On 11/27/23 18:03, Yu Kuai wrote:
I was worried that there might be missing wakeups, why not using
blk_mq_update_tag_set_shared() directly to disable tag sharing?
I think that calling blk_mq_update_tag_set_shared() to disable tag sharing
would be wrong because BLK_MQ_F_TAG_QUEUE_SHARED is also used for other
purposes than fair tag sharing. See e.g. blk_mq_mark_tag_wait().
>> +#define QUEUE_RW_ENTRY_NO_SYSFS_MUTEX(_prefix, _name) \
+ static struct queue_sysfs_entry _prefix##_entry = { \
+ .attr = { .name = _name, .mode = 0644 }, \
+ .show = _prefix##_show, \
+ .store = _prefix##_store, \
+ .no_sysfs_mutex = true, \
+ };
+
This actually change all the queues from the same tagset, can we add
this new entry to /sys/class/scsi_host/hostx/xxx ?
That would make it impossible to disable fair tag sharing for block drivers
that are not based on the SCSI core. Are you sure that's what you want?
Yes, if there are other drivers that are sharing driver tags, this is
not good, can you give some examples?
There is one tag set for all NVMe namespaces associated with the same
controller. Anyway, I will move this sysfs attribute to the SCSI host and
will organize the code such that a similar sysfs attribute can be added
easily to other block drivers than the SCSI core if that would be considered
useful.
Bart.
