block: don't try to throttle split bio if iops limit isn't set

We need to throttle split bio in case of IOPS limit even though the
split bio has been marked as BIO_THROTTLED since block layer
accounts split bio actually.

If only throughput throttle is setup, no need to throttle any more
if BIO_THROTTLED is set since we have accounted & considered the
whole bio bytes already.

Add one flag of THROTL_TG_HAS_IOPS_LIMIT for serving this purpose.

Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20220216044514.2903784-8-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index c7aa26d52e84583357921337f1702d87e3ed6a6c..ec72eced24d2cb35d4f9fe5e9093c71d5e3b6fd0 100644 (file)
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -41,11 +41,6 @@
 /* A workqueue to queue throttle related work */
 static struct workqueue_struct *kthrotld_workqueue;
 
-enum tg_state_flags {
-       THROTL_TG_PENDING       = 1 << 0,       /* on parent's pending tree */
-       THROTL_TG_WAS_EMPTY     = 1 << 1,       /* bio_lists[] became non-empty */
-};
-
 #define rb_entry_tg(node)      rb_entry((node), struct throtl_grp, rb_node)
 
 /* We measure latency for request size from <= 4k to >= 1M */
@@ -425,12 +420,24 @@ static void tg_update_has_rules(struct throtl_grp *tg)
        struct throtl_grp *parent_tg = sq_to_tg(tg->service_queue.parent_sq);
        struct throtl_data *td = tg->td;
        int rw;
+       int has_iops_limit = 0;
+
+       for (rw = READ; rw <= WRITE; rw++) {
+               unsigned int iops_limit = tg_iops_limit(tg, rw);
 
-       for (rw = READ; rw <= WRITE; rw++)
                tg->has_rules[rw] = (parent_tg && parent_tg->has_rules[rw]) ||
                        (td->limit_valid[td->limit_index] &&
                         (tg_bps_limit(tg, rw) != U64_MAX ||
-                         tg_iops_limit(tg, rw) != UINT_MAX));
+                         iops_limit != UINT_MAX));
+
+               if (iops_limit != UINT_MAX)
+                       has_iops_limit = 1;
+       }
+
+       if (has_iops_limit)
+               tg->flags |= THROTL_TG_HAS_IOPS_LIMIT;
+       else
+               tg->flags &= ~THROTL_TG_HAS_IOPS_LIMIT;
 }
 
 static void throtl_pd_online(struct blkg_policy_data *pd)

diff --git a/block/blk-throttle.h b/block/blk-throttle.h
index cb43f4417d6ea0014778a45bb403b08f035e7c97..c996a15f290e8a145d1cc4f01de3b45349054f49 100644 (file)
--- a/block/blk-throttle.h
+++ b/block/blk-throttle.h
@@ -52,6 +52,12 @@ struct throtl_service_queue {
        struct timer_list       pending_timer;  /* fires on first_pending_disptime */
 };
 
+enum tg_state_flags {
+       THROTL_TG_PENDING       = 1 << 0,       /* on parent's pending tree */
+       THROTL_TG_WAS_EMPTY     = 1 << 1,       /* bio_lists[] became non-empty */
+       THROTL_TG_HAS_IOPS_LIMIT = 1 << 2,      /* tg has iops limit */
+};
+
 enum {
        LIMIT_LOW,
        LIMIT_MAX,
@@ -170,6 +176,11 @@ static inline bool blk_throtl_bio(struct bio *bio)
 {
        struct throtl_grp *tg = blkg_to_tg(bio->bi_blkg);
 
+       /* no need to throttle bps any more if the bio has been throttled */
+       if (bio_flagged(bio, BIO_THROTTLED) &&
+           !(tg->flags & THROTL_TG_HAS_IOPS_LIMIT))
+               return false;
+
        if (!tg->has_rules[bio_data_dir(bio)])
                return false;