block, bfq: save & resume weight on a queue merge/split

bfq saves the state of a queue each time a merge occurs, to be
able to resume such a state when the queue is associated again
with its original process, on a split.

Unfortunately bfq does not save & restore also the weight of the
queue. If the weight is not correctly resumed when the queue is
recycled, then the weight of the recycled queue could differ
from the weight of the original queue.

This commit adds the missing save & resume of the weight.

Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Signed-off-by: Francesco Pollicino <fra.fra.800@gmail.com>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 37cc8f127cf672faafb28ecaf0f391c257817a40..ceb06abd73df3e93f6a6dfc9e7d26adfbe004a29 100644 (file)
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -1028,6 +1028,7 @@ bfq_bfqq_resume_state(struct bfq_queue *bfqq, struct bfq_data *bfqd,
        else
                bfq_clear_bfqq_IO_bound(bfqq);
 
+       bfqq->entity.new_weight = bic->saved_weight;
        bfqq->ttime = bic->saved_ttime;
        bfqq->wr_coeff = bic->saved_wr_coeff;
        bfqq->wr_start_at_switch_to_srt = bic->saved_wr_start_at_switch_to_srt;
@@ -2502,6 +2503,7 @@ static void bfq_bfqq_save_state(struct bfq_queue *bfqq)
        if (!bic)
                return;
 
+       bic->saved_weight = bfqq->entity.orig_weight;
        bic->saved_ttime = bfqq->ttime;
        bic->saved_has_short_ttime = bfq_bfqq_has_short_ttime(bfqq);
        bic->saved_IO_bound = bfq_bfqq_IO_bound(bfqq);

diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h
index 67e63c276c7ac5c82ad73bd8a63d6b23e988416e..60c148728cc5013e0c112af019b76e4457dfcb5e 100644 (file)
--- a/block/bfq-iosched.h
+++ b/block/bfq-iosched.h
@@ -404,6 +404,15 @@ struct bfq_io_cq {
         */
        bool was_in_burst_list;
 
+       /*
+        * Save the weight when a merge occurs, to be able
+        * to restore it in case of split. If the weight is not
+        * correctly resumed when the queue is recycled,
+        * then the weight of the recycled queue could differ
+        * from the weight of the original queue.
+        */
+       unsigned int saved_weight;
+
        /*
         * Similar to previous fields: save wr information.
         */