Before SCSI target is removed, all vhost sessions need
to drain their pending I/O and put their I/O channels.
After a session puts it channel, it sends an async
notification to the entire vhost device. The device
will check if there are any other sessions still
referencing the SCSI target and if not - it will
continue removing the spdk_scsi_dev object. There may
be multiple sessions sending those async events at the
same time, and while we do protect from removing the
same spdk_scsi_dev twice, we can still remove
a different spdk_scsi_dev that was hot-attached in the
meantime with the same target ID.
1. SCSI target hotremove (e.g. via RPC or bdev hotremove)
/ \
/ \
session A session B
drain I/O drain I/O
| |
v |
done v
send event done
\ send event*
\
All sessions have detached the SCSI target, remove
it from the entire vhost device. From this point
a new target can be hot-attached (e.g. via RPC).
2. Attach a SCSI target with with same target ID.
3. Hotremove event* from the previous SCSI target gets
finally executed. SCSI target with that ID is
occupied (again) and may be hotremoved by mistake.
The role of that hotremove event is just to kick the
vhost device and make it remove any scsi targets that
can be removed, so add a check preventing it from
removing devices in states other than REMOVING.
Change-Id: Ia1cc7cae797fd8859d485e63f0ef37aeac2945d0
Signed-off-by: Darek Stojaczyk <dariusz.stojaczyk@intel.com>
Reviewed-on: https://review.gerrithub.io/c/spdk/spdk/+/449990
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Changpeng Liu <changpeng.liu@intel.com>
bf77d4b774