[PATCH 17/30] drbd: don't forget error completion when "unsuspending" IO

From: Philipp Reisner
Date: Mon Apr 25 2016 - 08:23:57 EST


From: Lars Ellenberg <lars.ellenberg@xxxxxxxxxx>

Possibly sequence of events:
SyncTarget is made Primary, then loses replication link
(only path to good data on SyncSource).

Behavior is then controlled by the on-no-data-accessible policy,
which defaults to OND_IO_ERROR (may be set to OND_SUSPEND_IO).

If OND_IO_ERROR is in fact the current policy, we clear the susp_fen
(IO suspended due to fencing policy) flag, do NOT set the susp_nod
(IO suspended due to no data) flag.

But we forgot to call the IO error completion for all pending,
suspended, requests.

While at it, also add a race check for a theoretically possible
race with a new handshake (network hickup), we may be able to
re-send requests, and can avoid passing IO errors up the stack.

Signed-off-by: Philipp Reisner <philipp.reisner@xxxxxxxxxx>
Signed-off-by: Lars Ellenberg <lars.ellenberg@xxxxxxxxxx>
---
drivers/block/drbd/drbd_nl.c | 48 +++++++++++++++++++++++++++++---------------
1 file changed, 32 insertions(+), 16 deletions(-)

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index f16084a..a703a0e 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -442,19 +442,17 @@ static enum drbd_fencing_p highest_fencing_policy(struct drbd_connection *connec
}
rcu_read_unlock();

- if (fp == FP_NOT_AVAIL) {
- /* IO Suspending works on the whole resource.
- Do it only for one device. */
- vnr = 0;
- peer_device = idr_get_next(&connection->peer_devices, &vnr);
- drbd_change_state(peer_device->device, CS_VERBOSE | CS_HARD, NS(susp_fen, 0));
- }
-
return fp;
}

+static bool resource_is_supended(struct drbd_resource *resource)
+{
+ return resource->susp || resource->susp_fen || resource->susp_nod;
+}
+
bool conn_try_outdate_peer(struct drbd_connection *connection)
{
+ struct drbd_resource * const resource = connection->resource;
unsigned int connect_cnt;
union drbd_state mask = { };
union drbd_state val = { };
@@ -462,21 +460,41 @@ bool conn_try_outdate_peer(struct drbd_connection *connection)
char *ex_to_string;
int r;

- spin_lock_irq(&connection->resource->req_lock);
+ spin_lock_irq(&resource->req_lock);
if (connection->cstate >= C_WF_REPORT_PARAMS) {
drbd_err(connection, "Expected cstate < C_WF_REPORT_PARAMS\n");
- spin_unlock_irq(&connection->resource->req_lock);
+ spin_unlock_irq(&resource->req_lock);
return false;
}

connect_cnt = connection->connect_cnt;
- spin_unlock_irq(&connection->resource->req_lock);
+ spin_unlock_irq(&resource->req_lock);

fp = highest_fencing_policy(connection);
switch (fp) {
case FP_NOT_AVAIL:
drbd_warn(connection, "Not fencing peer, I'm not even Consistent myself.\n");
- goto out;
+ spin_lock_irq(&resource->req_lock);
+ if (connection->cstate < C_WF_REPORT_PARAMS) {
+ _conn_request_state(connection,
+ (union drbd_state) { { .susp_fen = 1 } },
+ (union drbd_state) { { .susp_fen = 0 } },
+ CS_VERBOSE | CS_HARD | CS_DC_SUSP);
+ /* We are no longer suspended due to the fencing policy.
+ * We may still be suspended due to the on-no-data-accessible policy.
+ * If that was OND_IO_ERROR, fail pending requests. */
+ if (!resource_is_supended(resource))
+ _tl_restart(connection, CONNECTION_LOST_WHILE_PENDING);
+ }
+ /* Else: in case we raced with a connection handshake,
+ * let the handshake figure out if we maybe can RESEND,
+ * and do not resume/fail pending requests here.
+ * Worst case is we stay suspended for now, which may be
+ * resolved by either re-establishing the replication link, or
+ * the next link failure, or eventually the administrator. */
+ spin_unlock_irq(&resource->req_lock);
+ return false;
+
case FP_DONT_CARE:
return true;
default: ;
@@ -529,13 +547,11 @@ bool conn_try_outdate_peer(struct drbd_connection *connection)
drbd_info(connection, "fence-peer helper returned %d (%s)\n",
(r>>8) & 0xff, ex_to_string);

- out:
-
/* Not using
conn_request_state(connection, mask, val, CS_VERBOSE);
here, because we might were able to re-establish the connection in the
meantime. */
- spin_lock_irq(&connection->resource->req_lock);
+ spin_lock_irq(&resource->req_lock);
if (connection->cstate < C_WF_REPORT_PARAMS && !test_bit(STATE_SENT, &connection->flags)) {
if (connection->connect_cnt != connect_cnt)
/* In case the connection was established and droped
@@ -544,7 +560,7 @@ bool conn_try_outdate_peer(struct drbd_connection *connection)
else
_conn_request_state(connection, mask, val, CS_VERBOSE);
}
- spin_unlock_irq(&connection->resource->req_lock);
+ spin_unlock_irq(&resource->req_lock);

return conn_highest_pdsk(connection) <= D_OUTDATED;
}
--
1.9.1