fs: btrfs: Add single-device read-only BTRFS implementation

This adds the proper implementation for the BTRFS filesystem.
The implementation currently supports only read-only mode and
the filesystem can be only on a single device.

Checksums of data chunks is unimplemented.

Compression is implemented (ZLIB + LZO).

Signed-off-by: Marek Behun <marek.behun@nic.cz>

 create mode 100644 fs/btrfs/btrfs.h
 create mode 100644 fs/btrfs/chunk-map.c
 create mode 100644 fs/btrfs/compression.c
 create mode 100644 fs/btrfs/ctree.c
 create mode 100644 fs/btrfs/dev.c
 create mode 100644 fs/btrfs/dir-item.c
 create mode 100644 fs/btrfs/extent-io.c
 create mode 100644 fs/btrfs/hash.c
 create mode 100644 fs/btrfs/inode.c
 create mode 100644 fs/btrfs/root.c
 create mode 100644 fs/btrfs/subvolume.c
 create mode 100644 fs/btrfs/super.c

12 files changed, 1841 insertions, 0 deletions

diff --git a/fs/btrfs/btrfs.h b/fs/btrfs/btrfs.h
new file mode 100644
index 00000000000..4247cbbb097
--- /dev/null
+++ b/fs/btrfs/btrfs.h
@@ -0,0 +1,89 @@
+/*
+ * BTRFS filesystem implementation for U-Boot
+ *
+ * 2017 Marek Behun, CZ.NIC, marek.behun@nic.cz
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#ifndef __BTRFS_BTRFS_H__
+#define __BTRFS_BTRFS_H__
+
+#include <linux/rbtree.h>
+#include "conv-funcs.h"
+
+struct btrfs_info {
+	struct btrfs_super_block sb;
+	struct btrfs_root_backup *root_backup;
+
+	struct btrfs_root tree_root;
+	struct btrfs_root fs_root;
+	struct btrfs_root chunk_root;
+
+	struct rb_root chunks_root;
+};
+
+extern struct btrfs_info btrfs_info;
+
+/* hash.c */
+void btrfs_hash_init(void);
+u32 btrfs_crc32c(u32, const void *, size_t);
+u32 btrfs_csum_data(char *, u32, size_t);
+void btrfs_csum_final(u32, void *);
+
+static inline u64 btrfs_name_hash(const char *name, int len)
+{
+	return btrfs_crc32c((u32) ~1, name, len);
+}
+
+/* dev.c */
+extern struct blk_desc *btrfs_blk_desc;
+extern disk_partition_t *btrfs_part_info;
+
+int btrfs_devread(u64, int, void *);
+
+/* chunk-map.c */
+u64 btrfs_map_logical_to_physical(u64);
+int btrfs_chunk_map_init(void);
+void btrfs_chunk_map_exit(void);
+int btrfs_read_chunk_tree(void);
+
+/* compression.c */
+u32 btrfs_decompress(u8 type, const char *, u32, char *, u32);
+
+/* super.c */
+int btrfs_read_superblock(void);
+
+/* dir-item.c */
+typedef int (*btrfs_readdir_callback_t)(const struct btrfs_root *,
+					struct btrfs_dir_item *);
+
+int btrfs_lookup_dir_item(const struct btrfs_root *, u64, const char *, int,
+			   struct btrfs_dir_item *);
+int btrfs_readdir(const struct btrfs_root *, u64, btrfs_readdir_callback_t);
+
+/* root.c */
+int btrfs_find_root(u64, struct btrfs_root *, struct btrfs_root_item *);
+u64 btrfs_lookup_root_ref(u64, struct btrfs_root_ref *, char *);
+
+/* inode.c */
+u64 btrfs_lookup_inode_ref(struct btrfs_root *, u64, struct btrfs_inode_ref *,
+			    char *);
+int btrfs_lookup_inode(const struct btrfs_root *, struct btrfs_key *,
+		        struct btrfs_inode_item *, struct btrfs_root *);
+int btrfs_readlink(const struct btrfs_root *, u64, char *);
+u64 btrfs_lookup_path(struct btrfs_root *, u64, const char *, u8 *,
+		       struct btrfs_inode_item *, int);
+u64 btrfs_file_read(const struct btrfs_root *, u64, u64, u64, char *);
+
+/* subvolume.c */
+u64 btrfs_get_default_subvol_objectid(void);
+
+/* extent-io.c */
+u64 btrfs_read_extent_inline(struct btrfs_path *,
+			      struct btrfs_file_extent_item *, u64, u64,
+			      char *);
+u64 btrfs_read_extent_reg(struct btrfs_path *, struct btrfs_file_extent_item *,
+			   u64, u64, char *);
+
+#endif /* !__BTRFS_BTRFS_H__ */
diff --git a/fs/btrfs/chunk-map.c b/fs/btrfs/chunk-map.c
new file mode 100644
index 00000000000..48407f33316
--- /dev/null
+++ b/fs/btrfs/chunk-map.c
@@ -0,0 +1,178 @@
+/*
+ * BTRFS filesystem implementation for U-Boot
+ *
+ * 2017 Marek Behun, CZ.NIC, marek.behun@nic.cz
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include "btrfs.h"
+#include <malloc.h>
+
+struct chunk_map_item {
+	struct rb_node node;
+	u64 logical;
+	u64 length;
+	u64 physical;
+};
+
+static int add_chunk_mapping(struct btrfs_key *key, struct btrfs_chunk *chunk)
+{
+	struct btrfs_stripe *stripe;
+	u64 block_profile = chunk->type & BTRFS_BLOCK_GROUP_PROFILE_MASK;
+	struct rb_node **new = &(btrfs_info.chunks_root.rb_node), *prnt = NULL;
+	struct chunk_map_item *map_item;
+
+	if (block_profile && block_profile != BTRFS_BLOCK_GROUP_DUP) {
+		printf("%s: unsupported chunk profile %llu\n", __func__,
+		       block_profile);
+		return -1;
+	} else if (!chunk->length) {
+		printf("%s: zero length chunk\n", __func__);
+		return -1;
+	}
+
+	stripe = &chunk->stripe;
+	btrfs_stripe_to_cpu(stripe);
+
+	while (*new) {
+		struct chunk_map_item *this;
+
+		this = rb_entry(*new, struct chunk_map_item, node);
+
+		prnt = *new;
+		if (key->offset < this->logical) {
+			new = &((*new)->rb_left);
+		} else if (key->offset > this->logical) {
+			new = &((*new)->rb_right);
+		} else {
+			debug("%s: Logical address %llu already in map!\n",
+			      __func__, key->offset);
+			return 0;
+		}
+	}
+
+	map_item = malloc(sizeof(struct chunk_map_item));
+	if (!map_item)
+		return -1;
+
+	map_item->logical = key->offset;
+	map_item->length = chunk->length;
+	map_item->physical = le64_to_cpu(chunk->stripe.offset);
+	rb_link_node(&map_item->node, prnt, new);
+	rb_insert_color(&map_item->node, &btrfs_info.chunks_root);
+
+	debug("%s: Mapping %llu to %llu\n", __func__, map_item->logical,
+	      map_item->physical);
+
+	return 0;
+}
+
+u64 btrfs_map_logical_to_physical(u64 logical)
+{
+	struct rb_node *node = btrfs_info.chunks_root.rb_node;
+
+	while (node) {
+		struct chunk_map_item *item;
+
+		item = rb_entry(node, struct chunk_map_item, node);
+
+		if (item->logical > logical)
+			node = node->rb_left;
+		else if (logical > item->logical + item->length)
+			node = node->rb_right;
+		else
+			return item->physical + logical - item->logical;
+	}
+
+	printf("%s: Cannot map logical address %llu to physical\n", __func__,
+	       logical);
+
+	return -1ULL;
+}
+
+void btrfs_chunk_map_exit(void)
+{
+	struct rb_node *now, *next;
+	struct chunk_map_item *item;
+
+	for (now = rb_first_postorder(&btrfs_info.chunks_root); now; now = next)
+	{
+		item = rb_entry(now, struct chunk_map_item, node);
+		next = rb_next_postorder(now);
+		free(item);
+	}
+}
+
+int btrfs_chunk_map_init(void)
+{
+	u8 sys_chunk_array_copy[sizeof(btrfs_info.sb.sys_chunk_array)];
+	u8 * const start = sys_chunk_array_copy;
+	u8 * const end = start + btrfs_info.sb.sys_chunk_array_size;
+	u8 *cur;
+	struct btrfs_key *key;
+	struct btrfs_chunk *chunk;
+
+	btrfs_info.chunks_root = RB_ROOT;
+
+	memcpy(sys_chunk_array_copy, btrfs_info.sb.sys_chunk_array,
+	       sizeof(sys_chunk_array_copy));
+
+	for (cur = start; cur < end;) {
+		key = (struct btrfs_key *) cur;
+		cur += sizeof(struct btrfs_key);
+		chunk = (struct btrfs_chunk *) cur;
+
+		btrfs_key_to_cpu(key);
+		btrfs_chunk_to_cpu(chunk);
+
+		if (key->type != BTRFS_CHUNK_ITEM_KEY) {
+			printf("%s: invalid key type %u\n", __func__,
+			       key->type);
+			return -1;
+		}
+
+		if (add_chunk_mapping(key, chunk))
+			return -1;
+
+		cur += sizeof(struct btrfs_chunk);
+		cur += sizeof(struct btrfs_stripe) * (chunk->num_stripes - 1);
+	}
+
+	return 0;
+}
+
+int btrfs_read_chunk_tree(void)
+{
+	struct btrfs_path path;
+	struct btrfs_key key, *found_key;
+	struct btrfs_chunk *chunk;
+	int res;
+
+	key.objectid = BTRFS_FIRST_CHUNK_TREE_OBJECTID;
+	key.type = BTRFS_CHUNK_ITEM_KEY;
+	key.offset = 0;
+
+	if (btrfs_search_tree(&btrfs_info.chunk_root, &key, &path))
+		return -1;
+
+	do {
+		found_key = btrfs_path_leaf_key(&path);
+		if (btrfs_comp_keys_type(&key, found_key))
+			break;
+
+		chunk = btrfs_path_item_ptr(&path, struct btrfs_chunk);
+		btrfs_chunk_to_cpu(chunk);
+		if (add_chunk_mapping(found_key, chunk)) {
+			res = -1;
+			break;
+		}
+	} while (!(res = btrfs_next_slot(&path)));
+
+	btrfs_free_path(&path);
+
+	if (res < 0)
+		return -1;
+
+	return 0;
+}
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
new file mode 100644
index 00000000000..a59ff5a8bbf
--- /dev/null
+++ b/fs/btrfs/compression.c
@@ -0,0 +1,134 @@
+/*
+ * BTRFS filesystem implementation for U-Boot
+ *
+ * 2017 Marek Behun, CZ.NIC, marek.behun@nic.cz
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include "btrfs.h"
+#include <linux/lzo.h>
+#include <u-boot/zlib.h>
+
+static u32 decompress_lzo(const u8 *cbuf, u32 clen, u8 *dbuf, u32 dlen)
+{
+	u32 tot_len, in_len, res;
+	size_t out_len;
+	int ret;
+
+	if (clen < 4)
+		return -1;
+
+	tot_len = le32_to_cpu(*(u32 *) cbuf);
+	cbuf += 4;
+	clen -= 4;
+	tot_len -= 4;
+
+	if (tot_len == 0 && dlen)
+		return -1;
+	if (tot_len < 4)
+		return -1;
+
+	res = 0;
+
+	while (tot_len > 4) {
+		in_len = le32_to_cpu(*(u32 *) cbuf);
+		cbuf += 4;
+		clen -= 4;
+
+		if (in_len > clen || tot_len < 4 + in_len)
+			return -1;
+
+		tot_len -= 4 + in_len;
+
+		out_len = dlen;
+		ret = lzo1x_decompress_safe(cbuf, in_len, dbuf, &out_len);
+		if (ret != LZO_E_OK)
+			return -1;
+
+		cbuf += in_len;
+		clen -= in_len;
+		dbuf += out_len;
+		dlen -= out_len;
+
+		res += out_len;
+	}
+
+	return res;
+}
+
+/* from zutil.h */
+#define PRESET_DICT 0x20
+
+static u32 decompress_zlib(const u8 *_cbuf, u32 clen, u8 *dbuf, u32 dlen)
+{
+	int wbits = MAX_WBITS, ret = -1;
+	z_stream stream;
+	u8 *cbuf;
+	u32 res;
+
+	memset(&stream, 0, sizeof(stream));
+
+	cbuf = (u8 *) _cbuf;
+
+	stream.total_in = 0;
+
+	stream.next_out = dbuf;
+	stream.avail_out = dlen;
+	stream.total_out = 0;
+
+	/* skip adler32 check if deflate and no dictionary */
+	if (clen > 2 && !(cbuf[1] & PRESET_DICT) &&
+	    ((cbuf[0] & 0x0f) == Z_DEFLATED) &&
+	    !(((cbuf[0] << 8) + cbuf[1]) % 31)) {
+		wbits = -((cbuf[0] >> 4) + 8);
+		cbuf += 2;
+		clen -= 2;
+	}
+
+	if (Z_OK != inflateInit2(&stream, wbits))
+		return -1;
+
+	while (stream.total_in < clen) {
+		stream.next_in = cbuf + stream.total_in;
+		stream.avail_in = min((u32) (clen - stream.total_in),
+				      (u32) btrfs_info.sb.sectorsize);
+
+		ret = inflate(&stream, Z_NO_FLUSH);
+		if (ret != Z_OK)
+			break;
+	}
+
+	res = stream.total_out;
+	inflateEnd(&stream);
+
+	if (ret != Z_STREAM_END)
+		return -1;
+
+	return res;
+}
+
+u32 btrfs_decompress(u8 type, const char *c, u32 clen, char *d, u32 dlen)
+{
+	u32 res;
+	const u8 *cbuf;
+	u8 *dbuf;
+
+	cbuf = (const u8 *) c;
+	dbuf = (u8 *) d;
+
+	switch (type) {
+	case BTRFS_COMPRESS_NONE:
+		res = dlen < clen ? dlen : clen;
+		memcpy(dbuf, cbuf, res);
+		return res;
+	case BTRFS_COMPRESS_ZLIB:
+		return decompress_zlib(cbuf, clen, dbuf, dlen);
+	case BTRFS_COMPRESS_LZO:
+		return decompress_lzo(cbuf, clen, dbuf, dlen);
+	default:
+		printf("%s: Unsupported compression in extent: %i\n", __func__,
+		       type);
+		return -1;
+	}
+}
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
new file mode 100644
index 00000000000..b13ecb93764
--- /dev/null
+++ b/fs/btrfs/ctree.c
@@ -0,0 +1,289 @@
+/*
+ * BTRFS filesystem implementation for U-Boot
+ *
+ * 2017 Marek Behun, CZ.NIC, marek.behun@nic.cz
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include "btrfs.h"
+#include <malloc.h>
+
+int btrfs_comp_keys(struct btrfs_key *a, struct btrfs_key *b)
+{
+	if (a->objectid > b->objectid)
+		return 1;
+	if (a->objectid < b->objectid)
+		return -1;
+	if (a->type > b->type)
+		return 1;
+	if (a->type < b->type)
+		return -1;
+	if (a->offset > b->offset)
+		return 1;
+	if (a->offset < b->offset)
+		return -1;
+	return 0;
+}
+
+int btrfs_comp_keys_type(struct btrfs_key *a, struct btrfs_key *b)
+{
+	if (a->objectid > b->objectid)
+		return 1;
+	if (a->objectid < b->objectid)
+		return -1;
+	if (a->type > b->type)
+		return 1;
+	if (a->type < b->type)
+		return -1;
+	return 0;
+}
+
+static int generic_bin_search(void *addr, int item_size, struct btrfs_key *key,
+			      int max, int *slot)
+{
+	int low = 0, high = max, mid, ret;
+	struct btrfs_key *tmp;
+
+	if (0) {
+		int i;
+		printf("\tsearching %llu %i\n", key->objectid, key->type);
+		for (i = 0; i < max; ++i) {
+			tmp = (struct btrfs_key *) ((u8 *) addr + i*item_size);
+			printf("\t\t%llu %i\n", tmp->objectid, tmp->type);
+		}
+		printf("\n");
+	}
+
+	while (low < high) {
+		mid = (low + high) / 2;
+
+		tmp = (struct btrfs_key *) ((u8 *) addr + mid*item_size);
+		ret = btrfs_comp_keys(tmp, key);
+
+		if (ret < 0) {
+			low = mid + 1;
+		} else if (ret > 0) {
+			high = mid;
+		} else {
+			*slot = mid;
+			return 0;
+		}
+	}
+
+	*slot = low;
+	return 1;
+}
+
+int btrfs_bin_search(union btrfs_tree_node *p, struct btrfs_key *key,
+		     int *slot)
+{
+	void *addr;
+	unsigned long size;
+
+	if (p->header.level) {
+		addr = p->node.ptrs;
+		size = sizeof(struct btrfs_key_ptr);
+	} else {
+		addr = p->leaf.items;
+		size = sizeof(struct btrfs_item);
+	}
+
+	return generic_bin_search(addr, size, key, p->header.nritems, slot);
+}
+
+static void clear_path(struct btrfs_path *p)
+{
+	int i;
+
+	for (i = 0; i < BTRFS_MAX_LEVEL; ++i) {
+		p->nodes[i] = NULL;
+		p->slots[i] = 0;
+	}
+}
+
+void btrfs_free_path(struct btrfs_path *p)
+{
+	int i;
+
+	for (i = 0; i < BTRFS_MAX_LEVEL; ++i) {
+		if (p->nodes[i])
+			free(p->nodes[i]);
+	}
+
+	clear_path(p);
+}
+
+static int read_tree_node(u64 physical, union btrfs_tree_node **buf)
+{
+	struct btrfs_header hdr;
+	unsigned long size, offset = sizeof(hdr);
+	union btrfs_tree_node *res;
+	u32 i;
+
+	if (!btrfs_devread(physical, sizeof(hdr), &hdr))
+		return -1;
+
+	btrfs_header_to_cpu(&hdr);
+
+	if (hdr.level)
+		size = sizeof(struct btrfs_node)
+		       + hdr.nritems * sizeof(struct btrfs_key_ptr);
+	else
+		size = btrfs_info.sb.nodesize;
+
+	res = malloc(size);
+	if (!res) {
+		debug("%s: malloc failed\n", __func__);
+		return -1;
+	}
+
+	if (!btrfs_devread(physical + offset, size - offset,
+			   ((u8 *) res) + offset)) {
+		free(res);
+		return -1;
+	}
+
+	res->header = hdr;
+	if (hdr.level)
+		for (i = 0; i < hdr.nritems; ++i)
+			btrfs_key_ptr_to_cpu(&res->node.ptrs[i]);
+	else
+		for (i = 0; i < hdr.nritems; ++i)
+			btrfs_item_to_cpu(&res->leaf.items[i]);
+
+	*buf = res;
+
+	return 0;
+}
+
+int btrfs_search_tree(const struct btrfs_root *root, struct btrfs_key *key,
+		      struct btrfs_path *p)
+{
+	u8 lvl, prev_lvl;
+	int i, slot, ret;
+	u64 logical, physical;
+	union btrfs_tree_node *buf;
+
+	clear_path(p);
+
+	logical = root->bytenr;
+
+	for (i = 0; i < BTRFS_MAX_LEVEL; ++i) {
+		physical = btrfs_map_logical_to_physical(logical);
+		if (physical == -1ULL)
+			goto err;
+
+		if (read_tree_node(physical, &buf))
+			goto err;
+
+		lvl = buf->header.level;
+		if (i && prev_lvl != lvl + 1) {
+			printf("%s: invalid level in header at %llu\n",
+			       __func__, logical);
+			goto err;
+		}
+		prev_lvl = lvl;
+
+		ret = btrfs_bin_search(buf, key, &slot);
+		if (ret < 0)
+			goto err;
+		if (ret && slot > 0 && lvl)
+			slot -= 1;
+
+		p->slots[lvl] = slot;
+		p->nodes[lvl] = buf;
+
+		if (lvl)
+			logical = buf->node.ptrs[slot].blockptr;
+		else
+			break;
+	}
+
+	return 0;
+err:
+	btrfs_free_path(p);
+	return -1;
+}
+
+static int jump_leaf(struct btrfs_path *path, int dir)
+{
+	struct btrfs_path p;
+	u32 slot;
+	int level = 1, from_level, i;
+
+	dir = dir >= 0 ? 1 : -1;
+
+	p = *path;
+
+	while (level < BTRFS_MAX_LEVEL) {
+		if (!p.nodes[level])
+			return 1;
+
+		slot = p.slots[level];
+		if ((dir > 0 && slot + dir >= p.nodes[level]->header.nritems)
+		    || (dir < 0 && !slot))
+			level++;
+		else
+			break;
+	}
+
+	if (level == BTRFS_MAX_LEVEL)
+		return 1;
+
+	p.slots[level] = slot + dir;
+	level--;
+	from_level = level;
+
+	while (level >= 0) {
+		u64 logical, physical;
+
+		slot = p.slots[level + 1];
+		logical = p.nodes[level + 1]->node.ptrs[slot].blockptr;
+		physical = btrfs_map_logical_to_physical(logical);
+		if (physical == -1ULL)
+			goto err;
+
+		if (read_tree_node(physical, &p.nodes[level]))
+			goto err;
+
+		if (dir > 0)
+			p.slots[level] = 0;
+		else
+			p.slots[level] = p.nodes[level]->header.nritems - 1;
+		level--;
+	}
+
+	/* Free rewritten nodes in path */
+	for (i = 0; i <= from_level; ++i)
+		free(path->nodes[i]);
+
+	*path = p;
+	return 0;
+
+err:
+	/* Free rewritten nodes in p */
+	for (i = level + 1; i <= from_level; ++i)
+		free(p.nodes[i]);
+	return -1;
+}
+
+int btrfs_prev_slot(struct btrfs_path *p)
+{
+	if (!p->slots[0])
+		return jump_leaf(p, -1);
+
+	p->slots[0]--;
+	return 0;
+}
+
+int btrfs_next_slot(struct btrfs_path *p)
+{
+	struct btrfs_leaf *leaf = &p->nodes[0]->leaf;
+
+	if (p->slots[0] >= leaf->header.nritems)
+		return jump_leaf(p, 1);
+
+	p->slots[0]++;
+	return 0;
+}
diff --git a/fs/btrfs/dev.c b/fs/btrfs/dev.c
new file mode 100644
index 00000000000..fd2e9b61279
--- /dev/null
+++ b/fs/btrfs/dev.c
@@ -0,0 +1,26 @@
+/*
+ * BTRFS filesystem implementation for U-Boot
+ *
+ * 2017 Marek Behun, CZ.NIC, marek.behun@nic.cz
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <compiler.h>
+#include <fs_internal.h>
+
+struct blk_desc *btrfs_blk_desc;
+disk_partition_t *btrfs_part_info;
+
+int btrfs_devread(u64 address, int byte_len, void *buf)
+{
+	lbaint_t sector;
+	int byte_offset;
+
+	sector = address >> btrfs_blk_desc->log2blksz;
+	byte_offset = address % btrfs_blk_desc->blksz;
+
+	return fs_devread(btrfs_blk_desc, btrfs_part_info, sector, byte_offset,
+			  byte_len, buf);
+}
diff --git a/fs/btrfs/dir-item.c b/fs/btrfs/dir-item.c
new file mode 100644
index 00000000000..decf86eb53e
--- /dev/null
+++ b/fs/btrfs/dir-item.c
@@ -0,0 +1,125 @@
+/*
+ * BTRFS filesystem implementation for U-Boot
+ *
+ * 2017 Marek Behun, CZ.NIC, marek.behun@nic.cz
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include "btrfs.h"
+
+static int verify_dir_item(struct btrfs_dir_item *item, u32 start, u32 total)
+{
+	u16 max_len = BTRFS_NAME_LEN;
+	u32 end;
+
+	if (item->type >= BTRFS_FT_MAX) {
+		printf("%s: invalid dir item type: %i\n", __func__, item->type);
+		return 1;
+	}
+
+	if (item->type == BTRFS_FT_XATTR)
+		max_len = 255; /* XATTR_NAME_MAX */
+
+	end = start + sizeof(*item) + item->name_len;
+	if (item->name_len > max_len || end > total) {
+		printf("%s: invalid dir item name len: %u\n", __func__,
+		       item->name_len);
+		return 1;
+	}
+
+	return 0;
+}
+
+static struct btrfs_dir_item *
+btrfs_match_dir_item_name(struct btrfs_path *path, const char *name,
+			  int name_len)
+{
+	struct btrfs_dir_item *item;
+	u32 total_len, cur = 0, this_len;
+	const char *name_ptr;
+
+	item = btrfs_path_item_ptr(path, struct btrfs_dir_item);
+
+	total_len = btrfs_path_item_size(path);
+
+	while (cur < total_len) {
+		btrfs_dir_item_to_cpu(item);
+		this_len = sizeof(*item) + item->name_len + item->data_len;
+		name_ptr = (const char *) (item + 1);
+
+		if (verify_dir_item(item, cur, total_len))
+			return NULL;
+		if (item->name_len == name_len && !memcmp(name_ptr, name,
+							  name_len))
+			return item;
+
+		cur += this_len;
+		item = (struct btrfs_dir_item *) ((u8 *) item + this_len);
+	}
+
+	return NULL;
+}
+
+int btrfs_lookup_dir_item(const struct btrfs_root *root, u64 dir,
+			  const char *name, int name_len,
+			  struct btrfs_dir_item *item)
+{
+	struct btrfs_path path;
+	struct btrfs_key key;
+	struct btrfs_dir_item *res = NULL;
+
+	key.objectid = dir;
+	key.type = BTRFS_DIR_ITEM_KEY;
+	key.offset = btrfs_name_hash(name, name_len);
+
+	if (btrfs_search_tree(root, &key, &path))
+		return -1;
+
+	if (btrfs_comp_keys_type(&key, btrfs_path_leaf_key(&path)))
+		goto out;
+
+	res = btrfs_match_dir_item_name(&path, name, name_len);
+	if (res)
+		*item = *res;
+out:
+	btrfs_free_path(&path);
+	return res ? 0 : -1;
+}
+
+int btrfs_readdir(const struct btrfs_root *root, u64 dir,
+		  btrfs_readdir_callback_t callback)
+{
+	struct btrfs_path path;
+	struct btrfs_key key, *found_key;
+	struct btrfs_dir_item *item;
+	int res;
+
+	key.objectid = dir;
+	key.type = BTRFS_DIR_INDEX_KEY;
+	key.offset = 0;
+
+	if (btrfs_search_tree(root, &key, &path))
+		return -1;
+
+	do {
+		found_key = btrfs_path_leaf_key(&path);
+		if (btrfs_comp_keys_type(&key, found_key))
+			break;
+
+		item = btrfs_path_item_ptr(&path, struct btrfs_dir_item);
+		btrfs_dir_item_to_cpu(item);
+
+		if (verify_dir_item(item, 0, sizeof(*item) + item->name_len))
+			continue;
+		if (item->type == BTRFS_FT_XATTR)
+			continue;
+
+		if (callback(root, item))
+			break;
+	} while (!(res = btrfs_next_slot(&path)));
+
+	btrfs_free_path(&path);
+
+	return res < 0 ? -1 : 0;
+}
diff --git a/fs/btrfs/extent-io.c b/fs/btrfs/extent-io.c
new file mode 100644
index 00000000000..feb91432e97
--- /dev/null
+++ b/fs/btrfs/extent-io.c
@@ -0,0 +1,120 @@
+/*
+ * BTRFS filesystem implementation for U-Boot
+ *
+ * 2017 Marek Behun, CZ.NIC, marek.behun@nic.cz
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include "btrfs.h"
+#include <malloc.h>
+
+u64 btrfs_read_extent_inline(struct btrfs_path *path,
+			     struct btrfs_file_extent_item *extent, u64 offset,
+			     u64 size, char *out)
+{
+	u32 clen, dlen, orig_size = size, res;
+	const char *cbuf;
+	char *dbuf;
+	const int data_off = offsetof(struct btrfs_file_extent_item,
+				      disk_bytenr);
+
+	clen = btrfs_path_item_size(path) - data_off;
+	cbuf = (const char *) extent + data_off;
+	dlen = extent->ram_bytes;
+
+	if (offset > dlen)
+		return -1ULL;
+
+	if (size > dlen - offset)
+		size = dlen - offset;
+
+	if (extent->compression == BTRFS_COMPRESS_NONE) {
+		memcpy(out, cbuf + offset, size);
+		return size;
+	}
+
+	if (dlen > orig_size) {
+		dbuf = malloc(dlen);
+		if (!dbuf)
+			return -1ULL;
+	} else {
+		dbuf = out;
+	}
+
+	res = btrfs_decompress(extent->compression, cbuf, clen, dbuf, dlen);
+	if (res == -1 || res != dlen)
+		goto err;
+
+	if (dlen > orig_size) {
+		memcpy(out, dbuf + offset, size);
+		free(dbuf);
+	} else if (offset) {
+		memmove(out, dbuf + offset, size);
+	}
+
+	return size;
+
+err:
+	if (dlen > orig_size)
+		free(dbuf);
+	return -1ULL;
+}
+
+u64 btrfs_read_extent_reg(struct btrfs_path *path,
+			  struct btrfs_file_extent_item *extent, u64 offset,
+			  u64 size, char *out)
+{
+	u64 physical, clen, dlen, orig_size = size;
+	u32 res;
+	char *cbuf, *dbuf;
+
+	clen = extent->disk_num_bytes;
+	dlen = extent->num_bytes;
+
+	if (offset > dlen)
+		return -1ULL;
+
+	if (size > dlen - offset)
+		size = dlen - offset;
+
+	physical = btrfs_map_logical_to_physical(extent->disk_bytenr);
+	if (physical == -1ULL)
+		return -1ULL;
+
+	if (extent->compression == BTRFS_COMPRESS_NONE) {
+		physical += extent->offset + offset;
+		if (!btrfs_devread(physical, size, out))
+			return -1ULL;
+
+		return size;
+	}
+
+	cbuf = malloc(dlen > size ? clen + dlen : clen);
+	if (!cbuf)
+		return -1ULL;
+
+	if (dlen > orig_size)
+		dbuf = cbuf + clen;
+	else
+		dbuf = out;
+
+	if (!btrfs_devread(physical, clen, cbuf))
+		goto err;
+
+	res = btrfs_decompress(extent->compression, cbuf, clen, dbuf, dlen);
+	if (res == -1)
+		goto err;
+
+	if (dlen > orig_size)
+		memcpy(out, dbuf + offset, size);
+	else
+		memmove(out, dbuf + offset, size);
+
+	free(cbuf);
+	return res;
+
+err:
+	free(cbuf);
+	return -1ULL;
+}
diff --git a/fs/btrfs/hash.c b/fs/btrfs/hash.c
new file mode 100644
index 00000000000..f8a50e532ae
--- /dev/null
+++ b/fs/btrfs/hash.c
@@ -0,0 +1,38 @@
+/*
+ * BTRFS filesystem implementation for U-Boot
+ *
+ * 2017 Marek Behun, CZ.NIC, marek.behun@nic.cz
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include "btrfs.h"
+#include <u-boot/crc.h>
+
+static u32 btrfs_crc32c_table[256];
+
+void btrfs_hash_init(void)
+{
+	static int inited = 0;
+
+	if (!inited) {
+		crc32c_init(btrfs_crc32c_table, 0x82F63B78);
+		inited = 1;
+	}
+}
+
+u32 btrfs_crc32c(u32 crc, const void *data, size_t length)
+{
+	return crc32c_cal(crc, (const char *) data, length,
+			  btrfs_crc32c_table);
+}
+
+u32 btrfs_csum_data(char *data, u32 seed, size_t len)
+{
+	return btrfs_crc32c(seed, data, len);
+}
+
+void btrfs_csum_final(u32 crc, void *result)
+{
+	*((u32 *) result) = cpu_to_le32(~crc);
+}
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
new file mode 100644
index 00000000000..0d3da282966
--- /dev/null
+++ b/fs/btrfs/inode.c
@@ -0,0 +1,385 @@
+/*
+ * BTRFS filesystem implementation for U-Boot
+ *
+ * 2017 Marek Behun, CZ.NIC, marek.behun@nic.cz
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include "btrfs.h"
+#include <malloc.h>
+
+u64 btrfs_lookup_inode_ref(struct btrfs_root *root, u64 inr,
+			   struct btrfs_inode_ref *refp, char *name)
+{
+	struct btrfs_path path;
+	struct btrfs_key *key;
+	struct btrfs_inode_ref *ref;
+	u64 res = -1ULL;
+
+	key = btrfs_search_tree_key_type(root, inr, BTRFS_INODE_REF_KEY,
+					       &path);
+
+	if (!key)
+		return -1ULL;
+
+	ref = btrfs_path_item_ptr(&path, struct btrfs_inode_ref);
+	btrfs_inode_ref_to_cpu(ref);
+
+	if (refp)
+		*refp = *ref;
+
+	if (name) {
+		if (ref->name_len > BTRFS_NAME_MAX) {
+			printf("%s: inode name too long: %u\n", __func__,
+			        ref->name_len);
+			goto out;
+		}
+
+		memcpy(name, ref + 1, ref->name_len);
+	}
+
+	res = key->offset;
+out:
+	btrfs_free_path(&path);
+	return res;
+}
+
+int btrfs_lookup_inode(const struct btrfs_root *root,
+		       struct btrfs_key *location,
+		       struct btrfs_inode_item *item,
+		       struct btrfs_root *new_root)
+{
+	struct btrfs_root tmp_root = *root;
+	struct btrfs_path path;
+	int res = -1;
+
+	if (location->type == BTRFS_ROOT_ITEM_KEY) {
+		if (btrfs_find_root(location->objectid, &tmp_root, NULL))
+			return -1;
+
+		location->objectid = tmp_root.root_dirid;
+		location->type = BTRFS_INODE_ITEM_KEY;
+		location->offset = 0;
+	}
+
+	if (btrfs_search_tree(&tmp_root, location, &path))
+		return res;
+
+	if (btrfs_comp_keys(location, btrfs_path_leaf_key(&path)))
+		goto out;
+
+	if (item) {
+		*item = *btrfs_path_item_ptr(&path, struct btrfs_inode_item);
+		btrfs_inode_item_to_cpu(item);
+	}
+
+	if (new_root)
+		*new_root = tmp_root;
+
+	res = 0;
+
+out:
+	btrfs_free_path(&path);
+	return res;
+}
+
+int btrfs_readlink(const struct btrfs_root *root, u64 inr, char *target)
+{
+	struct btrfs_path path;
+	struct btrfs_key key;
+	struct btrfs_file_extent_item *extent;
+	const char *data_ptr;
+	int res = -1;
+
+	key.objectid = inr;
+	key.type = BTRFS_EXTENT_DATA_KEY;
+	key.offset = 0;
+
+	if (btrfs_search_tree(root, &key, &path))
+		return -1;
+
+	if (btrfs_comp_keys(&key, btrfs_path_leaf_key(&path)))
+		goto out;
+
+	extent = btrfs_path_item_ptr(&path, struct btrfs_file_extent_item);
+	if (extent->type != BTRFS_FILE_EXTENT_INLINE) {
+		printf("%s: Extent for symlink %llu not of INLINE type\n",
+		       __func__, inr);
+		goto out;
+	}
+
+	btrfs_file_extent_item_to_cpu_inl(extent);
+
+	if (extent->compression != BTRFS_COMPRESS_NONE) {
+		printf("%s: Symlink %llu extent data compressed!\n", __func__,
+		       inr);
+		goto out;
+	} else if (extent->encryption != 0) {
+		printf("%s: Symlink %llu extent data encrypted!\n", __func__,
+		       inr);
+		goto out;
+	} else if (extent->ram_bytes >= btrfs_info.sb.sectorsize) {
+		printf("%s: Symlink %llu extent data too long (%llu)!\n",
+		       __func__, inr, extent->ram_bytes);
+		goto out;
+	}
+
+	data_ptr = (const char *) extent
+		   + offsetof(struct btrfs_file_extent_item, disk_bytenr);
+
+	memcpy(target, data_ptr, extent->ram_bytes);
+	target[extent->ram_bytes] = '\0';
+	res = 0;
+out:
+	btrfs_free_path(&path);
+	return res;
+}
+
+/* inr must be a directory (for regular files with multiple hard links this
+   function returns only one of the parents of the file) */
+static u64 get_parent_inode(struct btrfs_root *root, u64 inr,
+			    struct btrfs_inode_item *inode_item)
+{
+	struct btrfs_key key;
+	u64 res;
+
+	if (inr == BTRFS_FIRST_FREE_OBJECTID) {
+		if (root->objectid != btrfs_info.fs_root.objectid) {
+			u64 parent;
+			struct btrfs_root_ref ref;
+
+			parent = btrfs_lookup_root_ref(root->objectid, &ref,
+						       NULL);
+			if (parent == -1ULL)
+				return -1ULL;
+
+			if (btrfs_find_root(parent, root, NULL))
+				return -1ULL;
+
+			inr = ref.dirid;
+		}
+
+		if (inode_item) {
+			key.objectid = inr;
+			key.type = BTRFS_INODE_ITEM_KEY;
+			key.offset = 0;
+
+			if (btrfs_lookup_inode(root, &key, inode_item, NULL))
+				return -1ULL;
+		}
+
+		return inr;
+	}
+
+	res = btrfs_lookup_inode_ref(root, inr, NULL, NULL);
+	if (res == -1ULL)
+		return -1ULL;
+
+	if (inode_item) {
+		key.objectid = res;
+		key.type = BTRFS_INODE_ITEM_KEY;
+		key.offset = 0;
+
+		if (btrfs_lookup_inode(root, &key, inode_item, NULL))
+			return -1ULL;
+	}
+
+	return res;
+}
+
+static inline int next_length(const char *path)
+{
+	int res = 0;
+	while (*path != '\0' && *path != '/' && res <= BTRFS_NAME_LEN)
+		++res, ++path;
+	return res;
+}
+
+static inline const char *skip_current_directories(const char *cur)
+{
+	while (1) {
+		if (cur[0] == '/')
+			++cur;
+		else if (cur[0] == '.' && cur[1] == '/')
+			cur += 2;
+		else
+			break;
+	}
+
+	return cur;
+}
+
+/* inode.c, musi vratit aj root stromu kde sa inoda najde */
+u64 btrfs_lookup_path(struct btrfs_root *root, u64 inr, const char *path,
+		      u8 *type_p, struct btrfs_inode_item *inode_item_p,
+		      int symlink_limit)
+{
+	struct btrfs_dir_item item;
+	struct btrfs_inode_item inode_item;
+	u8 type = BTRFS_FT_DIR;
+	int len, have_inode = 0;
+	const char *cur = path;
+
+	if (*cur == '/') {
+		++cur;
+		inr = root->root_dirid;
+	}
+
+	do {
+		cur = skip_current_directories(cur);
+
+		len = next_length(cur);
+		if (len > BTRFS_NAME_LEN) {
+			printf("%s: Name too long at \"%.*s\"\n", __func__,
+			       BTRFS_NAME_LEN, cur);
+			return -1ULL;
+		}
+
+		if (len == 1 && cur[0] == '.')
+			break;
+
+		if (len == 2 && cur[0] == '.' && cur[1] == '.') {
+			cur += 2;
+			inr = get_parent_inode(root, inr, &inode_item);
+			if (inr == -1ULL)
+				return -1ULL;
+
+			type = BTRFS_FT_DIR;
+			continue;
+		}
+
+		if (!*cur)
+			break;
+		
+		if (btrfs_lookup_dir_item(root, inr, cur, len, &item))
+			return -1ULL;
+
+		type = item.type;
+		have_inode = 1;
+		if (btrfs_lookup_inode(root, &item.location, &inode_item, root))
+			return -1ULL;
+
+		if (item.type == BTRFS_FT_SYMLINK && symlink_limit >= 0) {
+			char *target;
+
+			if (!symlink_limit) {
+				printf("%s: Too much symlinks!\n", __func__);
+				return -1ULL;
+			}
+
+			target = malloc(min(inode_item.size + 1,
+					    (u64) btrfs_info.sb.sectorsize));
+			if (!target)
+				return -1ULL;
+
+			if (btrfs_readlink(root, item.location.objectid,
+					   target)) {
+				free(target);
+				return -1ULL;
+			}
+
+			inr = btrfs_lookup_path(root, inr, target, &type,
+						&inode_item, symlink_limit - 1);
+
+			free(target);
+
+			if (inr == -1ULL)
+				return -1ULL;
+		} else if (item.type != BTRFS_FT_DIR && cur[len]) {
+			printf("%s: \"%.*s\" not a directory\n", __func__,
+			       (int) (cur - path + len), path);
+			return -1ULL;
+		} else {
+			inr = item.location.objectid;
+		}
+
+		cur += len;
+	} while (*cur);
+
+	if (type_p)
+		*type_p = type;
+
+	if (inode_item_p) {
+		if (!have_inode) {
+			struct btrfs_key key;
+
+			key.objectid = inr;
+			key.type = BTRFS_INODE_ITEM_KEY;
+			key.offset = 0;
+
+			if (btrfs_lookup_inode(root, &key, &inode_item, NULL))
+				return -1ULL;
+		}
+
+		*inode_item_p = inode_item;
+	}
+
+	return inr;
+}
+
+u64 btrfs_file_read(const struct btrfs_root *root, u64 inr, u64 offset,
+		    u64 size, char *buf)
+{
+	struct btrfs_path path;
+	struct btrfs_key key;
+	struct btrfs_file_extent_item *extent;
+	int res;
+	u64 rd, rd_all = -1ULL;
+
+	key.objectid = inr;
+	key.type = BTRFS_EXTENT_DATA_KEY;
+	key.offset = offset;
+
+	if (btrfs_search_tree(root, &key, &path))
+		return -1ULL;
+
+	if (btrfs_comp_keys(&key, btrfs_path_leaf_key(&path)) < 0) {
+		if (btrfs_prev_slot(&path))
+			goto out;
+
+		if (btrfs_comp_keys_type(&key, btrfs_path_leaf_key(&path)))
+			goto out;
+	}
+
+	rd_all = 0;
+
+	do {
+		if (btrfs_comp_keys_type(&key, btrfs_path_leaf_key(&path)))
+			break;
+
+		extent = btrfs_path_item_ptr(&path,
+					     struct btrfs_file_extent_item);
+
+		if (extent->type == BTRFS_FILE_EXTENT_INLINE) {
+			btrfs_file_extent_item_to_cpu_inl(extent);
+			rd = btrfs_read_extent_inline(&path, extent, offset,
+						      size, buf);
+		} else {
+			btrfs_file_extent_item_to_cpu(extent);
+			rd = btrfs_read_extent_reg(&path, extent, offset, size,
+						   buf);
+		}
+
+		if (rd == -1ULL) {
+			printf("%s: Error reading extent\n", __func__);
+			rd_all = -1;
+			goto out;
+		}
+
+		offset = 0;
+		buf += rd;
+		rd_all += rd;
+		size -= rd;
+
+		if (!size)
+			break;
+	} while (!(res = btrfs_next_slot(&path)));
+
+	if (res)
+		return -1ULL;
+
+out:
+	btrfs_free_path(&path);
+	return rd_all;
+}
diff --git a/fs/btrfs/root.c b/fs/btrfs/root.c
new file mode 100644
index 00000000000..c405813b692
--- /dev/null
+++ b/fs/btrfs/root.c
@@ -0,0 +1,93 @@
+/*
+ * BTRFS filesystem implementation for U-Boot
+ *
+ * 2017 Marek Behun, CZ.NIC, marek.behun@nic.cz
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include "btrfs.h"
+
+static void read_root_item(struct btrfs_path *p, struct btrfs_root_item *item)
+{
+	u32 len;
+	int reset = 0;
+
+	len = btrfs_path_item_size(p);
+	memcpy(item, btrfs_path_item_ptr(p, struct btrfs_root_item), len);
+	btrfs_root_item_to_cpu(item);
+
+	if (len < sizeof(*item))
+		reset = 1;
+	if (!reset && item->generation != item->generation_v2) {
+		if (item->generation_v2 != 0)
+			printf("%s: generation != generation_v2 in root item",
+			       __func__);
+		reset = 1;
+	}
+	if (reset) {
+		memset(&item->generation_v2, 0,
+		       sizeof(*item) - offsetof(struct btrfs_root_item,
+						generation_v2));
+	}
+}
+
+int btrfs_find_root(u64 objectid, struct btrfs_root *root,
+		    struct btrfs_root_item *root_item)
+{
+	struct btrfs_path path;
+	struct btrfs_root_item my_root_item;
+
+	if (!btrfs_search_tree_key_type(&btrfs_info.tree_root, objectid,
+					BTRFS_ROOT_ITEM_KEY, &path))
+		return -1;
+
+	if (!root_item)
+		root_item = &my_root_item;
+	read_root_item(&path, root_item);
+
+	if (root) {
+		root->objectid = objectid;
+		root->bytenr = root_item->bytenr;
+		root->root_dirid = root_item->root_dirid;
+	}
+
+	btrfs_free_path(&path);
+	return 0;
+}
+
+u64 btrfs_lookup_root_ref(u64 subvolid, struct btrfs_root_ref *refp, char *name)
+{
+	struct btrfs_path path;
+	struct btrfs_key *key;
+	struct btrfs_root_ref *ref;
+	u64 res = -1ULL;
+
+	key = btrfs_search_tree_key_type(&btrfs_info.tree_root, subvolid,
+					       BTRFS_ROOT_BACKREF_KEY, &path);
+
+	if (!key)
+		return -1ULL;
+
+	ref = btrfs_path_item_ptr(&path, struct btrfs_root_ref);
+	btrfs_root_ref_to_cpu(ref);
+
+	if (refp)
+		*refp = *ref;
+
+	if (name) {
+		if (ref->name_len > BTRFS_VOL_NAME_MAX) {
+			printf("%s: volume name too long: %u\n", __func__,
+			       ref->name_len);
+			goto out;
+		}
+
+		memcpy(name, ref + 1, ref->name_len);
+	}
+
+	res = key->offset;
+out:
+	btrfs_free_path(&path);
+	return res;
+}
+
diff --git a/fs/btrfs/subvolume.c b/fs/btrfs/subvolume.c
new file mode 100644
index 00000000000..54e0ab45463
--- /dev/null
+++ b/fs/btrfs/subvolume.c
@@ -0,0 +1,131 @@
+/*
+ * BTRFS filesystem implementation for U-Boot
+ *
+ * 2017 Marek Behun, CZ.NIC, marek.behun@nic.cz
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include "btrfs.h"
+#include <malloc.h>
+
+static int get_subvol_name(u64 subvolid, char *name, int max_len)
+{
+	struct btrfs_root_ref rref;
+	struct btrfs_inode_ref iref;
+	struct btrfs_root root;
+	u64 dir;
+	char tmp[max(BTRFS_VOL_NAME_MAX, BTRFS_NAME_MAX)];
+	char *ptr;
+
+	ptr = name + max_len - 1;
+	*ptr = '\0';
+
+	while (subvolid != BTRFS_FS_TREE_OBJECTID) {
+		subvolid = btrfs_lookup_root_ref(subvolid, &rref, tmp);
+
+		if (subvolid == -1ULL)
+			return -1;
+
+		ptr -= rref.name_len + 1;
+		if (ptr < name)
+			goto too_long;
+
+		memcpy(ptr + 1, tmp, rref.name_len);
+		*ptr = '/';
+
+		if (btrfs_find_root(subvolid, &root, NULL))
+			return -1;
+
+		dir = rref.dirid;
+
+		while (dir != BTRFS_FIRST_FREE_OBJECTID) {
+			dir = btrfs_lookup_inode_ref(&root, dir, &iref, tmp);
+
+			if (dir == -1ULL)
+				return -1;
+
+			ptr -= iref.name_len + 1;
+			if (ptr < name)
+				goto too_long;
+
+			memcpy(ptr + 1, tmp, iref.name_len);
+			*ptr = '/';
+		}
+	}
+
+	if (ptr == name + max_len - 1) {
+		name[0] = '/';
+		name[1] = '\0';
+	} else {
+		memmove(name, ptr, name + max_len - ptr);
+	}
+
+	return 0;
+
+too_long:
+	printf("%s: subvolume name too long\n", __func__);
+	return -1;
+}
+
+u64 btrfs_get_default_subvol_objectid(void)
+{
+	struct btrfs_dir_item item;
+
+	if (btrfs_lookup_dir_item(&btrfs_info.tree_root,
+				  btrfs_info.sb.root_dir_objectid, "default", 7,
+				  &item))
+		return BTRFS_FS_TREE_OBJECTID;
+	return item.location.objectid;
+}
+
+static void list_subvols(u64 tree, char *nameptr, int max_name_len, int level)
+{
+	struct btrfs_key key, *found_key;
+	struct btrfs_path path;
+	struct btrfs_root_ref *ref;
+	int res;
+
+	key.objectid = tree;
+	key.type = BTRFS_ROOT_REF_KEY;
+	key.offset = 0;
+
+	if (btrfs_search_tree(&btrfs_info.tree_root, &key, &path))
+		return;
+
+	do {
+		found_key = btrfs_path_leaf_key(&path);
+		if (btrfs_comp_keys_type(&key, found_key))
+			break;
+
+		ref = btrfs_path_item_ptr(&path, struct btrfs_root_ref);
+		btrfs_root_ref_to_cpu(ref);
+
+		printf("ID %llu parent %llu name ", found_key->offset, tree);
+		if (nameptr && !get_subvol_name(found_key->offset, nameptr,
+						max_name_len))
+			printf("%s\n", nameptr);
+		else
+			printf("%.*s\n", (int) ref->name_len,
+			       (const char *) (ref + 1));
+
+		if (level > 0)
+			list_subvols(found_key->offset, nameptr, max_name_len,
+				     level - 1);
+		else
+			printf("%s: Too much recursion, maybe skipping some "
+			       "subvolumes\n", __func__);
+	} while (!(res = btrfs_next_slot(&path)));
+
+	btrfs_free_path(&path);
+}
+
+void btrfs_list_subvols(void)
+{
+	char *nameptr = malloc(4096);
+
+	list_subvols(BTRFS_FS_TREE_OBJECTID, nameptr, nameptr ? 4096 : 0, 40);
+
+	if (nameptr)
+		free(nameptr);
+}
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
new file mode 100644
index 00000000000..706286ee2d8
--- /dev/null
+++ b/fs/btrfs/super.c
@@ -0,0 +1,233 @@
+/*
+ * BTRFS filesystem implementation for U-Boot
+ *
+ * 2017 Marek Behun, CZ.NIC, marek.behun@nic.cz
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include "btrfs.h"
+
+#define BTRFS_SUPER_FLAG_SUPP	(BTRFS_HEADER_FLAG_WRITTEN	\
+				 | BTRFS_HEADER_FLAG_RELOC	\
+				 | BTRFS_SUPER_FLAG_ERROR	\
+				 | BTRFS_SUPER_FLAG_SEEDING	\
+				 | BTRFS_SUPER_FLAG_METADUMP)
+
+#define BTRFS_SUPER_INFO_SIZE	4096
+
+static int btrfs_newest_root_backup(struct btrfs_super_block *sb)
+{
+	struct btrfs_root_backup *root_backup;
+	int i, newest = -1;
+
+	for (i = 0; i < BTRFS_NUM_BACKUP_ROOTS; ++i) {
+		root_backup = sb->super_roots + i;
+		if (root_backup->tree_root_gen == sb->generation)
+			newest = i;
+	}
+
+	return newest;
+}
+
+static inline int is_power_of_2(u64 x)
+{
+	return !(x & (x - 1));
+}
+
+static int btrfs_check_super_csum(char *raw_disk_sb)
+{
+	struct btrfs_super_block *disk_sb =
+		(struct btrfs_super_block *) raw_disk_sb;
+	u16 csum_type = le16_to_cpu(disk_sb->csum_type);
+
+	if (csum_type == BTRFS_CSUM_TYPE_CRC32) {
+		u32 crc = ~(u32) 0;
+		const int csum_size = sizeof(crc);
+		char result[csum_size];
+
+		crc = btrfs_csum_data(raw_disk_sb + BTRFS_CSUM_SIZE, crc,
+				      BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE);
+		btrfs_csum_final(crc, result);
+
+		if (memcmp(raw_disk_sb, result, csum_size))
+			return -1;
+	} else {
+		return -1;
+	}
+
+	return 0;
+}
+
+static int btrfs_check_super(struct btrfs_super_block *sb)
+{
+	int ret = 0;
+
+	if (sb->flags & ~BTRFS_SUPER_FLAG_SUPP) {
+		printf("%s: Unsupported flags: %llu\n", __func__,
+		       sb->flags & ~BTRFS_SUPER_FLAG_SUPP);
+	}
+
+	if (sb->root_level > BTRFS_MAX_LEVEL) {
+		printf("%s: tree_root level too big: %d >= %d\n", __func__,
+		       sb->root_level, BTRFS_MAX_LEVEL);
+		ret = -1;
+	}
+
+	if (sb->chunk_root_level > BTRFS_MAX_LEVEL) {
+		printf("%s: chunk_root level too big: %d >= %d\n", __func__,
+		       sb->chunk_root_level, BTRFS_MAX_LEVEL);
+		ret = -1;
+	}
+
+	if (sb->log_root_level > BTRFS_MAX_LEVEL) {
+		printf("%s: log_root level too big: %d >= %d\n", __func__,
+		       sb->log_root_level, BTRFS_MAX_LEVEL);
+		ret = -1;
+	}
+
+	if (!is_power_of_2(sb->sectorsize) || sb->sectorsize < 4096 ||
+	    sb->sectorsize > BTRFS_MAX_METADATA_BLOCKSIZE) {
+		printf("%s: invalid sectorsize %u\n", __func__,
+		       sb->sectorsize);
+		ret = -1;
+	}
+
+	if (!is_power_of_2(sb->nodesize) || sb->nodesize < sb->sectorsize ||
+	    sb->nodesize > BTRFS_MAX_METADATA_BLOCKSIZE) {
+		printf("%s: invalid nodesize %u\n", __func__, sb->nodesize);
+		ret = -1;
+	}
+
+	if (sb->nodesize != sb->__unused_leafsize) {
+		printf("%s: invalid leafsize %u, should be %u\n", __func__,
+		       sb->__unused_leafsize, sb->nodesize);
+		ret = -1;
+	}
+
+	if (!IS_ALIGNED(sb->root, sb->sectorsize)) {
+		printf("%s: tree_root block unaligned: %llu\n", __func__,
+		       sb->root);
+		ret = -1;
+	}
+
+	if (!IS_ALIGNED(sb->chunk_root, sb->sectorsize)) {
+		printf("%s: chunk_root block unaligned: %llu\n", __func__,
+		       sb->chunk_root);
+		ret = -1;
+	}
+
+	if (!IS_ALIGNED(sb->log_root, sb->sectorsize)) {
+		printf("%s: log_root block unaligned: %llu\n", __func__,
+		       sb->log_root);
+		ret = -1;
+	}
+
+	if (memcmp(sb->fsid, sb->dev_item.fsid, BTRFS_UUID_SIZE) != 0) {
+		printf("%s: dev_item UUID does not match fsid\n", __func__);
+		ret = -1;
+	}
+
+	if (sb->bytes_used < 6*sb->nodesize) {
+		printf("%s: bytes_used is too small %llu\n", __func__,
+		       sb->bytes_used);
+		ret = -1;
+	}
+
+	if (!is_power_of_2(sb->stripesize)) {
+		printf("%s: invalid stripesize %u\n", __func__, sb->stripesize);
+		ret = -1;
+	}
+
+	if (sb->sys_chunk_array_size > BTRFS_SYSTEM_CHUNK_ARRAY_SIZE) {
+		printf("%s: system chunk array too big %u > %u\n", __func__,
+		       sb->sys_chunk_array_size, BTRFS_SYSTEM_CHUNK_ARRAY_SIZE);
+		ret = -1;
+	}
+
+	if (sb->sys_chunk_array_size < sizeof(struct btrfs_key) +
+	    sizeof(struct btrfs_chunk)) {
+		printf("%s: system chunk array too small %u < %u\n", __func__,
+		       sb->sys_chunk_array_size, (u32) sizeof(struct btrfs_key)
+		       + sizeof(struct btrfs_chunk));
+		ret = -1;
+	}
+
+	return ret;
+}
+
+int btrfs_read_superblock(void)
+{
+	const u64 superblock_offsets[4] = {
+		0x10000ull,
+		0x4000000ull,
+		0x4000000000ull,
+		0x4000000000000ull
+	};
+	char raw_sb[BTRFS_SUPER_INFO_SIZE];
+	struct btrfs_super_block *sb = (struct btrfs_super_block *) raw_sb;
+	u64 dev_total_bytes;
+	int i, root_backup_idx;
+
+	dev_total_bytes = (u64) btrfs_part_info->size * btrfs_part_info->blksz;
+
+	btrfs_info.sb.generation = 0;
+
+	for (i = 0; i < 4; ++i) {
+		if (superblock_offsets[i] + sizeof(sb) > dev_total_bytes)
+			break;
+
+		if (!btrfs_devread(superblock_offsets[i], BTRFS_SUPER_INFO_SIZE,
+				   raw_sb))
+			break;
+
+		if (btrfs_check_super_csum(raw_sb)) {
+			printf("%s: invalid checksum at superblock mirror %i\n",
+			       __func__, i);
+			continue;
+		}
+
+		btrfs_super_block_to_cpu(sb);
+
+		if (sb->magic != BTRFS_MAGIC) {
+			printf("%s: invalid BTRFS magic 0x%016llX at "
+			       "superblock mirror %i\n", __func__, sb->magic,
+			       i);
+		} else if (sb->bytenr != superblock_offsets[i]) {
+			printf("%s: invalid bytenr 0x%016llX (expected "
+			       "0x%016llX) at superblock mirror %i\n",
+			       __func__, sb->bytenr, superblock_offsets[i], i);
+		} else if (btrfs_check_super(sb)) {
+			printf("%s: Checking superblock mirror %i failed\n",
+			       __func__, i);
+		} else if (sb->generation > btrfs_info.sb.generation) {
+			memcpy(&btrfs_info.sb, sb, sizeof(*sb));
+		} else {
+			/* Nothing */
+		}
+	}
+
+	if (!btrfs_info.sb.generation) {
+		printf("%s: No valid BTRFS superblock found!\n", __func__);
+		return -1;
+	}
+
+	root_backup_idx = btrfs_newest_root_backup(&btrfs_info.sb);
+	if (root_backup_idx < 0) {
+		printf("%s: No valid root_backup found!\n", __func__);
+		return -1;
+	}
+	btrfs_info.root_backup = btrfs_info.sb.super_roots + root_backup_idx;
+
+	if (btrfs_info.root_backup->num_devices != 1) {
+		printf("%s: Unsupported number of devices (%lli). This driver "
+		       "only supports filesystem on one device.\n", __func__,
+		       btrfs_info.root_backup->num_devices);
+		return -1;
+	}
+
+	debug("Chosen superblock with generation = %llu\n",
+	      btrfs_info.sb.generation);
+
+	return 0;
+}