Merge tag 'for-5.8-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux

Pull btrfs updates from David Sterba:
 "Highlights:

   - speedup dead root detection during orphan cleanup, eg. when there
     are many deleted subvolumes waiting to be cleaned, the trees are
     now looked up in radix tree instead of a O(N^2) search

   - snapshot creation with inherited qgroup will mark the qgroup
     inconsistent, requires a rescan

   - send will emit file capabilities after chown, this produces a
     stream that does not need postprocessing to set the capabilities
     again

   - direct io ported to iomap infrastructure, cleaned up and simplified
     code, notably removing last use of struct buffer_head in btrfs code

  Core changes:

   - factor out backreference iteration, to be used by ordinary
     backreferences and relocation code

   - improved global block reserve utilization
      * better logic to serialize requests
      * increased maximum available for unlink
      * improved handling on large pages (64K)

   - direct io cleanups and fixes
      * simplify layering, where cloned bios were unnecessarily created
        for some cases
      * error handling fixes (submit, endio)
      * remove repair worker thread, used to avoid deadlocks during
        repair

   - refactored block group reading code, preparatory work for new type
     of block group storage that should improve mount time on large
     filesystems

  Cleanups:

   - cleaned up (and slightly sped up) set/get helpers for metadata data
     structure members

   - root bit REF_COWS got renamed to SHAREABLE to reflect the that the
     blocks of the tree get shared either among subvolumes or with the
     relocation trees

  Fixes:

   - when subvolume deletion fails due to ENOSPC, the filesystem is not
     turned read-only

   - device scan deals with devices from other filesystems that changed
     ownership due to overwrite (mkfs)

   - fix a race between scrub and block group removal/allocation

   - fix long standing bug of a runaway balance operation, printing the
     same line to the syslog, caused by a stale status bit on a reloc
     tree that prevented progress

   - fix corrupt log due to concurrent fsync of inodes with shared
     extents

   - fix space underflow for NODATACOW and buffered writes when it for
     some reason needs to fallback to COW mode"

* tag 'for-5.8-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux: (133 commits)
  btrfs: fix space_info bytes_may_use underflow during space cache writeout
  btrfs: fix space_info bytes_may_use underflow after nocow buffered write
  btrfs: fix wrong file range cleanup after an error filling dealloc range
  btrfs: remove redundant local variable in read_block_for_search
  btrfs: open code key_search
  btrfs: split btrfs_direct_IO to read and write part
  btrfs: remove BTRFS_INODE_READDIO_NEED_LOCK
  fs: remove dio_end_io()
  btrfs: switch to iomap_dio_rw() for dio
  iomap: remove lockdep_assert_held()
  iomap: add a filesystem hook for direct I/O bio submission
  fs: export generic_file_buffered_read()
  btrfs: turn space cache writeout failure messages into debug messages
  btrfs: include error on messages about failure to write space/inode caches
  btrfs: remove useless 'fail_unlock' label from btrfs_csum_file_blocks()
  btrfs: do not ignore error from btrfs_next_leaf() when inserting checksums
  btrfs: make checksum item extension more efficient
  btrfs: fix corrupt log due to concurrent fsync of inodes with shared extents
  btrfs: unexport btrfs_compress_set_level()
  btrfs: simplify iget helpers
  ...

52 files changed, 3224 insertions, 3045 deletions

diff --git a/.clang-format b/.clang-format
index e92e6dd1780d..a0a96088c74f 100644
--- a/.clang-format
+++ b/.clang-format
@@ -80,6 +80,7 @@ ForEachMacros:
   - 'ax25_uid_for_each'
   - '__bio_for_each_bvec'
   - 'bio_for_each_bvec'
+  - 'bio_for_each_bvec_all'
   - 'bio_for_each_integrity_vec'
   - '__bio_for_each_segment'
   - 'bio_for_each_segment'
diff --git a/Documentation/block/biovecs.rst b/Documentation/block/biovecs.rst
index ad303a2569d3..36771a131b56 100644
--- a/Documentation/block/biovecs.rst
+++ b/Documentation/block/biovecs.rst
@@ -129,6 +129,7 @@ Usage of helpers:
 ::
 
 	bio_for_each_segment_all()
+	bio_for_each_bvec_all()
 	bio_first_bvec_all()
 	bio_first_page_all()
 	bio_last_bvec_all()
@@ -143,4 +144,5 @@ Usage of helpers:
   bio_vec' will contain a multi-page IO vector during the iteration::
 
 	bio_for_each_bvec()
+	bio_for_each_bvec_all()
 	rq_for_each_bvec()
diff --git a/fs/btrfs/Kconfig b/fs/btrfs/Kconfig
index 575636f6491e..68b95ad82126 100644
--- a/fs/btrfs/Kconfig
+++ b/fs/btrfs/Kconfig
@@ -14,6 +14,7 @@ config BTRFS_FS
 	select LZO_DECOMPRESS
 	select ZSTD_COMPRESS
 	select ZSTD_DECOMPRESS
+	select FS_IOMAP
 	select RAID6_PQ
 	select XOR_BLOCKS
 	select SRCU
diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index 0cc02577577b..d888e71e66b6 100644
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -13,6 +13,7 @@
 #include "transaction.h"
 #include "delayed-ref.h"
 #include "locking.h"
+#include "misc.h"
 
 /* Just an arbitrary number so we can be sure this happened */
 #define BACKREF_FOUND_SHARED 6
@@ -537,18 +538,13 @@ static int resolve_indirect_ref(struct btrfs_fs_info *fs_info,
 				const u64 *extent_item_pos, bool ignore_offset)
 {
 	struct btrfs_root *root;
-	struct btrfs_key root_key;
 	struct extent_buffer *eb;
 	int ret = 0;
 	int root_level;
 	int level = ref->level;
 	struct btrfs_key search_key = ref->key_for_search;
 
-	root_key.objectid = ref->root_id;
-	root_key.type = BTRFS_ROOT_ITEM_KEY;
-	root_key.offset = (u64)-1;
-
-	root = btrfs_get_fs_root(fs_info, &root_key, false);
+	root = btrfs_get_fs_root(fs_info, ref->root_id, false);
 	if (IS_ERR(root)) {
 		ret = PTR_ERR(root);
 		goto out_free;
@@ -2295,3 +2291,832 @@ void free_ipath(struct inode_fs_paths *ipath)
 	kvfree(ipath->fspath);
 	kfree(ipath);
 }
+
+struct btrfs_backref_iter *btrfs_backref_iter_alloc(
+		struct btrfs_fs_info *fs_info, gfp_t gfp_flag)
+{
+	struct btrfs_backref_iter *ret;
+
+	ret = kzalloc(sizeof(*ret), gfp_flag);
+	if (!ret)
+		return NULL;
+
+	ret->path = btrfs_alloc_path();
+	if (!ret) {
+		kfree(ret);
+		return NULL;
+	}
+
+	/* Current backref iterator only supports iteration in commit root */
+	ret->path->search_commit_root = 1;
+	ret->path->skip_locking = 1;
+	ret->fs_info = fs_info;
+
+	return ret;
+}
+
+int btrfs_backref_iter_start(struct btrfs_backref_iter *iter, u64 bytenr)
+{
+	struct btrfs_fs_info *fs_info = iter->fs_info;
+	struct btrfs_path *path = iter->path;
+	struct btrfs_extent_item *ei;
+	struct btrfs_key key;
+	int ret;
+
+	key.objectid = bytenr;
+	key.type = BTRFS_METADATA_ITEM_KEY;
+	key.offset = (u64)-1;
+	iter->bytenr = bytenr;
+
+	ret = btrfs_search_slot(NULL, fs_info->extent_root, &key, path, 0, 0);
+	if (ret < 0)
+		return ret;
+	if (ret == 0) {
+		ret = -EUCLEAN;
+		goto release;
+	}
+	if (path->slots[0] == 0) {
+		WARN_ON(IS_ENABLED(CONFIG_BTRFS_DEBUG));
+		ret = -EUCLEAN;
+		goto release;
+	}
+	path->slots[0]--;
+
+	btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
+	if ((key.type != BTRFS_EXTENT_ITEM_KEY &&
+	     key.type != BTRFS_METADATA_ITEM_KEY) || key.objectid != bytenr) {
+		ret = -ENOENT;
+		goto release;
+	}
+	memcpy(&iter->cur_key, &key, sizeof(key));
+	iter->item_ptr = (u32)btrfs_item_ptr_offset(path->nodes[0],
+						    path->slots[0]);
+	iter->end_ptr = (u32)(iter->item_ptr +
+			btrfs_item_size_nr(path->nodes[0], path->slots[0]));
+	ei = btrfs_item_ptr(path->nodes[0], path->slots[0],
+			    struct btrfs_extent_item);
+
+	/*
+	 * Only support iteration on tree backref yet.
+	 *
+	 * This is an extra precaution for non skinny-metadata, where
+	 * EXTENT_ITEM is also used for tree blocks, that we can only use
+	 * extent flags to determine if it's a tree block.
+	 */
+	if (btrfs_extent_flags(path->nodes[0], ei) & BTRFS_EXTENT_FLAG_DATA) {
+		ret = -ENOTSUPP;
+		goto release;
+	}
+	iter->cur_ptr = (u32)(iter->item_ptr + sizeof(*ei));
+
+	/* If there is no inline backref, go search for keyed backref */
+	if (iter->cur_ptr >= iter->end_ptr) {
+		ret = btrfs_next_item(fs_info->extent_root, path);
+
+		/* No inline nor keyed ref */
+		if (ret > 0) {
+			ret = -ENOENT;
+			goto release;
+		}
+		if (ret < 0)
+			goto release;
+
+		btrfs_item_key_to_cpu(path->nodes[0], &iter->cur_key,
+				path->slots[0]);
+		if (iter->cur_key.objectid != bytenr ||
+		    (iter->cur_key.type != BTRFS_SHARED_BLOCK_REF_KEY &&
+		     iter->cur_key.type != BTRFS_TREE_BLOCK_REF_KEY)) {
+			ret = -ENOENT;
+			goto release;
+		}
+		iter->cur_ptr = (u32)btrfs_item_ptr_offset(path->nodes[0],
+							   path->slots[0]);
+		iter->item_ptr = iter->cur_ptr;
+		iter->end_ptr = (u32)(iter->item_ptr + btrfs_item_size_nr(
+				      path->nodes[0], path->slots[0]));
+	}
+
+	return 0;
+release:
+	btrfs_backref_iter_release(iter);
+	return ret;
+}
+
+/*
+ * Go to the next backref item of current bytenr, can be either inlined or
+ * keyed.
+ *
+ * Caller needs to check whether it's inline ref or not by iter->cur_key.
+ *
+ * Return 0 if we get next backref without problem.
+ * Return >0 if there is no extra backref for this bytenr.
+ * Return <0 if there is something wrong happened.
+ */
+int btrfs_backref_iter_next(struct btrfs_backref_iter *iter)
+{
+	struct extent_buffer *eb = btrfs_backref_get_eb(iter);
+	struct btrfs_path *path = iter->path;
+	struct btrfs_extent_inline_ref *iref;
+	int ret;
+	u32 size;
+
+	if (btrfs_backref_iter_is_inline_ref(iter)) {
+		/* We're still inside the inline refs */
+		ASSERT(iter->cur_ptr < iter->end_ptr);
+
+		if (btrfs_backref_has_tree_block_info(iter)) {
+			/* First tree block info */
+			size = sizeof(struct btrfs_tree_block_info);
+		} else {
+			/* Use inline ref type to determine the size */
+			int type;
+
+			iref = (struct btrfs_extent_inline_ref *)
+				((unsigned long)iter->cur_ptr);
+			type = btrfs_extent_inline_ref_type(eb, iref);
+
+			size = btrfs_extent_inline_ref_size(type);
+		}
+		iter->cur_ptr += size;
+		if (iter->cur_ptr < iter->end_ptr)
+			return 0;
+
+		/* All inline items iterated, fall through */
+	}
+
+	/* We're at keyed items, there is no inline item, go to the next one */
+	ret = btrfs_next_item(iter->fs_info->extent_root, iter->path);
+	if (ret)
+		return ret;
+
+	btrfs_item_key_to_cpu(path->nodes[0], &iter->cur_key, path->slots[0]);
+	if (iter->cur_key.objectid != iter->bytenr ||
+	    (iter->cur_key.type != BTRFS_TREE_BLOCK_REF_KEY &&
+	     iter->cur_key.type != BTRFS_SHARED_BLOCK_REF_KEY))
+		return 1;
+	iter->item_ptr = (u32)btrfs_item_ptr_offset(path->nodes[0],
+					path->slots[0]);
+	iter->cur_ptr = iter->item_ptr;
+	iter->end_ptr = iter->item_ptr + (u32)btrfs_item_size_nr(path->nodes[0],
+						path->slots[0]);
+	return 0;
+}
+
+void btrfs_backref_init_cache(struct btrfs_fs_info *fs_info,
+			      struct btrfs_backref_cache *cache, int is_reloc)
+{
+	int i;
+
+	cache->rb_root = RB_ROOT;
+	for (i = 0; i < BTRFS_MAX_LEVEL; i++)
+		INIT_LIST_HEAD(&cache->pending[i]);
+	INIT_LIST_HEAD(&cache->changed);
+	INIT_LIST_HEAD(&cache->detached);
+	INIT_LIST_HEAD(&cache->leaves);
+	INIT_LIST_HEAD(&cache->pending_edge);
+	INIT_LIST_HEAD(&cache->useless_node);
+	cache->fs_info = fs_info;
+	cache->is_reloc = is_reloc;
+}
+
+struct btrfs_backref_node *btrfs_backref_alloc_node(
+		struct btrfs_backref_cache *cache, u64 bytenr, int level)
+{
+	struct btrfs_backref_node *node;
+
+	ASSERT(level >= 0 && level < BTRFS_MAX_LEVEL);
+	node = kzalloc(sizeof(*node), GFP_NOFS);
+	if (!node)
+		return node;
+
+	INIT_LIST_HEAD(&node->list);
+	INIT_LIST_HEAD(&node->upper);
+	INIT_LIST_HEAD(&node->lower);
+	RB_CLEAR_NODE(&node->rb_node);
+	cache->nr_nodes++;
+	node->level = level;
+	node->bytenr = bytenr;
+
+	return node;
+}
+
+struct btrfs_backref_edge *btrfs_backref_alloc_edge(
+		struct btrfs_backref_cache *cache)
+{
+	struct btrfs_backref_edge *edge;
+
+	edge = kzalloc(sizeof(*edge), GFP_NOFS);
+	if (edge)
+		cache->nr_edges++;
+	return edge;
+}
+
+/*
+ * Drop the backref node from cache, also cleaning up all its
+ * upper edges and any uncached nodes in the path.
+ *
+ * This cleanup happens bottom up, thus the node should either
+ * be the lowest node in the cache or a detached node.
+ */
+void btrfs_backref_cleanup_node(struct btrfs_backref_cache *cache,
+				struct btrfs_backref_node *node)
+{
+	struct btrfs_backref_node *upper;
+	struct btrfs_backref_edge *edge;
+
+	if (!node)
+		return;
+
+	BUG_ON(!node->lowest && !node->detached);
+	while (!list_empty(&node->upper)) {
+		edge = list_entry(node->upper.next, struct btrfs_backref_edge,
+				  list[LOWER]);
+		upper = edge->node[UPPER];
+		list_del(&edge->list[LOWER]);
+		list_del(&edge->list[UPPER]);
+		btrfs_backref_free_edge(cache, edge);
+
+		if (RB_EMPTY_NODE(&upper->rb_node)) {
+			BUG_ON(!list_empty(&node->upper));
+			btrfs_backref_drop_node(cache, node);
+			node = upper;
+			node->lowest = 1;
+			continue;
+		}
+		/*
+		 * Add the node to leaf node list if no other child block
+		 * cached.
+		 */
+		if (list_empty(&upper->lower)) {
+			list_add_tail(&upper->lower, &cache->leaves);
+			upper->lowest = 1;
+		}
+	}
+
+	btrfs_backref_drop_node(cache, node);
+}
+
+/*
+ * Release all nodes/edges from current cache
+ */
+void btrfs_backref_release_cache(struct btrfs_backref_cache *cache)
+{
+	struct btrfs_backref_node *node;
+	int i;
+
+	while (!list_empty(&cache->detached)) {
+		node = list_entry(cache->detached.next,
+				  struct btrfs_backref_node, list);
+		btrfs_backref_cleanup_node(cache, node);
+	}
+
+	while (!list_empty(&cache->leaves)) {
+		node = list_entry(cache->leaves.next,
+				  struct btrfs_backref_node, lower);
+		btrfs_backref_cleanup_node(cache, node);
+	}
+
+	cache->last_trans = 0;
+
+	for (i = 0; i < BTRFS_MAX_LEVEL; i++)
+		ASSERT(list_empty(&cache->pending[i]));
+	ASSERT(list_empty(&cache->pending_edge));
+	ASSERT(list_empty(&cache->useless_node));
+	ASSERT(list_empty(&cache->changed));
+	ASSERT(list_empty(&cache->detached));
+	ASSERT(RB_EMPTY_ROOT(&cache->rb_root));
+	ASSERT(!cache->nr_nodes);
+	ASSERT(!cache->nr_edges);
+}
+
+/*
+ * Handle direct tree backref
+ *
+ * Direct tree backref means, the backref item shows its parent bytenr
+ * directly. This is for SHARED_BLOCK_REF backref (keyed or inlined).
+ *
+ * @ref_key:	The converted backref key.
+ *		For keyed backref, it's the item key.
+ *		For inlined backref, objectid is the bytenr,
+ *		type is btrfs_inline_ref_type, offset is
+ *		btrfs_inline_ref_offset.
+ */
+static int handle_direct_tree_backref(struct btrfs_backref_cache *cache,
+				      struct btrfs_key *ref_key,
+				      struct btrfs_backref_node *cur)
+{
+	struct btrfs_backref_edge *edge;
+	struct btrfs_backref_node *upper;
+	struct rb_node *rb_node;
+
+	ASSERT(ref_key->type == BTRFS_SHARED_BLOCK_REF_KEY);
+
+	/* Only reloc root uses backref pointing to itself */
+	if (ref_key->objectid == ref_key->offset) {
+		struct btrfs_root *root;
+
+		cur->is_reloc_root = 1;
+		/* Only reloc backref cache cares about a specific root */
+		if (cache->is_reloc) {
+			root = find_reloc_root(cache->fs_info, cur->bytenr);
+			if (WARN_ON(!root))
+				return -ENOENT;
+			cur->root = root;
+		} else {
+			/*
+			 * For generic purpose backref cache, reloc root node
+			 * is useless.
+			 */
+			list_add(&cur->list, &cache->useless_node);
+		}
+		return 0;
+	}
+
+	edge = btrfs_backref_alloc_edge(cache);
+	if (!edge)
+		return -ENOMEM;
+
+	rb_node = rb_simple_search(&cache->rb_root, ref_key->offset);
+	if (!rb_node) {
+		/* Parent node not yet cached */
+		upper = btrfs_backref_alloc_node(cache, ref_key->offset,
+					   cur->level + 1);
+		if (!upper) {
+			btrfs_backref_free_edge(cache, edge);
+			return -ENOMEM;
+		}
+
+		/*
+		 *  Backrefs for the upper level block isn't cached, add the
+		 *  block to pending list
+		 */
+		list_add_tail(&edge->list[UPPER], &cache->pending_edge);
+	} else {
+		/* Parent node already cached */
+		upper = rb_entry(rb_node, struct btrfs_backref_node, rb_node);
+		ASSERT(upper->checked);
+		INIT_LIST_HEAD(&edge->list[UPPER]);
+	}
+	btrfs_backref_link_edge(edge, cur, upper, LINK_LOWER);
+	return 0;
+}
+
+/*
+ * Handle indirect tree backref
+ *
+ * Indirect tree backref means, we only know which tree the node belongs to.
+ * We still need to do a tree search to find out the parents. This is for
+ * TREE_BLOCK_REF backref (keyed or inlined).
+ *
+ * @ref_key:	The same as @ref_key in  handle_direct_tree_backref()
+ * @tree_key:	The first key of this tree block.
+ * @path:	A clean (released) path, to avoid allocating path everytime
+ *		the function get called.
+ */
+static int handle_indirect_tree_backref(struct btrfs_backref_cache *cache,
+					struct btrfs_path *path,
+					struct btrfs_key *ref_key,
+					struct btrfs_key *tree_key,
+					struct btrfs_backref_node *cur)
+{
+	struct btrfs_fs_info *fs_info = cache->fs_info;
+	struct btrfs_backref_node *upper;
+	struct btrfs_backref_node *lower;
+	struct btrfs_backref_edge *edge;
+	struct extent_buffer *eb;
+	struct btrfs_root *root;
+	struct rb_node *rb_node;
+	int level;
+	bool need_check = true;
+	int ret;
+
+	root = btrfs_get_fs_root(fs_info, ref_key->offset, false);
+	if (IS_ERR(root))
+		return PTR_ERR(root);
+	if (!test_bit(BTRFS_ROOT_SHAREABLE, &root->state))
+		cur->cowonly = 1;
+
+	if (btrfs_root_level(&root->root_item) == cur->level) {
+		/* Tree root */
+		ASSERT(btrfs_root_bytenr(&root->root_item) == cur->bytenr);
+		/*
+		 * For reloc backref cache, we may ignore reloc root.  But for
+		 * general purpose backref cache, we can't rely on
+		 * btrfs_should_ignore_reloc_root() as it may conflict with
+		 * current running relocation and lead to missing root.
+		 *
+		 * For general purpose backref cache, reloc root detection is
+		 * completely relying on direct backref (key->offset is parent
+		 * bytenr), thus only do such check for reloc cache.
+		 */
+		if (btrfs_should_ignore_reloc_root(root) && cache->is_reloc) {
+			btrfs_put_root(root);
+			list_add(&cur->list, &cache->useless_node);
+		} else {
+			cur->root = root;
+		}
+		return 0;
+	}
+
+	level = cur->level + 1;
+
+	/* Search the tree to find parent blocks referring to the block */
+	path->search_commit_root = 1;
+	path->skip_locking = 1;
+	path->lowest_level = level;
+	ret = btrfs_search_slot(NULL, root, tree_key, path, 0, 0);
+	path->lowest_level = 0;
+	if (ret < 0) {
+		btrfs_put_root(root);
+		return ret;
+	}
+	if (ret > 0 && path->slots[level] > 0)
+		path->slots[level]--;
+
+	eb = path->nodes[level];
+	if (btrfs_node_blockptr(eb, path->slots[level]) != cur->bytenr) {
+		btrfs_err(fs_info,
+"couldn't find block (%llu) (level %d) in tree (%llu) with key (%llu %u %llu)",
+			  cur->bytenr, level - 1, root->root_key.objectid,
+			  tree_key->objectid, tree_key->type, tree_key->offset);
+		btrfs_put_root(root);
+		ret = -ENOENT;
+		goto out;
+	}
+	lower = cur;
+
+	/* Add all nodes and edges in the path */
+	for (; level < BTRFS_MAX_LEVEL; level++) {
+		if (!path->nodes[level]) {
+			ASSERT(btrfs_root_bytenr(&root->root_item) ==
+			       lower->bytenr);
+			/* Same as previous should_ignore_reloc_root() call */
+			if (btrfs_should_ignore_reloc_root(root) &&
+			    cache->is_reloc) {
+				btrfs_put_root(root);
+				list_add(&lower->list, &cache->useless_node);
+			} else {
+				lower->root = root;
+			}
+			break;
+		}
+
+		edge = btrfs_backref_alloc_edge(cache);
+		if (!edge) {
+			btrfs_put_root(root);
+			ret = -ENOMEM;
+			goto out;
+		}
+
+		eb = path->nodes[level];
+		rb_node = rb_simple_search(&cache->rb_root, eb->start);
+		if (!rb_node) {
+			upper = btrfs_backref_alloc_node(cache, eb->start,
+							 lower->level + 1);
+			if (!upper) {
+				btrfs_put_root(root);
+				btrfs_backref_free_edge(cache, edge);
+				ret = -ENOMEM;
+				goto out;
+			}
+			upper->owner = btrfs_header_owner(eb);
+			if (!test_bit(BTRFS_ROOT_SHAREABLE, &root->state))
+				upper->cowonly = 1;
+
+			/*
+			 * If we know the block isn't shared we can avoid
+			 * checking its backrefs.
+			 */
+			if (btrfs_block_can_be_shared(root, eb))
+				upper->checked = 0;
+			else
+				upper->checked = 1;
+
+			/*
+			 * Add the block to pending list if we need to check its
+			 * backrefs, we only do this once while walking up a
+			 * tree as we will catch anything else later on.
+			 */
+			if (!upper->checked && need_check) {
+				need_check = false;
+				list_add_tail(&edge->list[UPPER],
+					      &cache->pending_edge);
+			} else {
+				if (upper->checked)
+					need_check = true;
+				INIT_LIST_HEAD(&edge->list[UPPER]);
+			}
+		} else {
+			upper = rb_entry(rb_node, struct btrfs_backref_node,
+					 rb_node);
+			ASSERT(upper->checked);
+			INIT_LIST_HEAD(&edge->list[UPPER]);
+			if (!upper->owner)
+				upper->owner = btrfs_header_owner(eb);
+		}
+		btrfs_backref_link_edge(edge, lower, upper, LINK_LOWER);
+
+		if (rb_node) {
+			btrfs_put_root(root);
+			break;
+		}
+		lower = upper;
+		upper = NULL;
+	}
+out:
+	btrfs_release_path(path);
+	return ret;
+}
+
+/*
+ * Add backref node @cur into @cache.
+ *
+ * NOTE: Even if the function returned 0, @cur is not yet cached as its upper
+ *	 links aren't yet bi-directional. Needs to finish such links.
+ *	 Use btrfs_backref_finish_upper_links() to finish such linkage.
+ *
+ * @path:	Released path for indirect tree backref lookup
+ * @iter:	Released backref iter for extent tree search
+ * @node_key:	The first key of the tree block
+ */
+int btrfs_backref_add_tree_node(struct btrfs_backref_cache *cache,
+				struct btrfs_path *path,
+				struct btrfs_backref_iter *iter,
+				struct btrfs_key *node_key,
+				struct btrfs_backref_node *cur)
+{
+	struct btrfs_fs_info *fs_info = cache->fs_info;
+	struct btrfs_backref_edge *edge;
+	struct btrfs_backref_node *exist;
+	int ret;
+
+	ret = btrfs_backref_iter_start(iter, cur->bytenr);
+	if (ret < 0)
+		return ret;
+	/*
+	 * We skip the first btrfs_tree_block_info, as we don't use the key
+	 * stored in it, but fetch it from the tree block
+	 */
+	if (btrfs_backref_has_tree_block_info(iter)) {
+		ret = btrfs_backref_iter_next(iter);
+		if (ret < 0)
+			goto out;
+		/* No extra backref? This means the tree block is corrupted */
+		if (ret > 0) {
+			ret = -EUCLEAN;
+			goto out;
+		}
+	}
+	WARN_ON(cur->checked);
+	if (!list_empty(&cur->upper)) {
+		/*
+		 * The backref was added previously when processing backref of
+		 * type BTRFS_TREE_BLOCK_REF_KEY
+		 */
+		ASSERT(list_is_singular(&cur->upper));
+		edge = list_entry(cur->upper.next, struct btrfs_backref_edge,
+				  list[LOWER]);
+		ASSERT(list_empty(&edge->list[UPPER]));
+		exist = edge->node[UPPER];
+		/*
+		 * Add the upper level block to pending list if we need check
+		 * its backrefs
+		 */
+		if (!exist->checked)
+			list_add_tail(&edge->list[UPPER], &cache->pending_edge);
+	} else {
+		exist = NULL;
+	}
+