From: Steffen Maier maier@linux.ibm.com
commit 4da8c5f76825269f28d6a89fa752934a4bcb6dfa upstream.
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 18f87a67e6d6 ("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 828bc1212a68 ("[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: 5ab944f97e09 ("[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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/s390/scsi/zfcp_fc.c | 29 ++++++++++++++++++++--------- drivers/s390/scsi/zfcp_fc.h | 6 ++++-- drivers/s390/scsi/zfcp_fsf.c | 4 ++-- 3 files changed, 26 insertions(+), 13 deletions(-)
--- a/drivers/s390/scsi/zfcp_fc.c +++ b/drivers/s390/scsi/zfcp_fc.c @@ -145,27 +145,33 @@ void zfcp_fc_enqueue_event(struct zfcp_a
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(str
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 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; --- a/drivers/s390/scsi/zfcp_fc.h +++ b/drivers/s390/scsi/zfcp_fc.h @@ -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; --- a/drivers/s390/scsi/zfcp_fsf.c +++ b/drivers/s390/scsi/zfcp_fsf.c @@ -1907,7 +1907,7 @@ static void zfcp_fsf_open_wka_port_handl 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_hand }
wka_port->status = ZFCP_FC_WKA_PORT_OFFLINE; - wake_up(&wka_port->completion_wq); + wake_up(&wka_port->closed); }
/**