Adding upstream version 5.10.209.upstream/5.10.209

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 7541 insertions, 0 deletions

diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
new file mode 100644
index 000000000..af9701afc
--- /dev/null
+++ b/fs/btrfs/send.c
@@ -0,0 +1,7541 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2012 Alexander Block.  All rights reserved.
+ */
+
+#include <linux/bsearch.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/sort.h>
+#include <linux/mount.h>
+#include <linux/xattr.h>
+#include <linux/posix_acl_xattr.h>
+#include <linux/radix-tree.h>
+#include <linux/vmalloc.h>
+#include <linux/string.h>
+#include <linux/compat.h>
+#include <linux/crc32c.h>
+
+#include "send.h"
+#include "backref.h"
+#include "locking.h"
+#include "disk-io.h"
+#include "btrfs_inode.h"
+#include "transaction.h"
+#include "compression.h"
+#include "xattr.h"
+
+/*
+ * Maximum number of references an extent can have in order for us to attempt to
+ * issue clone operations instead of write operations. This currently exists to
+ * avoid hitting limitations of the backreference walking code (taking a lot of
+ * time and using too much memory for extents with large number of references).
+ */
+#define SEND_MAX_EXTENT_REFS	64
+
+/*
+ * A fs_path is a helper to dynamically build path names with unknown size.
+ * It reallocates the internal buffer on demand.
+ * It allows fast adding of path elements on the right side (normal path) and
+ * fast adding to the left side (reversed path). A reversed path can also be
+ * unreversed if needed.
+ */
+struct fs_path {
+	union {
+		struct {
+			char *start;
+			char *end;
+
+			char *buf;
+			unsigned short buf_len:15;
+			unsigned short reversed:1;
+			char inline_buf[];
+		};
+		/*
+		 * Average path length does not exceed 200 bytes, we'll have
+		 * better packing in the slab and higher chance to satisfy
+		 * a allocation later during send.
+		 */
+		char pad[256];
+	};
+};
+#define FS_PATH_INLINE_SIZE \
+	(sizeof(struct fs_path) - offsetof(struct fs_path, inline_buf))
+
+
+/* reused for each extent */
+struct clone_root {
+	struct btrfs_root *root;
+	u64 ino;
+	u64 offset;
+
+	u64 found_refs;
+};
+
+#define SEND_CTX_MAX_NAME_CACHE_SIZE 128
+#define SEND_CTX_NAME_CACHE_CLEAN_SIZE (SEND_CTX_MAX_NAME_CACHE_SIZE * 2)
+
+struct send_ctx {
+	struct file *send_filp;
+	loff_t send_off;
+	char *send_buf;
+	u32 send_size;
+	u32 send_max_size;
+	u64 total_send_size;
+	u64 cmd_send_size[BTRFS_SEND_C_MAX + 1];
+	u64 flags;	/* 'flags' member of btrfs_ioctl_send_args is u64 */
+
+	struct btrfs_root *send_root;
+	struct btrfs_root *parent_root;
+	struct clone_root *clone_roots;
+	int clone_roots_cnt;
+
+	/* current state of the compare_tree call */
+	struct btrfs_path *left_path;
+	struct btrfs_path *right_path;
+	struct btrfs_key *cmp_key;
+
+	/*
+	 * infos of the currently processed inode. In case of deleted inodes,
+	 * these are the values from the deleted inode.
+	 */
+	u64 cur_ino;
+	u64 cur_inode_gen;
+	int cur_inode_new;
+	int cur_inode_new_gen;
+	int cur_inode_deleted;
+	u64 cur_inode_size;
+	u64 cur_inode_mode;
+	u64 cur_inode_rdev;
+	u64 cur_inode_last_extent;
+	u64 cur_inode_next_write_offset;
+	bool ignore_cur_inode;
+
+	u64 send_progress;
+
+	struct list_head new_refs;
+	struct list_head deleted_refs;
+
+	struct radix_tree_root name_cache;
+	struct list_head name_cache_list;
+	int name_cache_size;
+
+	struct file_ra_state ra;
+
+	/*
+	 * We process inodes by their increasing order, so if before an
+	 * incremental send we reverse the parent/child relationship of
+	 * directories such that a directory with a lower inode number was
+	 * the parent of a directory with a higher inode number, and the one
+	 * becoming the new parent got renamed too, we can't rename/move the
+	 * directory with lower inode number when we finish processing it - we
+	 * must process the directory with higher inode number first, then
+	 * rename/move it and then rename/move the directory with lower inode
+	 * number. Example follows.
+	 *
+	 * Tree state when the first send was performed:
+	 *
+	 * .
+	 * |-- a                   (ino 257)
+	 *     |-- b               (ino 258)
+	 *         |
+	 *         |
+	 *         |-- c           (ino 259)
+	 *         |   |-- d       (ino 260)
+	 *         |
+	 *         |-- c2          (ino 261)
+	 *
+	 * Tree state when the second (incremental) send is performed:
+	 *
+	 * .
+	 * |-- a                   (ino 257)
+	 *     |-- b               (ino 258)
+	 *         |-- c2          (ino 261)
+	 *             |-- d2      (ino 260)
+	 *                 |-- cc  (ino 259)
+	 *
+	 * The sequence of steps that lead to the second state was:
+	 *
+	 * mv /a/b/c/d /a/b/c2/d2
+	 * mv /a/b/c /a/b/c2/d2/cc
+	 *
+	 * "c" has lower inode number, but we can't move it (2nd mv operation)
+	 * before we move "d", which has higher inode number.
+	 *
+	 * So we just memorize which move/rename operations must be performed
+	 * later when their respective parent is processed and moved/renamed.
+	 */
+
+	/* Indexed by parent directory inode number. */
+	struct rb_root pending_dir_moves;
+
+	/*
+	 * Reverse index, indexed by the inode number of a directory that
+	 * is waiting for the move/rename of its immediate parent before its
+	 * own move/rename can be performed.
+	 */
+	struct rb_root waiting_dir_moves;
+
+	/*
+	 * A directory that is going to be rm'ed might have a child directory
+	 * which is in the pending directory moves index above. In this case,
+	 * the directory can only be removed after the move/rename of its child
+	 * is performed. Example:
+	 *
+	 * Parent snapshot:
+	 *
+	 * .                        (ino 256)
+	 * |-- a/                   (ino 257)
+	 *     |-- b/               (ino 258)
+	 *         |-- c/           (ino 259)
+	 *         |   |-- x/       (ino 260)
+	 *         |
+	 *         |-- y/           (ino 261)
+	 *
+	 * Send snapshot:
+	 *
+	 * .                        (ino 256)
+	 * |-- a/                   (ino 257)
+	 *     |-- b/               (ino 258)
+	 *         |-- YY/          (ino 261)
+	 *              |-- x/      (ino 260)
+	 *
+	 * Sequence of steps that lead to the send snapshot:
+	 * rm -f /a/b/c/foo.txt
+	 * mv /a/b/y /a/b/YY
+	 * mv /a/b/c/x /a/b/YY
+	 * rmdir /a/b/c
+	 *
+	 * When the child is processed, its move/rename is delayed until its
+	 * parent is processed (as explained above), but all other operations
+	 * like update utimes, chown, chgrp, etc, are performed and the paths
+	 * that it uses for those operations must use the orphanized name of
+	 * its parent (the directory we're going to rm later), so we need to
+	 * memorize that name.
+	 *
+	 * Indexed by the inode number of the directory to be deleted.
+	 */
+	struct rb_root orphan_dirs;
+};
+
+struct pending_dir_move {
+	struct rb_node node;
+	struct list_head list;
+	u64 parent_ino;
+	u64 ino;
+	u64 gen;
+	struct list_head update_refs;
+};
+
+struct waiting_dir_move {
+	struct rb_node node;
+	u64 ino;
+	/*
+	 * There might be some directory that could not be removed because it
+	 * was waiting for this directory inode to be moved first. Therefore
+	 * after this directory is moved, we can try to rmdir the ino rmdir_ino.
+	 */
+	u64 rmdir_ino;
+	u64 rmdir_gen;
+	bool orphanized;
+};
+
+struct orphan_dir_info {
+	struct rb_node node;
+	u64 ino;
+	u64 gen;
+	u64 last_dir_index_offset;
+};
+
+struct name_cache_entry {
+	struct list_head list;
+	/*
+	 * radix_tree has only 32bit entries but we need to handle 64bit inums.
+	 * We use the lower 32bit of the 64bit inum to store it in the tree. If
+	 * more then one inum would fall into the same entry, we use radix_list
+	 * to store the additional entries. radix_list is also used to store
+	 * entries where two entries have the same inum but different
+	 * generations.
+	 */
+	struct list_head radix_list;
+	u64 ino;
+	u64 gen;
+	u64 parent_ino;
+	u64 parent_gen;
+	int ret;
+	int need_later_update;
+	int name_len;
+	char name[];
+};
+
+#define ADVANCE							1
+#define ADVANCE_ONLY_NEXT					-1
+
+enum btrfs_compare_tree_result {
+	BTRFS_COMPARE_TREE_NEW,
+	BTRFS_COMPARE_TREE_DELETED,
+	BTRFS_COMPARE_TREE_CHANGED,
+	BTRFS_COMPARE_TREE_SAME,
+};
+
+__cold
+static void inconsistent_snapshot_error(struct send_ctx *sctx,
+					enum btrfs_compare_tree_result result,
+					const char *what)
+{
+	const char *result_string;
+
+	switch (result) {
+	case BTRFS_COMPARE_TREE_NEW:
+		result_string = "new";
+		break;
+	case BTRFS_COMPARE_TREE_DELETED:
+		result_string = "deleted";
+		break;
+	case BTRFS_COMPARE_TREE_CHANGED:
+		result_string = "updated";
+		break;
+	case BTRFS_COMPARE_TREE_SAME:
+		ASSERT(0);
+		result_string = "unchanged";
+		break;
+	default:
+		ASSERT(0);
+		result_string = "unexpected";
+	}
+
+	btrfs_err(sctx->send_root->fs_info,
+		  "Send: inconsistent snapshot, found %s %s for inode %llu without updated inode item, send root is %llu, parent root is %llu",
+		  result_string, what, sctx->cmp_key->objectid,
+		  sctx->send_root->root_key.objectid,
+		  (sctx->parent_root ?
+		   sctx->parent_root->root_key.objectid : 0));
+}
+
+static int is_waiting_for_move(struct send_ctx *sctx, u64 ino);
+
+static struct waiting_dir_move *
+get_waiting_dir_move(struct send_ctx *sctx, u64 ino);
+
+static int is_waiting_for_rm(struct send_ctx *sctx, u64 dir_ino, u64 gen);
+
+static int need_send_hole(struct send_ctx *sctx)
+{
+	return (sctx->parent_root && !sctx->cur_inode_new &&
+		!sctx->cur_inode_new_gen && !sctx->cur_inode_deleted &&
+		S_ISREG(sctx->cur_inode_mode));
+}
+
+static void fs_path_reset(struct fs_path *p)
+{
+	if (p->reversed) {
+		p->start = p->buf + p->buf_len - 1;
+		p->end = p->start;
+		*p->start = 0;
+	} else {
+		p->start = p->buf;
+		p->end = p->start;
+		*p->start = 0;
+	}
+}
+
+static struct fs_path *fs_path_alloc(void)
+{
+	struct fs_path *p;
+
+	p = kmalloc(sizeof(*p), GFP_KERNEL);
+	if (!p)
+		return NULL;
+	p->reversed = 0;
+	p->buf = p->inline_buf;
+	p->buf_len = FS_PATH_INLINE_SIZE;
+	fs_path_reset(p);
+	return p;
+}
+
+static struct fs_path *fs_path_alloc_reversed(void)
+{
+	struct fs_path *p;
+
+	p = fs_path_alloc();
+	if (!p)
+		return NULL;
+	p->reversed = 1;
+	fs_path_reset(p);
+	return p;
+}
+
+static void fs_path_free(struct fs_path *p)
+{
+	if (!p)
+		return;
+	if (p->buf != p->inline_buf)
+		kfree(p->buf);
+	kfree(p);
+}
+
+static int fs_path_len(struct fs_path *p)
+{
+	return p->end - p->start;
+}
+
+static int fs_path_ensure_buf(struct fs_path *p, int len)
+{
+	char *tmp_buf;
+	int path_len;
+	int old_buf_len;
+
+	len++;
+
+	if (p->buf_len >= len)
+		return 0;
+
+	if (len > PATH_MAX) {
+		WARN_ON(1);
+		return -ENOMEM;
+	}
+
+	path_len = p->end - p->start;
+	old_buf_len = p->buf_len;
+
+	/*
+	 * First time the inline_buf does not suffice
+	 */
+	if (p->buf == p->inline_buf) {
+		tmp_buf = kmalloc(len, GFP_KERNEL);
+		if (tmp_buf)
+			memcpy(tmp_buf, p->buf, old_buf_len);
+	} else {
+		tmp_buf = krealloc(p->buf, len, GFP_KERNEL);
+	}
+	if (!tmp_buf)
+		return -ENOMEM;
+	p->buf = tmp_buf;
+	/*
+	 * The real size of the buffer is bigger, this will let the fast path
+	 * happen most of the time
+	 */
+	p->buf_len = ksize(p->buf);
+
+	if (p->reversed) {
+		tmp_buf = p->buf + old_buf_len - path_len - 1;
+		p->end = p->buf + p->buf_len - 1;
+		p->start = p->end - path_len;
+		memmove(p->start, tmp_buf, path_len + 1);
+	} else {
+		p->start = p->buf;
+		p->end = p->start + path_len;
+	}
+	return 0;
+}
+
+static int fs_path_prepare_for_add(struct fs_path *p, int name_len,
+				   char **prepared)
+{
+	int ret;
+	int new_len;
+
+	new_len = p->end - p->start + name_len;
+	if (p->start != p->end)
+		new_len++;
+	ret = fs_path_ensure_buf(p, new_len);
+	if (ret < 0)
+		goto out;
+
+	if (p->reversed) {
+		if (p->start != p->end)
+			*--p->start = '/';
+		p->start -= name_len;
+		*prepared = p->start;
+	} else {
+		if (p->start != p->end)
+			*p->end++ = '/';
+		*prepared = p->end;
+		p->end += name_len;
+		*p->end = 0;
+	}
+
+out:
+	return ret;
+}
+
+static int fs_path_add(struct fs_path *p, const char *name, int name_len)
+{
+	int ret;
+	char *prepared;
+
+	ret = fs_path_prepare_for_add(p, name_len, &prepared);
+	if (ret < 0)
+		goto out;
+	memcpy(prepared, name, name_len);
+
+out:
+	return ret;
+}
+
+static int fs_path_add_path(struct fs_path *p, struct fs_path *p2)
+{
+	int ret;
+	char *prepared;
+
+	ret = fs_path_prepare_for_add(p, p2->end - p2->start, &prepared);
+	if (ret < 0)
+		goto out;
+	memcpy(prepared, p2->start, p2->end - p2->start);
+
+out:
+	return ret;
+}
+
+static int fs_path_add_from_extent_buffer(struct fs_path *p,
+					  struct extent_buffer *eb,
+					  unsigned long off, int len)
+{
+	int ret;
+	char *prepared;
+
+	ret = fs_path_prepare_for_add(p, len, &prepared);
+	if (ret < 0)
+		goto out;
+
+	read_extent_buffer(eb, prepared, off, len);
+
+out:
+	return ret;
+}
+
+static int fs_path_copy(struct fs_path *p, struct fs_path *from)
+{
+	int ret;
+
+	p->reversed = from->reversed;
+	fs_path_reset(p);
+
+	ret = fs_path_add_path(p, from);
+
+	return ret;
+}
+
+
+static void fs_path_unreverse(struct fs_path *p)
+{
+	char *tmp;
+	int len;
+
+	if (!p->reversed)
+		return;
+
+	tmp = p->start;
+	len = p->end - p->start;
+	p->start = p->buf;
+	p->end = p->start + len;
+	memmove(p->start, tmp, len + 1);
+	p->reversed = 0;
+}
+
+static struct btrfs_path *alloc_path_for_send(void)
+{
+	struct btrfs_path *path;
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return NULL;
+	path->search_commit_root = 1;
+	path->skip_locking = 1;
+	path->need_commit_sem = 1;
+	return path;
+}
+
+static int write_buf(struct file *filp, const void *buf, u32 len, loff_t *off)
+{
+	int ret;
+	u32 pos = 0;
+
+	while (pos < len) {
+		ret = kernel_write(filp, buf + pos, len - pos, off);
+		/* TODO handle that correctly */
+		/*if (ret == -ERESTARTSYS) {
+			continue;
+		}*/
+		if (ret < 0)
+			return ret;
+		if (ret == 0) {
+			return -EIO;
+		}
+		pos += ret;
+	}
+
+	return 0;
+}
+
+static int tlv_put(struct send_ctx *sctx, u16 attr, const void *data, int len)
+{
+	struct btrfs_tlv_header *hdr;
+	int total_len = sizeof(*hdr) + len;
+	int left = sctx->send_max_size - sctx->send_size;
+
+	if (unlikely(left < total_len))
+		return -EOVERFLOW;
+
+	hdr = (struct btrfs_tlv_header *) (sctx->send_buf + sctx->send_size);
+	put_unaligned_le16(attr, &hdr->tlv_type);
+	put_unaligned_le16(len, &hdr->tlv_len);
+	memcpy(hdr + 1, data, len);
+	sctx->send_size += total_len;
+
+	return 0;
+}
+
+#define TLV_PUT_DEFINE_INT(bits) \
+	static int tlv_put_u##bits(struct send_ctx *sctx,	 	\
+			u##bits attr, u##bits value)			\
+	{								\
+		__le##bits __tmp = cpu_to_le##bits(value);		\
+		return tlv_put(sctx, attr, &__tmp, sizeof(__tmp));	\
+	}
+
+TLV_PUT_DEFINE_INT(64)
+
+static int tlv_put_string(struct send_ctx *sctx, u16 attr,
+			  const char *str, int len)
+{
+	if (len == -1)
+		len = strlen(str);
+	return tlv_put(sctx, attr, str, len);
+}
+
+static int tlv_put_uuid(struct send_ctx *sctx, u16 attr,
+			const u8 *uuid)
+{
+	return tlv_put(sctx, attr, uuid, BTRFS_UUID_SIZE);
+}
+
+static int tlv_put_btrfs_timespec(struct send_ctx *sctx, u16 attr,
+				  struct extent_buffer *eb,
+				  struct btrfs_timespec *ts)
+{
+	struct btrfs_timespec bts;
+	read_extent_buffer(eb, &bts, (unsigned long)ts, sizeof(bts));
+	return tlv_put(sctx, attr, &bts, sizeof(bts));
+}
+
+
+#define TLV_PUT(sctx, attrtype, data, attrlen) \
+	do { \
+		ret = tlv_put(sctx, attrtype, data, attrlen); \
+		if (ret < 0) \
+			goto tlv_put_failure; \
+	} while (0)
+
+#define TLV_PUT_INT(sctx, attrtype, bits, value) \
+	do { \
+		ret = tlv_put_u##bits(sctx, attrtype, value); \
+		if (ret < 0) \
+			goto tlv_put_failure; \
+	} while (0)
+
+#define TLV_PUT_U8(sctx, attrtype, data) TLV_PUT_INT(sctx, attrtype, 8, data)
+#define TLV_PUT_U16(sctx, attrtype, data) TLV_PUT_INT(sctx, attrtype, 16, data)
+#define TLV_PUT_U32(sctx, attrtype, data) TLV_PUT_INT(sctx, attrtype, 32, data)
+#define TLV_PUT_U64(sctx, attrtype, data) TLV_PUT_INT(sctx, attrtype, 64, data)
+#define TLV_PUT_STRING(sctx, attrtype, str, len) \
+	do { \
+		ret = tlv_put_string(sctx, attrtype, str, len); \
+		if (ret < 0) \
+			goto tlv_put_failure; \
+	} while (0)
+#define TLV_PUT_PATH(sctx, attrtype, p) \
+	do { \
+		ret = tlv_put_string(sctx, attrtype, p->start, \
+			p->end - p->start); \
+		if (ret < 0) \
+			goto tlv_put_failure; \
+	} while(0)
+#define TLV_PUT_UUID(sctx, attrtype, uuid) \
+	do { \
+		ret = tlv_put_uuid(sctx, attrtype, uuid); \
+		if (ret < 0) \
+			goto tlv_put_failure; \
+	} while (0)
+#define TLV_PUT_BTRFS_TIMESPEC(sctx, attrtype, eb, ts) \
+	do { \
+		ret = tlv_put_btrfs_timespec(sctx, attrtype, eb, ts); \
+		if (ret < 0) \
+			goto tlv_put_failure; \
+	} while (0)
+
+static int send_header(struct send_ctx *sctx)
+{
+	struct btrfs_stream_header hdr;
+
+	strcpy(hdr.magic, BTRFS_SEND_STREAM_MAGIC);
+	hdr.version = cpu_to_le32(BTRFS_SEND_STREAM_VERSION);
+
+	return write_buf(sctx->send_filp, &hdr, sizeof(hdr),
+					&sctx->send_off);
+}
+
+/*
+ * For each command/item we want to send to userspace, we call this function.
+ */
+static int begin_cmd(struct send_ctx *sctx, int cmd)
+{
+	struct btrfs_cmd_header *hdr;
+
+	if (WARN_ON(!sctx->send_buf))
+		return -EINVAL;
+
+	BUG_ON(sctx->send_size);
+
+	sctx->send_size += sizeof(*hdr);
+	hdr = (struct btrfs_cmd_header *)sctx->send_buf;
+	put_unaligned_le16(cmd, &hdr->cmd);
+
+	return 0;
+}
+
+static int send_cmd(struct send_ctx *sctx)
+{
+	int ret;
+	struct btrfs_cmd_header *hdr;
+	u32 crc;
+
+	hdr = (struct btrfs_cmd_header *)sctx->send_buf;
+	put_unaligned_le32(sctx->send_size - sizeof(*hdr), &hdr->len);
+	put_unaligned_le32(0, &hdr->crc);
+
+	crc = btrfs_crc32c(0, (unsigned char *)sctx->send_buf, sctx->send_size);
+	put_unaligned_le32(crc, &hdr->crc);
+
+	ret = write_buf(sctx->send_filp, sctx->send_buf, sctx->send_size,
+					&sctx->send_off);
+
+	sctx->total_send_size += sctx->send_size;
+	sctx->cmd_send_size[get_unaligned_le16(&hdr->cmd)] += sctx->send_size;
+	sctx->send_size = 0;
+
+	return ret;
+}
+
+/*
+ * Sends a move instruction to user space
+ */
+static int send_rename(struct send_ctx *sctx,
+		     struct fs_path *from, struct fs_path *to)
+{
+	struct btrfs_fs_info *fs_info = sctx->send_root->fs_info;
+	int ret;
+
+	btrfs_debug(fs_info, "send_rename %s -> %s", from->start, to->start);
+
+	ret = begin_cmd(sctx, BTRFS_SEND_C_RENAME);
+	if (ret < 0)
+		goto out;
+
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, from);
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH_TO, to);
+
+	ret = send_cmd(sctx);
+
+tlv_put_failure:
+out:
+	return ret;
+}
+
+/*
+ * Sends a link instruction to user space
+ */
+static int send_link(struct send_ctx *sctx,
+		     struct fs_path *path, struct fs_path *lnk)
+{
+	struct btrfs_fs_info *fs_info = sctx->send_root->fs_info;
+	int ret;
+
+	btrfs_debug(fs_info, "send_link %s -> %s", path->start, lnk->start);
+
+	ret = begin_cmd(sctx, BTRFS_SEND_C_LINK);
+	if (ret < 0)
+		goto out;
+
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, path);
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH_LINK, lnk);
+
+	ret = send_cmd(sctx);
+
+tlv_put_failure:
+out:
+	return ret;
+}
+
+/*
+ * Sends an unlink instruction to user space
+ */
+static int send_unlink(struct send_ctx *sctx, struct fs_path *path)
+{
+	struct btrfs_fs_info *fs_info = sctx->send_root->fs_info;
+	int ret;
+
+	btrfs_debug(fs_info, "send_unlink %s", path->start);
+
+	ret = begin_cmd(sctx, BTRFS_SEND_C_UNLINK);
+	if (ret < 0)
+		goto out;
+
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, path);
+
+	ret = send_cmd(sctx);
+
+tlv_put_failure:
+out:
+	return ret;
+}
+
+/*
+ * Sends a rmdir instruction to user space
+ */
+static int send_rmdir(struct send_ctx *sctx, struct fs_path *path)
+{
+	struct btrfs_fs_info *fs_info = sctx->send_root->fs_info;
+	int ret;
+
+	btrfs_debug(fs_info, "send_rmdir %s", path->start);
+
+	ret = begin_cmd(sctx, BTRFS_SEND_C_RMDIR);
+	if (ret < 0)
+		goto out;
+
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, path);
+
+	ret = send_cmd(sctx);
+
+tlv_put_failure:
+out:
+	return ret;
+}
+
+/*
+ * Helper function to retrieve some fields from an inode item.
+ */
+static int __get_inode_info(struct btrfs_root *root, struct btrfs_path *path,
+			  u64 ino, u64 *size, u64 *gen, u64 *mode, u64 *uid,
+			  u64 *gid, u64 *rdev)
+{
+	int ret;
+	struct btrfs_inode_item *ii;
+	struct btrfs_key key;
+
+	key.objectid = ino;
+	key.type = BTRFS_INODE_ITEM_KEY;
+	key.offset = 0;
+	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+	if (ret) {
+		if (ret > 0)
+			ret = -ENOENT;
+		return ret;
+	}
+
+	ii = btrfs_item_ptr(path->nodes[0], path->slots[0],
+			struct btrfs_inode_item);
+	if (size)
+		*size = btrfs_inode_size(path->nodes[0], ii);
+	if (gen)
+		*gen = btrfs_inode_generation(path->nodes[0], ii);
+	if (mode)
+		*mode = btrfs_inode_mode(path->nodes[0], ii);
+	if (uid)
+		*uid = btrfs_inode_uid(path->nodes[0], ii);
+	if (gid)
+		*gid = btrfs_inode_gid(path->nodes[0], ii);
+	if (rdev)
+		*rdev = btrfs_inode_rdev(path->nodes[0], ii);
+
+	return ret;
+}
+
+static int get_inode_info(struct btrfs_root *root,
+			  u64 ino, u64 *size, u64 *gen,
+			  u64 *mode, u64 *uid, u64 *gid,
+			  u64 *rdev)
+{
+	struct btrfs_path *path;
+	int ret;
+
+	path = alloc_path_for_send();
+	if (!path)
+		return -ENOMEM;
+	ret = __get_inode_info(root, path, ino, size, gen, mode, uid, gid,
+			       rdev);
+	btrfs_free_path(path);
+	return ret;
+}
+
+typedef int (*iterate_inode_ref_t)(int num, u64 dir, int index,
+				   struct fs_path *p,
+				   void *ctx);
+
+/*
+ * Helper function to iterate the entries in ONE btrfs_inode_ref or
+ * btrfs_inode_extref.
+ * The iterate callback may return a non zero value to stop iteration. This can
+ * be a negative value for error codes or 1 to simply stop it.
+ *
+ * path must point to the INODE_REF or INODE_EXTREF when called.
+ */
+static int iterate_inode_ref(struct btrfs_root *root, struct btrfs_path *path,
+			     struct btrfs_key *found_key, int resolve,
+			     iterate_inode_ref_t iterate, void *ctx)
+{
+	struct extent_buffer *eb = path->nodes[0];
+	struct btrfs_item *item;
+	struct btrfs_inode_ref *iref;
+	struct btrfs_inode_extref *extref;
+	struct btrfs_path *tmp_path;
+	struct fs_path *p;
+	u32 cur = 0;
+	u32 total;
+	int slot = path->slots[0];
+	u32 name_len;
+	char *start;
+	int ret = 0;
+	int num = 0;
+	int index;
+	u64 dir;
+	unsigned long name_off;
+	unsigned long elem_size;
+	unsigned long ptr;
+
+	p = fs_path_alloc_reversed();
+	if (!p)
+		return -ENOMEM;
+
+	tmp_path = alloc_path_for_send();
+	if (!tmp_path) {
+		fs_path_free(p);
+		return -ENOMEM;
+	}
+
+
+	if (found_key->type == BTRFS_INODE_REF_KEY) {
+		ptr = (unsigned long)btrfs_item_ptr(eb, slot,
+						    struct btrfs_inode_ref);
+		item = btrfs_item_nr(slot);
+		total = btrfs_item_size(eb, item);
+		elem_size = sizeof(*iref);
+	} else {
+		ptr = btrfs_item_ptr_offset(eb, slot);
+		total = btrfs_item_size_nr(eb, slot);
+		elem_size = sizeof(*extref);
+	}
+
+	while (cur < total) {
+		fs_path_reset(p);
+
+		if (found_key->type == BTRFS_INODE_REF_KEY) {
+			iref = (struct btrfs_inode_ref *)(ptr + cur);
+			name_len = btrfs_inode_ref_name_len(eb, iref);
+			name_off = (unsigned long)(iref + 1);
+			index = btrfs_inode_ref_index(eb, iref);
+			dir = found_key->offset;
+		} else {
+			extref = (struct btrfs_inode_extref *)(ptr + cur);
+			name_len = btrfs_inode_extref_name_len(eb, extref);
+			name_off = (unsigned long)&extref->name;
+			index = btrfs_inode_extref_index(eb, extref);
+			dir = btrfs_inode_extref_parent(eb, extref);
+		}
+
+		if (resolve) {
+			start = btrfs_ref_to_path(root, tmp_path, name_len,
+						  name_off, eb, dir,
+						  p->buf, p->buf_len);
+			if (IS_ERR(start)) {
+				ret = PTR_ERR(start);
+				goto out;
+			}
+			if (start < p->buf) {
+				/* overflow , try again with larger buffer */
+				ret = fs_path_ensure_buf(p,
+						p->buf_len + p->buf - start);
+				if (ret < 0)
+					goto out;
+				start = btrfs_ref_to_path(root, tmp_path,
+							  name_len, name_off,
+							  eb, dir,
+							  p->buf, p->buf_len);
+				if (IS_ERR(start)) {
+					ret = PTR_ERR(start);
+					goto out;
+				}
+				BUG_ON(start < p->buf);
+			}
+			p->start = start;
+		} else {
+			ret = fs_path_add_from_extent_buffer(p, eb, name_off,
+							     name_len);
+			if (ret < 0)
+				goto out;
+		}
+
+		cur += elem_size + name_len;
+		ret = iterate(num, dir, index, p, ctx);
+		if (ret)
+			goto out;
+		num++;
+	}
+
+out:
+	btrfs_free_path(tmp_path);
+	fs_path_free(p);
+	return ret;
+}
+
+typedef int (*iterate_dir_item_t)(int num, struct btrfs_key *di_key,
+				  const char *name, int name_len,
+				  const char *data, int data_len,
+				  u8 type, void *ctx);
+
+/*
+ * Helper function to iterate the entries in ONE btrfs_dir_item.
+ * The iterate callback may return a non zero value to stop iteration. This can
+ * be a negative value for error codes or 1 to simply stop it.
+ *
+ * path must point to the dir item when called.
+ */
+static int iterate_dir_item(struct btrfs_root *root, struct btrfs_path *path,
+			    iterate_dir_item_t iterate, void *ctx)
+{
+	int ret = 0;
+	struct extent_buffer *eb;
+	struct btrfs_item *item;
+	struct btrfs_dir_item *di;
+	struct btrfs_key di_key;
+	char *buf = NULL;
+	int buf_len;
+	u32 name_len;
+	u32 data_len;
+	u32 cur;
+	u32 len;
+	u32 total;
+	int slot;
+	int num;
+	u8 type;
+
+	/*
+	 * Start with a small buffer (1 page). If later we end up needing more
+	 * space, which can happen for xattrs on a fs with a leaf size greater
+	 * then the page size, attempt to increase the buffer. Typically xattr
+	 * values are small.
+	 */
+	buf_len = PATH_MAX;
+	buf = kmalloc(buf_len, GFP_KERNEL);
+	if (!buf) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	eb = path->nodes[0];
+	slot = path->slots[0];
+	item = btrfs_item_nr(slot);
+	di = btrfs_item_ptr(eb, slot, struct btrfs_dir_item);
+	cur = 0;
+	len = 0;
+	total = btrfs_item_size(eb, item);
+
+	num = 0;
+	while (cur < total) {
+		name_len = btrfs_dir_name_len(eb, di);
+		data_len = btrfs_dir_data_len(eb, di);
+		type = btrfs_dir_type(eb, di);
+		btrfs_dir_item_key_to_cpu(eb, di, &di_key);
+
+		if (type == BTRFS_FT_XATTR) {
+			if (name_len > XATTR_NAME_MAX) {
+				ret = -ENAMETOOLONG;
+				goto out;
+			}
+			if (name_len + data_len >
+					BTRFS_MAX_XATTR_SIZE(root->fs_info)) {
+				ret = -E2BIG;
+				goto out;
+			}
+		} else {
+			/*
+			 * Path too long
+			 */
+			if (name_len + data_len > PATH_MAX) {
+				ret = -ENAMETOOLONG;
+				goto out;
+			}
+		}
+
+		if (name_len + data_len > buf_len) {
+			buf_len = name_len + data_len;
+			if (is_vmalloc_addr(buf)) {
+				vfree(buf);
+				buf = NULL;
+			} else {
+				char *tmp = krealloc(buf, buf_len,
+						GFP_KERNEL | __GFP_NOWARN);
+
+				if (!tmp)
+					kfree(buf);
+				buf = tmp;
+			}
+			if (!buf) {
+				buf = kvmalloc(buf_len, GFP_KERNEL);
+				if (!buf) {
+					ret = -ENOMEM;
+					goto out;
+				}
+			}
+		}
+
+		read_extent_buffer(eb, buf, (unsigned long)(di + 1),
+				name_len + data_len);
+
+		len = sizeof(*di) + name_len + data_len;
+		di = (struct btrfs_dir_item *)((char *)di + len);
+		cur += len;
+
+		ret = iterate(num, &di_key, buf, name_len, buf + name_len,
+				data_len, type, ctx);
+		if (ret < 0)
+			goto out;
+		if (ret) {
+			ret = 0;
+			goto out;
+		}
+
+		num++;
+	}
+
+out:
+	kvfree(buf);
+	return ret;
+}
+
+static int __copy_first_ref(int num, u64 dir, int index,
+			    struct fs_path *p, void *ctx)
+{
+	int ret;
+	struct fs_path *pt = ctx;
+
+	ret = fs_path_copy(pt, p);
+	if (ret < 0)
+		return ret;
+
+	/* we want the first only */
+	return 1;
+}
+
+/*
+ * Retrieve the first path of an inode. If an inode has more then one
+ * ref/hardlink, this is ignored.
+ */
+static int get_inode_path(struct btrfs_root *root,
+			  u64 ino, struct fs_path *path)
+{
+	int ret;
+	struct btrfs_key key, found_key;
+	struct btrfs_path *p;
+
+	p = alloc_path_for_send();
+	if (!p)
+		return -ENOMEM;
+
+	fs_path_reset(path);
+
+	key.objectid = ino;
+	key.type = BTRFS_INODE_REF_KEY;
+	key.offset = 0;
+
+	ret = btrfs_search_slot_for_read(root, &key, p, 1, 0);
+	if (ret < 0)
+		goto out;
+	if (ret) {
+		ret = 1;
+		goto out;
+	}
+	btrfs_item_key_to_cpu(p->nodes[0], &found_key, p->slots[0]);
+	if (found_key.objectid != ino ||
+	    (found_key.type != BTRFS_INODE_REF_KEY &&
+	     found_key.type != BTRFS_INODE_EXTREF_KEY)) {
+		ret = -ENOENT;
+		goto out;
+	}
+
+	ret = iterate_inode_ref(root, p, &found_key, 1,
+				__copy_first_ref, path);
+	if (ret < 0)
+		goto out;
+	ret = 0;
+
+out:
+	btrfs_free_path(p);
+	return ret;
+}
+
+struct backref_ctx {
+	struct send_ctx *sctx;
+
+	/* number of total found references */
+	u64 found;
+
+	/*
+	 * used for clones found in send_root. clones found behind cur_objectid
+	 * and cur_offset are not considered as allowed clones.
+	 */
+	u64 cur_objectid;
+	u64 cur_offset;
+
+	/* may be truncated in case it's the last extent in a file */
+	u64 extent_len;
+
+	/* data offset in the file extent item */
+	u64 data_offset;
+
+	/* Just to check for bugs in backref resolving */
+	int found_itself;
+};
+
+static int __clone_root_cmp_bsearch(const void *key, const void *elt)
+{
+	u64 root = (u64)(uintptr_t)key;
+	struct clone_root *cr = (struct clone_root *)elt;
+
+	if (root < cr->root->root_key.objectid)
+		return -1;
+	if (root > cr->root->root_key.objectid)
+		return 1;
+	return 0;
+}
+
+static int __clone_root_cmp_sort(const void *e1, const void *e2)
+{
+	struct clone_root *cr1 = (struct clone_root *)e1;
+	struct clone_root *cr2 = (struct clone_root *)e2;
+
+	if (cr1->root->root_key.objectid < cr2->root->root_key.objectid)
+		return -1;
+	if (cr1->root->root_key.objectid > cr2->root->root_key.objectid)
+		return 1;
+	return 0;
+}
+
+/*
+ * Called for every backref that is found for the current extent.
+ * Results are collected in sctx->clone_roots->ino/offset/found_refs
+ */
+static int __iterate_backrefs(u64 ino, u64 offset, u64 root, void *ctx_)
+{
+	struct backref_ctx *bctx = ctx_;
+	struct clone_root *found;
+
+	/* First check if the root is in the list of accepted clone sources */
+	found = bsearch((void *)(uintptr_t)root, bctx->sctx->clone_roots,
+			bctx->sctx->clone_roots_cnt,
+			sizeof(struct clone_root),
+			__clone_root_cmp_bsearch);
+	if (!found)
+		return 0;
+
+	if (found->root == bctx->sctx->send_root &&
+	    ino == bctx->cur_objectid &&
+	    offset == bctx->cur_offset) {
+		bctx->found_itself = 1;
+	}
+
+	/*
+	 * Make sure we don't consider clones from send_root that are
+	 * behind the current inode/offset.
+	 */
+	if (found->root == bctx->sctx->send_root) {
+		/*
+		 * If the source inode was not yet processed we can't issue a
+		 * clone operation, as the source extent does not exist yet at
+		 * the destination of the stream.
+		 */
+		if (ino > bctx->cur_objectid)
+			return 0;
+		/*
+		 * We clone from the inode currently being sent as long as the
+		 * source extent is already processed, otherwise we could try
+		 * to clone from an extent that does not exist yet at the
+		 * destination of the stream.
+		 */
+		if (ino == bctx->cur_objectid &&
+		    offset + bctx->extent_len >
+		    bctx->sctx->cur_inode_next_write_offset)
+			return 0;
+	}
+
+	bctx->found++;
+	found->found_refs++;
+	if (ino < found->ino) {
+		found->ino = ino;
+		found->offset = offset;
+	} else if (found->ino == ino) {
+		/*
+		 * same extent found more then once in the same file.
+		 */
+		if (found->offset > offset + bctx->extent_len)
+			found->offset = offset;
+	}
+
+	return 0;
+}
+
+/*
+ * Given an inode, offset and extent item, it finds a good clone for a clone
+ * instruction. Returns -ENOENT when none could be found. The function makes
+ * sure that the returned clone is usable at the point where sending is at the
+ * moment. This means, that no clones are accepted which lie behind the current
+ * inode+offset.
+ *
+ * path must point to the extent item when called.
+ */
+static int find_extent_clone(struct send_ctx *sctx,
+			     struct btrfs_path *path,
+			     u64 ino, u64 data_offset,
+			     u64 ino_size,
+			     struct clone_root **found)
+{
+	struct btrfs_fs_info *fs_info = sctx->send_root->fs_info;
+	int ret;
+	int extent_type;
+	u64 logical;
+	u64 disk_byte;
+	u64 num_bytes;
+	u64 extent_item_pos;
+	u64 flags = 0;
+	struct btrfs_file_extent_item *fi;
+	struct extent_buffer *eb = path->nodes[0];
+	struct backref_ctx *backref_ctx = NULL;
+	struct clone_root *cur_clone_root;
+	struct btrfs_key found_key;
+	struct btrfs_path *tmp_path;
+	struct btrfs_extent_item *ei;
+	int compressed;
+	u32 i;
+
+	tmp_path = alloc_path_for_send();
+	if (!tmp_path)
+		return -ENOMEM;
+
+	/* We only use this path under the commit sem */
+	tmp_path->need_commit_sem = 0;
+
+	backref_ctx = kmalloc(sizeof(*backref_ctx), GFP_KERNEL);
+	if (!backref_ctx) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	if (data_offset >= ino_size) {
+		/*
+		 * There may be extents that lie behind the file's size.
+		 * I at least had this in combination with snapshotting while
+		 * writing large files.
+		 */
+		ret = 0;
+		goto out;
+	}
+
+	fi = btrfs_item_ptr(eb, path->slots[0],
+			struct btrfs_file_extent_item);
+	extent_type = btrfs_file_extent_type(eb, fi);
+	if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
+		ret = -ENOENT;
+		goto out;
+	}
+	compressed = btrfs_file_extent_compression(eb, fi);
+
+	num_bytes = btrfs_file_extent_num_bytes(eb, fi);
+	disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
+	if (disk_byte == 0) {
+		ret = -ENOENT;
+		goto out;
+	}
+	logical = disk_byte + btrfs_file_extent_offset(eb, fi);
+
+	down_read(&fs_info->commit_root_sem);
+	ret = extent_from_logical(fs_info, disk_byte, tmp_path,
+				  &found_key, &flags);
+	up_read(&fs_info->commit_root_sem);
+
+	if (ret < 0)
+		goto out;
+	if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
+		ret = -EIO;
+		goto out;
+	}
+
+	ei = btrfs_item_ptr(tmp_path->nodes[0], tmp_path->slots[0],
+			    struct btrfs_extent_item);
+	/*
+	 * Backreference walking (iterate_extent_inodes() below) is currently
+	 * too expensive when an extent has a large number of references, both
+	 * in time spent and used memory. So for now just fallback to write
+	 * operations instead of clone operations when an extent has more than
+	 * a certain amount of references.
+	 */
+	if (btrfs_extent_refs(tmp_path->nodes[0], ei) > SEND_MAX_EXTENT_REFS) {
+		ret = -ENOENT;
+		goto out;
+	}
+	btrfs_release_path(tmp_path);
+
+	/*
+	 * Setup the clone roots.
+	 */
+	for (i = 0; i < sctx->clone_roots_cnt; i++) {
+		cur_clone_root = sctx->clone_roots + i;
+		cur_clone_root->ino = (u64)-1;
+		cur_clone_root->offset = 0;
+		cur_clone_root->found_refs = 0;
+	}
+
+	backref_ctx->sctx = sctx;
+	backref_ctx->found = 0;
+	backref_ctx->cur_objectid = ino;
+	backref_ctx->cur_offset = data_offset;
+	backref_ctx->found_itself = 0;
+	backref_ctx->extent_len = num_bytes;
+	/*
+	 * For non-compressed extents iterate_extent_inodes() gives us extent
+	 * offsets that already take into account the data offset, but not for
+	 * compressed extents, since the offset is logical and not relative to
+	 * the physical extent locations. We must take this into account to
+	 * avoid sending clone offsets that go beyond the source file's size,
+	 * which would result in the clone ioctl failing with -EINVAL on the
+	 * receiving end.
+	 */
+	if (compressed == BTRFS_COMPRESS_NONE)
+		backref_ctx->data_offset = 0;
+	else
+		backref_ctx->data_offset = btrfs_file_extent_offset(eb, fi);
+
+	/*
+	 * The last extent of a file may be too large due to page alignment.
+	 * We need to adjust extent_len in this case so that the checks in
+	 * __iterate_backrefs work.
+	 */
+	if (data_offset + num_bytes >= ino_size)
+		backref_ctx->extent_len = ino_size - data_offset;
+
+	/*
+	 * Now collect all backrefs.
+	 */
+	if (compressed == BTRFS_COMPRESS_NONE)
+		extent_item_pos = logical - found_key.objectid;
+	else
+		extent_item_pos = 0;
+	ret = iterate_extent_inodes(fs_info, found_key.objectid,
+				    extent_item_pos, 1, __iterate_backrefs,
+				    backref_ctx, false);
+
+	if (ret < 0)
+		goto out;
+
+	if (!backref_ctx->found_itself) {
+		/* found a bug in backref code? */
+		ret = -EIO;
+		btrfs_err(fs_info,
+			  "did not find backref in send_root. inode=%llu, offset=%llu, disk_byte=%llu found extent=%llu",
+			  ino, data_offset, disk_byte, found_key.objectid);
+		goto out;
+	}
+
+	btrfs_debug(fs_info,
+		    "find_extent_clone: data_offset=%llu, ino=%llu, num_bytes=%llu, logical=%llu",
+		    data_offset, ino, num_bytes, logical);
+
+	if (!backref_ctx->found)
+		btrfs_debug(fs_info, "no clones found");
+
+	cur_clone_root = NULL;
+	for (i = 0; i < sctx->clone_roots_cnt; i++) {
+		if (sctx->clone_roots[i].found_refs) {
+			if (!cur_clone_root)
+				cur_clone_root = sctx->clone_roots + i;
+			else if (sctx->clone_roots[i].root == sctx->send_root)
+				/* prefer clones from send_root over others */
+				cur_clone_root = sctx->clone_roots + i;
+		}
+
+	}
+
+	if (cur_clone_root) {
+		*found = cur_clone_root;
+		ret = 0;
+	} else {
+		ret = -ENOENT;
+	}
+
+out:
+	btrfs_free_path(tmp_path);
+	kfree(backref_ctx);
+	return ret;
+}
+
+static int read_symlink(struct btrfs_root *root,
+			u64 ino,
+			struct fs_path *dest)
+{
+	int ret;
+	struct btrfs_path *path;
+	struct btrfs_key key;
+	struct btrfs_file_extent_item *ei;
+	u8 type;
+	u8 compression;
+	unsigned long off;
+	int len;
+
+	path = alloc_path_for_send();
+	if (!path)
+		return -ENOMEM;
+
+	key.objectid = ino;
+	key.type = BTRFS_EXTENT_DATA_KEY;
+	key.offset = 0;
+	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+	if (ret < 0)
+		goto out;
+	if (ret) {
+		/*
+		 * An empty symlink inode. Can happen in rare error paths when
+		 * creating a symlink (transaction committed before the inode
+		 * eviction handler removed the symlink inode items and a crash
+		 * happened in between or the subvol was snapshoted in between).
+		 * Print an informative message to dmesg/syslog so that the user
+		 * can delete the symlink.
+		 */
+		btrfs_err(root->fs_info,
+			  "Found empty symlink inode %llu at root %llu",
+			  ino, root->root_key.objectid);
+		ret = -EIO;
+		goto out;
+	}
+
+	ei = btrfs_item_ptr(path->nodes[0], path->slots[0],
+			struct btrfs_file_extent_item);
+	type = btrfs_file_extent_type(path->nodes[0], ei);
+	compression = btrfs_file_extent_compression(path->nodes[0], ei);
+	BUG_ON(type != BTRFS_FILE_EXTENT_INLINE);
+	BUG_ON(compression);
+
+	off = btrfs_file_extent_inline_start(ei);
+	len = btrfs_file_extent_ram_bytes(path->nodes[0], ei);
+
+	ret = fs_path_add_from_extent_buffer(dest, path->nodes[0], off, len);
+
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+/*
+ * Helper function to generate a file name that is unique in the root of
+ * send_root and parent_root. This is used to generate names for orphan inodes.
+ */
+static int gen_unique_name(struct send_ctx *sctx,
+			   u64 ino, u64 gen,
+			   struct fs_path *dest)
+{
+	int ret = 0;
+	struct btrfs_path *path;
+	struct btrfs_dir_item *di;
+	char tmp[64];
+	int len;
+	u64 idx = 0;
+
+	path = alloc_path_for_send();
+	if (!path)
+		return -ENOMEM;
+
+	while (1) {
+		len = snprintf(tmp, sizeof(tmp), "o%llu-%llu-%llu",
+				ino, gen, idx);
+		ASSERT(len < sizeof(tmp));
+
+		di = btrfs_lookup_dir_item(NULL, sctx->send_root,
+				path, BTRFS_FIRST_FREE_OBJECTID,
+				tmp, strlen(tmp), 0);
+		btrfs_release_path(path);
+		if (IS_ERR(di)) {
+			ret = PTR_ERR(di);
+			goto out;
+		}
+		if (di) {
+			/* not unique, try again */
+			idx++;
+			continue;
+		}
+
+		if (!sctx->parent_root) {
+			/* unique */
+			ret = 0;
+			break;
+		}
+
+		di = btrfs_lookup_dir_item(NULL, sctx->parent_root,
+				path, BTRFS_FIRST_FREE_OBJECTID,
+				tmp, strlen(tmp), 0);
+		btrfs_release_path(path);
+		if (IS_ERR(di)) {
+			ret = PTR_ERR(di);
+			goto out;
+		}
+		if (di) {
+			/* not unique, try again */
+			idx++;
+			continue;
+		}
+		/* unique */
+		break;
+	}
+
+	ret = fs_path_add(dest, tmp, strlen(tmp));
+
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+enum inode_state {
+	inode_state_no_change,
+	inode_state_will_create,
+	inode_state_did_create,
+	inode_state_will_delete,
+	inode_state_did_delete,
+};
+
+static int get_cur_inode_state(struct send_ctx *sctx, u64 ino, u64 gen)
+{
+	int ret;
+	int left_ret;
+	int right_ret;
+	u64 left_gen;
+	u64 right_gen;
+
+	ret = get_inode_info(sctx->send_root, ino, NULL, &left_gen, NULL, NULL,
+			NULL, NULL);
+	if (ret < 0 && ret != -ENOENT)
+		goto out;
+	left_ret = ret;
+
+	if (!sctx->parent_root) {
+		right_ret = -ENOENT;
+	} else {
+		ret = get_inode_info(sctx->parent_root, ino, NULL, &right_gen,
+				NULL, NULL, NULL, NULL);
+		if (ret < 0 && ret != -ENOENT)
+			goto out;
+		right_ret = ret;
+	}
+
+	if (!left_ret && !right_ret) {
+		if (left_gen == gen && right_gen == gen) {
+			ret = inode_state_no_change;
+		} else if (left_gen == gen) {
+			if (ino < sctx->send_progress)
+				ret = inode_state_did_create;
+			else
+				ret = inode_state_will_create;
+		} else if (right_gen == gen) {
+			if (ino < sctx->send_progress)
+				ret = inode_state_did_delete;
+			else
+				ret = inode_state_will_delete;
+		} else  {
+			ret = -ENOENT;
+		}
+	} else if (!left_ret) {
+		if (left_gen == gen) {
+			if (ino < sctx->send_progress)
+				ret = inode_state_did_create;
+			else
+				ret = inode_state_will_create;
+		} else {
+			ret = -ENOENT;
+		}
+	} else if (!right_ret) {
+		if (right_gen == gen) {
+			if (ino < sctx->send_progress)
+				ret = inode_state_did_delete;
+			else
+				ret = inode_state_will_delete;
+		} else {
+			ret = -ENOENT;
+		}
+	} else {
+		ret = -ENOENT;
+	}
+
+out:
+	return ret;
+}
+
+static int is_inode_existent(struct send_ctx *sctx, u64 ino, u64 gen)
+{
+	int ret;
+
+	if (ino == BTRFS_FIRST_FREE_OBJECTID)
+		return 1;
+
+	ret = get_cur_inode_state(sctx, ino, gen);
+	if (ret < 0)
+		goto out;
+
+	if (ret == inode_state_no_change ||
+	    ret == inode_state_did_create ||
+	    ret == inode_state_will_delete)
+		ret = 1;
+	else
+		ret = 0;
+
+out:
+	return ret;
+}
+
+/*
+ * Helper function to lookup a dir item in a dir.
+ */
+static int lookup_dir_item_inode(struct btrfs_root *root,
+				 u64 dir, const char *name, int name_len,
+				 u64 *found_inode,
+				 u8 *found_type)
+{
+	int ret = 0;
+	struct btrfs_dir_item *di;
+	struct btrfs_key key;
+	struct btrfs_path *path;
+
+	path = alloc_path_for_send();
+	if (!path)
+		return -ENOMEM;
+
+	di = btrfs_lookup_dir_item(NULL, root, path,
+			dir, name, name_len, 0);
+	if (IS_ERR_OR_NULL(di)) {
+		ret = di ? PTR_ERR(di) : -ENOENT;
+		goto out;
+	}
+	btrfs_dir_item_key_to_cpu(path->nodes[0], di, &key);
+	if (key.type == BTRFS_ROOT_ITEM_KEY) {
+		ret = -ENOENT;
+		goto out;
+	}
+	*found_inode = key.objectid;
+	*found_type = btrfs_dir_type(path->nodes[0], di);
+
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+/*
+ * Looks up the first btrfs_inode_ref of a given ino. It returns the parent dir,
+ * generation of the parent dir and the name of the dir entry.
+ */
+static int get_first_ref(struct btrfs_root *root, u64 ino,
+			 u64 *dir, u64 *dir_gen, struct fs_path *name)
+{
+	int ret;
+	struct btrfs_key key;
+	struct btrfs_key found_key;
+	struct btrfs_path *path;
+	int len;
+	u64 parent_dir;
+
+	path = alloc_path_for_send();
+	if (!path)
+		return -ENOMEM;
+
+	key.objectid = ino;
+	key.type = BTRFS_INODE_REF_KEY;
+	key.offset = 0;
+
+	ret = btrfs_search_slot_for_read(root, &key, path, 1, 0);
+	if (ret < 0)
+		goto out;
+	if (!ret)
+		btrfs_item_key_to_cpu(path->nodes[0], &found_key,
+				path->slots[0]);
+	if (ret || found_key.objectid != ino ||
+	    (found_key.type != BTRFS_INODE_REF_KEY &&
+	     found_key.type != BTRFS_INODE_EXTREF_KEY)) {
+		ret = -ENOENT;
+		goto out;
+	}
+
+	if (found_key.type == BTRFS_INODE_REF_KEY) {
+		struct btrfs_inode_ref *iref;
+		iref = btrfs_item_ptr(path->nodes[0], path->slots[0],
+				      struct btrfs_inode_ref);
+		len = btrfs_inode_ref_name_len(path->nodes[0], iref);
+		ret = fs_path_add_from_extent_buffer(name, path->nodes[0],
+						     (unsigned long)(iref + 1),
+						     len);
+		parent_dir = found_key.offset;
+	} else {
+		struct btrfs_inode_extref *extref;
+		extref = btrfs_item_ptr(path->nodes[0], path->slots[0],
+					struct btrfs_inode_extref);
+		len = btrfs_inode_extref_name_len(path->nodes[0], extref);
+		ret = fs_path_add_from_extent_buffer(name, path->nodes[0],
+					(unsigned long)&extref->name, len);
+		parent_dir = btrfs_inode_extref_parent(path->nodes[0], extref);
+	}
+	if (ret < 0)
+		goto out;
+	btrfs_release_path(path);
+
+	if (dir_gen) {
+		ret = get_inode_info(root, parent_dir, NULL, dir_gen, NULL,
+				     NULL, NULL, NULL);
+		if (ret < 0)
+			goto out;
+	}
+
+	*dir = parent_dir;
+
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+static int is_first_ref(struct btrfs_root *root,
+			u64 ino, u64 dir,
+			const char *name, int name_len)
+{
+	int ret;
+	struct fs_path *tmp_name;
+	u64 tmp_dir;
+
+	tmp_name = fs_path_alloc();
+	if (!tmp_name)
+		return -ENOMEM;
+
+	ret = get_first_ref(root, ino, &tmp_dir, NULL, tmp_name);
+	if (ret < 0)
+		goto out;
+
+	if (dir != tmp_dir || name_len != fs_path_len(tmp_name)) {
+		ret = 0;
+		goto out;
+	}
+
+	ret = !memcmp(tmp_name->start, name, name_len);
+
+out:
+	fs_path_free(tmp_name);
+	return ret;
+}
+
+/*
+ * Used by process_recorded_refs to determine if a new ref would overwrite an
+ * already existing ref. In case it detects an overwrite, it returns the
+ * inode/gen in who_ino/who_gen.
+ * When an overwrite is detected, process_recorded_refs does proper orphanizing
+ * to make sure later references to the overwritten inode are possible.
+ * Orphanizing is however only required for the first ref of an inode.
+ * process_recorded_refs does an additional is_first_ref check to see if
+ * orphanizing is really required.
+ */
+static int will_overwrite_ref(struct send_ctx *sctx, u64 dir, u64 dir_gen,
+			      const char *name, int name_len,
+			      u64 *who_ino, u64 *who_gen, u64 *who_mode)
+{
+	int ret = 0;
+	u64 gen;
+	u64 other_inode = 0;
+	u8 other_type = 0;
+
+	if (!sctx->parent_root)
+		goto out;
+
+	ret = is_inode_existent(sctx, dir, dir_gen);
+	if (ret <= 0)
+		goto out;
+
+	/*
+	 * If we have a parent root we need to verify that the parent dir was
+	 * not deleted and then re-created, if it was then we have no overwrite
+	 * and we can just unlink this entry.
+	 */
+	if (sctx->parent_root && dir != BTRFS_FIRST_FREE_OBJECTID) {
+		ret = get_inode_info(sctx->parent_root, dir, NULL, &gen, NULL,
+				     NULL, NULL, NULL);
+		if (ret < 0 && ret != -ENOENT)
+			goto out;
+		if (ret) {
+			ret = 0;
+			goto out;
+		}
+		if (gen != dir_gen)
+			goto out;
+	}
+
+	ret = lookup_dir_item_inode(sctx->parent_root, dir, name, name_len,
+			&other_inode, &other_type);
+	if (ret < 0 && ret != -ENOENT)
+		goto out;
+	if (ret) {
+		ret = 0;
+		goto out;
+	}
+
+	/*
+	 * Check if the overwritten ref was already processed. If yes, the ref
+	 * was already unlinked/moved, so we can safely assume that we will not
+	 * overwrite anything at this point in time.
+	 */
+	if (other_inode > sctx->send_progress ||
+	    is_waiting_for_move(sctx, other_inode)) {
+		ret = get_inode_info(sctx->parent_root, other_inode, NULL,
+				who_gen, who_mode, NULL, NULL, NULL);
+		if (ret < 0)
+			goto out;
+
+		ret = 1;
+		*who_ino = other_inode;
+	} else {
+		ret = 0;
+	}
+
+out:
+	return ret;
+}
+
+/*
+ * Checks if the ref was overwritten by an already processed inode. This is
+ * used by __get_cur_name_and_parent to find out if the ref was orphanized and
+ * thus the orphan name needs be used.
+ * process_recorded_refs also uses it to avoid unlinking of refs that were
+ * overwritten.
+ */
+static int did_overwrite_ref(struct send_ctx *sctx,
+			    u64 dir, u64 dir_gen,
+			    u64 ino, u64 ino_gen,
+			    const char *name, int name_len)
+{
+	int ret = 0;
+	u64 gen;
+	u64 ow_inode;
+	u8 other_type;
+
+	if (!sctx->parent_root)
+		goto out;
+
+	ret = is_inode_existent(sctx, dir, dir_gen);
+	if (ret <= 0)
+		goto out;
+
+	if (dir != BTRFS_FIRST_FREE_OBJECTID) {
+		ret = get_inode_info(sctx->send_root, dir, NULL, &gen, NULL,
+				     NULL, NULL, NULL);
+		if (ret < 0 && ret != -ENOENT)
+			goto out;
+		if (ret) {
+			ret = 0;
+			goto out;
+		}
+		if (gen != dir_gen)
+			goto out;
+	}
+
+	/* check if the ref was overwritten by another ref */
+	ret = lookup_dir_item_inode(sctx->send_root, dir, name, name_len,
+			&ow_inode, &other_type);
+	if (ret < 0 && ret != -ENOENT)
+		goto out;
+	if (ret) {
+		/* was never and will never be overwritten */
+		ret = 0;
+		goto out;
+	}
+
+	ret = get_inode_info(sctx->send_root, ow_inode, NULL, &gen, NULL, NULL,
+			NULL, NULL);
+	if (ret < 0)
+		goto out;
+
+	if (ow_inode == ino && gen == ino_gen) {
+		ret = 0;
+		goto out;
+	}
+
+	/*
+	 * We know that it is or will be overwritten. Check this now.
+	 * The current inode being processed might have been the one that caused
+	 * inode 'ino' to be orphanized, therefore check if ow_inode matches
+	 * the current inode being processed.
+	 */
+	if ((ow_inode < sctx->send_progress) ||
+	    (ino != sctx->cur_ino && ow_inode == sctx->cur_ino &&
+	     gen == sctx->cur_inode_gen))
+		ret = 1;
+	else
+		ret = 0;
+
+out:
+	return ret;
+}
+
+/*
+ * Same as did_overwrite_ref, but also checks if it is the first ref of an inode
+ * that got overwritten. This is used by process_recorded_refs to determine
+ * if it has to use the path as returned by get_cur_path or the orphan name.
+ */
+static int did_overwrite_first_ref(struct send_ctx *sctx, u64 ino, u64 gen)
+{
+	int ret = 0;
+	struct fs_path *name = NULL;
+	u64 dir;
+	u64 dir_gen;
+
+	if (!sctx->parent_root)
+		goto out;
+
+	name = fs_path_alloc();
+	if (!name)
+		return -ENOMEM;
+
+	ret = get_first_ref(sctx->parent_root, ino, &dir, &dir_gen, name);
+	if (ret < 0)
+		goto out;
+
+	ret = did_overwrite_ref(sctx, dir, dir_gen, ino, gen,
+			name->start, fs_path_len(name));
+
+out:
+	fs_path_free(name);
+	return ret;
+}
+
+/*
+ * Insert a name cache entry. On 32bit kernels the radix tree index is 32bit,
+ * so we need to do some special handling in case we have clashes. This function
+ * takes care of this with the help of name_cache_entry::radix_list.
+ * In case of error, nce is kfreed.
+ */
+static int name_cache_insert(struct send_ctx *sctx,
+			     struct name_cache_entry *nce)
+{
+	int ret = 0;
+	struct list_head *nce_head;
+
+	nce_head = radix_tree_lookup(&sctx->name_cache,
+			(unsigned long)nce->ino);
+	if (!nce_head) {
+		nce_head = kmalloc(sizeof(*nce_head), GFP_KERNEL);
+		if (!nce_head) {
+			kfree(nce);
+			return -ENOMEM;
+		}
+		INIT_LIST_HEAD(nce_head);
+
+		ret = radix_tree_insert(&sctx->name_cache, nce->ino, nce_head);
+		if (ret < 0) {
+			kfree(nce_head);
+			kfree(nce);
+			return ret;
+		}
+	}
+	list_add_tail(&nce->radix_list, nce_head);
+	list_add_tail(&nce->list, &sctx->name_cache_list);
+	sctx->name_cache_size++;
+
+	return ret;
+}
+
+static void name_cache_delete(struct send_ctx *sctx,
+			      struct name_cache_entry *nce)
+{
+	struct list_head *nce_head;
+
+	nce_head = radix_tree_lookup(&sctx->name_cache,
+			(unsigned long)nce->ino);
+	if (!nce_head) {
+		btrfs_err(sctx->send_root->fs_info,
+	      "name_cache_delete lookup failed ino %llu cache size %d, leaking memory",
+			nce->ino, sctx->name_cache_size);
+	}
+
+	list_del(&nce->radix_list);
+	list_del(&nce->list);
+	sctx->name_cache_size--;
+
+	/*
+	 * We may not get to the final release of nce_head if the lookup fails
+	 */
+	if (nce_head && list_empty(nce_head)) {
+		radix_tree_delete(&sctx->name_cache, (unsigned long)nce->ino);
+		kfree(nce_head);
+	}
+}
+
+static struct name_cache_entry *name_cache_search(struct send_ctx *sctx,
+						    u64 ino, u64 gen)
+{
+	struct list_head *nce_head;
+	struct name_cache_entry *cur;
+
+	nce_head = radix_tree_lookup(&sctx->name_cache, (unsigned long)ino);
+	if (!nce_head)
+		return NULL;
+
+	list_for_each_entry(cur, nce_head, radix_list) {
+		if (cur->ino == ino && cur->gen == gen)
+			return cur;
+	}
+	return NULL;
+}
+
+/*
+ * Removes the entry from the list and adds it back to the end. This marks the
+ * entry as recently used so that name_cache_clean_unused does not remove it.
+ */
+static void name_cache_used(struct send_ctx *sctx, struct name_cache_entry *nce)
+{
+	list_del(&nce->list);
+	list_add_tail(&nce->list, &sctx->name_cache_list);
+}
+
+/*
+ * Remove some entries from the beginning of name_cache_list.
+ */
+static void name_cache_clean_unused(struct send_ctx *sctx)
+{
+	struct name_cache_entry *nce;
+
+	if (sctx->name_cache_size < SEND_CTX_NAME_CACHE_CLEAN_SIZE)
+		return;
+
+	while (sctx->name_cache_size > SEND_CTX_MAX_NAME_CACHE_SIZE) {
+		nce = list_entry(sctx->name_cache_list.next,
+				struct name_cache_entry, list);
+		name_cache_delete(sctx, nce);
+		kfree(nce);
+	}
+}
+
+static void name_cache_free(struct send_ctx *sctx)
+{
+	struct name_cache_entry *nce;
+
+	while (!list_empty(&sctx->name_cache_list)) {
+		nce = list_entry(sctx->name_cache_list.next,
+				struct name_cache_entry, list);
+		name_cache_delete(sctx, nce);
+		kfree(nce);
+	}
+}
+
+/*
+ * Used by get_cur_path for each ref up to the root.
+ * Returns 0 if it succeeded.
+ * Returns 1 if the inode is not existent or got overwritten. In that case, the
+ * name is an orphan name. This instructs get_cur_path to stop iterating. If 1
+ * is returned, parent_ino/parent_gen are not guaranteed to be valid.
+ * Returns <0 in case of error.
+ */
+static int __get_cur_name_and_parent(struct send_ctx *sctx,
+				     u64 ino, u64 gen,
+				     u64 *parent_ino,
+				     u64 *parent_gen,
+				     struct fs_path *dest)
+{
+	int ret;
+	int nce_ret;
+	struct name_cache_entry *nce = NULL;
+
+	/*
+	 * First check if we already did a call to this function with the same
+	 * ino/gen. If yes, check if the cache entry is still up-to-date. If yes
+	 * return the cached result.
+	 */
+	nce = name_cache_search(sctx, ino, gen);
+	if (nce) {
+		if (ino < sctx->send_progress && nce->need_later_update) {
+			name_cache_delete(sctx, nce);
+			kfree(nce);
+			nce = NULL;
+		} else {
+			name_cache_used(sctx, nce);
+			*parent_ino = nce->parent_ino;
+			*parent_gen = nce->parent_gen;
+			ret = fs_path_add(dest, nce->name, nce->name_len);
+			if (ret < 0)
+				goto out;
+			ret = nce->ret;
+			goto out;
+		}
+	}
+
+	/*
+	 * If the inode is not existent yet, add the orphan name and return 1.
+	 * This should only happen for the parent dir that we determine in
+	 * __record_new_ref
+	 */
+	ret = is_inode_existent(sctx, ino, gen);
+	if (ret < 0)
+		goto out;
+
+	if (!ret) {
+		ret = gen_unique_name(sctx, ino, gen, dest);
+		if (ret < 0)
+			goto out;
+		ret = 1;
+		goto out_cache;
+	}
+
+	/*
+	 * Depending on whether the inode was already processed or not, use
+	 * send_root or parent_root for ref lookup.
+	 */
+	if (ino < sctx->send_progress)
+		ret = get_first_ref(sctx->send_root, ino,
+				    parent_ino, parent_gen, dest);
+	else
+		ret = get_first_ref(sctx->parent_root, ino,
+				    parent_ino, parent_gen, dest);
+	if (ret < 0)
+		goto out;
+
+	/*
+	 * Check if the ref was overwritten by an inode's ref that was processed
+	 * earlier. If yes, treat as orphan and return 1.
+	 */
+	ret = did_overwrite_ref(sctx, *parent_ino, *parent_gen, ino, gen,
+			dest->start, dest->end - dest->start);
+	if (ret < 0)
+		goto out;
+	if (ret) {
+		fs_path_reset(dest);
+		ret = gen_unique_name(sctx, ino, gen, dest);
+		if (ret < 0)
+			goto out;
+		ret = 1;
+	}
+
+out_cache:
+	/*
+	 * Store the result of the lookup in the name cache.
+	 */
+	nce = kmalloc(sizeof(*nce) + fs_path_len(dest) + 1, GFP_KERNEL);
+	if (!nce) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	nce->ino = ino;
+	nce->gen = gen;
+	nce->parent_ino = *parent_ino;
+	nce->parent_gen = *parent_gen;
+	nce->name_len = fs_path_len(dest);
+	nce->ret = ret;
+	strcpy(nce->name, dest->start);
+
+	if (ino < sctx->send_progress)
+		nce->need_later_update = 0;
+	else
+		nce->need_later_update = 1;
+
+	nce_ret = name_cache_insert(sctx, nce);
+	if (nce_ret < 0)
+		ret = nce_ret;
+	name_cache_clean_unused(sctx);
+
+out:
+	return ret;
+}
+
+/*
+ * Magic happens here. This function returns the first ref to an inode as it
+ * would look like while receiving the stream at this point in time.
+ * We walk the path up to the root. For every inode in between, we check if it
+ * was already processed/sent. If yes, we continue with the parent as found
+ * in send_root. If not, we continue with the parent as found in parent_root.
+ * If we encounter an inode that was deleted at this point in time, we use the
+ * inodes "orphan" name instead of the real name and stop. Same with new inodes
+ * that were not created yet and overwritten inodes/refs.
+ *
+ * When do we have orphan inodes:
+ * 1. When an inode is freshly created and thus no valid refs are available yet
+ * 2. When a directory lost all it's refs (deleted) but still has dir items
+ *    inside which were not processed yet (pending for move/delete). If anyone
+ *    tried to get the path to the dir items, it would get a path inside that
+ *    orphan directory.
+ * 3. When an inode is moved around or gets new links, it may overwrite the ref
+ *    of an unprocessed inode. If in that case the first ref would be
+ *    overwritten, the overwritten inode gets "orphanized". Later when we
+ *    process this overwritten inode, it is restored at a new place by moving
+ *    the orphan inode.
+ *
+ * sctx->send_progress tells this function at which point in time receiving
+ * would be.
+ */
+static int get_cur_path(struct send_ctx *sctx, u64 ino, u64 gen,
+			struct fs_path *dest)
+{
+	int ret = 0;
+	struct fs_path *name = NULL;
+	u64 parent_inode = 0;
+	u64 parent_gen = 0;
+	int stop = 0;
+
+	name = fs_path_alloc();
+	if (!name) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	dest->reversed = 1;
+	fs_path_reset(dest);
+
+	while (!stop && ino != BTRFS_FIRST_FREE_OBJECTID) {
+		struct waiting_dir_move *wdm;
+
+		fs_path_reset(name);
+
+		if (is_waiting_for_rm(sctx, ino, gen)) {
+			ret = gen_unique_name(sctx, ino, gen, name);
+			if (ret < 0)
+				goto out;
+			ret = fs_path_add_path(dest, name);
+			break;
+		}
+
+		wdm = get_waiting_dir_move(sctx, ino);
+		if (wdm && wdm->orphanized) {
+			ret = gen_unique_name(sctx, ino, gen, name);
+			stop = 1;
+		} else if (wdm) {
+			ret = get_first_ref(sctx->parent_root, ino,
+					    &parent_inode, &parent_gen, name);
+		} else {
+			ret = __get_cur_name_and_parent(sctx, ino, gen,
+							&parent_inode,
+							&parent_gen, name);
+			if (ret)
+				stop = 1;
+		}
+
+		if (ret < 0)
+			goto out;
+
+		ret = fs_path_add_path(dest, name);
+		if (ret < 0)
+			goto out;
+
+		ino = parent_inode;
+		gen = parent_gen;
+	}
+
+out:
+	fs_path_free(name);
+	if (!ret)
+		fs_path_unreverse(dest);
+	return ret;
+}
+
+/*
+ * Sends a BTRFS_SEND_C_SUBVOL command/item to userspace
+ */
+static int send_subvol_begin(struct send_ctx *sctx)
+{
+	int ret;
+	struct btrfs_root *send_root = sctx->send_root;
+	struct btrfs_root *parent_root = sctx->parent_root;
+	struct btrfs_path *path;
+	struct btrfs_key key;
+	struct btrfs_root_ref *ref;
+	struct extent_buffer *leaf;
+	char *name = NULL;
+	int namelen;
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return -ENOMEM;
+
+	name = kmalloc(BTRFS_PATH_NAME_MAX, GFP_KERNEL);
+	if (!name) {
+		btrfs_free_path(path);
+		return -ENOMEM;
+	}
+
+	key.objectid = send_root->root_key.objectid;
+	key.type = BTRFS_ROOT_BACKREF_KEY;
+	key.offset = 0;
+
+	ret = btrfs_search_slot_for_read(send_root->fs_info->tree_root,
+				&key, path, 1, 0);
+	if (ret < 0)
+		goto out;
+	if (ret) {
+		ret = -ENOENT;
+		goto out;
+	}
+
+	leaf = path->nodes[0];
+	btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
+	if (key.type != BTRFS_ROOT_BACKREF_KEY ||
+	    key.objectid != send_root->root_key.objectid) {
+		ret = -ENOENT;
+		goto out;
+	}
+	ref = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_root_ref);
+	namelen = btrfs_root_ref_name_len(leaf, ref);
+	read_extent_buffer(leaf, name, (unsigned long)(ref + 1), namelen);
+	btrfs_release_path(path);
+
+	if (parent_root) {
+		ret = begin_cmd(sctx, BTRFS_SEND_C_SNAPSHOT);
+		if (ret < 0)
+			goto out;
+	} else {
+		ret = begin_cmd(sctx, BTRFS_SEND_C_SUBVOL);
+		if (ret < 0)
+			goto out;
+	}
+
+	TLV_PUT_STRING(sctx, BTRFS_SEND_A_PATH, name, namelen);
+
+	if (!btrfs_is_empty_uuid(sctx->send_root->root_item.received_uuid))
+		TLV_PUT_UUID(sctx, BTRFS_SEND_A_UUID,
+			    sctx->send_root->root_item.received_uuid);
+	else
+		TLV_PUT_UUID(sctx, BTRFS_SEND_A_UUID,
+			    sctx->send_root->root_item.uuid);
+
+	TLV_PUT_U64(sctx, BTRFS_SEND_A_CTRANSID,
+		    le64_to_cpu(sctx->send_root->root_item.ctransid));
+	if (parent_root) {
+		if (!btrfs_is_empty_uuid(parent_root->root_item.received_uuid))
+			TLV_PUT_UUID(sctx, BTRFS_SEND_A_CLONE_UUID,
+				     parent_root->root_item.received_uuid);
+		else
+			TLV_PUT_UUID(sctx, BTRFS_SEND_A_CLONE_UUID,
+				     parent_root->root_item.uuid);
+		TLV_PUT_U64(sctx, BTRFS_SEND_A_CLONE_CTRANSID,
+			    le64_to_cpu(sctx->parent_root->root_item.ctransid));
+	}
+
+	ret = send_cmd(sctx);
+
+tlv_put_failure:
+out:
+	btrfs_free_path(path);
+	kfree(name);
+	return ret;
+}
+
+static int send_truncate(struct send_ctx *sctx, u64 ino, u64 gen, u64 size)
+{
+	struct btrfs_fs_info *fs_info = sctx->send_root->fs_info;
+	int ret = 0;
+	struct fs_path *p;
+
+	btrfs_debug(fs_info, "send_truncate %llu size=%llu", ino, size);
+
+	p = fs_path_alloc();
+	if (!p)
+		return -ENOMEM;
+
+	ret = begin_cmd(sctx, BTRFS_SEND_C_TRUNCATE);
+	if (ret < 0)
+		goto out;
+
+	ret = get_cur_path(sctx, ino, gen, p);
+	if (ret < 0)
+		goto out;
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, p);
+	TLV_PUT_U64(sctx, BTRFS_SEND_A_SIZE, size);
+
+	ret = send_cmd(sctx);
+
+tlv_put_failure:
+out:
+	fs_path_free(p);
+	return ret;
+}
+
+static int send_chmod(struct send_ctx *sctx, u64 ino, u64 gen, u64 mode)
+{
+	struct btrfs_fs_info *fs_info = sctx->send_root->fs_info;
+	int ret = 0;
+	struct fs_path *p;
+
+	btrfs_debug(fs_info, "send_chmod %llu mode=%llu", ino, mode);
+
+	p = fs_path_alloc();
+	if (!p)
+		return -ENOMEM;
+
+	ret = begin_cmd(sctx, BTRFS_SEND_C_CHMOD);
+	if (ret < 0)
+		goto out;
+
+	ret = get_cur_path(sctx, ino, gen, p);
+	if (ret < 0)
+		goto out;
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, p);
+	TLV_PUT_U64(sctx, BTRFS_SEND_A_MODE, mode & 07777);
+
+	ret = send_cmd(sctx);
+
+tlv_put_failure:
+out:
+	fs_path_free(p);
+	return ret;
+}
+
+static int send_chown(struct send_ctx *sctx, u64 ino, u64 gen, u64 uid, u64 gid)
+{
+	struct btrfs_fs_info *fs_info = sctx->send_root->fs_info;
+	int ret = 0;
+	struct fs_path *p;
+
+	btrfs_debug(fs_info, "send_chown %llu uid=%llu, gid=%llu",
+		    ino, uid, gid);
+
+	p = fs_path_alloc();
+	if (!p)
+		return -ENOMEM;
+
+	ret = begin_cmd(sctx, BTRFS_SEND_C_CHOWN);
+	if (ret < 0)
+		goto out;
+
+	ret = get_cur_path(sctx, ino, gen, p);
+	if (ret < 0)
+		goto out;
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, p);
+	TLV_PUT_U64(sctx, BTRFS_SEND_A_UID, uid);
+	TLV_PUT_U64(sctx, BTRFS_SEND_A_GID, gid);
+
+	ret = send_cmd(sctx);
+
+tlv_put_failure:
+out:
+	fs_path_free(p);
+	return ret;
+}
+
+static int send_utimes(struct send_ctx *sctx, u64 ino, u64 gen)
+{
+	struct btrfs_fs_info *fs_info = sctx->send_root->fs_info;
+	int ret = 0;
+	struct fs_path *p = NULL;
+	struct btrfs_inode_item *ii;
+	struct btrfs_path *path = NULL;
+	struct extent_buffer *eb;
+	struct btrfs_key key;
+	int slot;
+
+	btrfs_debug(fs_info, "send_utimes %llu", ino);
+
+	p = fs_path_alloc();
+	if (!p)
+		return -ENOMEM;
+
+	path = alloc_path_for_send();
+	if (!path) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	key.objectid = ino;
+	key.type = BTRFS_INODE_ITEM_KEY;
+	key.offset = 0;
+	ret = btrfs_search_slot(NULL, sctx->send_root, &key, path, 0, 0);
+	if (ret > 0)
+		ret = -ENOENT;
+	if (ret < 0)
+		goto out;
+
+	eb = path->nodes[0];
+	slot = path->slots[0];
+	ii = btrfs_item_ptr(eb, slot, struct btrfs_inode_item);
+
+	ret = begin_cmd(sctx, BTRFS_SEND_C_UTIMES);
+	if (ret < 0)
+		goto out;
+
+	ret = get_cur_path(sctx, ino, gen, p);
+	if (ret < 0)
+		goto out;
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, p);
+	TLV_PUT_BTRFS_TIMESPEC(sctx, BTRFS_SEND_A_ATIME, eb, &ii->atime);
+	TLV_PUT_BTRFS_TIMESPEC(sctx, BTRFS_SEND_A_MTIME, eb, &ii->mtime);
+	TLV_PUT_BTRFS_TIMESPEC(sctx, BTRFS_SEND_A_CTIME, eb, &ii->ctime);
+	/* TODO Add otime support when the otime patches get into upstream */
+
+	ret = send_cmd(sctx);
+
+tlv_put_failure:
+out:
+	fs_path_free(p);
+	btrfs_free_path(path);
+	return ret;
+}
+
+/*
+ * Sends a BTRFS_SEND_C_MKXXX or SYMLINK command to user space. We don't have
+ * a valid path yet because we did not process the refs yet. So, the inode
+ * is created as orphan.
+ */
+static int send_create_inode(struct send_ctx *sctx, u64 ino)
+{
+	struct btrfs_fs_info *fs_info = sctx->send_root->fs_info;
+	int ret = 0;
+	struct fs_path *p;
+	int cmd;
+	u64 gen;
+	u64 mode;
+	u64 rdev;
+
+	btrfs_debug(fs_info, "send_create_inode %llu", ino);
+
+	p = fs_path_alloc();
+	if (!p)
+		return -ENOMEM;
+
+	if (ino != sctx->cur_ino) {
+		ret = get_inode_info(sctx->send_root, ino, NULL, &gen, &mode,
+				     NULL, NULL, &rdev);
+		if (ret < 0)
+			goto out;
+	} else {
+		gen = sctx->cur_inode_gen;
+		mode = sctx->cur_inode_mode;
+		rdev = sctx->cur_inode_rdev;
+	}
+
+	if (S_ISREG(mode)) {
+		cmd = BTRFS_SEND_C_MKFILE;
+	} else if (S_ISDIR(mode)) {
+		cmd = BTRFS_SEND_C_MKDIR;
+	} else if (S_ISLNK(mode)) {
+		cmd = BTRFS_SEND_C_SYMLINK;
+	} else if (S_ISCHR(mode) || S_ISBLK(mode)) {
+		cmd = BTRFS_SEND_C_MKNOD;
+	} else if (S_ISFIFO(mode)) {
+		cmd = BTRFS_SEND_C_MKFIFO;
+	} else if (S_ISSOCK(mode)) {
+		cmd = BTRFS_SEND_C_MKSOCK;
+	} else {
+		btrfs_warn(sctx->send_root->fs_info, "unexpected inode type %o",
+				(int)(mode & S_IFMT));
+		ret = -EOPNOTSUPP;
+		goto out;
+	}
+
+	ret = begin_cmd(sctx, cmd);
+	if (ret < 0)
+		goto out;
+
+	ret = gen_unique_name(sctx, ino, gen, p);
+	if (ret < 0)
+		goto out;
+
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, p);
+	TLV_PUT_U64(sctx, BTRFS_SEND_A_INO, ino);
+
+	if (S_ISLNK(mode)) {
+		fs_path_reset(p);
+		ret = read_symlink(sctx->send_root, ino, p);
+		if (ret < 0)
+			goto out;
+		TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH_LINK, p);
+	} else if (S_ISCHR(mode) || S_ISBLK(mode) ||
+		   S_ISFIFO(mode) || S_ISSOCK(mode)) {
+		TLV_PUT_U64(sctx, BTRFS_SEND_A_RDEV, new_encode_dev(rdev));
+		TLV_PUT_U64(sctx, BTRFS_SEND_A_MODE, mode);
+	}
+
+	ret = send_cmd(sctx);
+	if (ret < 0)
+		goto out;
+
+
+tlv_put_failure:
+out:
+	fs_path_free(p);
+	return ret;
+}
+
+/*
+ * We need some special handling for inodes that get processed before the parent
+ * directory got created. See process_recorded_refs for details.
+ * This function does the check if we already created the dir out of order.
+ */
+static int did_create_dir(struct send_ctx *sctx, u64 dir)
+{
+	int ret = 0;
+	struct btrfs_path *path = NULL;
+	struct btrfs_key key;
+	struct btrfs_key found_key;
+	struct btrfs_key di_key;
+	struct extent_buffer *eb;
+	struct btrfs_dir_item *di;
+	int slot;
+
+	path = alloc_path_for_send();
+	if (!path) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	key.objectid = dir;
+	key.type = BTRFS_DIR_INDEX_KEY;
+	key.offset = 0;
+	ret = btrfs_search_slot(NULL, sctx->send_root, &key, path, 0, 0);
+	if (ret < 0)
+		goto out;
+
+	while (1) {
+		eb = path->nodes[0];
+		slot = path->slots[0];
+		if (slot >= btrfs_header_nritems(eb)) {
+			ret = btrfs_next_leaf(sctx->send_root, path);
+			if (ret < 0) {
+				goto out;
+			} else if (ret > 0) {
+				ret = 0;
+				break;
+			}
+			continue;
+		}
+
+		btrfs_item_key_to_cpu(eb, &found_key, slot);
+		if (found_key.objectid != key.objectid ||
+		    found_key.type != key.type) {
+			ret = 0;
+			goto out;
+		}
+
+		di = btrfs_item_ptr(eb, slot, struct btrfs_dir_item);
+		btrfs_dir_item_key_to_cpu(eb, di, &di_key);
+
+		if (di_key.type != BTRFS_ROOT_ITEM_KEY &&
+		    di_key.objectid < sctx->send_progress) {
+			ret = 1;
+			goto out;
+		}
+
+		path->slots[0]++;
+	}
+
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+/*
+ * Only creates the inode if it is:
+ * 1. Not a directory
+ * 2. Or a directory which was not created already due to out of order
+ *    directories. See did_create_dir and process_recorded_refs for details.
+ */
+static int send_create_inode_if_needed(struct send_ctx *sctx)
+{
+	int ret;
+
+	if (S_ISDIR(sctx->cur_inode_mode)) {
+		ret = did_create_dir(sctx, sctx->cur_ino);
+		if (ret < 0)
+			goto out;
+		if (ret) {
+			ret = 0;
+			goto out;
+		}
+	}
+
+	ret = send_create_inode(sctx, sctx->cur_ino);
+	if (ret < 0)
+		goto out;
+
+out:
+	return ret;
+}
+
+struct recorded_ref {
+	struct list_head list;
+	char *name;
+	struct fs_path *full_path;
+	u64 dir;
+	u64 dir_gen;
+	int name_len;
+};
+
+static void set_ref_path(struct recorded_ref *ref, struct fs_path *path)
+{
+	ref->full_path = path;
+	ref->name = (char *)kbasename(ref->full_path->start);
+	ref->name_len = ref->full_path->end - ref->name;
+}
+
+/*
+ * We need to process new refs before deleted refs, but compare_tree gives us
+ * everything mixed. So we first record all refs and later process them.
+ * This function is a helper to record one ref.
+ */
+static int __record_ref(struct list_head *head, u64 dir,
+		      u64 dir_gen, struct fs_path *path)
+{
+	struct recorded_ref *ref;
+
+	ref = kmalloc(sizeof(*ref), GFP_KERNEL);
+	if (!ref)
+		return -ENOMEM;
+
+	ref->dir = dir;
+	ref->dir_gen = dir_gen;
+	set_ref_path(ref, path);
+	list_add_tail(&ref->list, head);
+	return 0;
+}
+
+static int dup_ref(struct recorded_ref *ref, struct list_head *list)
+{
+	struct recorded_ref *new;
+
+	new = kmalloc(sizeof(*ref), GFP_KERNEL);
+	if (!new)
+		return -ENOMEM;
+
+	new->dir = ref->dir;
+	new->dir_gen = ref->dir_gen;
+	new->full_path = NULL;
+	INIT_LIST_HEAD(&new->list);
+	list_add_tail(&new->list, list);
+	return 0;
+}
+
+static void __free_recorded_refs(struct list_head *head)
+{
+	struct recorded_ref *cur;
+
+	while (!list_empty(head)) {
+		cur = list_entry(head->next, struct recorded_ref, list);
+		fs_path_free(cur->full_path);
+		list_del(&cur->list);
+		kfree(cur);
+	}
+}
+
+static void free_recorded_refs(struct send_ctx *sctx)
+{
+	__free_recorded_refs(&sctx->new_refs);
+	__free_recorded_refs(&sctx->deleted_refs);
+}
+
+/*
+ * Renames/moves a file/dir to its orphan name. Used when the first
+ * ref of an unprocessed inode gets overwritten and for all non empty
+ * directories.
+ */
+static int orphanize_inode(struct send_ctx *sctx, u64 ino, u64 gen,
+			  struct fs_path *path)
+{
+	int ret;
+	struct fs_path *orphan;
+
+	orphan = fs_path_alloc();
+	if (!orphan)
+		return -ENOMEM;
+
+	ret = gen_unique_name(sctx, ino, gen, orphan);
+	if (ret < 0)
+		goto out;
+
+	ret = send_rename(sctx, path, orphan);
+
+out:
+	fs_path_free(orphan);
+	return ret;
+}
+
+static struct orphan_dir_info *add_orphan_dir_info(struct send_ctx *sctx,
+						   u64 dir_ino, u64 dir_gen)
+{
+	struct rb_node **p = &sctx->orphan_dirs.rb_node;
+	struct rb_node *parent = NULL;
+	struct orphan_dir_info *entry, *odi;
+
+	while (*p) {
+		parent = *p;
+		entry = rb_entry(parent, struct orphan_dir_info, node);
+		if (dir_ino < entry->ino)
+			p = &(*p)->rb_left;
+		else if (dir_ino > entry->ino)
+			p = &(*p)->rb_right;
+		else if (dir_gen < entry->gen)
+			p = &(*p)->rb_left;
+		else if (dir_gen > entry->gen)
+			p = &(*p)->rb_right;
+		else
+			return entry;
+	}
+
+	odi = kmalloc(sizeof(*odi), GFP_KERNEL);
+	if (!odi)
+		return ERR_PTR(-ENOMEM);
+	odi->ino = dir_ino;
+	odi->gen = dir_gen;
+	odi->last_dir_index_offset = 0;
+
+	rb_link_node(&odi->node, parent, p);
+	rb_insert_color(&odi->node, &sctx->orphan_dirs);
+	return odi;
+}
+
+static struct orphan_dir_info *get_orphan_dir_info(struct send_ctx *sctx,
+						   u64 dir_ino, u64 gen)
+{
+	struct rb_node *n = sctx->orphan_dirs.rb_node;
+	struct orphan_dir_info *entry;
+
+	while (n) {
+		entry = rb_entry(n, struct orphan_dir_info, node);
+		if (dir_ino < entry->ino)
+			n = n->rb_left;
+		else if (dir_ino > entry->ino)
+			n = n->rb_right;
+		else if (gen < entry->gen)
+			n = n->rb_left;
+		else if (gen > entry->gen)
+			n = n->rb_right;
+		else
+			return entry;
+	}
+	return NULL;
+}
+
+static int is_waiting_for_rm(struct send_ctx *sctx, u64 dir_ino, u64 gen)
+{
+	struct orphan_dir_info *odi = get_orphan_dir_info(sctx, dir_ino, gen);
+
+	return odi != NULL;
+}
+
+static void free_orphan_dir_info(struct send_ctx *sctx,
+				 struct orphan_dir_info *odi)
+{
+	if (!odi)
+		return;
+	rb_erase(&odi->node, &sctx->orphan_dirs);
+	kfree(odi);
+}
+
+/*
+ * Returns 1 if a directory can be removed at this point in time.
+ * We check this by iterating all dir items and checking if the inode behind
+ * the dir item was already processed.
+ */
+static int can_rmdir(struct send_ctx *sctx, u64 dir, u64 dir_gen,
+		     u64 send_progress)
+{
+	int ret = 0;
+	struct btrfs_root *root = sctx->parent_root;
+	struct btrfs_path *path;
+	struct btrfs_key key;
+	struct btrfs_key found_key;
+	struct btrfs_key loc;
+	struct btrfs_dir_item *di;
+	struct orphan_dir_info *odi = NULL;
+
+	/*
+	 * Don't try to rmdir the top/root subvolume dir.
+	 */
+	if (dir == BTRFS_FIRST_FREE_OBJECTID)
+		return 0;
+
+	path = alloc_path_for_send();
+	if (!path)
+		return -ENOMEM;
+
+	key.objectid = dir;
+	key.type = BTRFS_DIR_INDEX_KEY;
+	key.offset = 0;
+
+	odi = get_orphan_dir_info(sctx, dir, dir_gen);
+	if (odi)
+		key.offset = odi->last_dir_index_offset;
+
+	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+	if (ret < 0)
+		goto out;
+
+	while (1) {
+		struct waiting_dir_move *dm;
+
+		if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) {
+			ret = btrfs_next_leaf(root, path);
+			if (ret < 0)
+				goto out;
+			else if (ret > 0)
+				break;
+			continue;
+		}
+		btrfs_item_key_to_cpu(path->nodes[0], &found_key,
+				      path->slots[0]);
+		if (found_key.objectid != key.objectid ||
+		    found_key.type != key.type)
+			break;
+
+		di = btrfs_item_ptr(path->nodes[0], path->slots[0],
+				struct btrfs_dir_item);
+		btrfs_dir_item_key_to_cpu(path->nodes[0], di, &loc);
+
+		dm = get_waiting_dir_move(sctx, loc.objectid);
+		if (dm) {
+			odi = add_orphan_dir_info(sctx, dir, dir_gen);
+			if (IS_ERR(odi)) {
+				ret = PTR_ERR(odi);
+				goto out;
+			}
+			odi->gen = dir_gen;
+			odi->last_dir_index_offset = found_key.offset;
+			dm->rmdir_ino = dir;
+			dm->rmdir_gen = dir_gen;
+			ret = 0;
+			goto out;
+		}
+
+		if (loc.objectid > send_progress) {
+			odi = add_orphan_dir_info(sctx, dir, dir_gen);
+			if (IS_ERR(odi)) {
+				ret = PTR_ERR(odi);
+				goto out;
+			}
+			odi->gen = dir_gen;
+			odi->last_dir_index_offset = found_key.offset;
+			ret = 0;
+			goto out;
+		}
+
+		path->slots[0]++;
+	}
+	free_orphan_dir_info(sctx, odi);
+
+	ret = 1;
+
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+static int is_waiting_for_move(struct send_ctx *sctx, u64 ino)
+{
+	struct waiting_dir_move *entry = get_waiting_dir_move(sctx, ino);
+
+	return entry != NULL;
+}
+
+static int add_waiting_dir_move(struct send_ctx *sctx, u64 ino, bool orphanized)
+{
+	struct rb_node **p = &sctx->waiting_dir_moves.rb_node;
+	struct rb_node *parent = NULL;
+	struct waiting_dir_move *entry, *dm;
+
+	dm = kmalloc(sizeof(*dm), GFP_KERNEL);
+	if (!dm)
+		return -ENOMEM;
+	dm->ino = ino;
+	dm->rmdir_ino = 0;
+	dm->rmdir_gen = 0;
+	dm->orphanized = orphanized;
+
+	while (*p) {
+		parent = *p;
+		entry = rb_entry(parent, struct waiting_dir_move, node);
+		if (ino < entry->ino) {
+			p = &(*p)->rb_left;
+		} else if (ino > entry->ino) {
+			p = &(*p)->rb_right;
+		} else {
+			kfree(dm);
+			return -EEXIST;
+		}
+	}
+
+	rb_link_node(&dm->node, parent, p);
+	rb_insert_color(&dm->node, &sctx->waiting_dir_moves);
+	return 0;
+}
+
+static struct waiting_dir_move *
+get_waiting_dir_move(struct send_ctx *sctx, u64 ino)
+{
+	struct rb_node *n = sctx->waiting_dir_moves.rb_node;
+	struct waiting_dir_move *entry;
+
+	while (n) {
+		entry = rb_entry(n, struct waiting_dir_move, node);
+		if (ino < entry->ino)
+			n = n->rb_left;
+		else if (ino > entry->ino)
+			n = n->rb_right;
+		else
+			return entry;
+	}
+	return NULL;
+}
+
+static void free_waiting_dir_move(struct send_ctx *sctx,
+				  struct waiting_dir_move *dm)
+{
+	if (!dm)
+		return;
+	rb_erase(&dm->node, &sctx->waiting_dir_moves);
+	kfree(dm);
+}
+
+static int add_pending_dir_move(struct send_ctx *sctx,
+				u64 ino,
+				u64 ino_gen,
+				u64 parent_ino,
+				struct list_head *new_refs,
+				struct list_head *deleted_refs,
+				const bool is_orphan)
+{
+	struct rb_node **p = &sctx->pending_dir_moves.rb_node;
+	struct rb_node *parent = NULL;
+	struct pending_dir_move *entry = NULL, *pm;
+	struct recorded_ref *cur;
+	int exists = 0;
+	int ret;
+
+	pm = kmalloc(sizeof(*pm), GFP_KERNEL);
+	if (!pm)
+		return -ENOMEM;
+	pm->parent_ino = parent_ino;
+	pm->ino = ino;
+	pm->gen = ino_gen;
+	INIT_LIST_HEAD(&pm->list);
+	INIT_LIST_HEAD(&pm->update_refs);
+	RB_CLEAR_NODE(&pm->node);
+
+	while (*p) {
+		parent = *p;
+		entry = rb_entry(parent, struct pending_dir_move, node);
+		if (parent_ino < entry->parent_ino) {
+			p = &(*p)->rb_left;
+		} else if (parent_ino > entry->parent_ino) {
+			p = &(*p)->rb_right;
+		} else {
+			exists = 1;
+			break;
+		}
+	}
+
+	list_for_each_entry(cur, deleted_refs, list) {
+		ret = dup_ref(cur, &pm->update_refs);
+		if (ret < 0)
+			goto out;
+	}
+	list_for_each_entry(cur, new_refs, list) {
+		ret = dup_ref(cur, &pm->update_refs);
+		if (ret < 0)
+			goto out;
+	}
+
+	ret = add_waiting_dir_move(sctx, pm->ino, is_orphan);
+	if (ret)
+		goto out;
+
+	if (exists) {
+		list_add_tail(&pm->list, &entry->list);
+	} else {
+		rb_link_node(&pm->node, parent, p);
+		rb_insert_color(&pm->node, &sctx->pending_dir_moves);
+	}
+	ret = 0;
+out:
+	if (ret) {
+		__free_recorded_refs(&pm->update_refs);
+		kfree(pm);
+	}
+	return ret;
+}
+
+static struct pending_dir_move *get_pending_dir_moves(struct send_ctx *sctx,
+						      u64 parent_ino)
+{
+	struct rb_node *n = sctx->pending_dir_moves.rb_node;
+	struct pending_dir_move *entry;
+
+	while (n) {
+		entry = rb_entry(n, struct pending_dir_move, node);
+		if (parent_ino < entry->parent_ino)
+			n = n->rb_left;
+		else if (parent_ino > entry->parent_ino)
+			n = n->rb_right;
+		else
+			return entry;
+	}
+	return NULL;
+}
+
+static int path_loop(struct send_ctx *sctx, struct fs_path *name,
+		     u64 ino, u64 gen, u64 *ancestor_ino)
+{
+	int ret = 0;
+	u64 parent_inode = 0;
+	u64 parent_gen = 0;
+	u64 start_ino = ino;
+
+	*ancestor_ino = 0;
+	while (ino != BTRFS_FIRST_FREE_OBJECTID) {
+		fs_path_reset(name);
+
+		if (is_waiting_for_rm(sctx, ino, gen))
+			break;
+		if (is_waiting_for_move(sctx, ino)) {
+			if (*ancestor_ino == 0)
+				*ancestor_ino = ino;
+			ret = get_first_ref(sctx->parent_root, ino,
+					    &parent_inode, &parent_gen, name);
+		} else {
+			ret = __get_cur_name_and_parent(sctx, ino, gen,
+							&parent_inode,
+							&parent_gen, name);
+			if (ret > 0) {
+				ret = 0;
+				break;
+			}
+		}
+		if (ret < 0)
+			break;
+		if (parent_inode == start_ino) {
+			ret = 1;
+			if (*ancestor_ino == 0)
+				*ancestor_ino = ino;
+			break;
+		}
+		ino = parent_inode;
+		gen = parent_gen;
+	}
+	return ret;
+}
+
+static int apply_dir_move(struct send_ctx *sctx, struct pending_dir_move *pm)
+{
+	struct fs_path *from_path = NULL;
+	struct fs_path *to_path = NULL;
+	struct fs_path *name = NULL;
+	u64 orig_progress = sctx->send_progress;
+	struct recorded_ref *cur;
+	u64 parent_ino, parent_gen;
+	struct waiting_dir_move *dm = NULL;
+	u64 rmdir_ino = 0;
+	u64 rmdir_gen;
+	u64 ancestor;
+	bool is_orphan;
+	int ret;
+
+	name = fs_path_alloc();
+	from_path = fs_path_alloc();
+	if (!name || !from_path) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	dm = get_waiting_dir_move(sctx, pm->ino);
+	ASSERT(dm);
+	rmdir_ino = dm->rmdir_ino;
+	rmdir_gen = dm->rmdir_gen;
+	is_orphan = dm->orphanized;
+	free_waiting_dir_move(sctx, dm);
+
+	if (is_orphan) {
+		ret = gen_unique_name(sctx, pm->ino,
+				      pm->gen, from_path);
+	} else {
+		ret = get_first_ref(sctx->parent_root, pm->ino,
+				    &parent_ino, &parent_gen, name);
+		if (ret < 0)
+			goto out;
+		ret = get_cur_path(sctx, parent_ino, parent_gen,
+				   from_path);
+		if (ret < 0)
+			goto out;
+		ret = fs_path_add_path(from_path, name);
+	}
+	if (ret < 0)
+		goto out;
+
+	sctx->send_progress = sctx->cur_ino + 1;
+	ret = path_loop(sctx, name, pm->ino, pm->gen, &ancestor);
+	if (ret < 0)
+		goto out;
+	if (ret) {
+		LIST_HEAD(deleted_refs);
+		ASSERT(ancestor > BTRFS_FIRST_FREE_OBJECTID);
+		ret = add_pending_dir_move(sctx, pm->ino, pm->gen, ancestor,
+					   &pm->update_refs, &deleted_refs,
+					   is_orphan);
+		if (ret < 0)
+			goto out;
+		if (rmdir_ino) {
+			dm = get_waiting_dir_move(sctx, pm->ino);
+			ASSERT(dm);
+			dm->rmdir_ino = rmdir_ino;
+			dm->rmdir_gen = rmdir_gen;
+		}
+		goto out;
+	}
+	fs_path_reset(name);
+	to_path = name;
+	name = NULL;
+	ret = get_cur_path(sctx, pm->ino, pm->gen, to_path);
+	if (ret < 0)
+		goto out;
+
+	ret = send_rename(sctx, from_path, to_path);
+	if (ret < 0)
+		goto out;
+
+	if (rmdir_ino) {
+		struct orphan_dir_info *odi;
+		u64 gen;
+
+		odi = get_orphan_dir_info(sctx, rmdir_ino, rmdir_gen);
+		if (!odi) {
+			/* already deleted */
+			goto finish;
+		}
+		gen = odi->gen;
+
+		ret = can_rmdir(sctx, rmdir_ino, gen, sctx->cur_ino);
+		if (ret < 0)
+			goto out;
+		if (!ret)
+			goto finish;
+
+		name = fs_path_alloc();
+		if (!name) {
+			ret = -ENOMEM;
+			goto out;
+		}
+		ret = get_cur_path(sctx, rmdir_ino, gen, name);
+		if (ret < 0)
+			goto out;
+		ret = send_rmdir(sctx, name);
+		if (ret < 0)
+			goto out;
+	}
+
+finish:
+	ret = send_utimes(sctx, pm->ino, pm->gen);
+	if (ret < 0)
+		goto out;
+
+	/*
+	 * After rename/move, need to update the utimes of both new parent(s)
+	 * and old parent(s).
+	 */
+	list_for_each_entry(cur, &pm->update_refs, list) {
+		/*
+		 * The parent inode might have been deleted in the send snapshot
+		 */
+		ret = get_inode_info(sctx->send_root, cur->dir, NULL,
+				     NULL, NULL, NULL, NULL, NULL);
+		if (ret == -ENOENT) {
+			ret = 0;
+			continue;
+		}
+		if (ret < 0)
+			goto out;
+
+		ret = send_utimes(sctx, cur->dir, cur->dir_gen);
+		if (ret < 0)
+			goto out;
+	}
+
+out:
+	fs_path_free(name);
+	fs_path_free(from_path);
+	fs_path_free(to_path);
+	sctx->send_progress = orig_progress;
+
+	return ret;
+}
+
+static void free_pending_move(struct send_ctx *sctx, struct pending_dir_move *m)
+{
+	if (!list_empty(&m->list))
+		list_del(&m->list);
+	if (!RB_EMPTY_NODE(&m->node))
+		rb_erase(&m->node, &sctx->pending_dir_moves);
+	__free_recorded_refs(&m->update_refs);
+	kfree(m);
+}
+
+static void tail_append_pending_moves(struct send_ctx *sctx,
+				      struct pending_dir_move *moves,
+				      struct list_head *stack)
+{
+	if (list_empty(&moves->list)) {
+		list_add_tail(&moves->list, stack);
+	} else {
+		LIST_HEAD(list);
+		list_splice_init(&moves->list, &list);
+		list_add_tail(&moves->list, stack);
+		list_splice_tail(&list, stack);
+	}
+	if (!RB_EMPTY_NODE(&moves->node)) {
+		rb_erase(&moves->node, &sctx->pending_dir_moves);
+		RB_CLEAR_NODE(&moves->node);
+	}
+}
+
+static int apply_children_dir_moves(struct send_ctx *sctx)
+{
+	struct pending_dir_move *pm;
+	struct list_head stack;
+	u64 parent_ino = sctx->cur_ino;
+	int ret = 0;
+
+	pm = get_pending_dir_moves(sctx, parent_ino);
+	if (!pm)
+		return 0;
+
+	INIT_LIST_HEAD(&stack);
+	tail_append_pending_moves(sctx, pm, &stack);
+
+	while (!list_empty(&stack)) {
+		pm = list_first_entry(&stack, struct pending_dir_move, list);
+		parent_ino = pm->ino;
+		ret = apply_dir_move(sctx, pm);
+		free_pending_move(sctx, pm);
+		if (ret)
+			goto out;
+		pm = get_pending_dir_moves(sctx, parent_ino);
+		if (pm)
+			tail_append_pending_moves(sctx, pm, &stack);
+	}
+	return 0;
+
+out:
+	while (!list_empty(&stack)) {
+		pm = list_first_entry(&stack, struct pending_dir_move, list);
+		free_pending_move(sctx, pm);
+	}
+	return ret;
+}
+
+/*
+ * We might need to delay a directory rename even when no ancestor directory
+ * (in the send root) with a higher inode number than ours (sctx->cur_ino) was
+ * renamed. This happens when we rename a directory to the old name (the name
+ * in the parent root) of some other unrelated directory that got its rename
+ * delayed due to some ancestor with higher number that got renamed.
+ *
+ * Example:
+ *
+ * Parent snapshot:
+ * .                                       (ino 256)
+ * |---- a/                                (ino 257)
+ * |     |---- file                        (ino 260)
+ * |
+ * |---- b/                                (ino 258)
+ * |---- c/                                (ino 259)
+ *
+ * Send snapshot:
+ * .                                       (ino 256)
+ * |---- a/                                (ino 258)
+ * |---- x/                                (ino 259)
+ *       |---- y/                          (ino 257)
+ *             |----- file                 (ino 260)
+ *
+ * Here we can not rename 258 from 'b' to 'a' without the rename of inode 257
+ * from 'a' to 'x/y' happening first, which in turn depends on the rename of
+ * inode 259 from 'c' to 'x'. So the order of rename commands the send stream
+ * must issue is:
+ *
+ * 1 - rename 259 from 'c' to 'x'
+ * 2 - rename 257 from 'a' to 'x/y'
+ * 3 - rename 258 from 'b' to 'a'
+ *
+ * Returns 1 if the rename of sctx->cur_ino needs to be delayed, 0 if it can
+ * be done right away and < 0 on error.
+ */
+static int wait_for_dest_dir_move(struct send_ctx *sctx,
+				  struct recorded_ref *parent_ref,
+				  const bool is_orphan)
+{
+	struct btrfs_fs_info *fs_info = sctx->parent_root->fs_info;
+	struct btrfs_path *path;
+	struct btrfs_key key;
+	struct btrfs_key di_key;
+	struct btrfs_dir_item *di;
+	u64 left_gen;
+	u64 right_gen;
+	int ret = 0;
+	struct waiting_dir_move *wdm;
+
+	if (RB_EMPTY_ROOT(&sctx->waiting_dir_moves))
+		return 0;
+
+	path = alloc_path_for_send();
+	if (!path)
+		return -ENOMEM;
+
+	key.objectid = parent_ref->dir;
+	key.type = BTRFS_DIR_ITEM_KEY;
+	key.offset = btrfs_name_hash(parent_ref->name, parent_ref->name_len);
+
+	ret = btrfs_search_slot(NULL, sctx->parent_root, &key, path, 0, 0);
+	if (ret < 0) {
+		goto out;
+	} else if (ret > 0) {
+		ret = 0;
+		goto out;
+	}
+
+	di = btrfs_match_dir_item_name(fs_info, path, parent_ref->name,
+				       parent_ref->name_len);
+	if (!di) {
+		ret = 0;
+		goto out;
+	}
+	/*
+	 * di_key.objectid has the number of the inode that has a dentry in the
+	 * parent directory with the same name that sctx->cur_ino is being
+	 * renamed to. We need to check if that inode is in the send root as
+	 * well and if it is currently marked as an inode with a pending rename,
+	 * if it is, we need to delay the rename of sctx->cur_ino as well, so
+	 * that it happens after that other inode is renamed.
+	 */
+	btrfs_dir_item_key_to_cpu(path->nodes[0], di, &di_key);
+	if (di_key.type != BTRFS_INODE_ITEM_KEY) {
+		ret = 0;
+		goto out;
+	}
+
+	ret = get_inode_info(sctx->parent_root, di_key.objectid, NULL,
+			     &left_gen, NULL, NULL, NULL, NULL);
+	if (ret < 0)
+		goto out;
+	ret = get_inode_info(sctx->send_root, di_key.objectid, NULL,
+			     &right_gen, NULL, NULL, NULL, NULL);
+	if (ret < 0) {
+		if (ret == -ENOENT)
+			ret = 0;
+		goto out;
+	}
+
+	/* Different inode, no need to delay the rename of sctx->cur_ino */
+	if (right_gen != left_gen) {
+		ret = 0;
+		goto out;
+	}
+
+	wdm = get_waiting_dir_move(sctx, di_key.objectid);
+	if (wdm && !wdm->orphanized) {
+		ret = add_pending_dir_move(sctx,
+					   sctx->cur_ino,
+					   sctx->cur_inode_gen,
+					   di_key.objectid,
+					   &sctx->new_refs,
+					   &sctx->deleted_refs,
+					   is_orphan);
+		if (!ret)
+			ret = 1;
+	}
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+/*
+ * Check if inode ino2, or any of its ancestors, is inode ino1.
+ * Return 1 if true, 0 if false and < 0 on error.
+ */
+static int check_ino_in_path(struct btrfs_root *root,
+			     const u64 ino1,
+			     const u64 ino1_gen,
+			     const u64 ino2,
+			     const u64 ino2_gen,
+			     struct fs_path *fs_path)
+{
+	u64 ino = ino2;
+
+	if (ino1 == ino2)
+		return ino1_gen == ino2_gen;
+
+	while (ino > BTRFS_FIRST_FREE_OBJECTID) {
+		u64 parent;
+		u64 parent_gen;
+		int ret;
+
+		fs_path_reset(fs_path);
+		ret = get_first_ref(root, ino, &parent, &parent_gen, fs_path);
+		if (ret < 0)
+			return ret;
+		if (parent == ino1)
+			return parent_gen == ino1_gen;
+		ino = parent;
+	}
+	return 0;
+}
+
+/*
+ * Check if ino ino1 is an ancestor of inode ino2 in the given root for any
+ * possible path (in case ino2 is not a directory and has multiple hard links).
+ * Return 1 if true, 0 if false and < 0 on error.
+ */
+static int is_ancestor(struct btrfs_root *root,
+		       const u64 ino1,
+		       const u64 ino1_gen,
+		       const u64 ino2,
+		       struct fs_path *fs_path)
+{
+	bool free_fs_path = false;
+	int ret = 0;
+	struct btrfs_path *path = NULL;
+	struct btrfs_key key;
+
+	if (!fs_path) {
+		fs_path = fs_path_alloc();
+		if (!fs_path)
+			return -ENOMEM;
+		free_fs_path = true;
+	}
+
+	path = alloc_path_for_send();
+	if (!path) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	key.objectid = ino2;
+	key.type = BTRFS_INODE_REF_KEY;
+	key.offset = 0;
+
+	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+	if (ret < 0)
+		goto out;
+
+	while (true) {
+		struct extent_buffer *leaf = path->nodes[0];
+		int slot = path->slots[0];
+		u32 cur_offset = 0;
+		u32 item_size;
+
+		if (slot >= btrfs_header_nritems(leaf)) {
+			ret = btrfs_next_leaf(root, path);
+			if (ret < 0)
+				goto out;
+			if (ret > 0)
+				break;
+			continue;
+		}
+
+		btrfs_item_key_to_cpu(leaf, &key, slot);
+		if (key.objectid != ino2)
+			break;
+		if (key.type != BTRFS_INODE_REF_KEY &&
+		    key.type != BTRFS_INODE_EXTREF_KEY)
+			break;
+
+		item_size = btrfs_item_size_nr(leaf, slot);
+		while (cur_offset < item_size) {
+			u64 parent;
+			u64 parent_gen;
+
+			if (key.type == BTRFS_INODE_EXTREF_KEY) {
+				unsigned long ptr;
+				struct btrfs_inode_extref *extref;
+
+				ptr = btrfs_item_ptr_offset(leaf, slot);
+				extref = (struct btrfs_inode_extref *)
+					(ptr + cur_offset);
+				parent = btrfs_inode_extref_parent(leaf,
+								   extref);
+				cur_offset += sizeof(*extref);
+				cur_offset += btrfs_inode_extref_name_len(leaf,
+								  extref);
+			} else {
+				parent = key.offset;
+				cur_offset = item_size;
+			}
+
+			ret = get_inode_info(root, parent, NULL, &parent_gen,
+					     NULL, NULL, NULL, NULL);
+			if (ret < 0)
+				goto out;
+			ret = check_ino_in_path(root, ino1, ino1_gen,
+						parent, parent_gen, fs_path);
+			if (ret)
+				goto out;
+		}
+		path->slots[0]++;
+	}
+	ret = 0;
+ out:
+	btrfs_free_path(path);
+	if (free_fs_path)
+		fs_path_free(fs_path);
+	return ret;
+}
+
+static int wait_for_parent_move(struct send_ctx *sctx,
+				struct recorded_ref *parent_ref,
+				const bool is_orphan)
+{
+	int ret = 0;
+	u64 ino = parent_ref->dir;
+	u64 ino_gen = parent_ref->dir_gen;
+	u64 parent_ino_before, parent_ino_after;
+	struct fs_path *path_before = NULL;
+	struct fs_path *path_after = NULL;
+	int len1, len2;
+
+	path_after = fs_path_alloc();
+	path_before = fs_path_alloc();
+	if (!path_after || !path_before) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	/*
+	 * Our current directory inode may not yet be renamed/moved because some
+	 * ancestor (immediate or not) has to be renamed/moved first. So find if
+	 * such ancestor exists and make sure our own rename/move happens after
+	 * that ancestor is processed to avoid path build infinite loops (done
+	 * at get_cur_path()).
+	 */
+	while (ino > BTRFS_FIRST_FREE_OBJECTID) {
+		u64 parent_ino_after_gen;
+
+		if (is_waiting_for_move(sctx, ino)) {
+			/*
+			 * If the current inode is an ancestor of ino in the
+			 * parent root, we need to delay the rename of the
+			 * current inode, otherwise don't delayed the rename
+			 * because we can end up with a circular dependency
+			 * of renames, resulting in some directories never
+			 * getting the respective rename operations issued in
+			 * the send stream or getting into infinite path build
+			 * loops.
+			 */
+			ret = is_ancestor(sctx->parent_root,
+					  sctx->cur_ino, sctx->cur_inode_gen,
+					  ino, path_before);
+			if (ret)
+				break;
+		}
+
+		fs_path_reset(path_before);
+		fs_path_reset(path_after);
+
+		ret = get_first_ref(sctx->send_root, ino, &parent_ino_after,
+				    &parent_ino_after_gen, path_after);
+		if (ret < 0)
+			goto out;
+		ret = get_first_ref(sctx->parent_root, ino, &parent_ino_before,
+				    NULL, path_before);
+		if (ret < 0 && ret != -ENOENT) {
+			goto out;
+		} else if (ret == -ENOENT) {
+			ret = 0;
+			break;
+		}
+
+		len1 = fs_path_len(path_before);
+		len2 = fs_path_len(path_after);
+		if (ino > sctx->cur_ino &&
+		    (parent_ino_before != parent_ino_after || len1 != len2 ||
+		     memcmp(path_before->start, path_after->start, len1))) {
+			u64 parent_ino_gen;
+
+			ret = get_inode_info(sctx->parent_root, ino, NULL,
+					     &parent_ino_gen, NULL, NULL, NULL,
+					     NULL);
+			if (ret < 0)
+				goto out;
+			if (ino_gen == parent_ino_gen) {
+				ret = 1;
+				break;
+			}
+		}
+		ino = parent_ino_after;
+		ino_gen = parent_ino_after_gen;
+	}
+
+out:
+	fs_path_free(path_before);
+	fs_path_free(path_after);
+
+	if (ret == 1) {
+		ret = add_pending_dir_move(sctx,
+					   sctx->cur_ino,
+					   sctx->cur_inode_gen,
+					   ino,
+					   &sctx->new_refs,
+					   &sctx->deleted_refs,
+					   is_orphan);
+		if (!ret)
+			ret = 1;
+	}
+
+	return ret;
+}
+
+static int update_ref_path(struct send_ctx *sctx, struct recorded_ref *ref)
+{
+	int ret;
+	struct fs_path *new_path;
+
+	/*
+	 * Our reference's name member points to its full_path member string, so
+	 * we use here a new path.
+	 */
+	new_path = fs_path_alloc();
+	if (!new_path)
+		return -ENOMEM;
+
+	ret = get_cur_path(sctx, ref->dir, ref->dir_gen, new_path);
+	if (ret < 0) {
+		fs_path_free(new_path);
+		return ret;
+	}
+	ret = fs_path_add(new_path, ref->name, ref->name_len);
+	if (ret < 0) {
+		fs_path_free(new_path);
+		return ret;
+	}
+
+	fs_path_free(ref->full_path);
+	set_ref_path(ref, new_path);
+
+	return 0;
+}
+
+/*
+ * When processing the new references for an inode we may orphanize an existing
+ * directory inode because its old name conflicts with one of the new references
+ * of the current inode. Later, when processing another new reference of our
+ * inode, we might need to orphanize another inode, but the path we have in the
+ * reference reflects the pre-orphanization name of the directory we previously
+ * orphanized. For example:
+ *
+ * parent snapshot looks like:
+ *
+ * .                                     (ino 256)
+ * |----- f1                             (ino 257)
+ * |----- f2                             (ino 258)
+ * |----- d1/                            (ino 259)
+ *        |----- d2/                     (ino 260)
+ *
+ * send snapshot looks like:
+ *
+ * .                                     (ino 256)
+ * |----- d1                             (ino 258)
+ * |----- f2/                            (ino 259)
+ *        |----- f2_link/                (ino 260)
+ *        |       |----- f1              (ino 257)
+ *        |
+ *        |----- d2                      (ino 258)
+ *
+ * When processing inode 257 we compute the name for inode 259 as "d1", and we
+ * cache it in the name cache. Later when we start processing inode 258, when
+ * collecting all its new references we set a full path of "d1/d2" for its new
+ * reference with name "d2". When we start processing the new references we
+ * start by processing the new reference with name "d1", and this results in
+ * orphanizing inode 259, since its old reference causes a conflict. Then we
+ * move on the next new reference, with name "d2", and we find out we must
+ * orphanize inode 260, as its old reference conflicts with ours - but for the
+ * orphanization we use a source path corresponding to the path we stored in the
+ * new reference, which is "d1/d2" and not "o259-6-0/d2" - this makes the
+ * receiver fail since the path component "d1/" no longer exists, it was renamed
+ * to "o259-6-0/" when processing the previous new reference. So in this case we
+ * must recompute the path in the new reference and use it for the new
+ * orphanization operation.
+ */
+static int refresh_ref_path(struct send_ctx *sctx, struct recorded_ref *ref)
+{
+	char *name;
+	int ret;
+
+	name = kmemdup(ref->name, ref->name_len, GFP_KERNEL);
+	if (!name)
+		return -ENOMEM;
+
+	fs_path_reset(ref->full_path);
+	ret = get_cur_path(sctx, ref->dir, ref->dir_gen, ref->full_path);
+	if (ret < 0)
+		goto out;
+
+	ret = fs_path_add(ref->full_path, name, ref->name_len);
+	if (ret < 0)
+		goto out;
+
+	/* Update the reference's base name pointer. */
+	set_ref_path(ref, ref->full_path);
+out:
+	kfree(name);
+	return ret;
+}
+
+/*
+ * This does all the move/link/unlink/rmdir magic.
+ */
+static int process_recorded_refs(struct send_ctx *sctx, int *pending_move)
+{
+	struct btrfs_fs_info *fs_info = sctx->send_root->fs_info;
+	int ret = 0;
+	struct recorded_ref *cur;
+	struct recorded_ref *cur2;
+	struct list_head check_dirs;
+	struct fs_path *valid_path = NULL;
+	u64 ow_inode = 0;
+	u64 ow_gen;
+	u64 ow_mode;
+	int did_overwrite = 0;
+	int is_orphan = 0;
+	u64 last_dir_ino_rm = 0;
+	bool can_rename = true;
+	bool orphanized_dir = false;
+	bool orphanized_ancestor = false;
+
+	btrfs_debug(fs_info, "process_recorded_refs %llu", sctx->cur_ino);
+
+	/*
+	 * This should never happen as the root dir always has the same ref
+	 * which is always '..'
+	 */
+	BUG_ON(sctx->cur_ino <= BTRFS_FIRST_FREE_OBJECTID);
+	INIT_LIST_HEAD(&check_dirs);
+
+	valid_path = fs_path_alloc();
+	if (!valid_path) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	/*
+	 * First, check if the first ref of the current inode was overwritten
+	 * before. If yes, we know that the current inode was already orphanized
+	 * and thus use the orphan name. If not, we can use get_cur_path to
+	 * get the path of the first ref as it would like while receiving at
+	 * this point in time.
+	 * New inodes are always orphan at the beginning, so force to use the
+	 * orphan name in this case.
+	 * The first ref is stored in valid_path and will be updated if it
+	 * gets moved around.
+	 */
+	if (!sctx->cur_inode_new) {
+		ret = did_overwrite_first_ref(sctx, sctx->cur_ino,
+				sctx->cur_inode_gen);
+		if (ret < 0)
+			goto out;
+		if (ret)
+			did_overwrite = 1;
+	}
+	if (sctx->cur_inode_new || did_overwrite) {
+		ret = gen_unique_name(sctx, sctx->cur_ino,
+				sctx->cur_inode_gen, valid_path);
+		if (ret < 0)
+			goto out;
+		is_orphan = 1;
+	} else {
+		ret = get_cur_path(sctx, sctx->cur_ino, sctx->cur_inode_gen,
+				valid_path);
+		if (ret < 0)
+			goto out;
+	}
+
+	/*
+	 * Before doing any rename and link operations, do a first pass on the
+	 * new references to orphanize any unprocessed inodes that may have a
+	 * reference that conflicts with one of the new references of the current
+	 * inode. This needs to happen first because a new reference may conflict
+	 * with the old reference of a parent directory, so we must make sure
+	 * that the path used for link and rename commands don't use an
+	 * orphanized name when an ancestor was not yet orphanized.
+	 *
+	 * Example:
+	 *
+	 * Parent snapshot:
+	 *
+	 * .                                                      (ino 256)
+	 * |----- testdir/                                        (ino 259)
+	 * |          |----- a                                    (ino 257)
+	 * |
+	 * |----- b                                               (ino 258)
+	 *
+	 * Send snapshot:
+	 *
+	 * .                                                      (ino 256)
+	 * |----- testdir_2/                                      (ino 259)
+	 * |          |----- a                                    (ino 260)
+	 * |
+	 * |----- testdir                                         (ino 257)
+	 * |----- b                                               (ino 257)
+	 * |----- b2                                              (ino 258)
+	 *
+	 * Processing the new reference for inode 257 with name "b" may happen
+	 * before processing the new reference with name "testdir". If so, we
+	 * must make sure that by the time we send a link command to create the
+	 * hard link "b", inode 259 was already orphanized, since the generated
+	 * path in "valid_path" already contains the orphanized name for 259.
+	 * We are processing inode 257, so only later when processing 259 we do
+	 * the rename operation to change its temporary (orphanized) name to
+	 * "testdir_2".
+	 */
+	list_for_each_entry(cur, &sctx->new_refs, list) {
+		ret = get_cur_inode_state(sctx, cur->dir, cur->dir_gen);
+		if (ret < 0)
+			goto out;
+		if (ret == inode_state_will_create)
+			continue;
+
+		/*
+		 * Check if this new ref would overwrite the first ref of another
+		 * unprocessed inode. If yes, orphanize the overwritten inode.
+		 * If we find an overwritten ref that is not the first ref,
+		 * simply unlink it.
+		 */
+		ret = will_overwrite_ref(sctx, cur->dir, cur->dir_gen,
+				cur->name, cur->name_len,
+				&ow_inode, &ow_gen, &ow_mode);
+		if (ret < 0)
+			goto out;
+		if (ret) {
+			ret = is_first_ref(sctx->parent_root,
+					   ow_inode, cur->dir, cur->name,
+					   cur->name_len);
+			if (ret < 0)
+				goto out;
+			if (ret) {
+				struct name_cache_entry *nce;
+				struct waiting_dir_move *wdm;
+
+				if (orphanized_dir) {
+					ret = refresh_ref_path(sctx, cur);
+					if (ret < 0)
+						goto out;
+				}
+
+				ret = orphanize_inode(sctx, ow_inode, ow_gen,
+						cur->full_path);
+				if (ret < 0)
+					goto out;
+				if (S_ISDIR(ow_mode))
+					orphanized_dir = true;
+
+				/*
+				 * If ow_inode has its rename operation delayed
+				 * make sure that its orphanized name is used in
+				 * the source path when performing its rename
+				 * operation.
+				 */
+				if (is_waiting_for_move(sctx, ow_inode)) {
+					wdm = get_waiting_dir_move(sctx,
+								   ow_inode);
+					ASSERT(wdm);
+					wdm->orphanized = true;
+				}
+
+				/*
+				 * Make sure we clear our orphanized inode's
+				 * name from the name cache. This is because the
+				 * inode ow_inode might be an ancestor of some
+				 * other inode that will be orphanized as well
+				 * later and has an inode number greater than
+				 * sctx->send_progress. We need to prevent
+				 * future name lookups from using the old name
+				 * and get instead the orphan name.
+				 */
+				nce = name_cache_search(sctx, ow_inode, ow_gen);
+				if (nce) {
+					name_cache_delete(sctx, nce);
+					kfree(nce);
+				}
+
+				/*
+				 * ow_inode might currently be an ancestor of
+				 * cur_ino, therefore compute valid_path (the
+				 * current path of cur_ino) again because it
+				 * might contain the pre-orphanization name of
+				 * ow_inode, which is no longer valid.
+				 */
+				ret = is_ancestor(sctx->parent_root,
+						  ow_inode, ow_gen,
+						  sctx->cur_ino, NULL);
+				if (ret > 0) {
+					orphanized_ancestor = true;
+					fs_path_reset(valid_path);
+					ret = get_cur_path(sctx, sctx->cur_ino,
+							   sctx->cur_inode_gen,
+							   valid_path);
+				}
+				if (ret < 0)
+					goto out;
+			} else {
+				/*
+				 * If we previously orphanized a directory that
+				 * collided with a new reference that we already
+				 * processed, recompute the current path because
+				 * that directory may be part of the path.
+				 */
+				if (orphanized_dir) {
+					ret = refresh_ref_path(sctx, cur);
+					if (ret < 0)
+						goto out;
+				}
+				ret = send_unlink(sctx, cur->full_path);
+				if (ret < 0)
+					goto out;
+			}
+		}
+
+	}
+
+	list_for_each_entry(cur, &sctx->new_refs, list) {
+		/*
+		 * We may have refs where the parent directory does not exist
+		 * yet. This happens if the parent directories inum is higher
+		 * than the current inum. To handle this case, we create the
+		 * parent directory out of order. But we need to check if this
+		 * did already happen before due to other refs in the same dir.
+		 */
+		ret = get_cur_inode_state(sctx, cur->dir, cur->dir_gen);
+		if (ret < 0)
+			goto out;
+		if (ret == inode_state_will_create) {
+			ret = 0;
+			/*
+			 * First check if any of the current inodes refs did
+			 * already create the dir.
+			 */
+			list_for_each_entry(cur2, &sctx->new_refs, list) {
+				if (cur == cur2)
+					break;
+				if (cur2->dir == cur->dir) {
+					ret = 1;
+					break;
+				}
+			}
+
+			/*
+			 * If that did not happen, check if a previous inode
+			 * did already create the dir.
+			 */
+			if (!ret)
+				ret = did_create_dir(sctx, cur->dir);
+			if (ret < 0)
+				goto out;
+			if (!ret) {
+				ret = send_create_inode(sctx, cur->dir);
+				if (ret < 0)
+					goto out;
+			}
+		}
+
+		if (S_ISDIR(sctx->cur_inode_mode) && sctx->parent_root) {
+			ret = wait_for_dest_dir_move(sctx, cur, is_orphan);
+			if (ret < 0)
+				goto out;
+			if (ret == 1) {
+				can_rename = false;
+				*pending_move = 1;
+			}
+		}
+
+		if (S_ISDIR(sctx->cur_inode_mode) && sctx->parent_root &&
+		    can_rename) {
+			ret = wait_for_parent_move(sctx, cur, is_orphan);
+			if (ret < 0)
+				goto out;
+			if (ret == 1) {
+				can_rename = false;
+				*pending_move = 1;
+			}
+		}
+
+		/*
+		 * link/move the ref to the new place. If we have an orphan
+		 * inode, move it and update valid_path. If not, link or move
+		 * it depending on the inode mode.
+		 */
+		if (is_orphan && can_rename) {
+			ret = send_rename(sctx, valid_path, cur->full_path);
+			if (ret < 0)
+				goto out;
+			is_orphan = 0;
+			ret = fs_path_copy(valid_path, cur->full_path);
+			if (ret < 0)
+				goto out;
+		} else if (can_rename) {
+			if (S_ISDIR(sctx->cur_inode_mode)) {
+				/*
+				 * Dirs can't be linked, so move it. For moved
+				 * dirs, we always have one new and one deleted
+				 * ref. The deleted ref is ignored later.
+				 */
+				ret = send_rename(sctx, valid_path,
+						  cur->full_path);
+				if (!ret)
+					ret = fs_path_copy(valid_path,
+							   cur->full_path);
+				if (ret < 0)
+					goto out;
+			} else {
+				/*
+				 * We might have previously orphanized an inode
+				 * which is an ancestor of our current inode,
+				 * so our reference's full path, which was
+				 * computed before any such orphanizations, must
+				 * be updated.
+				 */
+				if (orphanized_dir) {
+					ret = update_ref_path(sctx, cur);
+					if (ret < 0)
+						goto out;
+				}
+				ret = send_link(sctx, cur->full_path,
+						valid_path);
+				if (ret < 0)
+					goto out;
+			}
+		}
+		ret = dup_ref(cur, &check_dirs);
+		if (ret < 0)
+			goto out;
+	}
+
+	if (S_ISDIR(sctx->cur_inode_mode) && sctx->cur_inode_deleted) {
+		/*
+		 * Check if we can already rmdir the directory. If not,
+		 * orphanize it. For every dir item inside that gets deleted
+		 * later, we do this check again and rmdir it then if possible.
+		 * See the use of check_dirs for more details.
+		 */
+		ret = can_rmdir(sctx, sctx->cur_ino, sctx->cur_inode_gen,
+				sctx->cur_ino);
+		if (ret < 0)
+			goto out;
+		if (ret) {
+			ret = send_rmdir(sctx, valid_path);
+			if (ret < 0)
+				goto out;
+		} else if (!is_orphan) {
+			ret = orphanize_inode(sctx, sctx->cur_ino,
+					sctx->cur_inode_gen, valid_path);
+			if (ret < 0)
+				goto out;
+			is_orphan = 1;
+		}
+
+		list_for_each_entry(cur, &sctx->deleted_refs, list) {
+			ret = dup_ref(cur, &check_dirs);
+			if (ret < 0)
+				goto out;
+		}
+	} else if (S_ISDIR(sctx->cur_inode_mode) &&
+		   !list_empty(&sctx->deleted_refs)) {
+		/*
+		 * We have a moved dir. Add the old parent to check_dirs
+		 */
+		cur = list_entry(sctx->deleted_refs.next, struct recorded_ref,
+				list);
+		ret = dup_ref(cur, &check_dirs);
+		if (ret < 0)
+			goto out;
+	} else if (!S_ISDIR(sctx->cur_inode_mode)) {
+		/*
+		 * We have a non dir inode. Go through all deleted refs and
+		 * unlink them if they were not already overwritten by other
+		 * inodes.
+		 */
+		list_for_each_entry(cur, &sctx->deleted_refs, list) {
+			ret = did_overwrite_ref(sctx, cur->dir, cur->dir_gen,
+					sctx->cur_ino, sctx->cur_inode_gen,
+					cur->name, cur->name_len);
+			if (ret < 0)
+				goto out;
+			if (!ret) {
+				/*
+				 * If we orphanized any ancestor before, we need
+				 * to recompute the full path for deleted names,
+				 * since any such path was computed before we
+				 * processed any references and orphanized any
+				 * ancestor inode.
+				 */
+				if (orphanized_ancestor) {
+					ret = update_ref_path(sctx, cur);
+					if (ret < 0)
+						goto out;
+				}
+				ret = send_unlink(sctx, cur->full_path);
+				if (ret < 0)
+					goto out;
+			}
+			ret = dup_ref(cur, &check_dirs);
+			if (ret < 0)
+				goto out;
+		}
+		/*
+		 * If the inode is still orphan, unlink the orphan. This may
+		 * happen when a previous inode did overwrite the first ref
+		 * of this inode and no new refs were added for the current
+		 * inode. Unlinking does not mean that the inode is deleted in
+		 * all cases. There may still be links to this inode in other
+		 * places.
+		 */
+		if (is_orphan) {
+			ret = send_unlink(sctx, valid_path);
+			if (ret < 0)
+				goto out;
+		}
+	}
+
+	/*
+	 * We did collect all parent dirs where cur_inode was once located. We
+	 * now go through all these dirs and check if they are pending for
+	 * deletion and if it's finally possible to perform the rmdir now.
+	 * We also update the inode stats of the parent dirs here.
+	 */
+	list_for_each_entry(cur, &check_dirs, list) {
+		/*
+		 * In case we had refs into dirs that were not processed yet,
+		 * we don't need to do the utime and rmdir logic for these dirs.
+		 * The dir will be processed later.
+		 */
+		if (cur->dir > sctx->cur_ino)
+			continue;
+
+		ret = get_cur_inode_state(sctx, cur->dir, cur->dir_gen);
+		if (ret < 0)
+			goto out;
+
+		if (ret == inode_state_did_create ||
+		    ret == inode_state_no_change) {
+			/* TODO delayed utimes */
+			ret = send_utimes(sctx, cur->dir, cur->dir_gen);
+			if (ret < 0)
+				goto out;
+		} else if (ret == inode_state_did_delete &&
+			   cur->dir != last_dir_ino_rm) {
+			ret = can_rmdir(sctx, cur->dir, cur->dir_gen,
+					sctx->cur_ino);
+			if (ret < 0)
+				goto out;
+			if (ret) {
+				ret = get_cur_path(sctx, cur->dir,
+						   cur->dir_gen, valid_path);
+				if (ret < 0)
+					goto out;
+				ret = send_rmdir(sctx, valid_path);
+				if (ret < 0)
+					goto out;
+				last_dir_ino_rm = cur->dir;
+			}
+		}
+	}
+
+	ret = 0;
+
+out:
+	__free_recorded_refs(&check_dirs);
+	free_recorded_refs(sctx);
+	fs_path_free(valid_path);
+	return ret;
+}
+
+static int record_ref(struct btrfs_root *root, u64 dir, struct fs_path *name,
+		      void *ctx, struct list_head *refs)
+{
+	int ret = 0;
+	struct send_ctx *sctx = ctx;
+	struct fs_path *p;
+	u64 gen;
+
+	p = fs_path_alloc();
+	if (!p)
+		return -ENOMEM;
+
+	ret = get_inode_info(root, dir, NULL, &gen, NULL, NULL,
+			NULL, NULL);
+	if (ret < 0)
+		goto out;
+
+	ret = get_cur_path(sctx, dir, gen, p);
+	if (ret < 0)
+		goto out;
+	ret = fs_path_add_path(p, name);
+	if (ret < 0)
+		goto out;
+
+	ret = __record_ref(refs, dir, gen, p);
+
+out:
+	if (ret)
+		fs_path_free(p);
+	return ret;
+}
+
+static int __record_new_ref(int num, u64 dir, int index,
+			    struct fs_path *name,
+			    void *ctx)
+{
+	struct send_ctx *sctx = ctx;
+	return record_ref(sctx->send_root, dir, name, ctx, &sctx->new_refs);
+}
+
+
+static int __record_deleted_ref(int num, u64 dir, int index,
+				struct fs_path *name,
+				void *ctx)
+{
+	struct send_ctx *sctx = ctx;
+	return record_ref(sctx->parent_root, dir, name, ctx,
+			  &sctx->deleted_refs);
+}
+
+static int record_new_ref(struct send_ctx *sctx)
+{
+	int ret;
+
+	ret = iterate_inode_ref(sctx->send_root, sctx->left_path,
+				sctx->cmp_key, 0, __record_new_ref, sctx);
+	if (ret < 0)
+		goto out;
+	ret = 0;
+
+out:
+	return ret;
+}
+
+static int record_deleted_ref(struct send_ctx *sctx)
+{
+	int ret;
+
+	ret = iterate_inode_ref(sctx->parent_root, sctx->right_path,
+				sctx->cmp_key, 0, __record_deleted_ref, sctx);
+	if (ret < 0)
+		goto out;
+	ret = 0;
+
+out:
+	return ret;
+}
+
+struct find_ref_ctx {
+	u64 dir;
+	u64 dir_gen;
+	struct btrfs_root *root;
+	struct fs_path *name;
+	int found_idx;
+};
+
+static int __find_iref(int num, u64 dir, int index,
+		       struct fs_path *name,
+		       void *ctx_)
+{
+	struct find_ref_ctx *ctx = ctx_;
+	u64 dir_gen;
+	int ret;
+
+	if (dir == ctx->dir && fs_path_len(name) == fs_path_len(ctx->name) &&
+	    strncmp(name->start, ctx->name->start, fs_path_len(name)) == 0) {
+		/*
+		 * To avoid doing extra lookups we'll only do this if everything
+		 * else matches.
+		 */
+		ret = get_inode_info(ctx->root, dir, NULL, &dir_gen, NULL,
+				     NULL, NULL, NULL);
+		if (ret)
+			return ret;
+		if (dir_gen != ctx->dir_gen)
+			return 0;
+		ctx->found_idx = num;
+		return 1;
+	}
+	return 0;
+}
+
+static int find_iref(struct btrfs_root *root,
+		     struct btrfs_path *path,
+		     struct btrfs_key *key,
+		     u64 dir, u64 dir_gen, struct fs_path *name)
+{
+	int ret;
+	struct find_ref_ctx ctx;
+
+	ctx.dir = dir;
+	ctx.name = name;
+	ctx.dir_gen = dir_gen;
+	ctx.found_idx = -1;
+	ctx.root = root;
+
+	ret = iterate_inode_ref(root, path, key, 0, __find_iref, &ctx);
+	if (ret < 0)
+		return ret;
+
+	if (ctx.found_idx == -1)
+		return -ENOENT;
+
+	return ctx.found_idx;
+}
+
+static int __record_changed_new_ref(int num, u64 dir, int index,
+				    struct fs_path *name,
+				    void *ctx)
+{
+	u64 dir_gen;
+	int ret;
+	struct send_ctx *sctx = ctx;
+
+	ret = get_inode_info(sctx->send_root, dir, NULL, &dir_gen, NULL,
+			     NULL, NULL, NULL);
+	if (ret)
+		return ret;
+
+	ret = find_iref(sctx->parent_root, sctx->right_path,
+			sctx->cmp_key, dir, dir_gen, name);
+	if (ret == -ENOENT)
+		ret = __record_new_ref(num, dir, index, name, sctx);
+	else if (ret > 0)
+		ret = 0;
+
+	return ret;
+}
+
+static int __record_changed_deleted_ref(int num, u64 dir, int index,
+					struct fs_path *name,
+					void *ctx)
+{
+	u64 dir_gen;
+	int ret;
+	struct send_ctx *sctx = ctx;
+
+	ret = get_inode_info(sctx->parent_root, dir, NULL, &dir_gen, NULL,
+			     NULL, NULL, NULL);
+	if (ret)
+		return ret;
+
+	ret = find_iref(sctx->send_root, sctx->left_path, sctx->cmp_key,
+			dir, dir_gen, name);
+	if (ret == -ENOENT)
+		ret = __record_deleted_ref(num, dir, index, name, sctx);
+	else if (ret > 0)
+		ret = 0;
+
+	return ret;
+}
+
+static int record_changed_ref(struct send_ctx *sctx)
+{
+	int ret = 0;
+
+	ret = iterate_inode_ref(sctx->send_root, sctx->left_path,
+			sctx->cmp_key, 0, __record_changed_new_ref, sctx);
+	if (ret < 0)
+		goto out;
+	ret = iterate_inode_ref(sctx->parent_root, sctx->right_path,
+			sctx->cmp_key, 0, __record_changed_deleted_ref, sctx);
+	if (ret < 0)
+		goto out;
+	ret = 0;
+
+out:
+	return ret;
+}
+
+/*
+ * Record and process all refs at once. Needed when an inode changes the
+ * generation number, which means that it was deleted and recreated.
+ */
+static int process_all_refs(struct send_ctx *sctx,
+			    enum btrfs_compare_tree_result cmd)
+{
+	int ret;
+	struct btrfs_root *root;
+	struct btrfs_path *path;
+	struct btrfs_key key;
+	struct btrfs_key found_key;
+	struct extent_buffer *eb;
+	int slot;
+	iterate_inode_ref_t cb;
+	int pending_move = 0;
+
+	path = alloc_path_for_send();
+	if (!path)
+		return -ENOMEM;
+
+	if (cmd == BTRFS_COMPARE_TREE_NEW) {
+		root = sctx->send_root;
+		cb = __record_new_ref;
+	} else if (cmd == BTRFS_COMPARE_TREE_DELETED) {
+		root = sctx->parent_root;
+		cb = __record_deleted_ref;
+	} else {
+		btrfs_err(sctx->send_root->fs_info,
+				"Wrong command %d in process_all_refs", cmd);
+		ret = -EINVAL;
+		goto out;
+	}
+
+	key.objectid = sctx->cmp_key->objectid;
+	key.type = BTRFS_INODE_REF_KEY;
+	key.offset = 0;
+	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+	if (ret < 0)
+		goto out;
+
+	while (1) {
+		eb = path->nodes[0];
+		slot = path->slots[0];
+		if (slot >= btrfs_header_nritems(eb)) {
+			ret = btrfs_next_leaf(root, path);
+			if (ret < 0)
+				goto out;
+			else if (ret > 0)
+				break;
+			continue;
+		}
+
+		btrfs_item_key_to_cpu(eb, &found_key, slot);
+
+		if (found_key.objectid != key.objectid ||
+		    (found_key.type != BTRFS_INODE_REF_KEY &&
+		     found_key.type != BTRFS_INODE_EXTREF_KEY))
+			break;
+
+		ret = iterate_inode_ref(root, path, &found_key, 0, cb, sctx);
+		if (ret < 0)
+			goto out;
+
+		path->slots[0]++;
+	}
+	btrfs_release_path(path);
+
+	/*
+	 * We don't actually care about pending_move as we are simply
+	 * re-creating this inode and will be rename'ing it into place once we
+	 * rename the parent directory.
+	 */
+	ret = process_recorded_refs(sctx, &pending_move);
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+static int send_set_xattr(struct send_ctx *sctx,
+			  struct fs_path *path,
+			  const char *name, int name_len,
+			  const char *data, int data_len)
+{
+	int ret = 0;
+
+	ret = begin_cmd(sctx, BTRFS_SEND_C_SET_XATTR);
+	if (ret < 0)
+		goto out;
+
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, path);
+	TLV_PUT_STRING(sctx, BTRFS_SEND_A_XATTR_NAME, name, name_len);
+	TLV_PUT(sctx, BTRFS_SEND_A_XATTR_DATA, data, data_len);
+
+	ret = send_cmd(sctx);
+
+tlv_put_failure:
+out:
+	return ret;
+}
+
+static int send_remove_xattr(struct send_ctx *sctx,
+			  struct fs_path *path,
+			  const char *name, int name_len)
+{
+	int ret = 0;
+
+	ret = begin_cmd(sctx, BTRFS_SEND_C_REMOVE_XATTR);
+	if (ret < 0)
+		goto out;
+
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, path);
+	TLV_PUT_STRING(sctx, BTRFS_SEND_A_XATTR_NAME, name, name_len);
+
+	ret = send_cmd(sctx);
+
+tlv_put_failure:
+out:
+	return ret;
+}
+
+static int __process_new_xattr(int num, struct btrfs_key *di_key,
+			       const char *name, int name_len,
+			       const char *data, int data_len,
+			       u8 type, void *ctx)
+{
+	int ret;
+	struct send_ctx *sctx = ctx;
+	struct fs_path *p;
+	struct posix_acl_xattr_header dummy_acl;
+
+	/* Capabilities are emitted by finish_inode_if_needed */
+	if (!strncmp(name, XATTR_NAME_CAPS, name_len))
+		return 0;
+
+	p = fs_path_alloc();
+	if (!p)
+		return -ENOMEM;
+
+	/*
+	 * This hack is needed because empty acls are stored as zero byte
+	 * data in xattrs. Problem with that is, that receiving these zero byte
+	 * acls will fail later. To fix this, we send a dummy acl list that
+	 * only contains the version number and no entries.
+	 */
+	if (!strncmp(name, XATTR_NAME_POSIX_ACL_ACCESS, name_len) ||
+	    !strncmp(name, XATTR_NAME_POSIX_ACL_DEFAULT, name_len)) {
+		if (data_len == 0) {
+			dummy_acl.a_version =
+					cpu_to_le32(POSIX_ACL_XATTR_VERSION);
+			data = (char *)&dummy_acl;
+			data_len = sizeof(dummy_acl);
+		}
+	}
+
+	ret = get_cur_path(sctx, sctx->cur_ino, sctx->cur_inode_gen, p);
+	if (ret < 0)
+		goto out;
+
+	ret = send_set_xattr(sctx, p, name, name_len, data, data_len);
+
+out:
+	fs_path_free(p);
+	return ret;
+}
+
+static int __process_deleted_xattr(int num, struct btrfs_key *di_key,
+				   const char *name, int name_len,
+				   const char *data, int data_len,
+				   u8 type, void *ctx)
+{
+	int ret;
+	struct send_ctx *sctx = ctx;
+	struct fs_path *p;
+
+	p = fs_path_alloc();
+	if (!p)
+		return -ENOMEM;
+
+	ret = get_cur_path(sctx, sctx->cur_ino, sctx->cur_inode_gen, p);
+	if (ret < 0)
+		goto out;
+
+	ret = send_remove_xattr(sctx, p, name, name_len);
+
+out:
+	fs_path_free(p);
+	return ret;
+}
+
+static int process_new_xattr(struct send_ctx *sctx)
+{
+	int ret = 0;
+
+	ret = iterate_dir_item(sctx->send_root, sctx->left_path,
+			       __process_new_xattr, sctx);
+
+	return ret;
+}
+
+static int process_deleted_xattr(struct send_ctx *sctx)
+{
+	return iterate_dir_item(sctx->parent_root, sctx->right_path,
+				__process_deleted_xattr, sctx);
+}
+
+struct find_xattr_ctx {
+	const char *name;
+	int name_len;
+	int found_idx;
+	char *found_data;
+	int found_data_len;
+};
+
+static int __find_xattr(int num, struct btrfs_key *di_key,
+			const char *name, int name_len,
+			const char *data, int data_len,
+			u8 type, void *vctx)
+{
+	struct find_xattr_ctx *ctx = vctx;
+
+	if (name_len == ctx->name_len &&
+	    strncmp(name, ctx->name, name_len) == 0) {
+		ctx->found_idx = num;
+		ctx->found_data_len = data_len;
+		ctx->found_data = kmemdup(data, data_len, GFP_KERNEL);
+		if (!ctx->found_data)
+			return -ENOMEM;
+		return 1;
+	}
+	return 0;
+}
+
+static int find_xattr(struct btrfs_root *root,
+		      struct btrfs_path *path,
+		      struct btrfs_key *key,
+		      const char *name, int name_len,
+		      char **data, int *data_len)
+{
+	int ret;
+	struct find_xattr_ctx ctx;
+
+	ctx.name = name;
+	ctx.name_len = name_len;
+	ctx.found_idx = -1;
+	ctx.found_data = NULL;
+	ctx.found_data_len = 0;
+
+	ret = iterate_dir_item(root, path, __find_xattr, &ctx);
+	if (ret < 0)
+		return ret;
+
+	if (ctx.found_idx == -1)
+		return -ENOENT;
+	if (data) {
+		*data = ctx.found_data;
+		*data_len = ctx.found_data_len;
+	} else {
+		kfree(ctx.found_data);
+	}
+	return ctx.found_idx;
+}
+
+
+static int __process_changed_new_xattr(int num, struct btrfs_key *di_key,
+				       const char *name, int name_len,
+				       const char *data, int data_len,
+				       u8 type, void *ctx)
+{
+	int ret;
+	struct send_ctx *sctx = ctx;
+	char *found_data = NULL;
+	int found_data_len  = 0;
+
+	ret = find_xattr(sctx->parent_root, sctx->right_path,
+			 sctx->cmp_key, name, name_len, &found_data,
+			 &found_data_len);
+	if (ret == -ENOENT) {
+		ret = __process_new_xattr(num, di_key, name, name_len, data,
+				data_len, type, ctx);
+	} else if (ret >= 0) {
+		if (data_len != found_data_len ||
+		    memcmp(data, found_data, data_len)) {
+			ret = __process_new_xattr(num, di_key, name, name_len,
+					data, data_len, type, ctx);
+		} else {
+			ret = 0;
+		}
+	}
+
+	kfree(found_data);
+	return ret;
+}
+
+static int __process_changed_deleted_xattr(int num, struct btrfs_key *di_key,
+					   const char *name, int name_len,
+					   const char *data, int data_len,
+					   u8 type, void *ctx)
+{
+	int ret;
+	struct send_ctx *sctx = ctx;
+
+	ret = find_xattr(sctx->send_root, sctx->left_path, sctx->cmp_key,
+			 name, name_len, NULL, NULL);
+	if (ret == -ENOENT)
+		ret = __process_deleted_xattr(num, di_key, name, name_len, data,
+				data_len, type, ctx);
+	else if (ret >= 0)
+		ret = 0;
+
+	return ret;
+}
+
+static int process_changed_xattr(struct send_ctx *sctx)
+{
+	int ret = 0;
+
+	ret = iterate_dir_item(sctx->send_root, sctx->left_path,
+			__process_changed_new_xattr, sctx);
+	if (ret < 0)
+		goto out;
+	ret = iterate_dir_item(sctx->parent_root, sctx->right_path,
+			__process_changed_deleted_xattr, sctx);
+
+out:
+	return ret;
+}
+
+static int process_all_new_xattrs(struct send_ctx *sctx)
+{
+	int ret;
+	struct btrfs_root *root;
+	struct btrfs_path *path;
+	struct btrfs_key key;
+	struct btrfs_key found_key;
+	struct extent_buffer *eb;
+	int slot;
+
+	path = alloc_path_for_send();
+	if (!path)
+		return -ENOMEM;
+
+	root = sctx->send_root;
+
+	key.objectid = sctx->cmp_key->objectid;
+	key.type = BTRFS_XATTR_ITEM_KEY;
+	key.offset = 0;
+	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+	if (ret < 0)
+		goto out;
+
+	while (1) {
+		eb = path->nodes[0];
+		slot = path->slots[0];
+		if (slot >= btrfs_header_nritems(eb)) {
+			ret = btrfs_next_leaf(root, path);
+			if (ret < 0) {
+				goto out;
+			} else if (ret > 0) {
+				ret = 0;
+				break;
+			}
+			continue;
+		}
+
+		btrfs_item_key_to_cpu(eb, &found_key, slot);
+		if (found_key.objectid != key.objectid ||
+		    found_key.type != key.type) {
+			ret = 0;
+			goto out;
+		}
+
+		ret = iterate_dir_item(root, path, __process_new_xattr, sctx);
+		if (ret < 0)
+			goto out;
+
+		path->slots[0]++;
+	}
+
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+static inline u64 max_send_read_size(const struct send_ctx *sctx)
+{
+	return sctx->send_max_size - SZ_16K;
+}
+
+static int put_data_header(struct send_ctx *sctx, u32 len)
+{
+	struct btrfs_tlv_header *hdr;
+
+	if (sctx->send_max_size - sctx->send_size < sizeof(*hdr) + len)
+		return -EOVERFLOW;
+	hdr = (struct btrfs_tlv_header *)(sctx->send_buf + sctx->send_size);
+	put_unaligned_le16(BTRFS_SEND_A_DATA, &hdr->tlv_type);
+	put_unaligned_le16(len, &hdr->tlv_len);
+	sctx->send_size += sizeof(*hdr);
+	return 0;
+}
+
+static int put_file_data(struct send_ctx *sctx, u64 offset, u32 len)
+{
+	struct btrfs_root *root = sctx->send_root;
+	struct btrfs_fs_info *fs_info = root->fs_info;
+	struct inode *inode;
+	struct page *page;
+	char *addr;
+	pgoff_t index = offset >> PAGE_SHIFT;
+	pgoff_t last_index;
+	unsigned pg_offset = offset_in_page(offset);
+	int ret;
+
+	ret = put_data_header(sctx, len);
+	if (ret)
+		return ret;
+
+	inode = btrfs_iget(fs_info->sb, sctx->cur_ino, root);
+	if (IS_ERR(inode))
+		return PTR_ERR(inode);
+
+	last_index = (offset + len - 1) >> PAGE_SHIFT;
+
+	/* initial readahead */
+	memset(&sctx->ra, 0, sizeof(struct file_ra_state));
+	file_ra_state_init(&sctx->ra, inode->i_mapping);
+
+	while (index <= last_index) {
+		unsigned cur_len = min_t(unsigned, len,
+					 PAGE_SIZE - pg_offset);
+
+		page = find_lock_page(inode->i_mapping, index);
+		if (!page) {
+			page_cache_sync_readahead(inode->i_mapping, &sctx->ra,
+				NULL, index, last_index + 1 - index);
+
+			page = find_or_create_page(inode->i_mapping, index,
+					GFP_KERNEL);
+			if (!page) {
+				ret = -ENOMEM;
+				break;
+			}
+		}
+
+		if (PageReadahead(page)) {
+			page_cache_async_readahead(inode->i_mapping, &sctx->ra,
+				NULL, page, index, last_index + 1 - index);
+		}
+
+		if (!PageUptodate(page)) {
+			btrfs_readpage(NULL, page);
+			lock_page(page);
+			if (!PageUptodate(page)) {
+				unlock_page(page);
+				btrfs_err(fs_info,
+			"send: IO error at offset %llu for inode %llu root %llu",
+					page_offset(page), sctx->cur_ino,
+					sctx->send_root->root_key.objectid);
+				put_page(page);
+				ret = -EIO;
+				break;
+			}
+		}
+
+		addr = kmap(page);
+		memcpy(sctx->send_buf + sctx->send_size, addr + pg_offset,
+		       cur_len);
+		kunmap(page);
+		unlock_page(page);
+		put_page(page);
+		index++;
+		pg_offset = 0;
+		len -= cur_len;
+		sctx->send_size += cur_len;
+	}
+	iput(inode);
+	return ret;
+}
+
+/*
+ * Read some bytes from the current inode/file and send a write command to
+ * user space.
+ */
+static int send_write(struct send_ctx *sctx, u64 offset, u32 len)
+{
+	struct btrfs_fs_info *fs_info = sctx->send_root->fs_info;
+	int ret = 0;
+	struct fs_path *p;
+
+	p = fs_path_alloc();
+	if (!p)
+		return -ENOMEM;
+
+	btrfs_debug(fs_info, "send_write offset=%llu, len=%d", offset, len);
+
+	ret = begin_cmd(sctx, BTRFS_SEND_C_WRITE);
+	if (ret < 0)
+		goto out;
+
+	ret = get_cur_path(sctx, sctx->cur_ino, sctx->cur_inode_gen, p);
+	if (ret < 0)
+		goto out;
+
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, p);
+	TLV_PUT_U64(sctx, BTRFS_SEND_A_FILE_OFFSET, offset);
+	ret = put_file_data(sctx, offset, len);
+	if (ret < 0)
+		goto out;
+
+	ret = send_cmd(sctx);
+
+tlv_put_failure:
+out:
+	fs_path_free(p);
+	return ret;
+}
+
+/*
+ * Send a clone command to user space.
+ */
+static int send_clone(struct send_ctx *sctx,
+		      u64 offset, u32 len,
+		      struct clone_root *clone_root)
+{
+	int ret = 0;
+	struct fs_path *p;
+	u64 gen;
+
+	btrfs_debug(sctx->send_root->fs_info,
+		    "send_clone offset=%llu, len=%d, clone_root=%llu, clone_inode=%llu, clone_offset=%llu",
+		    offset, len, clone_root->root->root_key.objectid,
+		    clone_root->ino, clone_root->offset);
+
+	p = fs_path_alloc();
+	if (!p)
+		return -ENOMEM;
+
+	ret = begin_cmd(sctx, BTRFS_SEND_C_CLONE);
+	if (ret < 0)
+		goto out;
+
+	ret = get_cur_path(sctx, sctx->cur_ino, sctx->cur_inode_gen, p);
+	if (ret < 0)
+		goto out;
+
+	TLV_PUT_U64(sctx, BTRFS_SEND_A_FILE_OFFSET, offset);
+	TLV_PUT_U64(sctx, BTRFS_SEND_A_CLONE_LEN, len);
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, p);
+
+	if (clone_root->root == sctx->send_root) {
+		ret = get_inode_info(sctx->send_root, clone_root->ino, NULL,
+				&gen, NULL, NULL, NULL, NULL);
+		if (ret < 0)
+			goto out;
+		ret = get_cur_path(sctx, clone_root->ino, gen, p);
+	} else {
+		ret = get_inode_path(clone_root->root, clone_root->ino, p);
+	}
+	if (ret < 0)
+		goto out;
+
+	/*
+	 * If the parent we're using has a received_uuid set then use that as
+	 * our clone source as that is what we will look for when doing a
+	 * receive.
+	 *
+	 * This covers the case that we create a snapshot off of a received
+	 * subvolume and then use that as the parent and try to receive on a
+	 * different host.
+	 */
+	if (!btrfs_is_empty_uuid(clone_root->root->root_item.received_uuid))
+		TLV_PUT_UUID(sctx, BTRFS_SEND_A_CLONE_UUID,
+			     clone_root->root->root_item.received_uuid);
+	else
+		TLV_PUT_UUID(sctx, BTRFS_SEND_A_CLONE_UUID,
+			     clone_root->root->root_item.uuid);
+	TLV_PUT_U64(sctx, BTRFS_SEND_A_CLONE_CTRANSID,
+		    le64_to_cpu(clone_root->root->root_item.ctransid));
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_CLONE_PATH, p);
+	TLV_PUT_U64(sctx, BTRFS_SEND_A_CLONE_OFFSET,
+			clone_root->offset);
+
+	ret = send_cmd(sctx);
+
+tlv_put_failure:
+out:
+	fs_path_free(p);
+	return ret;
+}
+
+/*
+ * Send an update extent command to user space.
+ */
+static int send_update_extent(struct send_ctx *sctx,
+			      u64 offset, u32 len)
+{
+	int ret = 0;
+	struct fs_path *p;
+
+	p = fs_path_alloc();
+	if (!p)
+		return -ENOMEM;
+
+	ret = begin_cmd(sctx, BTRFS_SEND_C_UPDATE_EXTENT);
+	if (ret < 0)
+		goto out;
+
+	ret = get_cur_path(sctx, sctx->cur_ino, sctx->cur_inode_gen, p);
+	if (ret < 0)
+		goto out;
+
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, p);
+	TLV_PUT_U64(sctx, BTRFS_SEND_A_FILE_OFFSET, offset);
+	TLV_PUT_U64(sctx, BTRFS_SEND_A_SIZE, len);
+
+	ret = send_cmd(sctx);
+
+tlv_put_failure:
+out:
+	fs_path_free(p);
+	return ret;
+}
+
+static int send_hole(struct send_ctx *sctx, u64 end)
+{
+	struct fs_path *p = NULL;
+	u64 read_size = max_send_read_size(sctx);
+	u64 offset = sctx->cur_inode_last_extent;
+	int ret = 0;
+
+	/*
+	 * A hole that starts at EOF or beyond it. Since we do not yet support
+	 * fallocate (for extent preallocation and hole punching), sending a
+	 * write of zeroes starting at EOF or beyond would later require issuing
+	 * a truncate operation which would undo the write and achieve nothing.
+	 */
+	if (offset >= sctx->cur_inode_size)
+		return 0;
+
+	/*
+	 * Don't go beyond the inode's i_size due to prealloc extents that start
+	 * after the i_size.
+	 */
+	end = min_t(u64, end, sctx->cur_inode_size);
+
+	if (sctx->flags & BTRFS_SEND_FLAG_NO_FILE_DATA)
+		return send_update_extent(sctx, offset, end - offset);
+
+	p = fs_path_alloc();
+	if (!p)
+		return -ENOMEM;
+	ret = get_cur_path(sctx, sctx->cur_ino, sctx->cur_inode_gen, p);
+	if (ret < 0)
+		goto tlv_put_failure;
+	while (offset < end) {
+		u64 len = min(end - offset, read_size);
+
+		ret = begin_cmd(sctx, BTRFS_SEND_C_WRITE);
+		if (ret < 0)
+			break;
+		TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, p);
+		TLV_PUT_U64(sctx, BTRFS_SEND_A_FILE_OFFSET, offset);
+		ret = put_data_header(sctx, len);
+		if (ret < 0)
+			break;
+		memset(sctx->send_buf + sctx->send_size, 0, len);
+		sctx->send_size += len;
+		ret = send_cmd(sctx);
+		if (ret < 0)
+			break;
+		offset += len;
+	}
+	sctx->cur_inode_next_write_offset = offset;
+tlv_put_failure:
+	fs_path_free(p);
+	return ret;
+}
+
+static int send_extent_data(struct send_ctx *sctx,
+			    const u64 offset,
+			    const u64 len)
+{
+	u64 read_size = max_send_read_size(sctx);
+	u64 sent = 0;
+
+	if (sctx->flags & BTRFS_SEND_FLAG_NO_FILE_DATA)
+		return send_update_extent(sctx, offset, len);
+
+	while (sent < len) {
+		u64 size = min(len - sent, read_size);
+		int ret;
+
+		ret = send_write(sctx, offset + sent, size);
+		if (ret < 0)
+			return ret;
+		sent += size;
+	}
+	return 0;
+}
+
+/*
+ * Search for a capability xattr related to sctx->cur_ino. If the capability is
+ * found, call send_set_xattr function to emit it.
+ *
+ * Return 0 if there isn't a capability, or when the capability was emitted
+ * successfully, or < 0 if an error occurred.
+ */
+static int send_capabilities(struct send_ctx *sctx)
+{
+	struct fs_path *fspath = NULL;
+	struct btrfs_path *path;
+	struct btrfs_dir_item *di;
+	struct extent_buffer *leaf;
+	unsigned long data_ptr;
+	char *buf = NULL;
+	int buf_len;
+	int ret = 0;
+
+	path = alloc_path_for_send();
+	if (!path)
+		return -ENOMEM;
+
+	di = btrfs_lookup_xattr(NULL, sctx->send_root, path, sctx->cur_ino,
+				XATTR_NAME_CAPS, strlen(XATTR_NAME_CAPS), 0);
+	if (!di) {
+		/* There is no xattr for this inode */
+		goto out;
+	} else if (IS_ERR(di)) {
+		ret = PTR_ERR(di);
+		goto out;
+	}
+
+	leaf = path->nodes[0];
+	buf_len = btrfs_dir_data_len(leaf, di);
+
+	fspath = fs_path_alloc();
+	buf = kmalloc(buf_len, GFP_KERNEL);
+	if (!fspath || !buf) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	ret = get_cur_path(sctx, sctx->cur_ino, sctx->cur_inode_gen, fspath);
+	if (ret < 0)
+		goto out;
+
+	data_ptr = (unsigned long)(di + 1) + btrfs_dir_name_len(leaf, di);
+	read_extent_buffer(leaf, buf, data_ptr, buf_len);
+
+	ret = send_set_xattr(sctx, fspath, XATTR_NAME_CAPS,
+			strlen(XATTR_NAME_CAPS), buf, buf_len);
+out:
+	kfree(buf);
+	fs_path_free(fspath);
+	btrfs_free_path(path);
+	return ret;
+}
+
+static int clone_range(struct send_ctx *sctx,
+		       struct clone_root *clone_root,
+		       const u64 disk_byte,
+		       u64 data_offset,
+		       u64 offset,
+		       u64 len)
+{
+	struct btrfs_path *path;
+	struct btrfs_key key;
+	int ret;
+	u64 clone_src_i_size = 0;
+
+	/*
+	 * Prevent cloning from a zero offset with a length matching the sector
+	 * size because in some scenarios this will make the receiver fail.
+	 *
+	 * For example, if in the source filesystem the extent at offset 0
+	 * has a length of sectorsize and it was written using direct IO, then
+	 * it can never be an inline extent (even if compression is enabled).
+	 * Then this extent can be cloned in the original filesystem to a non
+	 * zero file offset, but it may not be possible to clone in the
+	 * destination filesystem because it can be inlined due to compression
+	 * on the destination filesystem (as the receiver's write operations are
+	 * always done using buffered IO). The same happens when the original
+	 * filesystem does not have compression enabled but the destination
+	 * filesystem has.
+	 */
+	if (clone_root->offset == 0 &&
+	    len == sctx->send_root->fs_info->sectorsize)
+		return send_extent_data(sctx, offset, len);
+
+	path = alloc_path_for_send();
+	if (!path)
+		return -ENOMEM;
+
+	/*
+	 * There are inodes that have extents that lie behind its i_size. Don't
+	 * accept clones from these extents.
+	 */
+	ret = __get_inode_info(clone_root->root, path, clone_root->ino,
+			       &clone_src_i_size, NULL, NULL, NULL, NULL, NULL);
+	btrfs_release_path(path);
+	if (ret < 0)
+		goto out;
+
+	/*
+	 * We can't send a clone operation for the entire range if we find
+	 * extent items in the respective range in the source file that
+	 * refer to different extents or if we find holes.
+	 * So check for that and do a mix of clone and regular write/copy
+	 * operations if needed.
+	 *
+	 * Example:
+	 *
+	 * mkfs.btrfs -f /dev/sda
+	 * mount /dev/sda /mnt
+	 * xfs_io -f -c "pwrite -S 0xaa 0K 100K" /mnt/foo
+	 * cp --reflink=always /mnt/foo /mnt/bar
+	 * xfs_io -c "pwrite -S 0xbb 50K 50K" /mnt/foo
+	 * btrfs subvolume snapshot -r /mnt /mnt/snap
+	 *
+	 * If when we send the snapshot and we are processing file bar (which
+	 * has a higher inode number than foo) we blindly send a clone operation
+	 * for the [0, 100K[ range from foo to bar, the receiver ends up getting
+	 * a file bar that matches the content of file foo - iow, doesn't match
+	 * the content from bar in the original filesystem.
+	 */
+	key.objectid = clone_root->ino;
+	key.type = BTRFS_EXTENT_DATA_KEY;
+	key.offset = clone_root->offset;
+	ret = btrfs_search_slot(NULL, clone_root->root, &key, path, 0, 0);
+	if (ret < 0)
+		goto out;
+	if (ret > 0 && path->slots[0] > 0) {
+		btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0] - 1);
+		if (key.objectid == clone_root->ino &&
+		    key.type == BTRFS_EXTENT_DATA_KEY)
+			path->slots[0]--;
+	}
+
+	while (true) {
+		struct extent_buffer *leaf = path->nodes[0];
+		int slot = path->slots[0];
+		struct btrfs_file_extent_item *ei;
+		u8 type;
+		u64 ext_len;
+		u64 clone_len;
+		u64 clone_data_offset;
+		bool crossed_src_i_size = false;
+
+		if (slot >= btrfs_header_nritems(leaf)) {
+			ret = btrfs_next_leaf(clone_root->root, path);
+			if (ret < 0)
+				goto out;
+			else if (ret > 0)
+				break;
+			continue;
+		}
+
+		btrfs_item_key_to_cpu(leaf, &key, slot);
+
+		/*
+		 * We might have an implicit trailing hole (NO_HOLES feature
+		 * enabled). We deal with it after leaving this loop.
+		 */
+		if (key.objectid != clone_root->ino ||
+		    key.type != BTRFS_EXTENT_DATA_KEY)
+			break;
+
+		ei = btrfs_item_ptr(leaf, slot, struct btrfs_file_extent_item);
+		type = btrfs_file_extent_type(leaf, ei);
+		if (type == BTRFS_FILE_EXTENT_INLINE) {
+			ext_len = btrfs_file_extent_ram_bytes(leaf, ei);
+			ext_len = PAGE_ALIGN(ext_len);
+		} else {
+			ext_len = btrfs_file_extent_num_bytes(leaf, ei);
+		}
+
+		if (key.offset + ext_len <= clone_root->offset)
+			goto next;
+
+		if (key.offset > clone_root->offset) {
+			/* Implicit hole, NO_HOLES feature enabled. */
+			u64 hole_len = key.offset - clone_root->offset;
+
+			if (hole_len > len)
+				hole_len = len;
+			ret = send_extent_data(sctx, offset, hole_len);
+			if (ret < 0)
+				goto out;
+
+			len -= hole_len;
+			if (len == 0)
+				break;
+			offset += hole_len;
+			clone_root->offset += hole_len;
+			data_offset += hole_len;
+		}
+
+		if (key.offset >= clone_root->offset + len)
+			break;
+
+		if (key.offset >= clone_src_i_size)
+			break;
+
+		if (key.offset + ext_len > clone_src_i_size) {
+			ext_len = clone_src_i_size - key.offset;
+			crossed_src_i_size = true;
+		}
+
+		clone_data_offset = btrfs_file_extent_offset(leaf, ei);
+		if (btrfs_file_extent_disk_bytenr(leaf, ei) == disk_byte) {
+			clone_root->offset = key.offset;
+			if (clone_data_offset < data_offset &&
+				clone_data_offset + ext_len > data_offset) {
+				u64 extent_offset;
+
+				extent_offset = data_offset - clone_data_offset;
+				ext_len -= extent_offset;
+				clone_data_offset += extent_offset;
+				clone_root->offset += extent_offset;
+			}
+		}
+
+		clone_len = min_t(u64, ext_len, len);
+
+		if (btrfs_file_extent_disk_bytenr(leaf, ei) == disk_byte &&
+		    clone_data_offset == data_offset) {
+			const u64 src_end = clone_root->offset + clone_len;
+			const u64 sectorsize = SZ_64K;
+
+			/*
+			 * We can't clone the last block, when its size is not
+			 * sector size aligned, into the middle of a file. If we
+			 * do so, the receiver will get a failure (-EINVAL) when
+			 * trying to clone or will silently corrupt the data in
+			 * the destination file if it's on a kernel without the
+			 * fix introduced by commit ac765f83f1397646
+			 * ("Btrfs: fix data corruption due to cloning of eof
+			 * block).
+			 *
+			 * So issue a clone of the aligned down range plus a
+			 * regular write for the eof block, if we hit that case.
+			 *
+			 * Also, we use the maximum possible sector size, 64K,
+			 * because we don't know what's the sector size of the
+			 * filesystem that receives the stream, so we have to
+			 * assume the largest possible sector size.
+			 */
+			if (src_end == clone_src_i_size &&
+			    !IS_ALIGNED(src_end, sectorsize) &&
+			    offset + clone_len < sctx->cur_inode_size) {
+				u64 slen;
+
+				slen = ALIGN_DOWN(src_end - clone_root->offset,
+						  sectorsize);
+				if (slen > 0) {
+					ret = send_clone(sctx, offset, slen,
+							 clone_root);
+					if (ret < 0)
+						goto out;
+				}
+				ret = send_extent_data(sctx, offset + slen,
+						       clone_len - slen);
+			} else {
+				ret = send_clone(sctx, offset, clone_len,
+						 clone_root);
+			}
+		} else if (crossed_src_i_size && clone_len < len) {
+			/*
+			 * If we are at i_size of the clone source inode and we
+			 * can not clone from it, terminate the loop. This is
+			 * to avoid sending two write operations, one with a
+			 * length matching clone_len and the final one after
+			 * this loop with a length of len - clone_len.
+			 *
+			 * When using encoded writes (BTRFS_SEND_FLAG_COMPRESSED
+			 * was passed to the send ioctl), this helps avoid
+			 * sending an encoded write for an offset that is not
+			 * sector size aligned, in case the i_size of the source
+			 * inode is not sector size aligned. That will make the
+			 * receiver fallback to decompression of the data and
+			 * writing it using regular buffered IO, therefore while
+			 * not incorrect, it's not optimal due decompression and
+			 * possible re-compression at the receiver.
+			 */
+			break;
+		} else {
+			ret = send_extent_data(sctx, offset, clone_len);
+		}
+
+		if (ret < 0)
+			goto out;
+
+		len -= clone_len;
+		if (len == 0)
+			break;
+		offset += clone_len;
+		clone_root->offset += clone_len;
+
+		/*
+		 * If we are cloning from the file we are currently processing,
+		 * and using the send root as the clone root, we must stop once
+		 * the current clone offset reaches the current eof of the file
+		 * at the receiver, otherwise we would issue an invalid clone
+		 * operation (source range going beyond eof) and cause the
+		 * receiver to fail. So if we reach the current eof, bail out
+		 * and fallback to a regular write.
+		 */
+		if (clone_root->root == sctx->send_root &&
+		    clone_root->ino == sctx->cur_ino &&
+		    clone_root->offset >= sctx->cur_inode_next_write_offset)
+			break;
+
+		data_offset += clone_len;
+next:
+		path->slots[0]++;
+	}
+
+	if (len > 0)
+		ret = send_extent_data(sctx, offset, len);
+	else
+		ret = 0;
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+static int send_write_or_clone(struct send_ctx *sctx,
+			       struct btrfs_path *path,
+			       struct btrfs_key *key,
+			       struct clone_root *clone_root)
+{
+	int ret = 0;
+	u64 offset = key->offset;
+	u64 end;
+	u64 bs = sctx->send_root->fs_info->sb->s_blocksize;
+
+	end = min_t(u64, btrfs_file_extent_end(path), sctx->cur_inode_size);
+	if (offset >= end)
+		return 0;
+
+	if (clone_root && IS_ALIGNED(end, bs)) {
+		struct btrfs_file_extent_item *ei;
+		u64 disk_byte;
+		u64 data_offset;
+
+		ei = btrfs_item_ptr(path->nodes[0], path->slots[0],
+				    struct btrfs_file_extent_item);
+		disk_byte = btrfs_file_extent_disk_bytenr(path->nodes[0], ei);
+		data_offset = btrfs_file_extent_offset(path->nodes[0], ei);
+		ret = clone_range(sctx, clone_root, disk_byte, data_offset,
+				  offset, end - offset);
+	} else {
+		ret = send_extent_data(sctx, offset, end - offset);
+	}
+	sctx->cur_inode_next_write_offset = end;
+	return ret;
+}
+
+static int is_extent_unchanged(struct send_ctx *sctx,
+			       struct btrfs_path *left_path,
+			       struct btrfs_key *ekey)
+{
+	int ret = 0;
+	struct btrfs_key key;
+	struct btrfs_path *path = NULL;
+	struct extent_buffer *eb;
+	int slot;
+	struct btrfs_key found_key;
+	struct btrfs_file_extent_item *ei;
+	u64 left_disknr;
+	u64 right_disknr;
+	u64 left_offset;
+	u64 right_offset;
+	u64 left_offset_fixed;
+	u64 left_len;
+	u64 right_len;
+	u64 left_gen;
+	u64 right_gen;
+	u8 left_type;
+	u8 right_type;
+
+	path = alloc_path_for_send();
+	if (!path)
+		return -ENOMEM;
+
+	eb = left_path->nodes[0];
+	slot = left_path->slots[0];
+	ei = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
+	left_type = btrfs_file_extent_type(eb, ei);
+
+	if (left_type != BTRFS_FILE_EXTENT_REG) {
+		ret = 0;
+		goto out;
+	}
+	left_disknr = btrfs_file_extent_disk_bytenr(eb, ei);
+	left_len = btrfs_file_extent_num_bytes(eb, ei);
+	left_offset = btrfs_file_extent_offset(eb, ei);
+	left_gen = btrfs_file_extent_generation(eb, ei);
+
+	/*
+	 * Following comments will refer to these graphics. L is the left
+	 * extents which we are checking at the moment. 1-8 are the right
+	 * extents that we iterate.
+	 *
+	 *       |-----L-----|
+	 * |-1-|-2a-|-3-|-4-|-5-|-6-|
+	 *
+	 *       |-----L-----|
+	 * |--1--|-2b-|...(same as above)
+	 *
+	 * Alternative situation. Happens on files where extents got split.
+	 *       |-----L-----|
+	 * |-----------7-----------|-6-|
+	 *
+	 * Alternative situation. Happens on files which got larger.
+	 *       |-----L-----|
+	 * |-8-|
+	 * Nothing follows after 8.
+	 */
+
+	key.objectid = ekey->objectid;
+	key.type = BTRFS_EXTENT_DATA_KEY;
+	key.offset = ekey->offset;
+	ret = btrfs_search_slot_for_read(sctx->parent_root, &key, path, 0, 0);
+	if (ret < 0)
+		goto out;
+	if (ret) {
+		ret = 0;
+		goto out;
+	}
+
+	/*
+	 * Handle special case where the right side has no extents at all.
+	 */
+	eb = path->nodes[0];
+	slot = path->slots[0];
+	btrfs_item_key_to_cpu(eb, &found_key, slot);
+	if (found_key.objectid != key.objectid ||
+	    found_key.type != key.type) {
+		/* If we're a hole then just pretend nothing changed */
+		ret = (left_disknr) ? 0 : 1;
+		goto out;
+	}
+
+	/*
+	 * We're now on 2a, 2b or 7.
+	 */
+	key = found_key;
+	while (key.offset < ekey->offset + left_len) {
+		ei = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
+		right_type = btrfs_file_extent_type(eb, ei);
+		if (right_type != BTRFS_FILE_EXTENT_REG &&
+		    right_type != BTRFS_FILE_EXTENT_INLINE) {
+			ret = 0;
+			goto out;
+		}
+
+		if (right_type == BTRFS_FILE_EXTENT_INLINE) {
+			right_len = btrfs_file_extent_ram_bytes(eb, ei);
+			right_len = PAGE_ALIGN(right_len);
+		} else {
+			right_len = btrfs_file_extent_num_bytes(eb, ei);
+		}
+
+		/*
+		 * Are we at extent 8? If yes, we know the extent is changed.
+		 * This may only happen on the first iteration.
+		 */
+		if (found_key.offset + right_len <= ekey->offset) {
+			/* If we're a hole just pretend nothing changed */
+			ret = (left_disknr) ? 0 : 1;
+			goto out;
+		}
+
+		/*
+		 * We just wanted to see if when we have an inline extent, what
+		 * follows it is a regular extent (wanted to check the above
+		 * condition for inline extents too). This should normally not
+		 * happen but it's possible for example when we have an inline
+		 * compressed extent representing data with a size matching
+		 * the page size (currently the same as sector size).
+		 */
+		if (right_type == BTRFS_FILE_EXTENT_INLINE) {
+			ret = 0;
+			goto out;
+		}
+
+		right_disknr = btrfs_file_extent_disk_bytenr(eb, ei);
+		right_offset = btrfs_file_extent_offset(eb, ei);
+		right_gen = btrfs_file_extent_generation(eb, ei);
+
+		left_offset_fixed = left_offset;
+		if (key.offset < ekey->offset) {
+			/* Fix the right offset for 2a and 7. */
+			right_offset += ekey->offset - key.offset;
+		} else {
+			/* Fix the left offset for all behind 2a and 2b */
+			left_offset_fixed += key.offset - ekey->offset;
+		}
+
+		/*
+		 * Check if we have the same extent.
+		 */
+		if (left_disknr != right_disknr ||
+		    left_offset_fixed != right_offset ||
+		    left_gen != right_gen) {
+			ret = 0;
+			goto out;
+		}
+
+		/*
+		 * Go to the next extent.
+		 */
+		ret = btrfs_next_item(sctx->parent_root, path);
+		if (ret < 0)
+			goto out;
+		if (!ret) {
+			eb = path->nodes[0];
+			slot = path->slots[0];
+			btrfs_item_key_to_cpu(eb, &found_key, slot);
+		}
+		if (ret || found_key.objectid != key.objectid ||
+		    found_key.type != key.type) {
+			key.offset += right_len;
+			break;
+		}
+		if (found_key.offset != key.offset + right_len) {
+			ret = 0;
+			goto out;
+		}
+		key = found_key;
+	}
+
+	/*
+	 * We're now behind the left extent (treat as unchanged) or at the end
+	 * of the right side (treat as changed).
+	 */
+	if (key.offset >= ekey->offset + left_len)
+		ret = 1;
+	else
+		ret = 0;
+
+
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+static int get_last_extent(struct send_ctx *sctx, u64 offset)
+{
+	struct btrfs_path *path;
+	struct btrfs_root *root = sctx->send_root;
+	struct btrfs_key key;
+	int ret;
+
+	path = alloc_path_for_send();
+	if (!path)
+		return -ENOMEM;
+
+	sctx->cur_inode_last_extent = 0;
+
+	key.objectid = sctx->cur_ino;
+	key.type = BTRFS_EXTENT_DATA_KEY;
+	key.offset = offset;
+	ret = btrfs_search_slot_for_read(root, &key, path, 0, 1);
+	if (ret < 0)
+		goto out;
+	ret = 0;
+	btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
+	if (key.objectid != sctx->cur_ino || key.type != BTRFS_EXTENT_DATA_KEY)
+		goto out;
+
+	sctx->cur_inode_last_extent = btrfs_file_extent_end(path);
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+static int range_is_hole_in_parent(struct send_ctx *sctx,
+				   const u64 start,
+				   const u64 end)
+{
+	struct btrfs_path *path;
+	struct btrfs_key key;
+	struct btrfs_root *root = sctx->parent_root;
+	u64 search_start = start;
+	int ret;
+
+	path = alloc_path_for_send();
+	if (!path)
+		return -ENOMEM;
+
+	key.objectid = sctx->cur_ino;
+	key.type = BTRFS_EXTENT_DATA_KEY;
+	key.offset = search_start;
+	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+	if (ret < 0)
+		goto out;
+	if (ret > 0 && path->slots[0] > 0)
+		path->slots[0]--;
+
+	while (search_start < end) {
+		struct extent_buffer *leaf = path->nodes[0];
+		int slot = path->slots[0];
+		struct btrfs_file_extent_item *fi;
+		u64 extent_end;
+
+		if (slot >= btrfs_header_nritems(leaf)) {
+			ret = btrfs_next_leaf(root, path);
+			if (ret < 0)
+				goto out;
+			else if (ret > 0)
+				break;
+			continue;
+		}
+
+		btrfs_item_key_to_cpu(leaf, &key, slot);
+		if (key.objectid < sctx->cur_ino ||
+		    key.type < BTRFS_EXTENT_DATA_KEY)
+			goto next;
+		if (key.objectid > sctx->cur_ino ||
+		    key.type > BTRFS_EXTENT_DATA_KEY ||
+		    key.offset >= end)
+			break;
+
+		fi = btrfs_item_ptr(leaf, slot, struct btrfs_file_extent_item);
+		extent_end = btrfs_file_extent_end(path);
+		if (extent_end <= start)
+			goto next;
+		if (btrfs_file_extent_disk_bytenr(leaf, fi) == 0) {
+			search_start = extent_end;
+			goto next;
+		}
+		ret = 0;
+		goto out;
+next:
+		path->slots[0]++;
+	}
+	ret = 1;
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+static int maybe_send_hole(struct send_ctx *sctx, struct btrfs_path *path,
+			   struct btrfs_key *key)
+{
+	int ret = 0;
+
+	if (sctx->cur_ino != key->objectid || !need_send_hole(sctx))
+		return 0;
+
+	if (sctx->cur_inode_last_extent == (u64)-1) {
+		ret = get_last_extent(sctx, key->offset - 1);
+		if (ret)
+			return ret;
+	}
+
+	if (path->slots[0] == 0 &&
+	    sctx->cur_inode_last_extent < key->offset) {
+		/*
+		 * We might have skipped entire leafs that contained only
+		 * file extent items for our current inode. These leafs have
+		 * a generation number smaller (older) than the one in the
+		 * current leaf and the leaf our last extent came from, and
+		 * are located between these 2 leafs.
+		 */
+		ret = get_last_extent(sctx, key->offset - 1);
+		if (ret)
+			return ret;
+	}
+
+	if (sctx->cur_inode_last_extent < key->offset) {
+		ret = range_is_hole_in_parent(sctx,
+					      sctx->cur_inode_last_extent,
+					      key->offset);
+		if (ret < 0)
+			return ret;
+		else if (ret == 0)
+			ret = send_hole(sctx, key->offset);
+		else
+			ret = 0;
+	}
+	sctx->cur_inode_last_extent = btrfs_file_extent_end(path);
+	return ret;
+}
+
+static int process_extent(struct send_ctx *sctx,
+			  struct btrfs_path *path,
+			  struct btrfs_key *key)
+{
+	struct clone_root *found_clone = NULL;
+	int ret = 0;
+
+	if (S_ISLNK(sctx->cur_inode_mode))
+		return 0;
+
+	if (sctx->parent_root && !sctx->cur_inode_new) {
+		ret = is_extent_unchanged(sctx, path, key);
+		if (ret < 0)
+			goto out;
+		if (ret) {
+			ret = 0;
+			goto out_hole;
+		}
+	} else {
+		struct btrfs_file_extent_item *ei;
+		u8 type;
+
+		ei = btrfs_item_ptr(path->nodes[0], path->slots[0],
+				    struct btrfs_file_extent_item);
+		type = btrfs_file_extent_type(path->nodes[0], ei);
+		if (type == BTRFS_FILE_EXTENT_PREALLOC ||
+		    type == BTRFS_FILE_EXTENT_REG) {
+			/*
+			 * The send spec does not have a prealloc command yet,
+			 * so just leave a hole for prealloc'ed extents until
+			 * we have enough commands queued up to justify rev'ing
+			 * the send spec.
+			 */
+			if (type == BTRFS_FILE_EXTENT_PREALLOC) {
+				ret = 0;
+				goto out;
+			}
+
+			/* Have a hole, just skip it. */
+			if (btrfs_file_extent_disk_bytenr(path->nodes[0], ei) == 0) {
+				ret = 0;
+				goto out;
+			}
+		}
+	}
+
+	ret = find_extent_clone(sctx, path, key->objectid, key->offset,
+			sctx->cur_inode_size, &found_clone);
+	if (ret != -ENOENT && ret < 0)
+		goto out;
+
+	ret = send_write_or_clone(sctx, path, key, found_clone);
+	if (ret)
+		goto out;
+out_hole:
+	ret = maybe_send_hole(sctx, path, key);
+out:
+	return ret;
+}
+
+static int process_all_extents(struct send_ctx *sctx)
+{
+	int ret;
+	struct btrfs_root *root;
+	struct btrfs_path *path;
+	struct btrfs_key key;
+	struct btrfs_key found_key;
+	struct extent_buffer *eb;
+	int slot;
+
+	root = sctx->send_root;
+	path = alloc_path_for_send();
+	if (!path)
+		return -ENOMEM;
+
+	key.objectid = sctx->cmp_key->objectid;
+	key.type = BTRFS_EXTENT_DATA_KEY;
+	key.offset = 0;
+	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+	if (ret < 0)
+		goto out;
+
+	while (1) {
+		eb = path->nodes[0];
+		slot = path->slots[0];
+
+		if (slot >= btrfs_header_nritems(eb)) {
+			ret = btrfs_next_leaf(root, path);
+			if (ret < 0) {
+				goto out;
+			} else if (ret > 0) {
+				ret = 0;
+				break;
+			}
+			continue;
+		}
+
+		btrfs_item_key_to_cpu(eb, &found_key, slot);
+
+		if (found_key.objectid != key.objectid ||
+		    found_key.type != key.type) {
+			ret = 0;
+			goto out;
+		}
+
+		ret = process_extent(sctx, path, &found_key);
+		if (ret < 0)
+			goto out;
+
+		path->slots[0]++;
+	}
+
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+static int process_recorded_refs_if_needed(struct send_ctx *sctx, int at_end,
+					   int *pending_move,
+					   int *refs_processed)
+{
+	int ret = 0;
+
+	if (sctx->cur_ino == 0)
+		goto out;
+	if (!at_end && sctx->cur_ino == sctx->cmp_key->objectid &&
+	    sctx->cmp_key->type <= BTRFS_INODE_EXTREF_KEY)
+		goto out;
+	if (list_empty(&sctx->new_refs) && list_empty(&sctx->deleted_refs))
+		goto out;
+
+	ret = process_recorded_refs(sctx, pending_move);
+	if (ret < 0)
+		goto out;
+
+	*refs_processed = 1;
+out:
+	return ret;
+}
+
+static int finish_inode_if_needed(struct send_ctx *sctx, int at_end)
+{
+	int ret = 0;
+	u64 left_mode;
+	u64 left_uid;
+	u64 left_gid;
+	u64 right_mode;
+	u64 right_uid;
+	u64 right_gid;
+	int need_chmod = 0;
+	int need_chown = 0;
+	int need_truncate = 1;
+	int pending_move = 0;
+	int refs_processed = 0;
+
+	if (sctx->ignore_cur_inode)
+		return 0;
+
+	ret = process_recorded_refs_if_needed(sctx, at_end, &pending_move,
+					      &refs_processed);
+	if (ret < 0)
+		goto out;
+
+	/*
+	 * We have processed the refs and thus need to advance send_progress.
+	 * Now, calls to get_cur_xxx will take the updated refs of the current
+	 * inode into account.
+	 *
+	 * On the other hand, if our current inode is a directory and couldn't
+	 * be moved/renamed because its parent was renamed/moved too and it has
+	 * a higher inode number, we can only move/rename our current inode
+	 * after we moved/renamed its parent. Therefore in this case operate on
+	 * the old path (pre move/rename) of our current inode, and the
+	 * move/rename will be performed later.
+	 */
+	if (refs_processed && !pending_move)
+		sctx->send_progress = sctx->cur_ino + 1;
+
+	if (sctx->cur_ino == 0 || sctx->cur_inode_deleted)
+		goto out;
+	if (!at_end && sctx->cmp_key->objectid == sctx->cur_ino)
+		goto out;
+
+	ret = get_inode_info(sctx->send_root, sctx->cur_ino, NULL, NULL,
+			&left_mode, &left_uid, &left_gid, NULL);
+	if (ret < 0)
+		goto out;
+
+	if (!sctx->parent_root || sctx->cur_inode_new) {
+		need_chown = 1;
+		if (!S_ISLNK(sctx->cur_inode_mode))
+			need_chmod = 1;
+		if (sctx->cur_inode_next_write_offset == sctx->cur_inode_size)
+			need_truncate = 0;
+	} else {
+		u64 old_size;
+
+		ret = get_inode_info(sctx->parent_root, sctx->cur_ino,
+				&old_size, NULL, &right_mode, &right_uid,
+				&right_gid, NULL);
+		if (ret < 0)
+			goto out;
+
+		if (left_uid != right_uid || left_gid != right_gid)
+			need_chown = 1;
+		if (!S_ISLNK(sctx->cur_inode_mode) && left_mode != right_mode)
+			need_chmod = 1;
+		if ((old_size == sctx->cur_inode_size) ||
+		    (sctx->cur_inode_size > old_size &&
+		     sctx->cur_inode_next_write_offset == sctx->cur_inode_size))
+			need_truncate = 0;
+	}
+
+	if (S_ISREG(sctx->cur_inode_mode)) {
+		if (need_send_hole(sctx)) {
+			if (sctx->cur_inode_last_extent == (u64)-1 ||
+			    sctx->cur_inode_last_extent <
+			    sctx->cur_inode_size) {
+				ret = get_last_extent(sctx, (u64)-1);
+				if (ret)
+					goto out;
+			}
+			if (sctx->cur_inode_last_extent <
+			    sctx->cur_inode_size) {
+				ret = send_hole(sctx, sctx->cur_inode_size);
+				if (ret)
+					goto out;
+			}
+		}
+		if (need_truncate) {
+			ret = send_truncate(sctx, sctx->cur_ino,
+					    sctx->cur_inode_gen,
+					    sctx->cur_inode_size);
+			if (ret < 0)
+				goto out;
+		}
+	}
+
+	if (need_chown) {
+		ret = send_chown(sctx, sctx->cur_ino, sctx->cur_inode_gen,
+				left_uid, left_gid);
+		if (ret < 0)
+			goto out;
+	}
+	if (need_chmod) {
+		ret = send_chmod(sctx, sctx->cur_ino, sctx->cur_inode_gen,
+				left_mode);
+		if (ret < 0)
+			goto out;
+	}
+
+	ret = send_capabilities(sctx);
+	if (ret < 0)
+		goto out;
+
+	/*
+	 * If other directory inodes depended on our current directory
+	 * inode's move/rename, now do their move/rename operations.
+	 */
+	if (!is_waiting_for_move(sctx, sctx->cur_ino)) {
+		ret = apply_children_dir_moves(sctx);
+		if (ret)
+			goto out;
+		/*
+		 * Need to send that every time, no matter if it actually
+		 * changed between the two trees as we have done changes to
+		 * the inode before. If our inode is a directory and it's
+		 * waiting to be moved/renamed, we will send its utimes when
+		 * it's moved/renamed, therefore we don't need to do it here.
+		 */
+		sctx->send_progress = sctx->cur_ino + 1;
+		ret = send_utimes(sctx, sctx->cur_ino, sctx->cur_inode_gen);
+		if (ret < 0)
+			goto out;
+	}
+
+out:
+	return ret;
+}
+
+struct parent_paths_ctx {
+	struct list_head *refs;
+	struct send_ctx *sctx;
+};
+
+static int record_parent_ref(int num, u64 dir, int index, struct fs_path *name,
+			     void *ctx)
+{
+	struct parent_paths_ctx *ppctx = ctx;
+
+	return record_ref(ppctx->sctx->parent_root, dir, name, ppctx->sctx,
+			  ppctx->refs);
+}
+
+/*
+ * Issue unlink operations for all paths of the current inode found in the
+ * parent snapshot.
+ */
+static int btrfs_unlink_all_paths(struct send_ctx *sctx)
+{
+	LIST_HEAD(deleted_refs);
+	struct btrfs_path *path;
+	struct btrfs_key key;
+	struct parent_paths_ctx ctx;
+	int ret;
+
+	path = alloc_path_for_send();
+	if (!path)
+		return -ENOMEM;
+
+	key.objectid = sctx->cur_ino;
+	key.type = BTRFS_INODE_REF_KEY;
+	key.offset = 0;
+	ret = btrfs_search_slot(NULL, sctx->parent_root, &key, path, 0, 0);
+	if (ret < 0)
+		goto out;
+
+	ctx.refs = &deleted_refs;
+	ctx.sctx = sctx;
+
+	while (true) {
+		struct extent_buffer *eb = path->nodes[0];
+		int slot = path->slots[0];
+
+		if (slot >= btrfs_header_nritems(eb)) {
+			ret = btrfs_next_leaf(sctx->parent_root, path);
+			if (ret < 0)
+				goto out;
+			else if (ret > 0)
+				break;
+			continue;
+		}
+
+		btrfs_item_key_to_cpu(eb, &key, slot);
+		if (key.objectid != sctx->cur_ino)
+			break;
+		if (key.type != BTRFS_INODE_REF_KEY &&
+		    key.type != BTRFS_INODE_EXTREF_KEY)
+			break;
+
+		ret = iterate_inode_ref(sctx->parent_root, path, &key, 1,
+					record_parent_ref, &ctx);
+		if (ret < 0)
+			goto out;
+
+		path->slots[0]++;
+	}
+
+	while (!list_empty(&deleted_refs)) {
+		struct recorded_ref *ref;
+
+		ref = list_first_entry(&deleted_refs, struct recorded_ref, list);
+		ret = send_unlink(sctx, ref->full_path);
+		if (ret < 0)
+			goto out;
+		fs_path_free(ref->full_path);
+		list_del(&ref->list);
+		kfree(ref);
+	}
+	ret = 0;
+out:
+	btrfs_free_path(path);
+	if (ret)
+		__free_recorded_refs(&deleted_refs);
+	return ret;
+}
+
+static int changed_inode(struct send_ctx *sctx,
+			 enum btrfs_compare_tree_result result)
+{
+	int ret = 0;
+	struct btrfs_key *key = sctx->cmp_key;
+	struct btrfs_inode_item *left_ii = NULL;
+	struct btrfs_inode_item *right_ii = NULL;
+	u64 left_gen = 0;
+	u64 right_gen = 0;
+
+	sctx->cur_ino = key->objectid;
+	sctx->cur_inode_new_gen = 0;
+	sctx->cur_inode_last_extent = (u64)-1;
+	sctx->cur_inode_next_write_offset = 0;
+	sctx->ignore_cur_inode = false;
+
+	/*
+	 * Set send_progress to current inode. This will tell all get_cur_xxx
+	 * functions that the current inode's refs are not updated yet. Later,
+	 * when process_recorded_refs is finished, it is set to cur_ino + 1.
+	 */
+	sctx->send_progress = sctx->cur_ino;
+
+	if (result == BTRFS_COMPARE_TREE_NEW ||
+	    result == BTRFS_COMPARE_TREE_CHANGED) {
+		left_ii = btrfs_item_ptr(sctx->left_path->nodes[0],
+				sctx->left_path->slots[0],
+				struct btrfs_inode_item);
+		left_gen = btrfs_inode_generation(sctx->left_path->nodes[0],
+				left_ii);
+	} else {
+		right_ii = btrfs_item_ptr(sctx->right_path->nodes[0],
+				sctx->right_path->slots[0],
+				struct btrfs_inode_item);
+		right_gen = btrfs_inode_generation(sctx->right_path->nodes[0],
+				right_ii);
+	}
+	if (result == BTRFS_COMPARE_TREE_CHANGED) {
+		right_ii = btrfs_item_ptr(sctx->right_path->nodes[0],
+				sctx->right_path->slots[0],
+				struct btrfs_inode_item);
+
+		right_gen = btrfs_inode_generation(sctx->right_path->nodes[0],
+				right_ii);
+
+		/*
+		 * The cur_ino = root dir case is special here. We can't treat
+		 * the inode as deleted+reused because it would generate a
+		 * stream that tries to delete/mkdir the root dir.
+		 */
+		if (left_gen != right_gen &&
+		    sctx->cur_ino != BTRFS_FIRST_FREE_OBJECTID)
+			sctx->cur_inode_new_gen = 1;
+	}
+
+	/*
+	 * Normally we do not find inodes with a link count of zero (orphans)
+	 * because the most common case is to create a snapshot and use it
+	 * for a send operation. However other less common use cases involve
+	 * using a subvolume and send it after turning it to RO mode just
+	 * after deleting all hard links of a file while holding an open
+	 * file descriptor against it or turning a RO snapshot into RW mode,
+	 * keep an open file descriptor against a file, delete it and then
+	 * turn the snapshot back to RO mode before using it for a send
+	 * operation. So if we find such cases, ignore the inode and all its
+	 * items completely if it's a new inode, or if it's a changed inode
+	 * make sure all its previous paths (from the parent snapshot) are all
+	 * unlinked and all other the inode items are ignored.
+	 */
+	if (result == BTRFS_COMPARE_TREE_NEW ||
+	    result == BTRFS_COMPARE_TREE_CHANGED) {
+		u32 nlinks;
+
+		nlinks = btrfs_inode_nlink(sctx->left_path->nodes[0], left_ii);
+		if (nlinks == 0) {
+			sctx->ignore_cur_inode = true;
+			if (result == BTRFS_COMPARE_TREE_CHANGED)
+				ret = btrfs_unlink_all_paths(sctx);
+			goto out;
+		}
+	}
+
+	if (result == BTRFS_COMPARE_TREE_NEW) {
+		sctx->cur_inode_gen = left_gen;
+		sctx->cur_inode_new = 1;
+		sctx->cur_inode_deleted = 0;
+		sctx->cur_inode_size = btrfs_inode_size(
+				sctx->left_path->nodes[0], left_ii);
+		sctx->cur_inode_mode = btrfs_inode_mode(
+				sctx->left_path->nodes[0], left_ii);
+		sctx->cur_inode_rdev = btrfs_inode_rdev(
+				sctx->left_path->nodes[0], left_ii);
+		if (sctx->cur_ino != BTRFS_FIRST_FREE_OBJECTID)
+			ret = send_create_inode_if_needed(sctx);
+	} else if (result == BTRFS_COMPARE_TREE_DELETED) {
+		sctx->cur_inode_gen = right_gen;
+		sctx->cur_inode_new = 0;
+		sctx->cur_inode_deleted = 1;
+		sctx->cur_inode_size = btrfs_inode_size(
+				sctx->right_path->nodes[0], right_ii);
+		sctx->cur_inode_mode = btrfs_inode_mode(
+				sctx->right_path->nodes[0], right_ii);
+	} else if (result == BTRFS_COMPARE_TREE_CHANGED) {
+		/*
+		 * We need to do some special handling in case the inode was
+		 * reported as changed with a changed generation number. This
+		 * means that the original inode was deleted and new inode
+		 * reused the same inum. So we have to treat the old inode as
+		 * deleted and the new one as new.
+		 */
+		if (sctx->cur_inode_new_gen) {
+			/*
+			 * First, process the inode as if it was deleted.
+			 */
+			sctx->cur_inode_gen = right_gen;
+			sctx->cur_inode_new = 0;
+			sctx->cur_inode_deleted = 1;
+			sctx->cur_inode_size = btrfs_inode_size(
+					sctx->right_path->nodes[0], right_ii);
+			sctx->cur_inode_mode = btrfs_inode_mode(
+					sctx->right_path->nodes[0], right_ii);
+			ret = process_all_refs(sctx,
+					BTRFS_COMPARE_TREE_DELETED);
+			if (ret < 0)
+				goto out;
+
+			/*
+			 * Now process the inode as if it was new.
+			 */
+			sctx->cur_inode_gen = left_gen;
+			sctx->cur_inode_new = 1;
+			sctx->cur_inode_deleted = 0;
+			sctx->cur_inode_size = btrfs_inode_size(
+					sctx->left_path->nodes[0], left_ii);
+			sctx->cur_inode_mode = btrfs_inode_mode(
+					sctx->left_path->nodes[0], left_ii);
+			sctx->cur_inode_rdev = btrfs_inode_rdev(
+					sctx->left_path->nodes[0], left_ii);
+			ret = send_create_inode_if_needed(sctx);
+			if (ret < 0)
+				goto out;
+
+			ret = process_all_refs(sctx, BTRFS_COMPARE_TREE_NEW);
+			if (ret < 0)
+				goto out;
+			/*
+			 * Advance send_progress now as we did not get into
+			 * process_recorded_refs_if_needed in the new_gen case.
+			 */
+			sctx->send_progress = sctx->cur_ino + 1;
+
+			/*
+			 * Now process all extents and xattrs of the inode as if
+			 * they were all new.
+			 */
+			ret = process_all_extents(sctx);
+			if (ret < 0)
+				goto out;
+			ret = process_all_new_xattrs(sctx);
+			if (ret < 0)
+				goto out;
+		} else {
+			sctx->cur_inode_gen = left_gen;
+			sctx->cur_inode_new = 0;
+			sctx->cur_inode_new_gen = 0;
+			sctx->cur_inode_deleted = 0;
+			sctx->cur_inode_size = btrfs_inode_size(
+					sctx->left_path->nodes[0], left_ii);
+			sctx->cur_inode_mode = btrfs_inode_mode(
+					sctx->left_path->nodes[0], left_ii);
+		}
+	}
+
+out:
+	return ret;
+}
+
+/*
+ * We have to process new refs before deleted refs, but compare_trees gives us
+ * the new and deleted refs mixed. To fix this, we record the new/deleted refs
+ * first and later process them in process_recorded_refs.
+ * For the cur_inode_new_gen case, we skip recording completely because
+ * changed_inode did already initiate processing of refs. The reason for this is
+ * that in this case, compare_tree actually compares the refs of 2 different
+ * inodes. To fix this, process_all_refs is used in changed_inode to handle all
+ * refs of the right tree as deleted and all refs of the left tree as new.
+ */
+static int changed_ref(struct send_ctx *sctx,
+		       enum btrfs_compare_tree_result result)
+{
+	int ret = 0;
+
+	if (sctx->cur_ino != sctx->cmp_key->objectid) {
+		inconsistent_snapshot_error(sctx, result, "reference");
+		return -EIO;
+	}
+
+	if (!sctx->cur_inode_new_gen &&
+	    sctx->cur_ino != BTRFS_FIRST_FREE_OBJECTID) {
+		if (result == BTRFS_COMPARE_TREE_NEW)
+			ret = record_new_ref(sctx);
+		else if (result == BTRFS_COMPARE_TREE_DELETED)
+			ret = record_deleted_ref(sctx);
+		else if (result == BTRFS_COMPARE_TREE_CHANGED)
+			ret = record_changed_ref(sctx);
+	}
+
+	return ret;
+}
+
+/*
+ * Process new/deleted/changed xattrs. We skip processing in the
+ * cur_inode_new_gen case because changed_inode did already initiate processing
+ * of xattrs. The reason is the same as in changed_ref
+ */
+static int changed_xattr(struct send_ctx *sctx,
+			 enum btrfs_compare_tree_result result)
+{
+	int ret = 0;
+
+	if (sctx->cur_ino != sctx->cmp_key->objectid) {
+		inconsistent_snapshot_error(sctx, result, "xattr");
+		return -EIO;
+	}
+
+	if (!sctx->cur_inode_new_gen && !sctx->cur_inode_deleted) {
+		if (result == BTRFS_COMPARE_TREE_NEW)
+			ret = process_new_xattr(sctx);
+		else if (result == BTRFS_COMPARE_TREE_DELETED)
+			ret = process_deleted_xattr(sctx);
+		else if (result == BTRFS_COMPARE_TREE_CHANGED)
+			ret = process_changed_xattr(sctx);
+	}
+
+	return ret;
+}
+
+/*
+ * Process new/deleted/changed extents. We skip processing in the
+ * cur_inode_new_gen case because changed_inode did already initiate processing
+ * of extents. The reason is the same as in changed_ref
+ */
+static int changed_extent(struct send_ctx *sctx,
+			  enum btrfs_compare_tree_result result)
+{
+	int ret = 0;
+
+	/*
+	 * We have found an extent item that changed without the inode item
+	 * having changed. This can happen either after relocation (where the
+	 * disk_bytenr of an extent item is replaced at
+	 * relocation.c:replace_file_extents()) or after deduplication into a
+	 * file in both the parent and send snapshots (where an extent item can
+	 * get modified or replaced with a new one). Note that deduplication
+	 * updates the inode item, but it only changes the iversion (sequence
+	 * field in the inode item) of the inode, so if a file is deduplicated
+	 * the same amount of times in both the parent and send snapshots, its
+	 * iversion becames the same in both snapshots, whence the inode item is
+	 * the same on both snapshots.
+	 */
+	if (sctx->cur_ino != sctx->cmp_key->objectid)
+		return 0;
+
+	if (!sctx->cur_inode_new_gen && !sctx->cur_inode_deleted) {
+		if (result != BTRFS_COMPARE_TREE_DELETED)
+			ret = process_extent(sctx, sctx->left_path,
+					sctx->cmp_key);
+	}
+
+	return ret;
+}
+
+static int dir_changed(struct send_ctx *sctx, u64 dir)
+{
+	u64 orig_gen, new_gen;
+	int ret;
+
+	ret = get_inode_info(sctx->send_root, dir, NULL, &new_gen, NULL, NULL,
+			     NULL, NULL);
+	if (ret)
+		return ret;
+
+	ret = get_inode_info(sctx->parent_root, dir, NULL, &orig_gen, NULL,
+			     NULL, NULL, NULL);
+	if (ret)
+		return ret;
+
+	return (orig_gen != new_gen) ? 1 : 0;
+}
+
+static int compare_refs(struct send_ctx *sctx, struct btrfs_path *path,
+			struct btrfs_key *key)
+{
+	struct btrfs_inode_extref *extref;
+	struct extent_buffer *leaf;
+	u64 dirid = 0, last_dirid = 0;
+	unsigned long ptr;
+	u32 item_size;
+	u32 cur_offset = 0;
+	int ref_name_len;
+	int ret = 0;
+
+	/* Easy case, just check this one dirid */
+	if (key->type == BTRFS_INODE_REF_KEY) {
+		dirid = key->offset;
+
+		ret = dir_changed(sctx, dirid);
+		goto out;
+	}
+
+	leaf = path->nodes[0];
+	item_size = btrfs_item_size_nr(leaf, path->slots[0]);
+	ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
+	while (cur_offset < item_size) {
+		extref = (struct btrfs_inode_extref *)(ptr +
+						       cur_offset);
+		dirid = btrfs_inode_extref_parent(leaf, extref);
+		ref_name_len = btrfs_inode_extref_name_len(leaf, extref);
+		cur_offset += ref_name_len + sizeof(*extref);
+		if (dirid == last_dirid)
+			continue;
+		ret = dir_changed(sctx, dirid);
+		if (ret)
+			break;
+		last_dirid = dirid;
+	}
+out:
+	return ret;
+}
+
+/*
+ * Updates compare related fields in sctx and simply forwards to the actual
+ * changed_xxx functions.
+ */
+static int changed_cb(struct btrfs_path *left_path,
+		      struct btrfs_path *right_path,
+		      struct btrfs_key *key,
+		      enum btrfs_compare_tree_result result,
+		      void *ctx)
+{
+	int ret = 0;
+	struct send_ctx *sctx = ctx;
+
+	if (result == BTRFS_COMPARE_TREE_SAME) {
+		if (key->type == BTRFS_INODE_REF_KEY ||
+		    key->type == BTRFS_INODE_EXTREF_KEY) {
+			ret = compare_refs(sctx, left_path, key);
+			if (!ret)
+				return 0;
+			if (ret < 0)
+				return ret;
+		} else if (key->type == BTRFS_EXTENT_DATA_KEY) {
+			return maybe_send_hole(sctx, left_path, key);
+		} else {
+			return 0;
+		}
+		result = BTRFS_COMPARE_TREE_CHANGED;
+		ret = 0;
+	}
+
+	sctx->left_path = left_path;
+	sctx->right_path = right_path;
+	sctx->cmp_key = key;
+
+	ret = finish_inode_if_needed(sctx, 0);
+	if (ret < 0)
+		goto out;
+
+	/* Ignore non-FS objects */
+	if (key->objectid == BTRFS_FREE_INO_OBJECTID ||
+	    key->objectid == BTRFS_FREE_SPACE_OBJECTID)
+		goto out;
+
+	if (key->type == BTRFS_INODE_ITEM_KEY) {
+		ret = changed_inode(sctx, result);
+	} else if (!sctx->ignore_cur_inode) {
+		if (key->type == BTRFS_INODE_REF_KEY ||
+		    key->type == BTRFS_INODE_EXTREF_KEY)
+			ret = changed_ref(sctx, result);
+		else if (key->type == BTRFS_XATTR_ITEM_KEY)
+			ret = changed_xattr(sctx, result);
+		else if (key->type == BTRFS_EXTENT_DATA_KEY)
+			ret = changed_extent(sctx, result);
+	}
+
+out:
+	return ret;
+}
+
+static int full_send_tree(struct send_ctx *sctx)
+{
+	int ret;
+	struct btrfs_root *send_root = sctx->send_root;
+	struct btrfs_key key;
+	struct btrfs_path *path;
+	struct extent_buffer *eb;
+	int slot;
+
+	path = alloc_path_for_send();
+	if (!path)
+		return -ENOMEM;
+
+	key.objectid = BTRFS_FIRST_FREE_OBJECTID;
+	key.type = BTRFS_INODE_ITEM_KEY;
+	key.offset = 0;
+
+	ret = btrfs_search_slot_for_read(send_root, &key, path, 1, 0);
+	if (ret < 0)
+		goto out;
+	if (ret)
+		goto out_finish;
+
+	while (1) {
+		eb = path->nodes[0];
+		slot = path->slots[0];
+		btrfs_item_key_to_cpu(eb, &key, slot);
+
+		ret = changed_cb(path, NULL, &key,
+				 BTRFS_COMPARE_TREE_NEW, sctx);
+		if (ret < 0)
+			goto out;
+
+		ret = btrfs_next_item(send_root, path);
+		if (ret < 0)
+			goto out;
+		if (ret) {
+			ret  = 0;
+			break;
+		}
+	}
+
+out_finish:
+	ret = finish_inode_if_needed(sctx, 1);
+
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+static int tree_move_down(struct btrfs_path *path, int *level)
+{
+	struct extent_buffer *eb;
+
+	BUG_ON(*level == 0);
+	eb = btrfs_read_node_slot(path->nodes[*level], path->slots[*level]);
+	if (IS_ERR(eb))
+		return PTR_ERR(eb);
+
+	path->nodes[*level - 1] = eb;
+	path->slots[*level - 1] = 0;
+	(*level)--;
+	return 0;
+}
+
+static int tree_move_next_or_upnext(struct btrfs_path *path,
+				    int *level, int root_level)
+{
+	int ret = 0;
+	int nritems;
+	nritems = btrfs_header_nritems(path->nodes[*level]);
+
+	path->slots[*level]++;
+
+	while (path->slots[*level] >= nritems) {
+		if (*level == root_level)
+			return -1;
+
+		/* move upnext */
+		path->slots[*level] = 0;
+		free_extent_buffer(path->nodes[*level]);
+		path->nodes[*level] = NULL;
+		(*level)++;
+		path->slots[*level]++;
+
+		nritems = btrfs_header_nritems(path->nodes[*level]);
+		ret = 1;
+	}
+	return ret;
+}
+
+/*
+ * Returns 1 if it had to move up and next. 0 is returned if it moved only next
+ * or down.
+ */
+static int tree_advance(struct btrfs_path *path,
+			int *level, int root_level,
+			int allow_down,
+			struct btrfs_key *key)
+{
+	int ret;
+
+	if (*level == 0 || !allow_down) {
+		ret = tree_move_next_or_upnext(path, level, root_level);
+	} else {
+		ret = tree_move_down(path, level);
+	}
+	if (ret >= 0) {
+		if (*level == 0)
+			btrfs_item_key_to_cpu(path->nodes[*level], key,
+					path->slots[*level]);
+		else
+			btrfs_node_key_to_cpu(path->nodes[*level], key,
+					path->slots[*level]);
+	}
+	return ret;
+}
+
+static int tree_compare_item(struct btrfs_path *left_path,
+			     struct btrfs_path *right_path,
+			     char *tmp_buf)
+{
+	int cmp;
+	int len1, len2;
+	unsigned long off1, off2;
+
+	len1 = btrfs_item_size_nr(left_path->nodes[0], left_path->slots[0]);
+	len2 = btrfs_item_size_nr(right_path->nodes[0], right_path->slots[0]);
+	if (len1 != len2)
+		return 1;
+
+	off1 = btrfs_item_ptr_offset(left_path->nodes[0], left_path->slots[0]);
+	off2 = btrfs_item_ptr_offset(right_path->nodes[0],
+				right_path->slots[0]);
+
+	read_extent_buffer(left_path->nodes[0], tmp_buf, off1, len1);
+
+	cmp = memcmp_extent_buffer(right_path->nodes[0], tmp_buf, off2, len1);
+	if (cmp)
+		return 1;
+	return 0;
+}
+
+/*
+ * This function compares two trees and calls the provided callback for
+ * every changed/new/deleted item it finds.
+ * If shared tree blocks are encountered, whole subtrees are skipped, making
+ * the compare pretty fast on snapshotted subvolumes.
+ *
+ * This currently works on commit roots only. As commit roots are read only,
+ * we don't do any locking. The commit roots are protected with transactions.
+ * Transactions are ended and rejoined when a commit is tried in between.
+ *
+ * This function checks for modifications done to the trees while comparing.
+ * If it detects a change, it aborts immediately.
+ */
+static int btrfs_compare_trees(struct btrfs_root *left_root,
+			struct btrfs_root *right_root, void *ctx)
+{
+	struct btrfs_fs_info *fs_info = left_root->fs_info;
+	int ret;
+	int cmp;
+	struct btrfs_path *left_path = NULL;
+	struct btrfs_path *right_path = NULL;
+	struct btrfs_key left_key;
+	struct btrfs_key right_key;
+	char *tmp_buf = NULL;
+	int left_root_level;
+	int right_root_level;
+	int left_level;
+	int right_level;
+	int left_end_reached;
+	int right_end_reached;
+	int advance_left;
+	int advance_right;
+	u64 left_blockptr;
+	u64 right_blockptr;
+	u64 left_gen;
+	u64 right_gen;
+
+	left_path = btrfs_alloc_path();
+	if (!left_path) {
+		ret = -ENOMEM;
+		goto out;
+	}
+	right_path = btrfs_alloc_path();
+	if (!right_path) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	tmp_buf = kvmalloc(fs_info->nodesize, GFP_KERNEL);
+	if (!tmp_buf) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	left_path->search_commit_root = 1;
+	left_path->skip_locking = 1;
+	right_path->search_commit_root = 1;
+	right_path->skip_locking = 1;
+
+	/*
+	 * Strategy: Go to the first items of both trees. Then do
+	 *
+	 * If both trees are at level 0
+	 *   Compare keys of current items
+	 *     If left < right treat left item as new, advance left tree
+	 *       and repeat
+	 *     If left > right treat right item as deleted, advance right tree
+	 *       and repeat
+	 *     If left == right do deep compare of items, treat as changed if
+	 *       needed, advance both trees and repeat
+	 * If both trees are at the same level but not at level 0
+	 *   Compare keys of current nodes/leafs
+	 *     If left < right advance left tree and repeat
+	 *     If left > right advance right tree and repeat
+	 *     If left == right compare blockptrs of the next nodes/leafs
+	 *       If they match advance both trees but stay at the same level
+	 *         and repeat
+	 *       If they don't match advance both trees while allowing to go
+	 *         deeper and repeat
+	 * If tree levels are different
+	 *   Advance the tree that needs it and repeat
+	 *
+	 * Advancing a tree means:
+	 *   If we are at level 0, try to go to the next slot. If that's not
+	 *   possible, go one level up and repeat. Stop when we found a level
+	 *   where we could go to the next slot. We may at this point be on a
+	 *   node or a leaf.
+	 *
+	 *   If we are not at level 0 and not on shared tree blocks, go one
+	 *   level deeper.
+	 *
+	 *   If we are not at level 0 and on shared tree blocks, go one slot to
+	 *   the right if possible or go up and right.
+	 */
+
+	down_read(&fs_info->commit_root_sem);
+	left_level = btrfs_header_level(left_root->commit_root);
+	left_root_level = left_level;
+	left_path->nodes[left_level] =
+			btrfs_clone_extent_buffer(left_root->commit_root);
+	if (!left_path->nodes[left_level]) {
+		up_read(&fs_info->commit_root_sem);
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	right_level = btrfs_header_level(right_root->commit_root);
+	right_root_level = right_level;
+	right_path->nodes[right_level] =
+			btrfs_clone_extent_buffer(right_root->commit_root);
+	if (!right_path->nodes[right_level]) {
+		up_read(&fs_info->commit_root_sem);
+		ret = -ENOMEM;
+		goto out;
+	}
+	up_read(&fs_info->commit_root_sem);
+
+	if (left_level == 0)
+		btrfs_item_key_to_cpu(left_path->nodes[left_level],
+				&left_key, left_path->slots[left_level]);
+	else
+		btrfs_node_key_to_cpu(left_path->nodes[left_level],
+				&left_key, left_path->slots[left_level]);
+	if (right_level == 0)
+		btrfs_item_key_to_cpu(right_path->nodes[right_level],
+				&right_key, right_path->slots[right_level]);
+	else
+		btrfs_node_key_to_cpu(right_path->nodes[right_level],
+				&right_key, right_path->slots[right_level]);
+
+	left_end_reached = right_end_reached = 0;
+	advance_left = advance_right = 0;
+
+	while (1) {
+		cond_resched();
+		if (advance_left && !left_end_reached) {
+			ret = tree_advance(left_path, &left_level,
+					left_root_level,
+					advance_left != ADVANCE_ONLY_NEXT,
+					&left_key);
+			if (ret == -1)
+				left_end_reached = ADVANCE;
+			else if (ret < 0)
+				goto out;
+			advance_left = 0;
+		}
+		if (advance_right && !right_end_reached) {
+			ret = tree_advance(right_path, &right_level,
+					right_root_level,
+					advance_right != ADVANCE_ONLY_NEXT,
+					&right_key);
+			if (ret == -1)
+				right_end_reached = ADVANCE;
+			else if (ret < 0)
+				goto out;
+			advance_right = 0;
+		}
+
+		if (left_end_reached && right_end_reached) {
+			ret = 0;
+			goto out;
+		} else if (left_end_reached) {
+			if (right_level == 0) {
+				ret = changed_cb(left_path, right_path,
+						&right_key,
+						BTRFS_COMPARE_TREE_DELETED,
+						ctx);
+				if (ret < 0)
+					goto out;
+			}
+			advance_right = ADVANCE;
+			continue;
+		} else if (right_end_reached) {
+			if (left_level == 0) {
+				ret = changed_cb(left_path, right_path,
+						&left_key,
+						BTRFS_COMPARE_TREE_NEW,
+						ctx);
+				if (ret < 0)
+					goto out;
+			}
+			advance_left = ADVANCE;
+			continue;
+		}
+
+		if (left_level == 0 && right_level == 0) {
+			cmp = btrfs_comp_cpu_keys(&left_key, &right_key);
+			if (cmp < 0) {
+				ret = changed_cb(left_path, right_path,
+						&left_key,
+						BTRFS_COMPARE_TREE_NEW,
+						ctx);
+				if (ret < 0)
+					goto out;
+				advance_left = ADVANCE;
+			} else if (cmp > 0) {
+				ret = changed_cb(left_path, right_path,
+						&right_key,
+						BTRFS_COMPARE_TREE_DELETED,
+						ctx);
+				if (ret < 0)
+					goto out;
+				advance_right = ADVANCE;
+			} else {
+				enum btrfs_compare_tree_result result;
+
+				WARN_ON(!extent_buffer_uptodate(left_path->nodes[0]));
+				ret = tree_compare_item(left_path, right_path,
+							tmp_buf);
+				if (ret)
+					result = BTRFS_COMPARE_TREE_CHANGED;
+				else
+					result = BTRFS_COMPARE_TREE_SAME;
+				ret = changed_cb(left_path, right_path,
+						 &left_key, result, ctx);
+				if (ret < 0)
+					goto out;
+				advance_left = ADVANCE;
+				advance_right = ADVANCE;
+			}
+		} else if (left_level == right_level) {
+			cmp = btrfs_comp_cpu_keys(&left_key, &right_key);
+			if (cmp < 0) {
+				advance_left = ADVANCE;
+			} else if (cmp > 0) {
+				advance_right = ADVANCE;
+			} else {
+				left_blockptr = btrfs_node_blockptr(
+						left_path->nodes[left_level],
+						left_path->slots[left_level]);
+				right_blockptr = btrfs_node_blockptr(
+						right_path->nodes[right_level],
+						right_path->slots[right_level]);
+				left_gen = btrfs_node_ptr_generation(
+						left_path->nodes[left_level],
+						left_path->slots[left_level]);
+				right_gen = btrfs_node_ptr_generation(
+						right_path->nodes[right_level],
+						right_path->slots[right_level]);
+				if (left_blockptr == right_blockptr &&
+				    left_gen == right_gen) {
+					/*
+					 * As we're on a shared block, don't
+					 * allow to go deeper.
+					 */
+					advance_left = ADVANCE_ONLY_NEXT;
+					advance_right = ADVANCE_ONLY_NEXT;
+				} else {
+					advance_left = ADVANCE;
+					advance_right = ADVANCE;
+				}
+			}
+		} else if (left_level < right_level) {
+			advance_right = ADVANCE;
+		} else {
+			advance_left = ADVANCE;
+		}
+	}
+
+out:
+	btrfs_free_path(left_path);
+	btrfs_free_path(right_path);
+	kvfree(tmp_buf);
+	return ret;
+}
+
+static int send_subvol(struct send_ctx *sctx)
+{
+	int ret;
+
+	if (!(sctx->flags & BTRFS_SEND_FLAG_OMIT_STREAM_HEADER)) {
+		ret = send_header(sctx);
+		if (ret < 0)
+			goto out;
+	}
+
+	ret = send_subvol_begin(sctx);
+	if (ret < 0)
+		goto out;
+
+	if (sctx->parent_root) {
+		ret = btrfs_compare_trees(sctx->send_root, sctx->parent_root, sctx);
+		if (ret < 0)
+			goto out;
+		ret = finish_inode_if_needed(sctx, 1);
+		if (ret < 0)
+			goto out;
+	} else {
+		ret = full_send_tree(sctx);
+		if (ret < 0)
+			goto out;
+	}
+
+out:
+	free_recorded_refs(sctx);
+	return ret;
+}
+
+/*
+ * If orphan cleanup did remove any orphans from a root, it means the tree
+ * was modified and therefore the commit root is not the same as the current
+ * root anymore. This is a problem, because send uses the commit root and
+ * therefore can see inode items that don't exist in the current root anymore,
+ * and for example make calls to btrfs_iget, which will do tree lookups based
+ * on the current root and not on the commit root. Those lookups will fail,
+ * returning a -ESTALE error, and making send fail with that error. So make
+ * sure a send does not see any orphans we have just removed, and that it will
+ * see the same inodes regardless of whether a transaction commit happened
+ * before it started (meaning that the commit root will be the same as the
+ * current root) or not.
+ */
+static int ensure_commit_roots_uptodate(struct send_ctx *sctx)
+{
+	int i;
+	struct btrfs_trans_handle *trans = NULL;
+
+again:
+	if (sctx->parent_root &&
+	    sctx->parent_root->node != sctx->parent_root->commit_root)
+		goto commit_trans;
+
+	for (i = 0; i < sctx->clone_roots_cnt; i++)
+		if (sctx->clone_roots[i].root->node !=
+		    sctx->clone_roots[i].root->commit_root)
+			goto commit_trans;
+
+	if (trans)
+		return btrfs_end_transaction(trans);
+
+	return 0;
+
+commit_trans:
+	/* Use any root, all fs roots will get their commit roots updated. */
+	if (!trans) {
+		trans = btrfs_join_transaction(sctx->send_root);
+		if (IS_ERR(trans))
+			return PTR_ERR(trans);
+		goto again;
+	}
+
+	return btrfs_commit_transaction(trans);
+}
+
+/*
+ * Make sure any existing dellaloc is flushed for any root used by a send
+ * operation so that we do not miss any data and we do not race with writeback
+ * finishing and changing a tree while send is using the tree. This could
+ * happen if a subvolume is in RW mode, has delalloc, is turned to RO mode and
+ * a send operation then uses the subvolume.
+ * After flushing delalloc ensure_commit_roots_uptodate() must be called.
+ */
+static int flush_delalloc_roots(struct send_ctx *sctx)
+{
+	struct btrfs_root *root = sctx->parent_root;
+	int ret;
+	int i;
+
+	if (root) {
+		ret = btrfs_start_delalloc_snapshot(root);
+		if (ret)
+			return ret;
+		btrfs_wait_ordered_extents(root, U64_MAX, 0, U64_MAX);
+	}
+
+	for (i = 0; i < sctx->clone_roots_cnt; i++) {
+		root = sctx->clone_roots[i].root;
+		ret = btrfs_start_delalloc_snapshot(root);
+		if (ret)
+			return ret;
+		btrfs_wait_ordered_extents(root, U64_MAX, 0, U64_MAX);
+	}
+
+	return 0;
+}
+
+static void btrfs_root_dec_send_in_progress(struct btrfs_root* root)
+{
+	spin_lock(&root->root_item_lock);
+	root->send_in_progress--;
+	/*
+	 * Not much left to do, we don't know why it's unbalanced and
+	 * can't blindly reset it to 0.
+	 */
+	if (root->send_in_progress < 0)
+		btrfs_err(root->fs_info,
+			  "send_in_progress unbalanced %d root %llu",
+			  root->send_in_progress, root->root_key.objectid);
+	spin_unlock(&root->root_item_lock);
+}
+
+static void dedupe_in_progress_warn(const struct btrfs_root *root)
+{
+	btrfs_warn_rl(root->fs_info,
+"cannot use root %llu for send while deduplications on it are in progress (%d in progress)",
+		      root->root_key.objectid, root->dedupe_in_progress);
+}
+
+long btrfs_ioctl_send(struct file *mnt_file, struct btrfs_ioctl_send_args *arg)
+{
+	int ret = 0;
+	struct btrfs_root *send_root = BTRFS_I(file_inode(mnt_file))->root;
+	struct btrfs_fs_info *fs_info = send_root->fs_info;
+	struct btrfs_root *clone_root;
+	struct send_ctx *sctx = NULL;
+	u32 i;
+	u64 *clone_sources_tmp = NULL;
+	int clone_sources_to_rollback = 0;
+	size_t alloc_size;
+	int sort_clone_roots = 0;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	/*
+	 * The subvolume must remain read-only during send, protect against
+	 * making it RW. This also protects against deletion.
+	 */
+	spin_lock(&send_root->root_item_lock);
+	if (btrfs_root_readonly(send_root) && send_root->dedupe_in_progress) {
+		dedupe_in_progress_warn(send_root);
+		spin_unlock(&send_root->root_item_lock);
+		return -EAGAIN;
+	}
+	send_root->send_in_progress++;
+	spin_unlock(&send_root->root_item_lock);
+
+	/*
+	 * Userspace tools do the checks and warn the user if it's
+	 * not RO.
+	 */
+	if (!btrfs_root_readonly(send_root)) {
+		ret = -EPERM;
+		goto out;
+	}
+
+	/*
+	 * Check that we don't overflow at later allocations, we request
+	 * clone_sources_count + 1 items, and compare to unsigned long inside
+	 * access_ok. Also set an upper limit for allocation size so this can't
+	 * easily exhaust memory. Max number of clone sources is about 200K.
+	 */
+	if (arg->clone_sources_count > SZ_8M / sizeof(struct clone_root)) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	if (arg->flags & ~BTRFS_SEND_FLAG_MASK) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	sctx = kzalloc(sizeof(struct send_ctx), GFP_KERNEL);
+	if (!sctx) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	INIT_LIST_HEAD(&sctx->new_refs);
+	INIT_LIST_HEAD(&sctx->deleted_refs);
+	INIT_RADIX_TREE(&sctx->name_cache, GFP_KERNEL);
+	INIT_LIST_HEAD(&sctx->name_cache_list);
+
+	sctx->flags = arg->flags;
+
+	sctx->send_filp = fget(arg->send_fd);
+	if (!sctx->send_filp || !(sctx->send_filp->f_mode & FMODE_WRITE)) {
+		ret = -EBADF;
+		goto out;
+	}
+
+	sctx->send_root = send_root;
+	/*
+	 * Unlikely but possible, if the subvolume is marked for deletion but
+	 * is slow to remove the directory entry, send can still be started
+	 */
+	if (btrfs_root_dead(sctx->send_root)) {
+		ret = -EPERM;
+		goto out;
+	}
+
+	sctx->clone_roots_cnt = arg->clone_sources_count;
+
+	sctx->send_max_size = BTRFS_SEND_BUF_SIZE;
+	sctx->send_buf = kvmalloc(sctx->send_max_size, GFP_KERNEL);
+	if (!sctx->send_buf) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	sctx->pending_dir_moves = RB_ROOT;
+	sctx->waiting_dir_moves = RB_ROOT;
+	sctx->orphan_dirs = RB_ROOT;
+
+	sctx->clone_roots = kvcalloc(sizeof(*sctx->clone_roots),
+				     arg->clone_sources_count + 1,
+				     GFP_KERNEL);
+	if (!sctx->clone_roots) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	alloc_size = array_size(sizeof(*arg->clone_sources),
+				arg->clone_sources_count);
+
+	if (arg->clone_sources_count) {
+		clone_sources_tmp = kvmalloc(alloc_size, GFP_KERNEL);
+		if (!clone_sources_tmp) {
+			ret = -ENOMEM;
+			goto out;
+		}
+
+		ret = copy_from_user(clone_sources_tmp, arg->clone_sources,
+				alloc_size);
+		if (ret) {
+			ret = -EFAULT;
+			goto out;
+		}
+
+		for (i = 0; i < arg->clone_sources_count; i++) {
+			clone_root = btrfs_get_fs_root(fs_info,
+						clone_sources_tmp[i], true);
+			if (IS_ERR(clone_root)) {
+				ret = PTR_ERR(clone_root);
+				goto out;
+			}
+			spin_lock(&clone_root->root_item_lock);
+			if (!btrfs_root_readonly(clone_root) ||
+			    btrfs_root_dead(clone_root)) {
+				spin_unlock(&clone_root->root_item_lock);
+				btrfs_put_root(clone_root);
+				ret = -EPERM;
+				goto out;
+			}
+			if (clone_root->dedupe_in_progress) {
+				dedupe_in_progress_warn(clone_root);
+				spin_unlock(&clone_root->root_item_lock);
+				btrfs_put_root(clone_root);
+				ret = -EAGAIN;
+				goto out;
+			}
+			clone_root->send_in_progress++;
+			spin_unlock(&clone_root->root_item_lock);
+
+			sctx->clone_roots[i].root = clone_root;
+			clone_sources_to_rollback = i + 1;
+		}
+		kvfree(clone_sources_tmp);
+		clone_sources_tmp = NULL;
+	}
+
+	if (arg->parent_root) {
+		sctx->parent_root = btrfs_get_fs_root(fs_info, arg->parent_root,
+						      true);
+		if (IS_ERR(sctx->parent_root)) {
+			ret = PTR_ERR(sctx->parent_root);
+			goto out;
+		}
+
+		spin_lock(&sctx->parent_root->root_item_lock);
+		sctx->parent_root->send_in_progress++;
+		if (!btrfs_root_readonly(sctx->parent_root) ||
+				btrfs_root_dead(sctx->parent_root)) {
+			spin_unlock(&sctx->parent_root->root_item_lock);
+			ret = -EPERM;
+			goto out;
+		}
+		if (sctx->parent_root->dedupe_in_progress) {
+			dedupe_in_progress_warn(sctx->parent_root);
+			spin_unlock(&sctx->parent_root->root_item_lock);
+			ret = -EAGAIN;
+			goto out;
+		}
+		spin_unlock(&sctx->parent_root->root_item_lock);
+	}
+
+	/*
+	 * Clones from send_root are allowed, but only if the clone source
+	 * is behind the current send position. This is checked while searching
+	 * for possible clone sources.
+	 */
+	sctx->clone_roots[sctx->clone_roots_cnt++].root =
+		btrfs_grab_root(sctx->send_root);
+
+	/* We do a bsearch later */
+	sort(sctx->clone_roots, sctx->clone_roots_cnt,
+			sizeof(*sctx->clone_roots), __clone_root_cmp_sort,
+			NULL);
+	sort_clone_roots = 1;
+
+	ret = flush_delalloc_roots(sctx);
+	if (ret)
+		goto out;
+
+	ret = ensure_commit_roots_uptodate(sctx);
+	if (ret)
+		goto out;
+
+	mutex_lock(&fs_info->balance_mutex);
+	if (test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags)) {
+		mutex_unlock(&fs_info->balance_mutex);
+		btrfs_warn_rl(fs_info,
+		"cannot run send because a balance operation is in progress");
+		ret = -EAGAIN;
+		goto out;
+	}
+	fs_info->send_in_progress++;
+	mutex_unlock(&fs_info->balance_mutex);
+
+	current->journal_info = BTRFS_SEND_TRANS_STUB;
+	ret = send_subvol(sctx);
+	current->journal_info = NULL;
+	mutex_lock(&fs_info->balance_mutex);
+	fs_info->send_in_progress--;
+	mutex_unlock(&fs_info->balance_mutex);
+	if (ret < 0)
+		goto out;
+
+	if (!(sctx->flags & BTRFS_SEND_FLAG_OMIT_END_CMD)) {
+		ret = begin_cmd(sctx, BTRFS_SEND_C_END);
+		if (ret < 0)
+			goto out;
+		ret = send_cmd(sctx);
+		if (ret < 0)
+			goto out;
+	}
+
+out:
+	WARN_ON(sctx && !ret && !RB_EMPTY_ROOT(&sctx->pending_dir_moves));
+	while (sctx && !RB_EMPTY_ROOT(&sctx->pending_dir_moves)) {
+		struct rb_node *n;
+		struct pending_dir_move *pm;
+
+		n = rb_first(&sctx->pending_dir_moves);
+		pm = rb_entry(n, struct pending_dir_move, node);
+		while (!list_empty(&pm->list)) {
+			struct pending_dir_move *pm2;
+
+			pm2 = list_first_entry(&pm->list,
+					       struct pending_dir_move, list);
+			free_pending_move(sctx, pm2);
+		}
+		free_pending_move(sctx, pm);
+	}
+
+	WARN_ON(sctx && !ret && !RB_EMPTY_ROOT(&sctx->waiting_dir_moves));
+	while (sctx && !RB_EMPTY_ROOT(&sctx->waiting_dir_moves)) {
+		struct rb_node *n;
+		struct waiting_dir_move *dm;
+
+		n = rb_first(&sctx->waiting_dir_moves);
+		dm = rb_entry(n, struct waiting_dir_move, node);
+		rb_erase(&dm->node, &sctx->waiting_dir_moves);
+		kfree(dm);
+	}
+
+	WARN_ON(sctx && !ret && !RB_EMPTY_ROOT(&sctx->orphan_dirs));
+	while (sctx && !RB_EMPTY_ROOT(&sctx->orphan_dirs)) {
+		struct rb_node *n;
+		struct orphan_dir_info *odi;
+
+		n = rb_first(&sctx->orphan_dirs);
+		odi = rb_entry(n, struct orphan_dir_info, node);
+		free_orphan_dir_info(sctx, odi);
+	}
+
+	if (sort_clone_roots) {
+		for (i = 0; i < sctx->clone_roots_cnt; i++) {
+			btrfs_root_dec_send_in_progress(
+					sctx->clone_roots[i].root);
+			btrfs_put_root(sctx->clone_roots[i].root);
+		}
+	} else {
+		for (i = 0; sctx && i < clone_sources_to_rollback; i++) {
+			btrfs_root_dec_send_in_progress(
+					sctx->clone_roots[i].root);
+			btrfs_put_root(sctx->clone_roots[i].root);
+		}
+
+		btrfs_root_dec_send_in_progress(send_root);
+	}
+	if (sctx && !IS_ERR_OR_NULL(sctx->parent_root)) {
+		btrfs_root_dec_send_in_progress(sctx->parent_root);
+		btrfs_put_root(sctx->parent_root);
+	}
+
+	kvfree(clone_sources_tmp);
+
+	if (sctx) {
+		if (sctx->send_filp)
+			fput(sctx->send_filp);
+
+		kvfree(sctx->clone_roots);
+		kvfree(sctx->send_buf);
+
+		name_cache_free(sctx);
+
+		kfree(sctx);
+	}
+
+	return ret;
+}