Hi, On Thu, Jul 13, 2023 at 12:49 PM Alexander Aring <aahri...@redhat.com> wrote: > > This patch implements dlm plock F_SETLKW interruption feature. If the > pending plock operation is not sent to user space yet it can simple be > dropped out of the send_list. In case it's already being sent we need to > try to remove the waiters in dlm user space tool. If it was successful a > reply with DLM_PLOCK_OP_CANCEL optype instead of DLM_PLOCK_OP_LOCK comes > back (flag DLM_PLOCK_FL_NO_REPLY was then being cleared in user space) > to signal the cancellation was successful. If a result with optype > DLM_PLOCK_OP_LOCK came back then the cancellation was not successful.
There is another use-case for this op that's only used kernel internally by nfs. It's F_CANCELLK [0]. I will try to implement this feature as I think the current behaviour is broken [1]. An unlock is not a revert and if the lock request is in waiting state, unlocking will do exactly nothing. I am still questioning how the API of [0] is supposed to work as [0] does not evaluate any return value if it was successfully canceled or not. Maybe they meant cancel and if it was not successful unlock it, but an unlock is not a revert and posix locks support up/downgrade locking e.g. read/write locks. However I think unlocking if cancellation wasn't successful is meant here. Besides that, I will change that DLM_PLOCK_OP_CANCEL will always expect a reply back. - Alex [0] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/fs/lockd/svclock.c#n705 [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/fs/gfs2/file.c?h=v6.5-rc1#n1439
