This is another stab at solving the problem of hostwide shared tags for SCSI HBAs. As discussed previously, Ming Lei's most recent series in [0] to use hctx[0] tags for all hctx for a host was a bit messy and intrusive, so seen as a no go. Indeed, blk-mq is designed for separate tags per hctx. Bart also followed up on my v1 RFC with another implementation along those same lines, which was neater, but I am concerned that the change in this approach may cause issues - see [1]. This series introduces a different approach to solve that problem, in keeping the per-hctx tags but introducing a new separate sbitmap per tagset. The shared sbitmap is used to generate a unique tag over all hctx per tagset. Currently I just fixed up the hisi_sas driver to use the shared tags, but should not be much trouble to change others over. Patch #3 is still quite experimental at this point - I added some code comments on this. I also threw in a minor tidy-up patch. [0] https://lore.kernel.org/linux-block/20190531022801.10003-1-ming.lei@xxxxxxxxxx/ [1] https://lore.kernel.org/linux-block/ff77beff-5fd9-9f05-12b6-826922bace1f@xxxxxxxxxx/T/#m3db0a602f095cbcbff27e9c884d6b4ae826144be Differences to v1: - Use a shared sbitmap, and not a separate shared tags (a big change!) - Drop request.shared_tag - Add RB tags Hannes Reinecke (1): scsi: Add template flag 'host_tagset' John Garry (3): blk-mq: Remove some unused function arguments blk-mq: Facilitate a shared sbitmap per tagset scsi: hisi_sas: Switch v3 hw to MQ Ming Lei (1): blk-mq: rename BLK_MQ_F_TAG_SHARED as BLK_MQ_F_TAG_QUEUE_SHARED block/bfq-iosched.c | 4 +- block/blk-mq-debugfs.c | 6 +- block/blk-mq-sched.c | 14 +++++ block/blk-mq-tag.c | 80 +++++++++++++++++------ block/blk-mq-tag.h | 18 ++++-- block/blk-mq.c | 87 ++++++++++++++++++++------ block/blk-mq.h | 7 ++- block/kyber-iosched.c | 4 +- drivers/scsi/hisi_sas/hisi_sas.h | 3 +- drivers/scsi/hisi_sas/hisi_sas_main.c | 36 ++++++----- drivers/scsi/hisi_sas/hisi_sas_v3_hw.c | 86 +++++++++++-------------- drivers/scsi/scsi_lib.c | 2 + include/linux/blk-mq.h | 9 ++- include/scsi/scsi_host.h | 3 + 14 files changed, 239 insertions(+), 120 deletions(-) -- 2.17.1
