On 02/25/15 18:36, Sagi Grimberg wrote: > - About shared tags. So for scsi commands and TMFs we don't have a > problem since we are guaranteed ITTs are unique. I wander how will we > allocate a unique ITT for iscsi specific tasks (LOGIN, TEXT, LOGOUT, > NOOP_OUT). My implementation did it per-session, so I reserved a range > of ITTs for iscsi specific commands (in a kfifo), I wander how we can > do that for multiple sessions. We need some kind of tag allocator for > iscsi specific commands. Perhaps Bart/Christoph can advise if a LLD > can allocate a unique tag for an LLD specific command using block > layer tags.
It is possible to allocate a reserved tag from the blk-mq layer by passing true as the fourth argument when calling blk_mq_alloc_request(). However, using that mechanism from inside a SCSI LLD driver would require changes in the SCSI core. The code in scsi_mq_setup_tags() initializes the number of reserved tags to zero. Additionally, the flag use_blk_tags in the SCSI host template makes it easy to use the same code paths in a SCSI LLD in multiqueue and single queue mode. However, the single queue block layer tag allocator does not support reserved tags (see also blk_queue_init_tags()). So it is probably easier to use a custom tag allocator in the iSCSI initiator for iSCSI-specific tasks instead of trying to allocate tags for these tasks from the block layer. Bart. -- You received this message because you are subscribed to the Google Groups "open-iscsi" group. To unsubscribe from this group and stop receiving emails from it, send an email to open-iscsi+unsubscr...@googlegroups.com. To post to this group, send email to open-iscsi@googlegroups.com. Visit this group at http://groups.google.com/group/open-iscsi. For more options, visit https://groups.google.com/d/optout.
