Alasdair G Kergon [agk@xxxxxxxxxx] wrote: > On Mon, Nov 09, 2009 at 09:57:30AM -0800, malahal@xxxxxxxxxx wrote: > > Why do we need dm_get() and dm_put() in dm_copy_name_and_uuid()? > > dm_copy_name_and_uuid() already has access to md and there shouldn't be > > any need to hold a reference. > > As Mike points out, struct dm_uevent holds a reference without > incrementing the ref count. > > dm_path_uevent() already takes a reference - can everything get > simplified if we move this code there (and replace the new mutex with > a spinlock of course)? Then dm_send_uevents won't need to use 'md'. I think the last dm_put() is calling the multipath destructor which eventually calls (through a work struct) dm_send_uevents. At that point, dm is guaranteed to exist but you *must* not place a hold on it. As the current code in dm_copy_name_and_uuid() places a hold on a FREEING md, it will result in a BUG_ON while calling the dm_put in the same function. So, removing the dm_get/dm_put from that function should also solve the BUG_ON issue. I agree, removing the "md" field from the dm_event struct probably simplifies other things. Thanks, Malahal. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
