[dm-devel] why command of multipath send reinstate message to all dm's paths

[Jiaojianbing]

Dear Christophe,
when dm-105 is in one state of below, paths of dm-105 will change to active if we run command of multipath. I check code of multipath, it sends messge "reinstate_path pathname" to kernel in routine reinstate_paths when status of pathgroup = "PGSTATE_ENABLED/PGSTATE_UNDEF" and path's state = "PSTATE_FAILED".
why command of multipath do above action to all dm devices? actually, parts of these paths are already offline or failed which can't be recovered. Maybe we can check these devices's status by sending io to these sd device at first. according to return of io, multipath send reinstate to running devices and do nothing to failed devices?

# multipath -ll
36d0d04b100b8cba665a187f0000000f9 dm-105 HUAWEI  ,XSG1
size=1.0G features='0' hwhandler='0' wp=rw
`-+- policy='service-time 0' prio=0 status=enabled
  |- 17:0:0:101 sdcy 70:96   failed faulty offline
  |- 18:0:0:101 sdgw 132:192 failed faulty offline
  `- 19:0:0:101 sdku 67:288  failed faulty offline

# multipath -ll
36d0d04b100b8cba665a187f0000000f9 dm-105 HUAWEI  ,XSG1
size=1.0G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='service-time 0' prio=1 status=active
  |- 17:0:0:101 sdcy 70:96   failed ready running
  |- 18:0:0:101 sdgw 132:192 failed ready running
  `- 19:0:0:101 sdku 67:288  failed ready running
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