RDS: RDS-core fixes
Subsystems (3)
v3 cover RDS: RDS-core fixes
This patch-series updates the RDS core and rds-tcp modules with some bug fixes that were originally authored by Andy Grover, Zach Brown, and Chris Mason.
v2: Code review comment by Sergei Shtylov
V3: DaveM comments:
- dropped patches 3, 5 for "heuristic" changes in rds_send_xmit(). Investigation into the root-cause of these IB-triggered changes produced the feedback: "I don't remember seeing "RDS: Stuck RM" message in last 1-1.5 years and checking with other folks. It may very well be some old workaround for stale connection for which long term fix is already made and this part of code not exercised anymore."
Any such fixes, *if* they are needed, can/should be done in the IB specific RDS transport modules.
- similarly dropped the LL_SEND_FULL patch (patch 6 in v2 set)
Sowmini Varadhan (3):
RDS: Re-add pf/sol access via sysctl
RDS: only use passive connections when addresses match
RDS: make sure not to loop forever inside rds_send_xmit
net/rds/connection.c | 3 ++- net/rds/rds.h | 1 + net/rds/send.c | 33 +++++++++++++++++++++++++++++++-- net/rds/sysctl.c | 20 ++++++++++++++++++++ 4 files changed, 54 insertions(+), 3 deletions(-)
PATCH v3 1/3 RDS: Re-add pf/sol access via sysctl
Although RDS has an official PF_RDS value now, existing software expects to look for rds sysctls to determine it. We need to maintain these for now, for backwards compatibility.
Original patch by Andy Grover
--- net/rds/sysctl.c | 20 ++++++++++++++++++++ 1 files changed, 20 insertions(+), 0 deletions(-)
net/rds/sysctl.c +20 -0
@@ -49,6 +49,12 @@ unsigned int rds_sysctl_max_unacked_bytes = (16 << 20);unsigned int rds_sysctl_ping_enable =1 ; +/* We have official values, but must maintain the sysctl interface for existing +* software that expects to find these values here. +*/ +static int rds_sysctl_pf_rds =PF_RDS ; +static int rds_sysctl_sol_rds =SOL_RDS ; +static struct ctl_table rds_sysctl_rds_table[] = { { .procname ="reconnect_min_delay_ms" ,
@@ -69,6 +75,20 @@ static struct ctl_table rds_sysctl_rds_table[] = { .extra2 = &rds_sysctl_reconnect_max, }, { + .procname = "pf_rds", + .data = &rds_sysctl_pf_rds, + .maxlen = sizeof(int), + .mode = 0444, + .proc_handler = proc_dointvec, + }, + { + .procname = "sol_rds", + .data = &rds_sysctl_sol_rds, + .maxlen = sizeof(int), + .mode = 0444, + .proc_handler = proc_dointvec, + }, + { .procname = "max_unacked_packets", .data = &rds_sysctl_max_unacked_packets, .maxlen = sizeof(int),
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1.7.1
David Miller
maintainerRe: [PATCH v3 1/3] RDS: Re-add pf/sol access via sysctl
From: Sowmini Varadhan <[email protected]>
Date: Sat, 4 Apr 2015 08:45:44 -0400
Quoted 8 lines
Although RDS has an official
PF_RDSvalue now, existing software expects to look for rds sysctls to determine it. We need to maintain these for now, for backwards compatibility.Original patch by Andy Grover
Signed-off-by Sowmini Varadhan <[email protected]>Cc Ajaykumar Hotchandani <[email protected]>
If these never existed before, this is a feature patch and is not appropriate for 'net'.
If they did exist before and were mistakenly removed, you need to provide a proper "Fixes: " tag showing what commit introduced the problem.
PATCH v3 2/3 RDS: only use passive connections when addresses match
In reply to Sowmini VaradhanPassive connections were added for the case where one loopback IB connection between identical addresses needs another connection to store the second QP. Unfortunately, they were also created in the case where the addesses differ and we already have both QPs.
This lead to a message reordering bug.
- two different IB interfaces and addresses on a machine: A B
- traffic is sent from A to B
- connection from A-B is created, connect request sent
- listening accepts connect request, B-A is created
- traffic flows, next_rx is incremented
- unacked messages exist on the retrans list
- connection A-B is shut down, new connect request sent
- listen sees existing loopback B-A, creates new passive B-A
- retrans messages are sent and delivered because of 0 next_rx
The problem is that the second connection request saw the previously existing parent connection. Instead of using it, and using the existing next_rx_seq state for the traffic between those IPs, it mistakenly thought that it had to create a passive connection.
We fix this by only using passive connections in the special case where laddr and faddr match. In this case we'll only ever have one parent sending connection requests and one passive connection created as the listening path sees the existing parent connection which initiated the request.
Original patch by Zach Brown
--- net/rds/connection.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)
net/rds/connection.c +1 -1
@@ -130,7 +130,7 @@ static struct rds_connection *__rds_conn_create(__be32 laddr, __be32 faddr,rcu_read_lock (); conn =rds_conn_lookup (head, laddr, faddr, trans);if (conn && conn->c_loopback && conn->c_trans != &rds_loop_transport && - !is_outgoing) { + laddr == faddr && !is_outgoing) {/* This is a looped back IB connection, and we're * called by the code handling the incoming connect. * We need a second connection object into which we
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1.7.1
PATCH v3 3/3 RDS: make sure not to loop forever inside rds_send_xmit
In reply to Sowmini VaradhanIf a determined set of concurrent senders keep the send queue full, we can loop forever inside rds_send_xmit. This fix has two parts.
First we are dropping out of the while(1) loop after we've processed a large batch of messages.
Second we add a generation number that gets bumped each time the xmit bit lock is acquired. If someone else has jumped in and made progress in the queue, we skip our goto restart.
Original patch by Chris Mason.
Ajaykumar Hotchandani <[email protected]>
--- net/rds/connection.c | 1 + net/rds/rds.h | 1 + net/rds/send.c | 33 +++++++++++++++++++++++++++++++-- 3 files changed, 33 insertions(+), 2 deletions(-)
net/rds/connection.c +1 -0
@@ -193,6 +193,7 @@ static struct rds_connection *__rds_conn_create(__be32 laddr, __be32 faddr, }atomic_set (&conn->c_state,RDS_CONN_DOWN ); + conn->c_send_gen =0 ; conn->c_reconnect_jiffies =0 ;INIT_DELAYED_WORK (&conn->c_send_w, rds_send_worker);INIT_DELAYED_WORK (&conn->c_recv_w, rds_recv_worker);
net/rds/rds.h +1 -0
@@ -110,6 +110,7 @@ struct rds_connection {void *c_transport_data;atomic_t c_state; +unsigned long c_send_gen;unsigned long c_flags;unsigned long c_reconnect_jiffies;struct delayed_work c_send_w;
net/rds/send.c +31 -2
@@ -140,8 +140,11 @@ int rds_send_xmit(struct rds_connection *conn)struct scatterlist *sg;int ret =0 ;LIST_HEAD (to_be_dropped); +int batch_count; +unsigned long send_gen =0 ; restart: + batch_count =0 ;/* * sendmsg calls here after having queued its message on the send
@@ -157,6 +160,17 @@ int rds_send_xmit(struct rds_connection *conn) }/* +* we record the send generation after doing the xmit acquire. +* if someone else manages to jump in and do some work, we'll use +* this to avoid a goto restart farther down. +* +* we don't need a lock because the counter is only incremented +* while we have the in_xmit bit held. +*/ + conn->c_send_gen++; + send_gen = conn->c_send_gen; + +/* * rds_conn_shutdown() sets the conn state and then tests RDS_IN_XMIT, * we do the opposite to avoid races. */
@@ -202,6 +216,16 @@ int rds_send_xmit(struct rds_connection *conn)if (!rm) {unsigned int len; + batch_count++; + +/* we want to process as big a batch as we can, but +* we also want to avoid softlockups. If we've been +* through a lot of messages, lets back off and see +* if anyone else jumps in +*/ +if (batch_count >=1024 ) + goto over_batch; +spin_lock_irqsave (&conn->c_lock, flags);if (!list_empty (&conn->c_send_queue)) {
@@ -357,9 +381,9 @@ int rds_send_xmit(struct rds_connection *conn) } } +over_batch:if (conn->c_trans->xmit_complete) conn->c_trans->xmit_complete (conn); -release_in_xmit (conn);/* Nuke any messages we decided not to retransmit. */
@@ -380,10 +404,15 @@ int rds_send_xmit(struct rds_connection *conn)* If the transport cannot continue (i.e ret != 0), then it must * call us when more room is available, such as from the tx * completion handler. +* +* We have an extra generation check here so that if someone manages +* to jump in after our release_in_xmit, we'll see that they have done +* some work and we will skip our goto */ if (ret ==0 ) {smp_mb (); -if (!list_empty (&conn->c_send_queue)) { +if (!list_empty (&conn->c_send_queue) && + send_gen == conn->c_send_gen) {rds_stats_inc (s_send_lock_queue_raced); goto restart; }
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1.7.1