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    Subject[PATCH 5.6 188/254] scsi: zfcp: fix missing erp_lock in port recovery trigger for point-to-point
    Date
    From: Steffen Maier <maier@linux.ibm.com>

    commit 819732be9fea728623e1ed84eba28def7384ad1f upstream.

    v2.6.27 commit cc8c282963bd ("[SCSI] zfcp: Automatically attach remote
    ports") introduced zfcp automatic port scan.

    Before that, the user had to use the sysfs attribute "port_add" of an FCP
    device (adapter) to add and open remote (target) ports, even for the remote
    peer port in point-to-point topology. That code path did a proper port open
    recovery trigger taking the erp_lock.

    Since above commit, a new helper function zfcp_erp_open_ptp_port()
    performed an UNlocked port open recovery trigger. This can race with other
    parallel recovery triggers. In zfcp_erp_action_enqueue() this could corrupt
    e.g. adapter->erp_total_count or adapter->erp_ready_head.

    As already found for fabric topology in v4.17 commit fa89adba1941 ("scsi:
    zfcp: fix infinite iteration on ERP ready list"), there was an endless loop
    during tracing of rport (un)block. A subsequent v4.18 commit 9e156c54ace3
    ("scsi: zfcp: assert that the ERP lock is held when tracing a recovery
    trigger") introduced a lockdep assertion for that case.

    As a side effect, that lockdep assertion now uncovered the unlocked code
    path for PtP. It is from within an adapter ERP action:

    zfcp_erp_strategy[1479] intentionally DROPs erp lock around
    zfcp_erp_strategy_do_action()
    zfcp_erp_strategy_do_action[1441] NO erp lock
    zfcp_erp_adapter_strategy[876] NO erp lock
    zfcp_erp_adapter_strategy_open[855] NO erp lock
    zfcp_erp_adapter_strategy_open_fsf[806]NO erp lock
    zfcp_erp_adapter_strat_fsf_xconf[772] erp lock only around
    zfcp_erp_action_to_running(),
    BUT *_not_* around
    zfcp_erp_enqueue_ptp_port()
    zfcp_erp_enqueue_ptp_port[728] BUG: *_not_* taking erp lock
    _zfcp_erp_port_reopen[432] assumes to be called with erp lock
    zfcp_erp_action_enqueue[314] assumes to be called with erp lock
    zfcp_dbf_rec_trig[288] _checks_ to be called with erp lock:
    lockdep_assert_held(&adapter->erp_lock);

    It causes the following lockdep warning:

    WARNING: CPU: 2 PID: 775 at drivers/s390/scsi/zfcp_dbf.c:288
    zfcp_dbf_rec_trig+0x16a/0x188
    no locks held by zfcperp0.0.17c0/775.

    Fix this by using the proper locked recovery trigger helper function.

    Link: https://lore.kernel.org/r/20200312174505.51294-2-maier@linux.ibm.com
    Fixes: cc8c282963bd ("[SCSI] zfcp: Automatically attach remote ports")
    Cc: <stable@vger.kernel.org> #v2.6.27+
    Reviewed-by: Jens Remus <jremus@linux.ibm.com>
    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_erp.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/drivers/s390/scsi/zfcp_erp.c
    +++ b/drivers/s390/scsi/zfcp_erp.c
    @@ -725,7 +725,7 @@ static void zfcp_erp_enqueue_ptp_port(st
    adapter->peer_d_id);
    if (IS_ERR(port)) /* error or port already attached */
    return;
    - _zfcp_erp_port_reopen(port, 0, "ereptp1");
    + zfcp_erp_port_reopen(port, 0, "ereptp1");
    }

    static enum zfcp_erp_act_result zfcp_erp_adapter_strat_fsf_xconf(

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