Merge branch 'fix' of git://git.kernel.org/pub/scm/linux/kernel/git/ycmiao/pxa-linux-2.6

[mv-sheeva.git] / block / blk-throttle.c

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 004be80fd89402efbdc3f4a89a894570b7f27e59..381b09bb562b277620479fa92313cc6631995630 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;
@@ -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],