blk-throttle: Trim/adjust slice_end once a bio has been dispatched

[linux-2.6-block.git] / block / blk-throttle.c

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 004be80fd89402efbdc3f4a89a894570b7f27e59..2d134b7c40a3599cb58f2f446f7c8f952339b541 100644 (file)
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -355,6 +355,12 @@ throtl_start_new_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)
                        tg->slice_end[rw], jiffies);
 }
 
+static inline void throtl_set_slice_end(struct throtl_data *td,
+               struct throtl_grp *tg, bool rw, unsigned long jiffy_end)
+{
+       tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
+}
+
 static inline void throtl_extend_slice(struct throtl_data *td,
                struct throtl_grp *tg, bool rw, unsigned long jiffy_end)
 {
@@ -391,6 +397,16 @@ throtl_trim_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)
        if (throtl_slice_used(td, tg, rw))
                return;
 
+       /*
+        * A bio has been dispatched. Also adjust slice_end. It might happen
+        * that initially cgroup limit was very low resulting in high
+        * slice_end, but later limit was bumped up and bio was dispached
+        * sooner, then we need to reduce slice_end. A high bogus slice_end
+        * is bad because it does not allow new slice to start.
+        */
+
+       throtl_set_slice_end(td, tg, rw, jiffies + throtl_slice);
+
        time_elapsed = jiffies - tg->slice_start[rw];
 
        nr_slices = time_elapsed / throtl_slice;