On 10/27/22 03:18, Damien Le Moal wrote:
On 10/25/22 19:17, John Garry wrote:
From: Hannes Reinecke <hare@xxxxxxx>
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@xxxxxxx>
#jpg: Set tag_set->queue_depth = shost->can_queue, and not
= shost->can_queue + shost->nr_reserved_cmds;
Signed-off-by: John Garry <john.garry@xxxxxxxxxx>
---
drivers/scsi/hosts.c | 3 +++
drivers/scsi/scsi_lib.c | 2 ++
include/scsi/scsi_host.h | 15 ++++++++++++++-
3 files changed, 19 insertions(+), 1 deletion(-)
diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index 12346e2297fd..db89afc37bc9 100644
--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -489,6 +489,9 @@ struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize)
if (sht->virt_boundary_mask)
shost->virt_boundary_mask = sht->virt_boundary_mask;
+ if (sht->nr_reserved_cmds)
+ shost->nr_reserved_cmds = sht->nr_reserved_cmds;
+
Nit: the if is not really necessary I think. But it does not hurt.
Yes, we do.
Not all HBAs are able to figure out the number of reserved commands
upfront; some modify that based on the PCI device used etc.
So I'd keep it for now.
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@xxxxxxx +49 911 74053 688
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