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-rw-r--r--block/blk-throttle.c30
1 files changed, 25 insertions, 5 deletions
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 2875ff66e1b9..420eaa150d11 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -757,7 +757,22 @@ static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
tg->bytes_disp[rw] += bio->bi_size;
tg->io_disp[rw]++;
- throtl_update_dispatch_stats(tg_to_blkg(tg), bio->bi_size, bio->bi_rw);
+ /*
+ * REQ_THROTTLED is used to prevent the same bio to be throttled
+ * more than once as a throttled bio will go through blk-throtl the
+ * second time when it eventually gets issued. Set it when a bio
+ * is being charged to a tg.
+ *
+ * Dispatch stats aren't recursive and each @bio should only be
+ * accounted by the @tg it was originally associated with. Let's
+ * update the stats when setting REQ_THROTTLED for the first time
+ * which is guaranteed to be for the @bio's original tg.
+ */
+ if (!(bio->bi_rw & REQ_THROTTLED)) {
+ bio->bi_rw |= REQ_THROTTLED;
+ throtl_update_dispatch_stats(tg_to_blkg(tg), bio->bi_size,
+ bio->bi_rw);
+ }
}
static void throtl_add_bio_tg(struct bio *bio, struct throtl_grp *tg)
@@ -821,7 +836,6 @@ static void tg_dispatch_one_bio(struct throtl_grp *tg, bool rw)
throtl_charge_bio(tg, bio);
bio_list_add(&sq->parent_sq->bio_lists[rw], bio);
- bio->bi_rw |= REQ_THROTTLED;
throtl_trim_slice(tg, rw);
}
@@ -1128,10 +1142,9 @@ bool blk_throtl_bio(struct request_queue *q, struct bio *bio)
struct blkcg *blkcg;
bool throttled = false;
- if (bio->bi_rw & REQ_THROTTLED) {
- bio->bi_rw &= ~REQ_THROTTLED;
+ /* see throtl_charge_bio() */
+ if (bio->bi_rw & REQ_THROTTLED)
goto out;
- }
/*
* A throtl_grp pointer retrieved under rcu can be used to access
@@ -1205,6 +1218,13 @@ out_unlock:
out_unlock_rcu:
rcu_read_unlock();
out:
+ /*
+ * As multiple blk-throtls may stack in the same issue path, we
+ * don't want bios to leave with the flag set. Clear the flag if
+ * being issued.
+ */
+ if (!throttled)
+ bio->bi_rw &= ~REQ_THROTTLED;
return throttled;
}