Commit 8c7d9fe0 authored by Omar Sandoval's avatar Omar Sandoval Committed by David Sterba
Browse files

btrfs: send: avoid copying file data 



send_write() currently copies from the page cache to sctx->read_buf, and
then from sctx->read_buf to sctx->send_buf. Similarly, send_hole()
zeroes sctx->read_buf and then copies from sctx->read_buf to
sctx->send_buf. However, if we write the TLV header manually, we can
copy to sctx->send_buf directly and get rid of sctx->read_buf.

Reviewed-by: default avatarFilipe Manana <fdmanana@suse.com>
Reviewed-by: default avatarJosef Bacik <josef@toxicpanda.com>
Signed-off-by: default avatarOmar Sandoval <osandov@fb.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent a9b2e0de

fs/btrfs/send.c

+39 −26
Original line number Diff line number Diff line
@@ -122,8 +122,6 @@ struct send_ctx { 


	struct file_ra_state ra;



	char *read_buf;



	/*

	 * We process inodes by their increasing order, so if before an

	 * incremental send we reverse the parent/child relationship of
@@ -4794,7 +4792,25 @@ out: 
	return ret;

}



static int fill_read_buf(struct send_ctx *sctx, u64 offset, u32 len)

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;
@@ -4804,8 +4820,11 @@ static int fill_read_buf(struct send_ctx *sctx, u64 offset, u32 len) 
	pgoff_t index = offset >> PAGE_SHIFT;

	pgoff_t last_index;

	unsigned pg_offset = offset_in_page(offset);

	int ret = 0;

	size_t read = 0;

	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))
@@ -4851,14 +4870,15 @@ static int fill_read_buf(struct send_ctx *sctx, u64 offset, u32 len) 
		}



		addr = kmap(page);

		memcpy(sctx->read_buf + read, addr + pg_offset, cur_len);

		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;

		read += cur_len;

		sctx->send_size += cur_len;

	}

	iput(inode);

	return ret;
@@ -4880,10 +4900,6 @@ static int send_write(struct send_ctx *sctx, u64 offset, u32 len) 


	btrfs_debug(fs_info, "send_write offset=%llu, len=%d", offset, len);



	ret = fill_read_buf(sctx, offset, len);

	if (ret < 0)

		goto out;



	ret = begin_cmd(sctx, BTRFS_SEND_C_WRITE);

	if (ret < 0)

		goto out;
@@ -4894,7 +4910,9 @@ static int send_write(struct send_ctx *sctx, u64 offset, u32 len) 


	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, p);

	TLV_PUT_U64(sctx, BTRFS_SEND_A_FILE_OFFSET, offset);

	TLV_PUT(sctx, BTRFS_SEND_A_DATA, sctx->read_buf, len);

	ret = put_file_data(sctx, offset, len);

	if (ret < 0)

		goto out;



	ret = send_cmd(sctx);
@@ -5013,8 +5031,8 @@ out: 
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;

	u64 len;

	int ret = 0;



	/*
@@ -5041,16 +5059,19 @@ static int send_hole(struct send_ctx *sctx, u64 end) 
	ret = get_cur_path(sctx, sctx->cur_ino, sctx->cur_inode_gen, p);

	if (ret < 0)

		goto tlv_put_failure;

	memset(sctx->read_buf, 0, BTRFS_SEND_READ_SIZE);

	while (offset < end) {

		len = min_t(u64, end - offset, BTRFS_SEND_READ_SIZE);

		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);

		TLV_PUT(sctx, BTRFS_SEND_A_DATA, sctx->read_buf, len);

		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;
@@ -5066,17 +5087,16 @@ 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 = len - sent;

		u64 size = min(len - sent, read_size);

		int ret;



		if (size > BTRFS_SEND_READ_SIZE)

			size = BTRFS_SEND_READ_SIZE;

		ret = send_write(sctx, offset + sent, size);

		if (ret < 0)

			return ret;
@@ -7145,12 +7165,6 @@ long btrfs_ioctl_send(struct file *mnt_file, struct btrfs_ioctl_send_args *arg) 
		goto out;

	}



	sctx->read_buf = kvmalloc(BTRFS_SEND_READ_SIZE, GFP_KERNEL);

	if (!sctx->read_buf) {

		ret = -ENOMEM;

		goto out;

	}



	sctx->pending_dir_moves = RB_ROOT;

	sctx->waiting_dir_moves = RB_ROOT;

	sctx->orphan_dirs = RB_ROOT;
@@ -7354,7 +7368,6 @@ out: 


		kvfree(sctx->clone_roots);

		kvfree(sctx->send_buf);

		kvfree(sctx->read_buf);



		name_cache_free(sctx);

fs/btrfs/send.h

+0 −1
Original line number Diff line number Diff line
@@ -13,7 +13,6 @@ 
#define BTRFS_SEND_STREAM_VERSION 1



#define BTRFS_SEND_BUF_SIZE SZ_64K

#define BTRFS_SEND_READ_SIZE (48 * SZ_1K)



enum btrfs_tlv_type {

	BTRFS_TLV_U8,

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