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-rw-r--r--block/blk-throttle.c41
1 files changed, 26 insertions, 15 deletions
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 56ad453..381b09b 100644
--- 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;
@@ -645,7 +661,7 @@ static int throtl_dispatch_tg(struct throtl_data *td, struct throtl_grp *tg,
{
unsigned int nr_reads = 0, nr_writes = 0;
unsigned int max_nr_reads = throtl_grp_quantum*3/4;
- unsigned int max_nr_writes = throtl_grp_quantum - nr_reads;
+ unsigned int max_nr_writes = throtl_grp_quantum - max_nr_reads;
struct bio *bio;
/* Try to dispatch 75% READS and 25% WRITES */
@@ -709,26 +725,21 @@ static void throtl_process_limit_change(struct throtl_data *td)
struct throtl_grp *tg;
struct hlist_node *pos, *n;
- /*
- * Make sure atomic_inc() effects from
- * throtl_update_blkio_group_read_bps(), group of functions are
- * visible.
- * Is this required or smp_mb__after_atomic_inc() was suffcient
- * after the atomic_inc().
- */
- smp_rmb();
if (!atomic_read(&td->limits_changed))
return;
throtl_log(td, "limit changed =%d", atomic_read(&td->limits_changed));
- hlist_for_each_entry_safe(tg, pos, n, &td->tg_list, tg_node) {
- /*
- * Do I need an smp_rmb() here to make sure tg->limits_changed
- * update is visible. I am relying on smp_rmb() at the
- * beginning of function and not putting a new one here.
- */
+ /*
+ * Make sure updates from throtl_update_blkio_group_read_bps() group
+ * of functions to tg->limits_changed are visible. We do not
+ * want update td->limits_changed to be visible but update to
+ * tg->limits_changed not being visible yet on this cpu. Hence
+ * the read barrier.
+ */
+ smp_rmb();
+ hlist_for_each_entry_safe(tg, pos, n, &td->tg_list, tg_node) {
if (throtl_tg_on_rr(tg) && tg->limits_changed) {
throtl_log_tg(td, tg, "limit change rbps=%llu wbps=%llu"
" riops=%u wiops=%u", tg->bps[READ],
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