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-rw-r--r--block/blk-cgroup.h17
1 files changed, 17 insertions, 0 deletions
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 3e91803c4a55..47e1e38390c9 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -15,6 +15,7 @@
*/
#include <linux/blk-cgroup.h>
+#include <linux/blk-mq.h>
/* percpu_counter batch for blkg_[rw]stats, per-cpu drift doesn't matter */
#define BLKG_STAT_CPU_BATCH (INT_MAX / 2)
@@ -428,6 +429,21 @@ static inline void blkcg_clear_delay(struct blkcg_gq *blkg)
atomic_dec(&blkg->blkcg->css.cgroup->congestion_count);
}
+/**
+ * blk_cgroup_mergeable - Determine whether to allow or disallow merges
+ * @rq: request to merge into
+ * @bio: bio to merge
+ *
+ * @bio and @rq should belong to the same cgroup and their issue_as_root should
+ * match. The latter is necessary as we don't want to throttle e.g. a metadata
+ * update because it happens to be next to a regular IO.
+ */
+static inline bool blk_cgroup_mergeable(struct request *rq, struct bio *bio)
+{
+ return rq->bio->bi_blkg == bio->bi_blkg &&
+ bio_issue_as_root_blkg(rq->bio) == bio_issue_as_root_blkg(bio);
+}
+
void blk_cgroup_bio_start(struct bio *bio);
void blkcg_add_delay(struct blkcg_gq *blkg, u64 now, u64 delta);
#else /* CONFIG_BLK_CGROUP */
@@ -467,6 +483,7 @@ static inline void blkg_put(struct blkcg_gq *blkg) { }
static inline bool blkcg_punt_bio_submit(struct bio *bio) { return false; }
static inline void blkcg_bio_issue_init(struct bio *bio) { }
static inline void blk_cgroup_bio_start(struct bio *bio) { }
+static inline bool blk_cgroup_mergeable(struct request *rq, struct bio *bio) { return true; }
#define blk_queue_for_each_rl(rl, q) \
for ((rl) = &(q)->root_rl; (rl); (rl) = NULL)