On Thu, Oct 17 2013 at 5:47pm -0400, Hannes Reinecke <hare@xxxxxxx> wrote: > On 10/17/2013 08:53 PM, Mike Snitzer wrote: > >Thanks for reporting this. Much appreciated. More comments below. > > > >On Thu, Oct 17 2013 at 1:31pm -0400, > >Merla, ShivaKrishna <ShivaKrishna.Merla@xxxxxxxxxx> wrote: > > > >>Whenever multipath_dtr is happening, we should prevent queueing any further path > >>activation work. There was a kernel panic where after pg_init_done() decrements > >>pg_init_in_progress to 0, wait_for_pg_init_completion call assumes there are no > >>more pending path management commands. But if pg_init_required is set by > >>pg_init_done call due to retriable mode_select errors , then process_queued_ios() > >>will again queue the path activation work. If free_multipath call has been > >>completed by the time activate_path work is called, kernel panic was seen on > >>accessing multipath members. > > > >Your locking looks suspect to me, see comment inlined below multipath_dtr > > > >But shouldn't we just train multipath_wait_for_pg_init_completion() to > >look at m->pg_init_required? Have it wait for both pg_init_required and > >pg_init_in_progress to be zero? We'd also have to audit that > >pg_init_required cannot be set while pg_init_in_progress. > > > Hmm. > > We _could_ try to resolve it by pushing I/O back onto the request queue > (cf my earlier post 'requeue I/O during pg_init'). > > I was hoping to excite some comments with that, but seems to be my > fate nowadays to send out patches with no reply. patchwork caught it: https://patchwork.kernel.org/patch/2969111/ I've just been distracted with other stuff the past week; but I'll be looking closer at this issue (and your earlier patch) shortly and we'll get a fix queued for 3.13. > Anyway, maybe this will be giving it some more attention. > It definitely would avoid this problem, by virtue of not having to > queue I/O internally during pg_init, so we could easily tear down > the queue. Sounds good. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
