drbd: New configuration parameters for dealing with network congestion

net {
    on_congestion {block|pull-ahead|disconnect};
    congestion-fill {sectors};
    congestion-extents {al-extents};
}
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

drivers/block/drbd/drbd_nl.c

@@ -1323,6 +1323,8 @@ static int drbd_nl_net_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
 	new_conf->wire_protocol    = DRBD_PROT_C;
 	new_conf->ping_timeo	   = DRBD_PING_TIMEO_DEF;
 	new_conf->rr_conflict	   = DRBD_RR_CONFLICT_DEF;
+	new_conf->on_congestion    = DRBD_ON_CONGESTION_DEF;
+	new_conf->cong_extents     = DRBD_CONG_EXTENTS_DEF;
 
 	if (!net_conf_from_tags(mdev, nlp->tag_list, new_conf)) {
 		retcode = ERR_MANDATORY_TAG;
@@ -1344,6 +1346,11 @@ static int drbd_nl_net_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
 		}
 	}
 
+	if (new_conf->on_congestion != OC_BLOCK && new_conf->wire_protocol != DRBD_PROT_A) {
+		retcode = ERR_CONG_NOT_PROTO_A;
+		goto fail;
+	}
+
 	if (mdev->state.role == R_PRIMARY && new_conf->want_lose) {
 		retcode = ERR_DISCARD;
 		goto fail;

include/linux/drbd.h

@@ -96,6 +96,12 @@ enum drbd_on_no_data {
 	OND_SUSPEND_IO
 };
 
+enum drbd_on_congestion {
+	OC_BLOCK,
+	OC_PULL_AHEAD,
+	OC_DISCONNECT,
+};
+
 /* KEEP the order, do not delete or insert. Only append. */
 enum drbd_ret_codes {
 	ERR_CODE_BASE		= 100,
@@ -146,6 +152,7 @@ enum drbd_ret_codes {
 	ERR_PERM		= 152,
 	ERR_NEED_APV_93		= 153,
 	ERR_STONITH_AND_PROT_A  = 154,
+	ERR_CONG_NOT_PROTO_A	= 155,
 
 	/* insert new ones above this line */
 	AFTER_LAST_ERR_CODE

include/linux/drbd_limits.h

@@ -129,6 +129,7 @@
 #define DRBD_AFTER_SB_2P_DEF ASB_DISCONNECT
 #define DRBD_RR_CONFLICT_DEF ASB_DISCONNECT
 #define DRBD_ON_NO_DATA_DEF OND_IO_ERROR
+#define DRBD_ON_CONGESTION_DEF OC_BLOCK
 
 #define DRBD_MAX_BIO_BVECS_MIN 0
 #define DRBD_MAX_BIO_BVECS_MAX 128
@@ -154,5 +155,13 @@
 #define DRBD_C_MIN_RATE_MAX     (4 << 20)
 #define DRBD_C_MIN_RATE_DEF     4096
 
+#define DRBD_CONG_FILL_MIN	0
+#define DRBD_CONG_FILL_MAX	(10<<21) /* 10GByte in sectors */
+#define DRBD_CONG_FILL_DEF	0
+
+#define DRBD_CONG_EXTENTS_MIN	DRBD_AL_EXTENTS_MIN
+#define DRBD_CONG_EXTENTS_MAX	DRBD_AL_EXTENTS_MAX
+#define DRBD_CONG_EXTENTS_DEF	DRBD_AL_EXTENTS_DEF
+
 #undef RANGE
 #endif

include/linux/drbd_nl.h

@@ -56,6 +56,9 @@ NL_PACKET(net_conf, 5,
 	NL_INTEGER(	39,	T_MAY_IGNORE,	rr_conflict)
 	NL_INTEGER(	40,	T_MAY_IGNORE,	ping_timeo)
 	NL_INTEGER(	67,	T_MAY_IGNORE,	rcvbuf_size)
+	NL_INTEGER(	81,	T_MAY_IGNORE,	on_congestion)
+	NL_INTEGER(	82,	T_MAY_IGNORE,	cong_fill)
+	NL_INTEGER(	83,	T_MAY_IGNORE,	cong_extents)
 	  /* 59 addr_family was available in GIT, never released */
 	NL_BIT(		60,	T_MANDATORY,	mind_af)
 	NL_BIT(		27,	T_MAY_IGNORE,	want_lose)