On 11/22/23 22:29, Yu Kuai wrote:
在 2023/11/22 3:32, Bart Van Assche 写道:+static ssize_t queue_fair_sharing_store(struct request_queue *q, + const char *page, size_t count) +{ + const unsigned int DFTS_BIT = ilog2(BLK_MQ_F_DISABLE_FAIR_TAG_SHARING); + struct blk_mq_tag_set *set = q->tag_set; + struct blk_mq_hw_ctx *hctx; + unsigned long i; + int res; + bool val; + + res = kstrtobool(page, &val); + if (res < 0) + return res; + + mutex_lock(&set->tag_list_lock); + clear_bit(DFTS_BIT, &set->flags); + list_for_each_entry(q, &set->tag_list, tag_set_list) { + /* Serialize against blk_mq_realloc_hw_ctxs() */If set/clear bit concurrent with test bit from io path, will there be problem? Why don't freeze these queues?
If that happens the changes applied through this sysfs attribute may only take effect after a short delay (depending on how fast changes are propagated from one CPU to another). I don't think that this is an issue? >> +#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? Thanks, Bart.
