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

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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>
This commit is contained in:
Bart Van Assche 2013-02-21 17:20:00 +00:00 committed by Roland Dreier
parent c7c4e7ff80
commit 2ce19e72f4
2 changed files with 8 additions and 0 deletions
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7
drivers/infiniband/ulp/srp/ib_srp.c
View file

@ -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)

1
drivers/infiniband/ulp/srp/ib_srp.h
View file

@ -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.