Message ID | 20200629072021.9864-9-hare@suse.de (mailing list archive) |
---|---|
State | Superseded |
Headers | show |
Series | scsi: enable reserved commands for LLDDs | expand |
On 29/06/2020 08:20, Hannes Reinecke wrote: > Quite some drivers are using management commands internally, which > typically use the same hardware tag pool (ie they are being allocated > from the same hardware resources) as the 'normal' I/O commands. > These commands are set aside before allocating the block-mq tag bitmap, > so they'll never show up as busy in the tag map. > The block-layer, OTOH, already has 'reserved_tags' to handle precisely > this situation. > So this patch adds a new field 'nr_reserved_cmds' to the SCSI host > template It is only added to Scsi_Host here, but not scsi_host_template (which I think it should be also) to instruct the block layer to set aside a tag space for these > management commands by using reserved tags. > > Signed-off-by: Hannes Reinecke <hare@suse.de> > --- > drivers/scsi/scsi_lib.c | 10 +++++++++- > include/scsi/scsi_host.h | 11 +++++++++++ > 2 files changed, 20 insertions(+), 1 deletion(-) > > diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c > index c2277eff4e06..57ce390dd458 100644 > --- a/drivers/scsi/scsi_lib.c > +++ b/drivers/scsi/scsi_lib.c > @@ -1887,7 +1887,9 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost) > else > tag_set->ops = &scsi_mq_ops_no_commit; > tag_set->nr_hw_queues = shost->nr_hw_queues ? : 1; > - tag_set->queue_depth = shost->can_queue; > + tag_set->queue_depth = > + shost->can_queue + shost->nr_reserved_cmds; > + tag_set->reserved_tags = shost->nr_reserved_cmds; > tag_set->cmd_size = cmd_size; > tag_set->numa_node = NUMA_NO_NODE; > tag_set->flags = BLK_MQ_F_SHOULD_MERGE; > @@ -1910,6 +1912,9 @@ void scsi_mq_destroy_tags(struct Scsi_Host *shost) > * @op_flags: request allocation flags > * > * Allocates a SCSI command for internal LLDD use. > + * If 'nr_reserved_commands' is spectified by the host the spelling of "specified" > + * command will be allocated from the reserved tag pool; > + * otherwise the normal tag pool will be used. > */ > struct scsi_cmnd *scsi_get_internal_cmd(struct scsi_device *sdev, > enum dma_data_direction data_direction, int op_flags) > @@ -1919,6 +1924,9 @@ struct scsi_cmnd *scsi_get_internal_cmd(struct scsi_device *sdev, > blk_mq_req_flags_t flags = 0; > unsigned int op = REQ_INTERNAL | op_flags; > > + if (sdev->host->nr_reserved_cmds) > + flags = BLK_MQ_REQ_RESERVED; I'd use |= > + > op |= (data_direction == DMA_TO_DEVICE) ? > REQ_OP_SCSI_OUT : REQ_OP_SCSI_IN; > rq = blk_mq_alloc_request(sdev->request_queue, op, flags); > diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h > index 46ef8cccc982..b94938e87e3a 100644 > --- a/include/scsi/scsi_host.h > +++ b/include/scsi/scsi_host.h > @@ -590,6 +590,11 @@ struct Scsi_Host { > unsigned short max_cmd_len; > > int this_id; > + > + /* > + * Number of commands this host can handle at the same time. > + * This excludes reserved commands as specified by nr_reserved_cmds. > + */ > int can_queue; > short cmd_per_lun; > short unsigned int sg_tablesize; > @@ -606,6 +611,12 @@ struct Scsi_Host { > * is nr_hw_queues * can_queue. > */ > unsigned nr_hw_queues; > + > + /* > + * Number of reserved commands to allocate, if any. > + */ > + unsigned nr_reserved_cmds; > + > unsigned active_mode:2; > unsigned unchecked_isa_dma:1; > >
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index c2277eff4e06..57ce390dd458 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -1887,7 +1887,9 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost) else tag_set->ops = &scsi_mq_ops_no_commit; tag_set->nr_hw_queues = shost->nr_hw_queues ? : 1; - tag_set->queue_depth = shost->can_queue; + tag_set->queue_depth = + shost->can_queue + shost->nr_reserved_cmds; + tag_set->reserved_tags = shost->nr_reserved_cmds; tag_set->cmd_size = cmd_size; tag_set->numa_node = NUMA_NO_NODE; tag_set->flags = BLK_MQ_F_SHOULD_MERGE; @@ -1910,6 +1912,9 @@ void scsi_mq_destroy_tags(struct Scsi_Host *shost) * @op_flags: request allocation flags * * Allocates a SCSI command for internal LLDD use. + * If 'nr_reserved_commands' is spectified by the host the + * command will be allocated from the reserved tag pool; + * otherwise the normal tag pool will be used. */ struct scsi_cmnd *scsi_get_internal_cmd(struct scsi_device *sdev, enum dma_data_direction data_direction, int op_flags) @@ -1919,6 +1924,9 @@ struct scsi_cmnd *scsi_get_internal_cmd(struct scsi_device *sdev, blk_mq_req_flags_t flags = 0; unsigned int op = REQ_INTERNAL | op_flags; + if (sdev->host->nr_reserved_cmds) + flags = BLK_MQ_REQ_RESERVED; + op |= (data_direction == DMA_TO_DEVICE) ? REQ_OP_SCSI_OUT : REQ_OP_SCSI_IN; rq = blk_mq_alloc_request(sdev->request_queue, op, flags); diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h index 46ef8cccc982..b94938e87e3a 100644 --- a/include/scsi/scsi_host.h +++ b/include/scsi/scsi_host.h @@ -590,6 +590,11 @@ struct Scsi_Host { unsigned short max_cmd_len; int this_id; + + /* + * Number of commands this host can handle at the same time. + * This excludes reserved commands as specified by nr_reserved_cmds. + */ int can_queue; short cmd_per_lun; short unsigned int sg_tablesize; @@ -606,6 +611,12 @@ struct Scsi_Host { * is nr_hw_queues * can_queue. */ unsigned nr_hw_queues; + + /* + * Number of reserved commands to allocate, if any. + */ + unsigned nr_reserved_cmds; + unsigned active_mode:2; unsigned unchecked_isa_dma:1;
Quite some drivers are using management commands internally, which typically use the same hardware tag pool (ie they are being allocated from the same hardware resources) as the 'normal' I/O commands. These commands are set aside before allocating the block-mq tag bitmap, so they'll never show up as busy in the tag map. The block-layer, OTOH, already has 'reserved_tags' to handle precisely this situation. So this patch adds a new field 'nr_reserved_cmds' to the SCSI host template to instruct the block layer to set aside a tag space for these management commands by using reserved tags. Signed-off-by: Hannes Reinecke <hare@suse.de> --- drivers/scsi/scsi_lib.c | 10 +++++++++- include/scsi/scsi_host.h | 11 +++++++++++ 2 files changed, 20 insertions(+), 1 deletion(-)