diff options
Diffstat (limited to 'drivers/block/drbd/drbd_protocol.h')
| -rw-r--r-- | drivers/block/drbd/drbd_protocol.h | 66 |
1 files changed, 58 insertions, 8 deletions
diff --git a/drivers/block/drbd/drbd_protocol.h b/drivers/block/drbd/drbd_protocol.h index 4d296800f706..56bbca9d7700 100644 --- a/drivers/block/drbd/drbd_protocol.h +++ b/drivers/block/drbd/drbd_protocol.h @@ -1,3 +1,4 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ #ifndef __DRBD_PROTOCOL_H #define __DRBD_PROTOCOL_H @@ -56,7 +57,7 @@ enum drbd_packet { P_PROTOCOL_UPDATE = 0x2d, /* data sock: is used in established connections */ /* 0x2e to 0x30 reserved, used in drbd 9 */ - /* REQ_DISCARD. We used "discard" in different contexts before, + /* REQ_OP_DISCARD. We used "discard" in different contexts before, * which is why I chose TRIM here, to disambiguate. */ P_TRIM = 0x31, @@ -69,6 +70,11 @@ enum drbd_packet { * we may fall back to an opencoded loop instead. */ P_WSAME = 0x34, + /* 0x35 already claimed in DRBD 9 */ + P_ZEROES = 0x36, /* data sock: zero-out, WRITE_ZEROES */ + + /* 0x40 .. 0x48 already claimed in DRBD 9 */ + P_MAY_IGNORE = 0x100, /* Flag to test if (cmd > P_MAY_IGNORE) ... */ P_MAX_OPT_CMD = 0x101, @@ -125,10 +131,16 @@ struct p_header100 { #define DP_UNPLUG 8 /* not used anymore */ #define DP_FUA 16 /* equals REQ_FUA */ #define DP_FLUSH 32 /* equals REQ_PREFLUSH */ -#define DP_DISCARD 64 /* equals REQ_DISCARD */ +#define DP_DISCARD 64 /* equals REQ_OP_DISCARD */ #define DP_SEND_RECEIVE_ACK 128 /* This is a proto B write request */ #define DP_SEND_WRITE_ACK 256 /* This is a proto C write request */ #define DP_WSAME 512 /* equiv. REQ_WRITE_SAME */ +#define DP_ZEROES 1024 /* equiv. REQ_OP_WRITE_ZEROES */ + +/* possible combinations: + * REQ_OP_WRITE_ZEROES: DP_DISCARD | DP_ZEROES + * REQ_OP_WRITE_ZEROES + REQ_NOUNMAP: DP_ZEROES + */ struct p_data { u64 sector; /* 64 bits sector number */ @@ -196,6 +208,42 @@ struct p_block_req { */ #define DRBD_FF_WSAME 4 +/* 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 8 + + struct p_connection_features { u32 protocol_min; u32 feature_flags; @@ -223,7 +271,7 @@ struct p_rs_param { u32 resync_rate; /* Since protocol version 88 and higher. */ - char verify_alg[0]; + char verify_alg[]; } __packed; struct p_rs_param_89 { @@ -235,8 +283,10 @@ struct p_rs_param_89 { struct p_rs_param_95 { u32 resync_rate; - char verify_alg[SHARED_SECRET_MAX]; - char csums_alg[SHARED_SECRET_MAX]; + struct_group(algs, + char verify_alg[SHARED_SECRET_MAX]; + char csums_alg[SHARED_SECRET_MAX]; + ); u32 c_plan_ahead; u32 c_delay_target; u32 c_fill_target; @@ -257,7 +307,7 @@ struct p_protocol { u32 two_primaries; /* Since protocol version 87 and higher. */ - char integrity_alg[0]; + char integrity_alg[]; } __packed; @@ -312,7 +362,7 @@ struct p_sizes { u16 dds_flags; /* use enum dds_flags here. */ /* optional queue_limits if (agreed_features & DRBD_FF_WSAME) */ - struct o_qlim qlim[0]; + struct o_qlim qlim[]; } __packed; struct p_state { @@ -361,7 +411,7 @@ struct p_compressed_bm { */ u8 encoding; - u8 code[0]; + u8 code[]; } __packed; struct p_delay_probe93 { |