md/dm-vdo/dedupe.c

838 		 * query agent didn't have an allocation. The UDS update was delayed in case there
1014 	 * We don't take the downgraded allocation lock from the agent unless we actually need to
1192  * be deduplicated against, otherwise a data_vio allocation will have to be written to and used for
1483 		 * compression, rollover, or the QUERYING agent not having an allocation.
1497 		 * agent will release its allocation lock in cleanup.
1504  * select_writing_agent() - Search through the lock waiters for a data_vio that has an allocation.
1507  * If an allocation is found, swap agents, put the old agent at the head of the wait queue, then
1518 	 * Move waiters to the temp queue one-by-one until we find an allocation. Not ideal to
1541 		/* No one has an allocation, so keep the current agent. */
1556  * with an allocation as a new agent, if necessary, then resuming the agent on the data_vio write
1564 	 * The agent might not have received an allocation and so can't be used for writing, but
1569 		/* If none of the waiters had an allocation, the writes all have to fail. */
1573 			 * fail immediately if they don't have an allocation? It might be possible
1685 		 * The agent will be used as the duplicate if has an allocation; if it does, that
1956  * transfer_allocation_lock() - Transfer a data_vio's downgraded allocation PBN lock to the
1958  * @data_vio: The data_vio holding the allocation lock to transfer.
1962 	struct allocation *allocation = &data_vio->allocation;
1965 	VDO_ASSERT_LOG_ONLY(data_vio->new_mapped.pbn == allocation->pbn,
1968 	allocation->pbn = VDO_ZERO_BLOCK;
1970 	VDO_ASSERT_LOG_ONLY(vdo_is_pbn_read_lock(allocation->lock),
1971 			    "must have downgraded the allocation lock before transfer");
1980 	hash_lock->duplicate_lock = vdo_forget(allocation->lock);