btrfs: send: add stream v2 definitions

This adds the definitions of the new commands for send stream version 2
and their respective attributes: fallocate, FS_IOC_SETFLAGS (a.k.a.
chattr), and encoded writes. It also documents two changes to the send
stream format in v2: the receiver shouldn't assume a maximum command
size, and the DATA attribute is encoded differently to allow for writes
larger than 64k. These will be implemented in subsequent changes, and
then the ioctl will accept the new version and flag.
Reviewed-by: NJosef Bacik <josef@toxicpanda.com>
Signed-off-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/send.c

@@ -7552,7 +7552,7 @@ long btrfs_ioctl_send(struct inode *inode, struct btrfs_ioctl_send_args *arg)
 
 	sctx->clone_roots_cnt = arg->clone_sources_count;
 
-	sctx->send_max_size = BTRFS_SEND_BUF_SIZE;
+	sctx->send_max_size = BTRFS_SEND_BUF_SIZE_V1;
 	sctx->send_buf = kvmalloc(sctx->send_max_size, GFP_KERNEL);
 	if (!sctx->send_buf) {
 		ret = -ENOMEM;

fs/btrfs/send.h

@@ -12,7 +12,11 @@
 #define BTRFS_SEND_STREAM_MAGIC "btrfs-stream"
 #define BTRFS_SEND_STREAM_VERSION 1
 
-#define BTRFS_SEND_BUF_SIZE SZ_64K
+/*
+ * In send stream v1, no command is larger than 64K. In send stream v2, no limit
+ * should be assumed.
+ */
+#define BTRFS_SEND_BUF_SIZE_V1				SZ_64K
 
 enum btrfs_tlv_type {
 	BTRFS_TLV_U8,
@@ -80,16 +84,20 @@ enum btrfs_send_cmd {
 	BTRFS_SEND_C_MAX_V1		= 22,
 
 	/* Version 2 */
-	BTRFS_SEND_C_MAX_V2		= 22,
+	BTRFS_SEND_C_FALLOCATE		= 23,
+	BTRFS_SEND_C_SETFLAGS		= 24,
+	BTRFS_SEND_C_ENCODED_WRITE	= 25,
+	BTRFS_SEND_C_MAX_V2		= 25,
 
 	/* End */
-	BTRFS_SEND_C_MAX		= 22,
+	BTRFS_SEND_C_MAX		= 25,
 };
 
 /* attributes in send stream */
 enum {
 	BTRFS_SEND_A_UNSPEC		= 0,
 
+	/* Version 1 */
 	BTRFS_SEND_A_UUID		= 1,
 	BTRFS_SEND_A_CTRANSID		= 2,
 
@@ -112,6 +120,11 @@ enum {
 	BTRFS_SEND_A_PATH_LINK		= 17,
 
 	BTRFS_SEND_A_FILE_OFFSET	= 18,
+	/*
+	 * As of send stream v2, this attribute is special: it must be the last
+	 * attribute in a command, its header contains only the type, and its
+	 * length is implicitly the remaining length of the command.
+	 */
 	BTRFS_SEND_A_DATA		= 19,
 
 	BTRFS_SEND_A_CLONE_UUID		= 20,
@@ -120,7 +133,26 @@ enum {
 	BTRFS_SEND_A_CLONE_OFFSET	= 23,
 	BTRFS_SEND_A_CLONE_LEN		= 24,
 
-	BTRFS_SEND_A_MAX		= 24,
+	BTRFS_SEND_A_MAX_V1		= 24,
+
+	/* Version 2 */
+	BTRFS_SEND_A_FALLOCATE_MODE	= 25,
+
+	BTRFS_SEND_A_SETFLAGS_FLAGS	= 26,
+
+	BTRFS_SEND_A_UNENCODED_FILE_LEN	= 27,
+	BTRFS_SEND_A_UNENCODED_LEN	= 28,
+	BTRFS_SEND_A_UNENCODED_OFFSET	= 29,
+	/*
+	 * COMPRESSION and ENCRYPTION default to NONE (0) if omitted from
+	 * BTRFS_SEND_C_ENCODED_WRITE.
+	 */
+	BTRFS_SEND_A_COMPRESSION	= 30,
+	BTRFS_SEND_A_ENCRYPTION		= 31,
+	BTRFS_SEND_A_MAX_V2		= 31,
+
+	/* End */
+	BTRFS_SEND_A_MAX		= 31,
 };
 
 #ifdef __KERNEL__

include/uapi/linux/btrfs.h

@@ -777,6 +777,13 @@ struct btrfs_ioctl_received_subvol_args {
  */
 #define BTRFS_SEND_FLAG_VERSION			0x8
 
+/*
+ * Send compressed data using the ENCODED_WRITE command instead of decompressing
+ * the data and sending it with the WRITE command. This requires protocol
+ * version >= 2.
+ */
+#define BTRFS_SEND_FLAG_COMPRESSED		0x10
+
 #define BTRFS_SEND_FLAG_MASK \
 	(BTRFS_SEND_FLAG_NO_FILE_DATA | \
 	 BTRFS_SEND_FLAG_OMIT_STREAM_HEADER | \