IB/srp: Fail I/O requests if the transport is offline

If an SRP target is no longer reachable and srp_reset_host() fails to
reconnect then ib_srp will invoke scsi_remove_host().  That function
will invoke __scsi_remove_device() for each LUN.  And that last
function will change the device state from SDEV_TRANSPORT_OFFLINE into
SDEV_CANCEL.  Certain user space software, e.g. older versions of
multipathd, continue queueing I/O to SCSI devices that are in the
SDEV_CANCEL state.

If these I/O requests are submitted as SG_IO that means that the
REQ_PREEMPT flag will be set and hence that these requests will be
passed to srp_queuecommand().  These requests will time out.  If new
requests are queued fast enough from user space these active requests
will prevent __scsi_remove_device() to finish.

Avoid this by failing I/O requests in the SDEV_CANCEL state if the
transport is offline.  Introduce a new variable to keep track of the
transport state instead of failing requests if (!target->connected ||
target->qp_in_error), so that the SCSI error handler has a chance to
retry commands after a transport layer failure occurred.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Cc: <stable@vger.kernel.org> # 3.8
Signed-off-by: Roland Dreier <roland@purestorage.com>

diff --git a/drivers/infiniband/ulp/srp/ib_srp.c b/drivers/infiniband/ulp/srp/ib_srp.c
index 8a7eb9f..7ccf328 100644 (file)
--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -734,6 +734,7 @@ static int srp_reconnect_target(struct srp_target_port *target)
 
        scsi_target_unblock(&shost->shost_gendev, ret == 0 ? SDEV_RUNNING :
                            SDEV_TRANSPORT_OFFLINE);
+       target->transport_offline = !!ret;
 
        if (ret)
                goto err;
@@ -1353,6 +1354,12 @@ static int srp_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *scmnd)
        unsigned long flags;
        int len;
 
+       if (unlikely(target->transport_offline)) {
+               scmnd->result = DID_NO_CONNECT << 16;
+               scmnd->scsi_done(scmnd);
+               return 0;
+       }
+
        spin_lock_irqsave(&target->lock, flags);
        iu = __srp_get_tx_iu(target, SRP_IU_CMD);
        if (!iu)

diff --git a/drivers/infiniband/ulp/srp/ib_srp.h b/drivers/infiniband/ulp/srp/ib_srp.h
index de2d0b3..66fbedd 100644 (file)
--- a/drivers/infiniband/ulp/srp/ib_srp.h
+++ b/drivers/infiniband/ulp/srp/ib_srp.h
@@ -140,6 +140,7 @@ struct srp_target_port {
        unsigned int            cmd_sg_cnt;
        unsigned int            indirect_size;
        bool                    allow_ext_sg;
+       bool                    transport_offline;
 
        /* Everything above this point is used in the hot path of
         * command processing. Try to keep them packed into cachelines.