrfs/raid-stripe-tree.c | 65 +++++++++++++++++++++++++++++++++++++
 fs/btrfs/raid-stripe-tree.h |  3 ++
 fs/btrfs/volumes.c          | 22 +++++++++++--
 3 files changed, 88 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/raid-stripe-tree.c b/fs/btrfs/raid-stripe-tree.c
index a673aaf8e703..5ee630a792fc 100644
--- a/fs/btrfs/raid-stripe-tree.c
+++ b/fs/btrfs/raid-stripe-tree.c
@@ -7,6 +7,7 @@
 #include "disk-io.h"
 #include "raid-stripe-tree.h"
 #include "volumes.h"
+#include "misc.h"
 
 static struct rb_node *stripe_tree_insert(struct rb_root *root, u64 logical,
 					  struct rb_node *node)
@@ -251,3 +252,67 @@ void btrfs_raid_stripe_update(struct work_struct *work)
 	btrfs_put_bioc(bioc);
 }
 
+int btrfs_get_raid_extent_offset(struct btrfs_fs_info *fs_info,
+				 u64 logical, u64 length, u64 map_type,
+				 u64 devid, u64 *physical)
+{
+	struct btrfs_root *stripe_root = fs_info->stripe_root;
+	struct btrfs_dp_stripe *raid_stripe;
+	struct btrfs_key stripe_key;
+	struct btrfs_key found_key;
+	struct btrfs_path *path;
+	struct extent_buffer *leaf;
+	u64 offset;
+	u64 found_logical, found_length;
+	int num_stripes;
+	int slot;
+	int ret;
+	int i;
+
+	stripe_key.objectid = logical;
+	stripe_key.type = BTRFS_RAID_STRIPE_KEY;
+	stripe_key.offset = length;
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return -ENOMEM;
+
+	num_stripes = btrfs_bg_type_to_factor(map_type);
+
+	ret = btrfs_search_slot_for_read(stripe_root, &stripe_key, path, 0, 0);
+	if (ret < 0) {
+		goto out;
+	}
+
+	if (ret == 1)
+		ret = 0;
+
+	while (1) {
+		leaf = path->nodes[0];
+		slot = path->slots[0];
+
+		btrfs_item_key_to_cpu(leaf, &found_key, slot);
+		found_logical = found_key.objectid;
+		found_length = found_key.offset;
+
+		if (!in_range(logical, found_logical, found_length))
+			goto next;
+		offset = logical - found_logical;
+
+		raid_stripe = btrfs_item_ptr(leaf, slot, struct btrfs_dp_stripe);
+		for (i = 0; i < num_stripes; i++) {
+			if (btrfs_stripe_extent_devid_nr(leaf, raid_stripe, i) != devid)
+				continue;
+			*physical = btrfs_stripe_extent_physical_nr(leaf, raid_stripe, i) + offset;
+			goto out;
+		}
+next:
+		ret = btrfs_next_item(stripe_root, path);
+		if (ret)
+			break;
+	}
+out:
+	btrfs_free_path(path);
+
+	return ret;
+}
diff --git a/fs/btrfs/raid-stripe-tree.h b/fs/btrfs/raid-stripe-tree.h
index d3cc24e37de1..75e17cad283a 100644
--- a/fs/btrfs/raid-stripe-tree.h
+++ b/fs/btrfs/raid-stripe-tree.h
@@ -16,6 +16,9 @@ struct btrfs_ordered_stripe {
 	refcount_t ref;
 };
 
+int btrfs_get_raid_extent_offset(struct btrfs_fs_info *fs_info,
+				 u64 logical, u64 length, u64 map_type,
+				 u64 devid, u64 *physical);
 int btrfs_delete_raid_extent(struct btrfs_trans_handle *trans, u64 start,
 			     u64 length);
 int btrfs_insert_raid_extent(struct btrfs_trans_handle *trans,
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index b8d4e92c7196..2569ef564c97 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -6526,9 +6526,27 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info,
 	}
 
 	for (i = 0; i < num_stripes; i++) {
-		bioc->stripes[i].physical = map->stripes[stripe_index].physical +
-			stripe_offset + stripe_nr * map->stripe_len;
+		u64 physical;
+
 		bioc->stripes[i].dev = map->stripes[stripe_index].dev;
+
+		if (fs_info->stripe_root && op == BTRFS_MAP_READ &&
+		   btrfs_need_stripe_tree_update(bioc->fs_info,
+						 map->type)) {
+			ret = btrfs_get_raid_extent_offset(fs_info, logical,
+							   map->stripe_len,
+							   map->type,
+							   bioc->stripes[i].dev->devid,
+							   &physical);
+			if (ret) {
+				btrfs_put_bioc(bioc);
+				goto out;
+			}
+		} else {
+			physical = map->stripes[stripe_index].physical +
+				stripe_offset + stripe_nr * map->stripe_len;
+		}
+		bioc->stripes[i].physical = physical;
 		stripe_index++;
 	}
 
-- 
2.35.3