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scsi: zfcp: Fix missing auto port scan and thus missing target ports

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Case (1):
  The only waiter on wka_port->completion_wq is zfcp_fc_wka_port_get()
  trying to open a WKA port. As such it should only be woken up by WKA port
  *open* responses, not by WKA port close responses.

Case (2):
  A close WKA port response coming in just after having sent a new open WKA
  port request and before blocking for the open response with wait_event()
  in zfcp_fc_wka_port_get() erroneously renders the wait_event a NOP
  because the close handler overwrites wka_port->status. Hence the
  wait_event condition is erroneously true and it does not enter blocking
  state.

With non-negligible probability, the following time space sequence happens
depending on timing without this fix:

user process        ERP thread zfcp work queue tasklet system work queue
============        ========== =============== ======= =================
$ echo 1 > online
zfcp_ccw_set_online
zfcp_ccw_activate
zfcp_erp_adapter_reopen
msleep scan backoff zfcp_erp_strategy
|                   ...
|                   zfcp_erp_action_cleanup
|                   ...
|                   queue delayed scan_work
|                   queue ns_up_work
|                              ns_up_work:
|                              zfcp_fc_wka_port_get
|                               open wka request
|                                              open response
|                              GSPN FC-GS
|                              RSPN FC-GS [NPIV-only]
|                              zfcp_fc_wka_port_put
|                               (--wka->refcount==0)
|                               sched delayed wka->work
|
~~~Case (1)~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
zfcp_erp_wait
flush scan_work
|                                                      wka->work:
|                                                      wka->status=CLOSING
|                                                      close wka request
|                              scan_work:
|                              zfcp_fc_wka_port_get
|                               (wka->status==CLOSING)
|                               wka->status=OPENING
|                               open wka request
|                               wait_event
|                               |              close response
|                               |              wka->status=OFFLINE
|                               |              wake_up /*WRONG*/
~~~Case (2)~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|                                                      wka->work:
|                                                      wka->status=CLOSING
|                                                      close wka request
zfcp_erp_wait
flush scan_work
|                              scan_work:
|                              zfcp_fc_wka_port_get
|                               (wka->status==CLOSING)
|                               wka->status=OPENING
|                               open wka request
|                                              close response
|                                              wka->status=OFFLINE
|                                              wake_up /*WRONG&NOP*/
|                               wait_event /*NOP*/
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|                               (wka->status!=ONLINE)
|                               return -EIO
|                              return early
                                               open response
                                               wka->status=ONLINE
                                               wake_up /*NOP*/

So we erroneously end up with no automatic port scan. This is a big problem
when it happens during boot. The timing is influenced by v3.19 commit
18f87a67e6 ("zfcp: auto port scan resiliency").

Fix it by fully mutually excluding zfcp_fc_wka_port_get() and
zfcp_fc_wka_port_offline(). For that to work, we make the latter block
until we got the response for a close WKA port. In order not to penalize
the system workqueue, we move wka_port->work to our own adapter workqueue.
Note that before v2.6.30 commit 828bc1212a ("[SCSI] zfcp: Set WKA-port to
offline on adapter deactivation"), zfcp did block in
zfcp_fc_wka_port_offline() as well, but with a different condition.

While at it, make non-functional cleanups to improve code reading in
zfcp_fc_wka_port_get(). If we cannot send the WKA port open request, don't
rely on the subsequent wait_event condition to immediately let this case
pass without blocking. Also don't want to rely on the additional condition
handling the refcount to be skipped just to finally return with -EIO.

Link: https://lore.kernel.org/r/20220729162529.1620730-1-maier@linux.ibm.com
Fixes: 5ab944f97e ("[SCSI] zfcp: attach and release SAN nameserver port on demand")
Cc: <stable@vger.kernel.org> #v2.6.28+
Reviewed-by: Benjamin Block <bblock@linux.ibm.com>
Signed-off-by: Steffen Maier <maier@linux.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
This commit is contained in:
Steffen Maier 2022-07-29 18:25:29 +02:00 committed by Martin K. Petersen
parent f323896fe6
commit 4da8c5f768
3 changed files with 26 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
drivers/s390/scsi/zfcp_fc.c
View File

@ -145,27 +145,33 @@ void zfcp_fc_enqueue_event(struct zfcp_adapter *adapter,
static int zfcp_fc_wka_port_get(struct zfcp_fc_wka_port *wka_port)
{
int ret = -EIO;
if (mutex_lock_interruptible(&wka_port->mutex))
return -ERESTARTSYS;
if (wka_port->status == ZFCP_FC_WKA_PORT_OFFLINE ||
wka_port->status == ZFCP_FC_WKA_PORT_CLOSING) {
wka_port->status = ZFCP_FC_WKA_PORT_OPENING;
if (zfcp_fsf_open_wka_port(wka_port))
if (zfcp_fsf_open_wka_port(wka_port)) {
/* could not even send request, nothing to wait for */
wka_port->status = ZFCP_FC_WKA_PORT_OFFLINE;
goto out;
}
}
mutex_unlock(&wka_port->mutex);
wait_event(wka_port->completion_wq,
wait_event(wka_port->opened,
wka_port->status == ZFCP_FC_WKA_PORT_ONLINE ||
wka_port->status == ZFCP_FC_WKA_PORT_OFFLINE);
if (wka_port->status == ZFCP_FC_WKA_PORT_ONLINE) {
atomic_inc(&wka_port->refcount);
return 0;
ret = 0;
goto out;
}
return -EIO;
out:
mutex_unlock(&wka_port->mutex);
return ret;
}
static void zfcp_fc_wka_port_offline(struct work_struct *work)
@ -181,9 +187,12 @@ static void zfcp_fc_wka_port_offline(struct work_struct *work)
wka_port->status = ZFCP_FC_WKA_PORT_CLOSING;
if (zfcp_fsf_close_wka_port(wka_port)) {
/* could not even send request, nothing to wait for */
wka_port->status = ZFCP_FC_WKA_PORT_OFFLINE;
wake_up(&wka_port->completion_wq);
goto out;
}
wait_event(wka_port->closed,
wka_port->status == ZFCP_FC_WKA_PORT_OFFLINE);
out:
mutex_unlock(&wka_port->mutex);
}
@ -193,13 +202,15 @@ static void zfcp_fc_wka_port_put(struct zfcp_fc_wka_port *wka_port)
if (atomic_dec_return(&wka_port->refcount) != 0)
return;
/* wait 10 milliseconds, other reqs might pop in */
schedule_delayed_work(&wka_port->work, HZ / 100);
queue_delayed_work(wka_port->adapter->work_queue, &wka_port->work,
msecs_to_jiffies(10));
}
static void zfcp_fc_wka_port_init(struct zfcp_fc_wka_port *wka_port, u32 d_id,
struct zfcp_adapter *adapter)
{
init_waitqueue_head(&wka_port->completion_wq);
init_waitqueue_head(&wka_port->opened);
init_waitqueue_head(&wka_port->closed);
wka_port->adapter = adapter;
wka_port->d_id = d_id;

6
drivers/s390/scsi/zfcp_fc.h
View File

@ -185,7 +185,8 @@ enum zfcp_fc_wka_status {
/**
* struct zfcp_fc_wka_port - representation of well-known-address (WKA) FC port
* @adapter: Pointer to adapter structure this WKA port belongs to
* @completion_wq: Wait for completion of open/close command
* @opened: Wait for completion of open command
* @closed: Wait for completion of close command
* @status: Current status of WKA port
* @refcount: Reference count to keep port open as long as it is in use
* @d_id: FC destination id or well-known-address
@ -195,7 +196,8 @@ enum zfcp_fc_wka_status {
*/
struct zfcp_fc_wka_port {
struct zfcp_adapter *adapter;
wait_queue_head_t completion_wq;
wait_queue_head_t opened;
wait_queue_head_t closed;
enum zfcp_fc_wka_status status;
atomic_t refcount;
u32 d_id;

4
drivers/s390/scsi/zfcp_fsf.c
View File

@ -1907,7 +1907,7 @@ static void zfcp_fsf_open_wka_port_handler(struct zfcp_fsf_req *req)
wka_port->status = ZFCP_FC_WKA_PORT_ONLINE;
}
out:
wake_up(&wka_port->completion_wq);
wake_up(&wka_port->opened);
}
/**
@ -1966,7 +1966,7 @@ static void zfcp_fsf_close_wka_port_handler(struct zfcp_fsf_req *req)
}
wka_port->status = ZFCP_FC_WKA_PORT_OFFLINE;
wake_up(&wka_port->completion_wq);
wake_up(&wka_port->closed);
}
/**