On 5/17/23 00:33, Bart Van Assche wrote:
Track the position (sector_t) of the most recently dispatched request
instead of tracking a pointer to the next request to dispatch. This
patch is the basis for patch "Handle requeued requests correctly".
Without this patch it would be significantly more complicated to make
sure that zoned writes are dispatched in LBA order per zone.
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Cc: Damien Le Moal <damien.lemoal@xxxxxxxxxxxxxxxxxx>
Cc: Ming Lei <ming.lei@xxxxxxxxxx>
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
---
block/mq-deadline.c | 45 +++++++++++++++++++++++++++++++--------------
1 file changed, 31 insertions(+), 14 deletions(-)
diff --git a/block/mq-deadline.c b/block/mq-deadline.c
index 06af9c28a3bf..6d0b99042c96 100644
--- a/block/mq-deadline.c
+++ b/block/mq-deadline.c
@@ -74,8 +74,8 @@ struct dd_per_prio {
struct list_head dispatch;
struct rb_root sort_list[DD_DIR_COUNT];
struct list_head fifo_list[DD_DIR_COUNT];
- /* Next request in FIFO order. Read, write or both are NULL. */
- struct request *next_rq[DD_DIR_COUNT];
+ /* Position of the most recently dispatched request. */
+ sector_t latest_pos[DD_DIR_COUNT];
struct io_stats_per_prio stats;
};
@@ -156,6 +156,25 @@ deadline_latter_request(struct request *rq)
return NULL;
}
+/* Return the first request for which blk_rq_pos() >= pos. */
+static inline struct request *deadline_from_pos(struct dd_per_prio *per_prio,
+ enum dd_data_dir data_dir, sector_t pos)
+{
+ struct rb_node *node = per_prio->sort_list[data_dir].rb_node;
+ struct request *rq, *res = NULL;
+
+ while (node) {
+ rq = rb_entry_rq(node);
+ if (blk_rq_pos(rq) >= pos) {
+ res = rq;
+ node = node->rb_left;
+ } else {
+ node = node->rb_right;
+ }
+ }
+ return res;
+}
+
This is getting ever more awkward; you have to traverse the entire tree
to get the result. Doesn't that impact performance?
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@xxxxxxx +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Ivo Totev, Andrew
Myers, Andrew McDonald, Martje Boudien Moerman
