linux/include/scsi/libfc.h

1153 lines
34 KiB

[SCSI] libfc: Fix remote port restart problem This patch somewhat combines two fixes to remote port handing in libfc. The first problem was that rport work could be queued on a deleted and freed rport. This is handled by not resetting rdata->event ton NONE if the rdata is about to be deleted. However, that fix led to the second problem, described by Bhanu Gollapudi, as follows: > Here is the sequence of events. T1 is first LOGO receive thread, T2 is > fc_rport_work() scheduled by T1 and T3 is second LOGO receive thread and > T4 is fc_rport_work scheduled by T3. > > 1. (T1)Received 1st LOGO in state Ready > 2. (T1)Delete port & enter to RESTART state. > 3. (T1)schdule event_work, since event is RPORT_EV_NONE. > 4. (T1)set event = RPORT_EV_LOGO > 5. (T1)Enter RESTART state as disc_id is set. > 6. (T2)remember to PLOGI, and set event = RPORT_EV_NONE > 6. (T3)Received 2nd LOGO > 7. (T3)Delete Port & enter to RESTART state. > 8. (T3)schedule event_work, since event is RPORT_EV_NONE. > 9. (T3)Enter RESTART state as disc_id is set. > 9. (T3)set event = RPORT_EV_LOGO > 10.(T2)work restart, enter PLOGI state and issues PLOGI > 11.(T4)Since state is not RESTART anymore, restart is not set, and the > event is not reset to RPORT_EV_NONE. (current event is RPORT_EV_LOGO). > 12. Now, PLOGI succeeds and fc_rport_enter_ready() will not schedule > event_work, and hence the rport will never be created, eventually losing > the target after dev_loss_tmo. So, the problem here is that we were tracking the desire for the rport be restarted by state RESTART, which was otherwise equivalent to DELETE. A contributing factor is that we dropped the lock between steps 6 and 10 in thread T2, which allows the state to change, and we didn't completely re-evaluate then. This is hopefully corrected by the following minor redesign: Simplify the rport restart logic by making the decision to restart after deleting the transport rport. That decision is based on a new STARTED flag that indicates fc_rport_login() has been called and fc_rport_logoff() has not been called since then. This replaces the need for the RESTART state. Only restart if the rdata is still in DELETED state and only if it still has the STARTED flag set. Also now, since we clear the event code much later in the work thread, allow for the possibility that the rport may have become READY again via incoming PLOGI, and if so, queue another event to handle that. In the problem scenario, the second LOGO received will cause the LOGO event to occur again. Reported-by: Bhanu Gollapudi <bprakash@broadcom.com> Signed-off-by: Joe Eykholt <jeykholt@cisco.com> Signed-off-by: Robert Love <robert.w.love@intel.com> Signed-off-by: James Bottomley <James.Bottomley@suse.de>
2010-06-11 16:44:51 -07:00
[SCSI] libfc: Fix remote port restart problem This patch somewhat combines two fixes to remote port handing in libfc. The first problem was that rport work could be queued on a deleted and freed rport. This is handled by not resetting rdata->event ton NONE if the rdata is about to be deleted. However, that fix led to the second problem, described by Bhanu Gollapudi, as follows: > Here is the sequence of events. T1 is first LOGO receive thread, T2 is > fc_rport_work() scheduled by T1 and T3 is second LOGO receive thread and > T4 is fc_rport_work scheduled by T3. > > 1. (T1)Received 1st LOGO in state Ready > 2. (T1)Delete port & enter to RESTART state. > 3. (T1)schdule event_work, since event is RPORT_EV_NONE. > 4. (T1)set event = RPORT_EV_LOGO > 5. (T1)Enter RESTART state as disc_id is set. > 6. (T2)remember to PLOGI, and set event = RPORT_EV_NONE > 6. (T3)Received 2nd LOGO > 7. (T3)Delete Port & enter to RESTART state. > 8. (T3)schedule event_work, since event is RPORT_EV_NONE. > 9. (T3)Enter RESTART state as disc_id is set. > 9. (T3)set event = RPORT_EV_LOGO > 10.(T2)work restart, enter PLOGI state and issues PLOGI > 11.(T4)Since state is not RESTART anymore, restart is not set, and the > event is not reset to RPORT_EV_NONE. (current event is RPORT_EV_LOGO). > 12. Now, PLOGI succeeds and fc_rport_enter_ready() will not schedule > event_work, and hence the rport will never be created, eventually losing > the target after dev_loss_tmo. So, the problem here is that we were tracking the desire for the rport be restarted by state RESTART, which was otherwise equivalent to DELETE. A contributing factor is that we dropped the lock between steps 6 and 10 in thread T2, which allows the state to change, and we didn't completely re-evaluate then. This is hopefully corrected by the following minor redesign: Simplify the rport restart logic by making the decision to restart after deleting the transport rport. That decision is based on a new STARTED flag that indicates fc_rport_login() has been called and fc_rport_logoff() has not been called since then. This replaces the need for the RESTART state. Only restart if the rdata is still in DELETED state and only if it still has the STARTED flag set. Also now, since we clear the event code much later in the work thread, allow for the possibility that the rport may have become READY again via incoming PLOGI, and if so, queue another event to handle that. In the problem scenario, the second LOGO received will cause the LOGO event to occur again. Reported-by: Bhanu Gollapudi <bprakash@broadcom.com> Signed-off-by: Joe Eykholt <jeykholt@cisco.com> Signed-off-by: Robert Love <robert.w.love@intel.com> Signed-off-by: James Bottomley <James.Bottomley@suse.de>
2010-06-11 16:44:51 -07:00
[SCSI] fcoe, fnic, libfc: modifies current code paths to use EM anchor list Modifies current code to use EM anchor list in EM allocation, EM free, EM reset, exch allocation and exch lookup code paths. 1. Modifies fc_exch_mgr_alloc to accept EM match function and then have allocated EM added to the lport using fc_exch_mgr_add API while also updating EM kref for newly added EM. 2. Updates fc_exch_mgr_free API to accept only lport pointer instead EM and then have this API free all EMs of the lport from EM anchor list. 3. Removes single lport pointer link from the EM, which was used in associating lport pointer in newly allocated exchange. Instead have lport pointer passed along new exchange allocation call path and then store passed lport pointer in newly allocated exchange, this will allow a single EM instance to be used across more than one lport and used in EM reset to reset only lport specific exchanges. 4. Modifies fc_exch_mgr_reset to reset all EMs from the EM anchor list of the lport, adds additional exch lport pointer (ep->lp) check for shared EM case to reset exchange specific to a lport requested reset. 5. Updates exch allocation API fc_exch_alloc to use EM anchor list and its anchor match func pointer. The fc_exch_alloc will walk the list of EMs until it finds a match, a match will be either null match func pointer or call to match function returning true value. 6. Updates fc_exch_recv to accept incoming frame on local port using only lport pointer and frame pointer without specifying EM instance of incoming frame. Instead modified fc_exch_recv to locate EM for the incoming frame by matching xid of incoming frame against a EM xid range. This change was required to use EM list in libfc Rx path and after this change the lport fc_exch_mgr pointer emp is not needed anymore, so removed emp pointer. 7. Updates fnic for removed lport emp pointer and above modified libfc APIs fc_exch_recv, fc_exch_mgr_alloc and fc_exch_mgr_free. 8. Removes exch_get and exch_put from libfc_function_template as these are no longer needed with EM anchor list and its match function use. Also removes its default function fc_exch_get. A defect this patch introduced regarding the libfc initialization order in the fnic driver was fixed by Joe Eykholt <jeykholt@cisco.com>. Signed-off-by: Vasu Dev <vasu.dev@intel.com> Signed-off-by: Robert Love <robert.w.love@intel.com> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com> Signed-off-by: James Bottomley <James.Bottomley@suse.de>
2009-07-29 17:05:10 -07:00