/* SPDX-License-Identifier: GPL-2.0-only */ #ifndef __DRBD_PROTOCOL_H #define __DRBD_PROTOCOL_H enum drbd_packet { … }; #ifndef __packed #define __packed … #endif /* This is the layout for a packet on the wire. * The byteorder is the network byte order. * (except block_id and barrier fields. * these are pointers to local structs * and have no relevance for the partner, * which just echoes them as received.) * * NOTE that the payload starts at a long aligned offset, * regardless of 32 or 64 bit arch! */ struct p_header80 { … } __packed; /* Header for big packets, Used for data packets exceeding 64kB */ struct p_header95 { … } __packed; struct p_header100 { … } __packed; /* These defines must not be changed without changing the protocol version. * New defines may only be introduced together with protocol version bump or * new protocol feature flags. */ #define DP_HARDBARRIER … #define DP_RW_SYNC … #define DP_MAY_SET_IN_SYNC … #define DP_UNPLUG … #define DP_FUA … #define DP_FLUSH … #define DP_DISCARD … #define DP_SEND_RECEIVE_ACK … #define DP_SEND_WRITE_ACK … #define DP_WSAME … #define DP_ZEROES … /* possible combinations: * REQ_OP_WRITE_ZEROES: DP_DISCARD | DP_ZEROES * REQ_OP_WRITE_ZEROES + REQ_NOUNMAP: DP_ZEROES */ struct p_data { … } __packed; struct p_trim { … } __packed; struct p_wsame { … } __packed; /* * commands which share a struct: * p_block_ack: * P_RECV_ACK (proto B), P_WRITE_ACK (proto C), * P_SUPERSEDED (proto C, two-primaries conflict detection) * p_block_req: * P_DATA_REQUEST, P_RS_DATA_REQUEST */ struct p_block_ack { … } __packed; struct p_block_req { … } __packed; /* * commands with their own struct for additional fields: * P_CONNECTION_FEATURES * P_BARRIER * P_BARRIER_ACK * P_SYNC_PARAM * ReportParams */ /* supports TRIM/DISCARD on the "wire" protocol */ #define DRBD_FF_TRIM … /* Detect all-zeros during resync, and rather TRIM/UNMAP/DISCARD those blocks * instead of fully allocate a supposedly thin volume on initial resync */ #define DRBD_FF_THIN_RESYNC … /* supports REQ_WRITE_SAME on the "wire" protocol. * Note: this flag is overloaded, * its presence also * - indicates support for 128 MiB "batch bios", * max discard size of 128 MiB * instead of 4M before that. * - indicates that we exchange additional settings in p_sizes * drbd_send_sizes()/receive_sizes() */ #define DRBD_FF_WSAME … /* supports REQ_OP_WRITE_ZEROES on the "wire" protocol. * * We used to map that to "discard" on the sending side, and if we cannot * guarantee that discard zeroes data, the receiving side would map discard * back to zero-out. * * With the introduction of REQ_OP_WRITE_ZEROES, * we started to use that for both WRITE_ZEROES and DISCARDS, * hoping that WRITE_ZEROES would "do what we want", * UNMAP if possible, zero-out the rest. * * The example scenario is some LVM "thin" backend. * * While an un-allocated block on dm-thin reads as zeroes, on a dm-thin * with "skip_block_zeroing=true", after a partial block write allocated * that block, that same block may well map "undefined old garbage" from * the backends on LBAs that have not yet been written to. * * If we cannot distinguish between zero-out and discard on the receiving * side, to avoid "undefined old garbage" to pop up randomly at later times * on supposedly zero-initialized blocks, we'd need to map all discards to * zero-out on the receiving side. But that would potentially do a full * alloc on thinly provisioned backends, even when the expectation was to * unmap/trim/discard/de-allocate. * * We need to distinguish on the protocol level, whether we need to guarantee * zeroes (and thus use zero-out, potentially doing the mentioned full-alloc), * or if we want to put the emphasis on discard, and only do a "best effort * zeroing" (by "discarding" blocks aligned to discard-granularity, and zeroing * only potential unaligned head and tail clippings), to at least *try* to * avoid "false positives" in an online-verify later, hoping that someone * set skip_block_zeroing=false. */ #define DRBD_FF_WZEROES … struct p_connection_features { … } __packed; struct p_barrier { … } __packed; struct p_barrier_ack { … } __packed; struct p_rs_param { … } __packed; struct p_rs_param_89 { … } __packed; struct p_rs_param_95 { … } __packed; enum drbd_conn_flags { … }; struct p_protocol { … } __packed; struct p_uuids { … } __packed; struct p_rs_uuid { … } __packed; /* optional queue_limits if (agreed_features & DRBD_FF_WSAME) * see also struct queue_limits, as of late 2015 */ struct o_qlim { … } __packed; struct p_sizes { … } __packed; struct p_state { … } __packed; struct p_req_state { … } __packed; struct p_req_state_reply { … } __packed; struct p_drbd06_param { … } __packed; struct p_block_desc { … } __packed; /* Valid values for the encoding field. * Bump proto version when changing this. */ enum drbd_bitmap_code { … }; struct p_compressed_bm { … } __packed; struct p_delay_probe93 { … } __packed; /* * Bitmap packets need to fit within a single page on the sender and receiver, * so we are limited to 4 KiB (and not to PAGE_SIZE, which can be bigger). */ #define DRBD_SOCKET_BUFFER_SIZE … #endif /* __DRBD_PROTOCOL_H */
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