Adding upstream version 6.6.15.upstream/6.6.15

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

1 files changed, 935 insertions, 0 deletions

diff --git a/fs/btrfs/reflink.c b/fs/btrfs/reflink.c
new file mode 100644
index 0000000000..65d2bd6910
--- /dev/null
+++ b/fs/btrfs/reflink.c
@@ -0,0 +1,935 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/blkdev.h>
+#include <linux/iversion.h>
+#include "ctree.h"
+#include "fs.h"
+#include "messages.h"
+#include "compression.h"
+#include "delalloc-space.h"
+#include "disk-io.h"
+#include "reflink.h"
+#include "transaction.h"
+#include "subpage.h"
+#include "accessors.h"
+#include "file-item.h"
+#include "file.h"
+#include "super.h"
+
+#define BTRFS_MAX_DEDUPE_LEN	SZ_16M
+
+static int clone_finish_inode_update(struct btrfs_trans_handle *trans,
+				     struct inode *inode,
+				     u64 endoff,
+				     const u64 destoff,
+				     const u64 olen,
+				     int no_time_update)
+{
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+	int ret;
+
+	inode_inc_iversion(inode);
+	if (!no_time_update) {
+		inode->i_mtime = inode_set_ctime_current(inode);
+	}
+	/*
+	 * We round up to the block size at eof when determining which
+	 * extents to clone above, but shouldn't round up the file size.
+	 */
+	if (endoff > destoff + olen)
+		endoff = destoff + olen;
+	if (endoff > inode->i_size) {
+		i_size_write(inode, endoff);
+		btrfs_inode_safe_disk_i_size_write(BTRFS_I(inode), 0);
+	}
+
+	ret = btrfs_update_inode(trans, root, BTRFS_I(inode));
+	if (ret) {
+		btrfs_abort_transaction(trans, ret);
+		btrfs_end_transaction(trans);
+		goto out;
+	}
+	ret = btrfs_end_transaction(trans);
+out:
+	return ret;
+}
+
+static int copy_inline_to_page(struct btrfs_inode *inode,
+			       const u64 file_offset,
+			       char *inline_data,
+			       const u64 size,
+			       const u64 datal,
+			       const u8 comp_type)
+{
+	struct btrfs_fs_info *fs_info = inode->root->fs_info;
+	const u32 block_size = fs_info->sectorsize;
+	const u64 range_end = file_offset + block_size - 1;
+	const size_t inline_size = size - btrfs_file_extent_calc_inline_size(0);
+	char *data_start = inline_data + btrfs_file_extent_calc_inline_size(0);
+	struct extent_changeset *data_reserved = NULL;
+	struct page *page = NULL;
+	struct address_space *mapping = inode->vfs_inode.i_mapping;
+	int ret;
+
+	ASSERT(IS_ALIGNED(file_offset, block_size));
+
+	/*
+	 * We have flushed and locked the ranges of the source and destination
+	 * inodes, we also have locked the inodes, so we are safe to do a
+	 * reservation here. Also we must not do the reservation while holding
+	 * a transaction open, otherwise we would deadlock.
+	 */
+	ret = btrfs_delalloc_reserve_space(inode, &data_reserved, file_offset,
+					   block_size);
+	if (ret)
+		goto out;
+
+	page = find_or_create_page(mapping, file_offset >> PAGE_SHIFT,
+				   btrfs_alloc_write_mask(mapping));
+	if (!page) {
+		ret = -ENOMEM;
+		goto out_unlock;
+	}
+
+	ret = set_page_extent_mapped(page);
+	if (ret < 0)
+		goto out_unlock;
+
+	clear_extent_bit(&inode->io_tree, file_offset, range_end,
+			 EXTENT_DELALLOC | EXTENT_DO_ACCOUNTING | EXTENT_DEFRAG,
+			 NULL);
+	ret = btrfs_set_extent_delalloc(inode, file_offset, range_end, 0, NULL);
+	if (ret)
+		goto out_unlock;
+
+	/*
+	 * After dirtying the page our caller will need to start a transaction,
+	 * and if we are low on metadata free space, that can cause flushing of
+	 * delalloc for all inodes in order to get metadata space released.
+	 * However we are holding the range locked for the whole duration of
+	 * the clone/dedupe operation, so we may deadlock if that happens and no
+	 * other task releases enough space. So mark this inode as not being
+	 * possible to flush to avoid such deadlock. We will clear that flag
+	 * when we finish cloning all extents, since a transaction is started
+	 * after finding each extent to clone.
+	 */
+	set_bit(BTRFS_INODE_NO_DELALLOC_FLUSH, &inode->runtime_flags);
+
+	if (comp_type == BTRFS_COMPRESS_NONE) {
+		memcpy_to_page(page, offset_in_page(file_offset), data_start,
+			       datal);
+	} else {
+		ret = btrfs_decompress(comp_type, data_start, page,
+				       offset_in_page(file_offset),
+				       inline_size, datal);
+		if (ret)
+			goto out_unlock;
+		flush_dcache_page(page);
+	}
+
+	/*
+	 * If our inline data is smaller then the block/page size, then the
+	 * remaining of the block/page is equivalent to zeroes. We had something
+	 * like the following done:
+	 *
+	 * $ xfs_io -f -c "pwrite -S 0xab 0 500" file
+	 * $ sync  # (or fsync)
+	 * $ xfs_io -c "falloc 0 4K" file
+	 * $ xfs_io -c "pwrite -S 0xcd 4K 4K"
+	 *
+	 * So what's in the range [500, 4095] corresponds to zeroes.
+	 */
+	if (datal < block_size)
+		memzero_page(page, datal, block_size - datal);
+
+	btrfs_page_set_uptodate(fs_info, page, file_offset, block_size);
+	btrfs_page_clear_checked(fs_info, page, file_offset, block_size);
+	btrfs_page_set_dirty(fs_info, page, file_offset, block_size);
+out_unlock:
+	if (page) {
+		unlock_page(page);
+		put_page(page);
+	}
+	if (ret)
+		btrfs_delalloc_release_space(inode, data_reserved, file_offset,
+					     block_size, true);
+	btrfs_delalloc_release_extents(inode, block_size);
+out:
+	extent_changeset_free(data_reserved);
+
+	return ret;
+}
+
+/*
+ * Deal with cloning of inline extents. We try to copy the inline extent from
+ * the source inode to destination inode when possible. When not possible we
+ * copy the inline extent's data into the respective page of the inode.
+ */
+static int clone_copy_inline_extent(struct inode *dst,
+				    struct btrfs_path *path,
+				    struct btrfs_key *new_key,
+				    const u64 drop_start,
+				    const u64 datal,
+				    const u64 size,
+				    const u8 comp_type,
+				    char *inline_data,
+				    struct btrfs_trans_handle **trans_out)
+{
+	struct btrfs_fs_info *fs_info = btrfs_sb(dst->i_sb);
+	struct btrfs_root *root = BTRFS_I(dst)->root;
+	const u64 aligned_end = ALIGN(new_key->offset + datal,
+				      fs_info->sectorsize);
+	struct btrfs_trans_handle *trans = NULL;
+	struct btrfs_drop_extents_args drop_args = { 0 };
+	int ret;
+	struct btrfs_key key;
+
+	if (new_key->offset > 0) {
+		ret = copy_inline_to_page(BTRFS_I(dst), new_key->offset,
+					  inline_data, size, datal, comp_type);
+		goto out;
+	}
+
+	key.objectid = btrfs_ino(BTRFS_I(dst));
+	key.type = BTRFS_EXTENT_DATA_KEY;
+	key.offset = 0;
+	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+	if (ret < 0) {
+		return ret;
+	} else if (ret > 0) {
+		if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) {
+			ret = btrfs_next_leaf(root, path);
+			if (ret < 0)
+				return ret;
+			else if (ret > 0)
+				goto copy_inline_extent;
+		}
+		btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
+		if (key.objectid == btrfs_ino(BTRFS_I(dst)) &&
+		    key.type == BTRFS_EXTENT_DATA_KEY) {
+			/*
+			 * There's an implicit hole at file offset 0, copy the
+			 * inline extent's data to the page.
+			 */
+			ASSERT(key.offset > 0);
+			goto copy_to_page;
+		}
+	} else if (i_size_read(dst) <= datal) {
+		struct btrfs_file_extent_item *ei;
+
+		ei = btrfs_item_ptr(path->nodes[0], path->slots[0],
+				    struct btrfs_file_extent_item);
+		/*
+		 * If it's an inline extent replace it with the source inline
+		 * extent, otherwise copy the source inline extent data into
+		 * the respective page at the destination inode.
+		 */
+		if (btrfs_file_extent_type(path->nodes[0], ei) ==
+		    BTRFS_FILE_EXTENT_INLINE)
+			goto copy_inline_extent;
+
+		goto copy_to_page;
+	}
+
+copy_inline_extent:
+	/*
+	 * We have no extent items, or we have an extent at offset 0 which may
+	 * or may not be inlined. All these cases are dealt the same way.
+	 */
+	if (i_size_read(dst) > datal) {
+		/*
+		 * At the destination offset 0 we have either a hole, a regular
+		 * extent or an inline extent larger then the one we want to
+		 * clone. Deal with all these cases by copying the inline extent
+		 * data into the respective page at the destination inode.
+		 */
+		goto copy_to_page;
+	}
+
+	/*
+	 * Release path before starting a new transaction so we don't hold locks
+	 * that would confuse lockdep.
+	 */
+	btrfs_release_path(path);
+	/*
+	 * If we end up here it means were copy the inline extent into a leaf
+	 * of the destination inode. We know we will drop or adjust at most one
+	 * extent item in the destination root.
+	 *
+	 * 1 unit - adjusting old extent (we may have to split it)
+	 * 1 unit - add new extent
+	 * 1 unit - inode update
+	 */
+	trans = btrfs_start_transaction(root, 3);
+	if (IS_ERR(trans)) {
+		ret = PTR_ERR(trans);
+		trans = NULL;
+		goto out;
+	}
+	drop_args.path = path;
+	drop_args.start = drop_start;
+	drop_args.end = aligned_end;
+	drop_args.drop_cache = true;
+	ret = btrfs_drop_extents(trans, root, BTRFS_I(dst), &drop_args);
+	if (ret)
+		goto out;
+	ret = btrfs_insert_empty_item(trans, root, path, new_key, size);
+	if (ret)
+		goto out;
+
+	write_extent_buffer(path->nodes[0], inline_data,
+			    btrfs_item_ptr_offset(path->nodes[0],
+						  path->slots[0]),
+			    size);
+	btrfs_update_inode_bytes(BTRFS_I(dst), datal, drop_args.bytes_found);
+	btrfs_set_inode_full_sync(BTRFS_I(dst));
+	ret = btrfs_inode_set_file_extent_range(BTRFS_I(dst), 0, aligned_end);
+out:
+	if (!ret && !trans) {
+		/*
+		 * No transaction here means we copied the inline extent into a
+		 * page of the destination inode.
+		 *
+		 * 1 unit to update inode item
+		 */
+		trans = btrfs_start_transaction(root, 1);
+		if (IS_ERR(trans)) {
+			ret = PTR_ERR(trans);
+			trans = NULL;
+		}
+	}
+	if (ret && trans) {
+		btrfs_abort_transaction(trans, ret);
+		btrfs_end_transaction(trans);
+	}
+	if (!ret)
+		*trans_out = trans;
+
+	return ret;
+
+copy_to_page:
+	/*
+	 * Release our path because we don't need it anymore and also because
+	 * copy_inline_to_page() needs to reserve data and metadata, which may
+	 * need to flush delalloc when we are low on available space and
+	 * therefore cause a deadlock if writeback of an inline extent needs to
+	 * write to the same leaf or an ordered extent completion needs to write
+	 * to the same leaf.
+	 */
+	btrfs_release_path(path);
+
+	ret = copy_inline_to_page(BTRFS_I(dst), new_key->offset,
+				  inline_data, size, datal, comp_type);
+	goto out;
+}
+
+/*
+ * Clone a range from inode file to another.
+ *
+ * @src:             Inode to clone from
+ * @inode:           Inode to clone to
+ * @off:             Offset within source to start clone from
+ * @olen:            Original length, passed by user, of range to clone
+ * @olen_aligned:    Block-aligned value of olen
+ * @destoff:         Offset within @inode to start clone
+ * @no_time_update:  Whether to update mtime/ctime on the target inode
+ */
+static int btrfs_clone(struct inode *src, struct inode *inode,
+		       const u64 off, const u64 olen, const u64 olen_aligned,
+		       const u64 destoff, int no_time_update)
+{
+	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
+	struct btrfs_path *path = NULL;
+	struct extent_buffer *leaf;
+	struct btrfs_trans_handle *trans;
+	char *buf = NULL;
+	struct btrfs_key key;
+	u32 nritems;
+	int slot;
+	int ret;
+	const u64 len = olen_aligned;
+	u64 last_dest_end = destoff;
+	u64 prev_extent_end = off;
+
+	ret = -ENOMEM;
+	buf = kvmalloc(fs_info->nodesize, GFP_KERNEL);
+	if (!buf)
+		return ret;
+
+	path = btrfs_alloc_path();
+	if (!path) {
+		kvfree(buf);
+		return ret;
+	}
+
+	path->reada = READA_FORWARD;
+	/* Clone data */
+	key.objectid = btrfs_ino(BTRFS_I(src));
+	key.type = BTRFS_EXTENT_DATA_KEY;
+	key.offset = off;
+
+	while (1) {
+		struct btrfs_file_extent_item *extent;
+		u64 extent_gen;
+		int type;
+		u32 size;
+		struct btrfs_key new_key;
+		u64 disko = 0, diskl = 0;
+		u64 datao = 0, datal = 0;
+		u8 comp;
+		u64 drop_start;
+
+		/* Note the key will change type as we walk through the tree */
+		ret = btrfs_search_slot(NULL, BTRFS_I(src)->root, &key, path,
+				0, 0);
+		if (ret < 0)
+			goto out;
+		/*
+		 * First search, if no extent item that starts at offset off was
+		 * found but the previous item is an extent item, it's possible
+		 * it might overlap our target range, therefore process it.
+		 */
+		if (key.offset == off && ret > 0 && path->slots[0] > 0) {
+			btrfs_item_key_to_cpu(path->nodes[0], &key,
+					      path->slots[0] - 1);
+			if (key.type == BTRFS_EXTENT_DATA_KEY)
+				path->slots[0]--;
+		}
+
+		nritems = btrfs_header_nritems(path->nodes[0]);
+process_slot:
+		if (path->slots[0] >= nritems) {
+			ret = btrfs_next_leaf(BTRFS_I(src)->root, path);
+			if (ret < 0)
+				goto out;
+			if (ret > 0)
+				break;
+			nritems = btrfs_header_nritems(path->nodes[0]);
+		}
+		leaf = path->nodes[0];
+		slot = path->slots[0];
+
+		btrfs_item_key_to_cpu(leaf, &key, slot);
+		if (key.type > BTRFS_EXTENT_DATA_KEY ||
+		    key.objectid != btrfs_ino(BTRFS_I(src)))
+			break;
+
+		ASSERT(key.type == BTRFS_EXTENT_DATA_KEY);
+
+		extent = btrfs_item_ptr(leaf, slot,
+					struct btrfs_file_extent_item);
+		extent_gen = btrfs_file_extent_generation(leaf, extent);
+		comp = btrfs_file_extent_compression(leaf, extent);
+		type = btrfs_file_extent_type(leaf, extent);
+		if (type == BTRFS_FILE_EXTENT_REG ||
+		    type == BTRFS_FILE_EXTENT_PREALLOC) {
+			disko = btrfs_file_extent_disk_bytenr(leaf, extent);
+			diskl = btrfs_file_extent_disk_num_bytes(leaf, extent);
+			datao = btrfs_file_extent_offset(leaf, extent);
+			datal = btrfs_file_extent_num_bytes(leaf, extent);
+		} else if (type == BTRFS_FILE_EXTENT_INLINE) {
+			/* Take upper bound, may be compressed */
+			datal = btrfs_file_extent_ram_bytes(leaf, extent);
+		}
+
+		/*
+		 * The first search might have left us at an extent item that
+		 * ends before our target range's start, can happen if we have
+		 * holes and NO_HOLES feature enabled.
+		 *
+		 * Subsequent searches may leave us on a file range we have
+		 * processed before - this happens due to a race with ordered
+		 * extent completion for a file range that is outside our source
+		 * range, but that range was part of a file extent item that
+		 * also covered a leading part of our source range.
+		 */
+		if (key.offset + datal <= prev_extent_end) {
+			path->slots[0]++;
+			goto process_slot;
+		} else if (key.offset >= off + len) {
+			break;
+		}
+
+		prev_extent_end = key.offset + datal;
+		size = btrfs_item_size(leaf, slot);
+		read_extent_buffer(leaf, buf, btrfs_item_ptr_offset(leaf, slot),
+				   size);
+
+		btrfs_release_path(path);
+
+		memcpy(&new_key, &key, sizeof(new_key));
+		new_key.objectid = btrfs_ino(BTRFS_I(inode));
+		if (off <= key.offset)
+			new_key.offset = key.offset + destoff - off;
+		else
+			new_key.offset = destoff;
+
+		/*
+		 * Deal with a hole that doesn't have an extent item that
+		 * represents it (NO_HOLES feature enabled).
+		 * This hole is either in the middle of the cloning range or at
+		 * the beginning (fully overlaps it or partially overlaps it).
+		 */
+		if (new_key.offset != last_dest_end)
+			drop_start = last_dest_end;
+		else
+			drop_start = new_key.offset;
+
+		if (type == BTRFS_FILE_EXTENT_REG ||
+		    type == BTRFS_FILE_EXTENT_PREALLOC) {
+			struct btrfs_replace_extent_info clone_info;
+
+			/*
+			 *    a  | --- range to clone ---|  b
+			 * | ------------- extent ------------- |
+			 */
+
+			/* Subtract range b */
+			if (key.offset + datal > off + len)
+				datal = off + len - key.offset;
+
+			/* Subtract range a */
+			if (off > key.offset) {
+				datao += off - key.offset;
+				datal -= off - key.offset;
+			}
+
+			clone_info.disk_offset = disko;
+			clone_info.disk_len = diskl;
+			clone_info.data_offset = datao;
+			clone_info.data_len = datal;
+			clone_info.file_offset = new_key.offset;
+			clone_info.extent_buf = buf;
+			clone_info.is_new_extent = false;
+			clone_info.update_times = !no_time_update;
+			ret = btrfs_replace_file_extents(BTRFS_I(inode), path,
+					drop_start, new_key.offset + datal - 1,
+					&clone_info, &trans);
+			if (ret)
+				goto out;
+		} else {
+			ASSERT(type == BTRFS_FILE_EXTENT_INLINE);
+			/*
+			 * Inline extents always have to start at file offset 0
+			 * and can never be bigger then the sector size. We can
+			 * never clone only parts of an inline extent, since all
+			 * reflink operations must start at a sector size aligned
+			 * offset, and the length must be aligned too or end at
+			 * the i_size (which implies the whole inlined data).
+			 */
+			ASSERT(key.offset == 0);
+			ASSERT(datal <= fs_info->sectorsize);
+			if (WARN_ON(type != BTRFS_FILE_EXTENT_INLINE) ||
+			    WARN_ON(key.offset != 0) ||
+			    WARN_ON(datal > fs_info->sectorsize)) {
+				ret = -EUCLEAN;
+				goto out;
+			}
+
+			ret = clone_copy_inline_extent(inode, path, &new_key,
+						       drop_start, datal, size,
+						       comp, buf, &trans);
+			if (ret)
+				goto out;
+		}
+
+		btrfs_release_path(path);
+
+		/*
+		 * Whenever we share an extent we update the last_reflink_trans
+		 * of each inode to the current transaction. This is needed to
+		 * make sure fsync does not log multiple checksum items with
+		 * overlapping ranges (because some extent items might refer
+		 * only to sections of the original extent). For the destination
+		 * inode we do this regardless of the generation of the extents
+		 * or even if they are inline extents or explicit holes, to make
+		 * sure a full fsync does not skip them. For the source inode,
+		 * we only need to update last_reflink_trans in case it's a new
+		 * extent that is not a hole or an inline extent, to deal with
+		 * the checksums problem on fsync.
+		 */
+		if (extent_gen == trans->transid && disko > 0)
+			BTRFS_I(src)->last_reflink_trans = trans->transid;
+
+		BTRFS_I(inode)->last_reflink_trans = trans->transid;
+
+		last_dest_end = ALIGN(new_key.offset + datal,
+				      fs_info->sectorsize);
+		ret = clone_finish_inode_update(trans, inode, last_dest_end,
+						destoff, olen, no_time_update);
+		if (ret)
+			goto out;
+		if (new_key.offset + datal >= destoff + len)
+			break;
+
+		btrfs_release_path(path);
+		key.offset = prev_extent_end;
+
+		if (fatal_signal_pending(current)) {
+			ret = -EINTR;
+			goto out;
+		}
+
+		cond_resched();
+	}
+	ret = 0;
+
+	if (last_dest_end < destoff + len) {
+		/*
+		 * We have an implicit hole that fully or partially overlaps our
+		 * cloning range at its end. This means that we either have the
+		 * NO_HOLES feature enabled or the implicit hole happened due to
+		 * mixing buffered and direct IO writes against this file.
+		 */
+		btrfs_release_path(path);
+
+		/*
+		 * When using NO_HOLES and we are cloning a range that covers
+		 * only a hole (no extents) into a range beyond the current
+		 * i_size, punching a hole in the target range will not create
+		 * an extent map defining a hole, because the range starts at or
+		 * beyond current i_size. If the file previously had an i_size
+		 * greater than the new i_size set by this clone operation, we
+		 * need to make sure the next fsync is a full fsync, so that it
+		 * detects and logs a hole covering a range from the current
+		 * i_size to the new i_size. If the clone range covers extents,
+		 * besides a hole, then we know the full sync flag was already
+		 * set by previous calls to btrfs_replace_file_extents() that
+		 * replaced file extent items.
+		 */
+		if (last_dest_end >= i_size_read(inode))
+			btrfs_set_inode_full_sync(BTRFS_I(inode));
+
+		ret = btrfs_replace_file_extents(BTRFS_I(inode), path,
+				last_dest_end, destoff + len - 1, NULL, &trans);
+		if (ret)
+			goto out;
+
+		ret = clone_finish_inode_update(trans, inode, destoff + len,
+						destoff, olen, no_time_update);
+	}
+
+out:
+	btrfs_free_path(path);
+	kvfree(buf);
+	clear_bit(BTRFS_INODE_NO_DELALLOC_FLUSH, &BTRFS_I(inode)->runtime_flags);
+
+	return ret;
+}
+
+static void btrfs_double_extent_unlock(struct inode *inode1, u64 loff1,
+				       struct inode *inode2, u64 loff2, u64 len)
+{
+	unlock_extent(&BTRFS_I(inode1)->io_tree, loff1, loff1 + len - 1, NULL);
+	unlock_extent(&BTRFS_I(inode2)->io_tree, loff2, loff2 + len - 1, NULL);
+}
+
+static void btrfs_double_extent_lock(struct inode *inode1, u64 loff1,
+				     struct inode *inode2, u64 loff2, u64 len)
+{
+	u64 range1_end = loff1 + len - 1;
+	u64 range2_end = loff2 + len - 1;
+
+	if (inode1 < inode2) {
+		swap(inode1, inode2);
+		swap(loff1, loff2);
+		swap(range1_end, range2_end);
+	} else if (inode1 == inode2 && loff2 < loff1) {
+		swap(loff1, loff2);
+		swap(range1_end, range2_end);
+	}
+
+	lock_extent(&BTRFS_I(inode1)->io_tree, loff1, range1_end, NULL);
+	lock_extent(&BTRFS_I(inode2)->io_tree, loff2, range2_end, NULL);
+
+	btrfs_assert_inode_range_clean(BTRFS_I(inode1), loff1, range1_end);
+	btrfs_assert_inode_range_clean(BTRFS_I(inode2), loff2, range2_end);
+}
+
+static void btrfs_double_mmap_lock(struct inode *inode1, struct inode *inode2)
+{
+	if (inode1 < inode2)
+		swap(inode1, inode2);
+	down_write(&BTRFS_I(inode1)->i_mmap_lock);
+	down_write_nested(&BTRFS_I(inode2)->i_mmap_lock, SINGLE_DEPTH_NESTING);
+}
+
+static void btrfs_double_mmap_unlock(struct inode *inode1, struct inode *inode2)
+{
+	up_write(&BTRFS_I(inode1)->i_mmap_lock);
+	up_write(&BTRFS_I(inode2)->i_mmap_lock);
+}
+
+static int btrfs_extent_same_range(struct inode *src, u64 loff, u64 len,
+				   struct inode *dst, u64 dst_loff)
+{
+	struct btrfs_fs_info *fs_info = BTRFS_I(src)->root->fs_info;
+	const u64 bs = fs_info->sb->s_blocksize;
+	int ret;
+
+	/*
+	 * Lock destination range to serialize with concurrent readahead() and
+	 * source range to serialize with relocation.
+	 */
+	btrfs_double_extent_lock(src, loff, dst, dst_loff, len);
+	ret = btrfs_clone(src, dst, loff, len, ALIGN(len, bs), dst_loff, 1);
+	btrfs_double_extent_unlock(src, loff, dst, dst_loff, len);
+
+	btrfs_btree_balance_dirty(fs_info);
+
+	return ret;
+}
+
+static int btrfs_extent_same(struct inode *src, u64 loff, u64 olen,
+			     struct inode *dst, u64 dst_loff)
+{
+	int ret = 0;
+	u64 i, tail_len, chunk_count;
+	struct btrfs_root *root_dst = BTRFS_I(dst)->root;
+
+	spin_lock(&root_dst->root_item_lock);
+	if (root_dst->send_in_progress) {
+		btrfs_warn_rl(root_dst->fs_info,
+"cannot deduplicate to root %llu while send operations are using it (%d in progress)",
+			      root_dst->root_key.objectid,
+			      root_dst->send_in_progress);
+		spin_unlock(&root_dst->root_item_lock);
+		return -EAGAIN;
+	}
+	root_dst->dedupe_in_progress++;
+	spin_unlock(&root_dst->root_item_lock);
+
+	tail_len = olen % BTRFS_MAX_DEDUPE_LEN;
+	chunk_count = div_u64(olen, BTRFS_MAX_DEDUPE_LEN);
+
+	for (i = 0; i < chunk_count; i++) {
+		ret = btrfs_extent_same_range(src, loff, BTRFS_MAX_DEDUPE_LEN,
+					      dst, dst_loff);
+		if (ret)
+			goto out;
+
+		loff += BTRFS_MAX_DEDUPE_LEN;
+		dst_loff += BTRFS_MAX_DEDUPE_LEN;
+	}
+
+	if (tail_len > 0)
+		ret = btrfs_extent_same_range(src, loff, tail_len, dst, dst_loff);
+out:
+	spin_lock(&root_dst->root_item_lock);
+	root_dst->dedupe_in_progress--;
+	spin_unlock(&root_dst->root_item_lock);
+
+	return ret;
+}
+
+static noinline int btrfs_clone_files(struct file *file, struct file *file_src,
+					u64 off, u64 olen, u64 destoff)
+{
+	struct inode *inode = file_inode(file);
+	struct inode *src = file_inode(file_src);
+	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
+	int ret;
+	int wb_ret;
+	u64 len = olen;
+	u64 bs = fs_info->sb->s_blocksize;
+
+	/*
+	 * VFS's generic_remap_file_range_prep() protects us from cloning the
+	 * eof block into the middle of a file, which would result in corruption
+	 * if the file size is not blocksize aligned. So we don't need to check
+	 * for that case here.
+	 */
+	if (off + len == src->i_size)
+		len = ALIGN(src->i_size, bs) - off;
+
+	if (destoff > inode->i_size) {
+		const u64 wb_start = ALIGN_DOWN(inode->i_size, bs);
+
+		ret = btrfs_cont_expand(BTRFS_I(inode), inode->i_size, destoff);
+		if (ret)
+			return ret;
+		/*
+		 * We may have truncated the last block if the inode's size is
+		 * not sector size aligned, so we need to wait for writeback to
+		 * complete before proceeding further, otherwise we can race
+		 * with cloning and attempt to increment a reference to an
+		 * extent that no longer exists (writeback completed right after
+		 * we found the previous extent covering eof and before we
+		 * attempted to increment its reference count).
+		 */
+		ret = btrfs_wait_ordered_range(inode, wb_start,
+					       destoff - wb_start);
+		if (ret)
+			return ret;
+	}
+
+	/*
+	 * Lock destination range to serialize with concurrent readahead() and
+	 * source range to serialize with relocation.
+	 */
+	btrfs_double_extent_lock(src, off, inode, destoff, len);
+	ret = btrfs_clone(src, inode, off, olen, len, destoff, 0);
+	btrfs_double_extent_unlock(src, off, inode, destoff, len);
+
+	/*
+	 * We may have copied an inline extent into a page of the destination
+	 * range, so wait for writeback to complete before truncating pages
+	 * from the page cache. This is a rare case.
+	 */
+	wb_ret = btrfs_wait_ordered_range(inode, destoff, len);
+	ret = ret ? ret : wb_ret;
+	/*
+	 * Truncate page cache pages so that future reads will see the cloned
+	 * data immediately and not the previous data.
+	 */
+	truncate_inode_pages_range(&inode->i_data,
+				round_down(destoff, PAGE_SIZE),
+				round_up(destoff + len, PAGE_SIZE) - 1);
+
+	btrfs_btree_balance_dirty(fs_info);
+
+	return ret;
+}
+
+static int btrfs_remap_file_range_prep(struct file *file_in, loff_t pos_in,
+				       struct file *file_out, loff_t pos_out,
+				       loff_t *len, unsigned int remap_flags)
+{
+	struct inode *inode_in = file_inode(file_in);
+	struct inode *inode_out = file_inode(file_out);
+	u64 bs = BTRFS_I(inode_out)->root->fs_info->sb->s_blocksize;
+	u64 wb_len;
+	int ret;
+
+	if (!(remap_flags & REMAP_FILE_DEDUP)) {
+		struct btrfs_root *root_out = BTRFS_I(inode_out)->root;
+
+		if (btrfs_root_readonly(root_out))
+			return -EROFS;
+
+		ASSERT(inode_in->i_sb == inode_out->i_sb);
+	}
+
+	/* Don't make the dst file partly checksummed */
+	if ((BTRFS_I(inode_in)->flags & BTRFS_INODE_NODATASUM) !=
+	    (BTRFS_I(inode_out)->flags & BTRFS_INODE_NODATASUM)) {
+		return -EINVAL;
+	}
+
+	/*
+	 * Now that the inodes are locked, we need to start writeback ourselves
+	 * and can not rely on the writeback from the VFS's generic helper
+	 * generic_remap_file_range_prep() because:
+	 *
+	 * 1) For compression we must call filemap_fdatawrite_range() range
+	 *    twice (btrfs_fdatawrite_range() does it for us), and the generic
+	 *    helper only calls it once;
+	 *
+	 * 2) filemap_fdatawrite_range(), called by the generic helper only
+	 *    waits for the writeback to complete, i.e. for IO to be done, and
+	 *    not for the ordered extents to complete. We need to wait for them
+	 *    to complete so that new file extent items are in the fs tree.
+	 */
+	if (*len == 0 && !(remap_flags & REMAP_FILE_DEDUP))
+		wb_len = ALIGN(inode_in->i_size, bs) - ALIGN_DOWN(pos_in, bs);
+	else
+		wb_len = ALIGN(*len, bs);
+
+	/*
+	 * Workaround to make sure NOCOW buffered write reach disk as NOCOW.
+	 *
+	 * Btrfs' back references do not have a block level granularity, they
+	 * work at the whole extent level.
+	 * NOCOW buffered write without data space reserved may not be able
+	 * to fall back to CoW due to lack of data space, thus could cause
+	 * data loss.
+	 *
+	 * Here we take a shortcut by flushing the whole inode, so that all
+	 * nocow write should reach disk as nocow before we increase the
+	 * reference of the extent. We could do better by only flushing NOCOW
+	 * data, but that needs extra accounting.
+	 *
+	 * Also we don't need to check ASYNC_EXTENT, as async extent will be
+	 * CoWed anyway, not affecting nocow part.
+	 */
+	ret = filemap_flush(inode_in->i_mapping);
+	if (ret < 0)
+		return ret;
+
+	ret = btrfs_wait_ordered_range(inode_in, ALIGN_DOWN(pos_in, bs),
+				       wb_len);
+	if (ret < 0)
+		return ret;
+	ret = btrfs_wait_ordered_range(inode_out, ALIGN_DOWN(pos_out, bs),
+				       wb_len);
+	if (ret < 0)
+		return ret;
+
+	return generic_remap_file_range_prep(file_in, pos_in, file_out, pos_out,
+					    len, remap_flags);
+}
+
+static bool file_sync_write(const struct file *file)
+{
+	if (file->f_flags & (__O_SYNC | O_DSYNC))
+		return true;
+	if (IS_SYNC(file_inode(file)))
+		return true;
+
+	return false;
+}
+
+loff_t btrfs_remap_file_range(struct file *src_file, loff_t off,
+		struct file *dst_file, loff_t destoff, loff_t len,
+		unsigned int remap_flags)
+{
+	struct inode *src_inode = file_inode(src_file);
+	struct inode *dst_inode = file_inode(dst_file);
+	bool same_inode = dst_inode == src_inode;
+	int ret;
+
+	if (remap_flags & ~(REMAP_FILE_DEDUP | REMAP_FILE_ADVISORY))
+		return -EINVAL;
+
+	if (same_inode) {
+		btrfs_inode_lock(BTRFS_I(src_inode), BTRFS_ILOCK_MMAP);
+	} else {
+		lock_two_nondirectories(src_inode, dst_inode);
+		btrfs_double_mmap_lock(src_inode, dst_inode);
+	}
+
+	ret = btrfs_remap_file_range_prep(src_file, off, dst_file, destoff,
+					  &len, remap_flags);
+	if (ret < 0 || len == 0)
+		goto out_unlock;
+
+	if (remap_flags & REMAP_FILE_DEDUP)
+		ret = btrfs_extent_same(src_inode, off, len, dst_inode, destoff);
+	else
+		ret = btrfs_clone_files(dst_file, src_file, off, len, destoff);
+
+out_unlock:
+	if (same_inode) {
+		btrfs_inode_unlock(BTRFS_I(src_inode), BTRFS_ILOCK_MMAP);
+	} else {
+		btrfs_double_mmap_unlock(src_inode, dst_inode);
+		unlock_two_nondirectories(src_inode, dst_inode);
+	}
+
+	/*
+	 * If either the source or the destination file was opened with O_SYNC,
+	 * O_DSYNC or has the S_SYNC attribute, fsync both the destination and
+	 * source files/ranges, so that after a successful return (0) followed
+	 * by a power failure results in the reflinked data to be readable from
+	 * both files/ranges.
+	 */
+	if (ret == 0 && len > 0 &&
+	    (file_sync_write(src_file) || file_sync_write(dst_file))) {
+		ret = btrfs_sync_file(src_file, off, off + len - 1, 0);
+		if (ret == 0)
+			ret = btrfs_sync_file(dst_file, destoff,
+					      destoff + len - 1, 0);
+	}
+
+	return ret < 0 ? ret : len;
+}