drbd: Remove headers from on-the-wire data structures (struct p_*)

Prepare the introduction of the protocol 100 headers. The actual protocol
header is removed for the packet declarations. I.e. allow us to use the
packets with different headers.
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

drivers/block/drbd/drbd_int.h

@@ -307,32 +307,8 @@ struct p_header95 {
 	u32	  length;	/* Use only 24 bits of that. Ignore the highest 8 bit. */
 } __packed;
 
-struct p_header {
-	union {
-		struct p_header80 h80;
-		struct p_header95 h95;
-	};
-	u8	  payload[0];
-};
-
 extern unsigned int drbd_header_size(struct drbd_tconn *tconn);
 
-/*
- * short commands, packets without payload, plain p_header:
- *   P_PING
- *   P_PING_ACK
- *   P_BECOME_SYNC_TARGET
- *   P_BECOME_SYNC_SOURCE
- *   P_UNPLUG_REMOTE
- */
-
-/*
- * commands with out-of-struct payload:
- *   P_BITMAP    (no additional fields)
- *   P_DATA, P_DATA_REPLY (see p_data)
- *   P_COMPRESSED_BITMAP (see receive_compressed_bitmap)
- */
-
 /* these defines must not be changed without changing the protocol version */
 #define DP_HARDBARRIER	      1 /* depricated */
 #define DP_RW_SYNC	      2 /* equals REQ_SYNC    */
@@ -343,7 +319,6 @@ extern unsigned int drbd_header_size(struct drbd_tconn *tconn);
 #define DP_DISCARD           64 /* equals REQ_DISCARD */
 
 struct p_data {
-	struct p_header head;
 	u64	    sector;    /* 64 bits sector number */
 	u64	    block_id;  /* to identify the request in protocol B&C */
 	u32	    seq_num;
@@ -359,7 +334,6 @@ struct p_data {
  *   P_DATA_REQUEST, P_RS_DATA_REQUEST
  */
 struct p_block_ack {
-	struct p_header head;
 	u64	    sector;
 	u64	    block_id;
 	u32	    blksize;
@@ -367,7 +341,6 @@ struct p_block_ack {
 } __packed;
 
 struct p_block_req {
-	struct p_header head;
 	u64 sector;
 	u64 block_id;
 	u32 blksize;
@@ -384,7 +357,6 @@ struct p_block_req {
  */
 
 struct p_connection_features {
-	struct p_header head;   /* Note: vnr will be ignored */
 	u32 protocol_min;
 	u32 feature_flags;
 	u32 protocol_max;
@@ -396,22 +368,18 @@ struct p_connection_features {
 	u32 _pad;
 	u64 reserverd[7];
 } __packed;
-/* 80 bytes, FIXED for the next century */
 
 struct p_barrier {
-	struct p_header head;
 	u32 barrier;	/* barrier number _handle_ only */
 	u32 pad;	/* to multiple of 8 Byte */
 } __packed;
 
 struct p_barrier_ack {
-	struct p_header head;
 	u32 barrier;
 	u32 set_size;
 } __packed;
 
 struct p_rs_param {
-	struct p_header head;
 	u32 rate;
 
 	      /* Since protocol version 88 and higher. */
@@ -419,7 +387,6 @@ struct p_rs_param {
 } __packed;
 
 struct p_rs_param_89 {
-	struct p_header head;
 	u32 rate;
         /* protocol version 89: */
 	char verify_alg[SHARED_SECRET_MAX];
@@ -427,7 +394,6 @@ struct p_rs_param_89 {
 } __packed;
 
 struct p_rs_param_95 {
-	struct p_header head;
 	u32 rate;
 	char verify_alg[SHARED_SECRET_MAX];
 	char csums_alg[SHARED_SECRET_MAX];
@@ -443,7 +409,6 @@ enum drbd_conn_flags {
 };
 
 struct p_protocol {
-	struct p_header head;
 	u32 protocol;
 	u32 after_sb_0p;
 	u32 after_sb_1p;
@@ -457,17 +422,14 @@ struct p_protocol {
 } __packed;
 
 struct p_uuids {
-	struct p_header head;
 	u64 uuid[UI_EXTENDED_SIZE];
 } __packed;
 
 struct p_rs_uuid {
-	struct p_header head;
 	u64	    uuid;
 } __packed;
 
 struct p_sizes {
-	struct p_header head;
 	u64	    d_size;  /* size of disk */
 	u64	    u_size;  /* user requested size */
 	u64	    c_size;  /* current exported size */
@@ -477,18 +439,15 @@ struct p_sizes {
 } __packed;
 
 struct p_state {
-	struct p_header head;
 	u32	    state;
 } __packed;
 
 struct p_req_state {
-	struct p_header head;
 	u32	    mask;
 	u32	    val;
 } __packed;
 
 struct p_req_state_reply {
-	struct p_header head;
 	u32	    retcode;
 } __packed;
 
@@ -503,14 +462,12 @@ struct p_drbd06_param {
 } __packed;
 
 struct p_discard {
-	struct p_header head;
 	u64	    block_id;
 	u32	    seq_num;
 	u32	    pad;
 } __packed;
 
 struct p_block_desc {
-	struct p_header head;
 	u64 sector;
 	u32 blksize;
 	u32 pad;	/* to multiple of 8 Byte */
@@ -526,7 +483,6 @@ enum drbd_bitmap_code {
 };
 
 struct p_compressed_bm {
-	struct p_header head;
 	/* (encoding & 0x0f): actual encoding, see enum drbd_bitmap_code
 	 * (encoding & 0x80): polarity (set/unset) of first runlength
 	 * ((encoding >> 4) & 0x07): pad_bits, number of trailing zero bits
@@ -538,7 +494,6 @@ struct p_compressed_bm {
 } __packed;
 
 struct p_delay_probe93 {
-	struct p_header head;
 	u32     seq_num; /* sequence number to match the two probe packets */
 	u32     offset;  /* usecs the probe got sent after the reference time point */
 } __packed;

drivers/block/drbd/drbd_main.c

@@ -703,27 +703,29 @@ unsigned int drbd_header_size(struct drbd_tconn *tconn)
 	return sizeof(struct p_header80);
 }
 
-static void prepare_header80(struct p_header80 *h, enum drbd_packet cmd, int size)
+static unsigned int prepare_header80(struct p_header80 *h, enum drbd_packet cmd, int size)
 {
 	h->magic   = cpu_to_be32(DRBD_MAGIC);
 	h->command = cpu_to_be16(cmd);
 	h->length  = cpu_to_be16(size);
+	return sizeof(struct p_header80);
 }
 
-static void prepare_header95(struct p_header95 *h, enum drbd_packet cmd, int size)
+static unsigned int prepare_header95(struct p_header95 *h, enum drbd_packet cmd, int size)
 {
 	h->magic   = cpu_to_be16(DRBD_MAGIC_BIG);
 	h->command = cpu_to_be16(cmd);
 	h->length  = cpu_to_be32(size);
+	return sizeof(struct p_header95);
 }
 
-static void prepare_header(struct drbd_tconn *tconn, int vnr, struct p_header *h,
+static unsigned int prepare_header(struct drbd_tconn *tconn, int vnr, void *buffer,
 				   enum drbd_packet cmd, int size)
 {
 	if (tconn->agreed_pro_version >= 95)
-		prepare_header95(&h->h95, cmd, size);
+		return prepare_header95(buffer, cmd, size);
 	else
-		prepare_header80(&h->h80, cmd, size);
+		return prepare_header80(buffer, cmd, size);
 }
 
 void *conn_prepare_command(struct drbd_tconn *tconn, struct drbd_socket *sock)
@@ -733,7 +735,7 @@ void *conn_prepare_command(struct drbd_tconn *tconn, struct drbd_socket *sock)
 		mutex_unlock(&sock->mutex);
 		return NULL;
 	}
-	return sock->sbuf;
+	return sock->sbuf + drbd_header_size(tconn);
 }
 
 void *drbd_prepare_command(struct drbd_conf *mdev, struct drbd_socket *sock)
@@ -758,8 +760,8 @@ static int __send_command(struct drbd_tconn *tconn, int vnr,
 	 */
 	msg_flags = data ? MSG_MORE : 0;
 
-	prepare_header(tconn, vnr, sock->sbuf, cmd,
-		       header_size - sizeof(struct p_header) + size);
+	header_size += prepare_header(tconn, vnr, sock->sbuf, cmd,
+				      header_size + size);
 	err = drbd_send_all(tconn, sock->socket, sock->sbuf, header_size,
 			    msg_flags);
 	if (data && !err)
@@ -797,7 +799,7 @@ int drbd_send_ping(struct drbd_tconn *tconn)
 	sock = &tconn->meta;
 	if (!conn_prepare_command(tconn, sock))
 		return -EIO;
-	return conn_send_command(tconn, sock, P_PING, sizeof(struct p_header), NULL, 0);
+	return conn_send_command(tconn, sock, P_PING, 0, NULL, 0);
 }
 
 int drbd_send_ping_ack(struct drbd_tconn *tconn)
@@ -807,7 +809,7 @@ int drbd_send_ping_ack(struct drbd_tconn *tconn)
 	sock = &tconn->meta;
 	if (!conn_prepare_command(tconn, sock))
 		return -EIO;
-	return conn_send_command(tconn, sock, P_PING_ACK, sizeof(struct p_header), NULL, 0);
+	return conn_send_command(tconn, sock, P_PING_ACK, 0, NULL, 0);
 }
 
 int drbd_send_sync_param(struct drbd_conf *mdev)
@@ -1205,10 +1207,11 @@ send_bitmap_rle_or_plain(struct drbd_conf *mdev, struct bm_xfer_ctx *c)
 {
 	struct drbd_socket *sock = &mdev->tconn->data;
 	unsigned int header_size = drbd_header_size(mdev->tconn);
-	struct p_compressed_bm *p = sock->sbuf;
+	struct p_compressed_bm *p = sock->sbuf + header_size;
 	int len, err;
 
-	len = fill_bitmap_rle_bits(mdev, p, DRBD_SOCKET_BUFFER_SIZE - sizeof(*p) /* FIXME */, c);
+	len = fill_bitmap_rle_bits(mdev, p,
+			DRBD_SOCKET_BUFFER_SIZE - header_size - sizeof(*p), c);
 	if (len < 0)
 		return -EIO;
 
@@ -1218,7 +1221,7 @@ send_bitmap_rle_or_plain(struct drbd_conf *mdev, struct bm_xfer_ctx *c)
 				     P_COMPRESSED_BITMAP, sizeof(*p) + len,
 				     NULL, 0);
 		c->packets[0]++;
-		c->bytes[0] += sizeof(*p) + len;
+		c->bytes[0] += header_size + sizeof(*p) + len;
 
 		if (c->bit_offset >= c->bm_bits)
 			len = 0; /* DONE */
@@ -1227,17 +1230,15 @@ send_bitmap_rle_or_plain(struct drbd_conf *mdev, struct bm_xfer_ctx *c)
 		 * send a buffer full of plain text bits instead. */
 		unsigned int data_size;
 		unsigned long num_words;
-		struct p_header *h = sock->sbuf;
+		unsigned long *p = sock->sbuf + header_size;
 
 		data_size = DRBD_SOCKET_BUFFER_SIZE - header_size;
-		num_words = min_t(size_t, data_size / sizeof(unsigned long),
+		num_words = min_t(size_t, data_size / sizeof(*p),
 				  c->bm_words - c->word_offset);
-		len = num_words * sizeof(unsigned long);
+		len = num_words * sizeof(*p);
 		if (len)
-			drbd_bm_get_lel(mdev, c->word_offset, num_words,
-					(unsigned long *)h->payload);
-		err = __send_command(mdev->tconn, mdev->vnr, sock, P_BITMAP,
-				     sizeof(*h) + len, NULL, 0);
+			drbd_bm_get_lel(mdev, c->word_offset, num_words, p);
+		err = __send_command(mdev->tconn, mdev->vnr, sock, P_BITMAP, len, NULL, 0);
 		c->word_offset += num_words;
 		c->bit_offset = c->word_offset * BITS_PER_LONG;
 
@@ -2556,8 +2557,6 @@ int __init drbd_init(void)
 {
 	int err;
 
-	BUILD_BUG_ON(sizeof(struct p_connection_features) != 80);
-
 	if (minor_count < DRBD_MINOR_COUNT_MIN || minor_count > DRBD_MINOR_COUNT_MAX) {
 		printk(KERN_ERR
 		       "drbd: invalid minor_count (%d)\n", minor_count);

drivers/block/drbd/drbd_worker.c

@@ -1229,7 +1229,7 @@ int w_send_write_hint(struct drbd_work *w, int cancel)
 	sock = &mdev->tconn->data;
 	if (!drbd_prepare_command(mdev, sock))
 		return -EIO;
-	return drbd_send_command(mdev, sock, P_UNPLUG_REMOTE, sizeof(struct p_header), NULL, 0);
+	return drbd_send_command(mdev, sock, P_UNPLUG_REMOTE, 0, NULL, 0);
 }
 
 int w_send_out_of_sync(struct drbd_work *w, int cancel)