• Vasu Dev's avatar
    [SCSI] libfc, fcoe: fixed locking issues with lport->lp_mutex around lport->link_status · bc0e17f6
    Vasu Dev authored
    The fcoe_xmit could call fc_pause in case the pending skb queue len is larger
    than FCOE_MAX_QUEUE_DEPTH, the fc_pause was trying to grab lport->lp_muex to
    change lport->link_status and that had these issues :-
    1. The fcoe_xmit was getting called with bh disabled, thus causing
    "BUG: scheduling while atomic" when grabbing lport->lp_muex with bh disabled.
    2. fc_linkup and fc_linkdown function calls lport_enter function with
    lport->lp_mutex held and these enter function in turn calls fcoe_xmit to send
    lport related FC frame, e.g. fc_linkup => fc_lport_enter_flogi to send flogi
    req. In this case grabbing the same lport->lp_mutex again in fc_puase from
    fcoe_xmit would cause deadlock.
    The lport->lp_mutex was used for setting FC_PAUSE in fcoe_xmit path but
    FC_PAUSE bit was not used anywhere beside just setting and clear this
    bit in lport->link_status, instead used a separate field qfull in fc_lport
    to eliminate need for lport->lp_mutex to track pending queue full condition
    and in turn avoid above described two locking issues.
    Also added check for lp->qfull in fc_fcp_lport_queue_ready to trigger
    SCSI_MLQUEUE_HOST_BUSY when lp->qfull is set to prevent more scsi-ml cmds
    while lp->qfull is set.
    This patch eliminated FC_LINK_UP and FC_PAUSE and instead used dedicated
    fields in fc_lport for this, this simplified all related conditional
    Also removed fc_pause and fc_unpause functions and instead used newly added
    lport->qfull directly in fcoe.
    Signed-off-by: default avatarVasu Dev <vasu.dev@intel.com>
    Signed-off-by: default avatarRobert Love <robert.w.love@intel.com>
    Signed-off-by: default avatarJames Bottomley <James.Bottomley@HansenPartnership.com>