On Thu, 26 Feb 2015, Mikulas Patocka wrote: > There was a bug when that resulted in a crash when there were pending > exceptions and snapshot exception store handover was performed at the > same time - and there was a patch that fixed it. > > However, a similar problem exists in snapshot merging. When snapshot > merging is in progress, we use the target "snapshot-merge" instead of > "snapshot-origin". Consequently, during exception store handover, we must > find the snapshot-merge target and suspend it's associated md. > > To avoid lockdep warnings, the target must be suspended and resumed > without holding _origins_lock. > > This patch introduces a function dm_hold that grabs a reference on > mapped_device, but unlike dm_get, it doesn't crash if the devices has the > flag DMF_FREEING, it returns and error in this case. > > In snapshot_resume we grab the reference to the origin device using > dm_hold while holding _origins_lock (_origins_lock guarantees that the > device won't disappear). Then we release _origins_lock, suspend the > device and grab _origins_lock again. > > Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx> I forgot to add Cc: stable@xxxxxxxxxxxxxxx When backporting to kernels 3.18 and older, use dm_internal_suspend and dm_internal_resume instead of dm_internal_suspend_fast and dm_internal_resume_fast. Mikulas -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
