blk-throttle: implement sq_to_tg(), sq_to_td() and throtl_log()

Now that both throtl_data and throtl_grp embed throtl_service_queue,
we can unify throtl_log() and throtl_log_tg().

* sq_to_tg() is added.  This returns the throtl_grp a service_queue is
  embedded in.  If the service_queue is the top-level one embedded in
  throtl_data, NULL is returned.

* sq_to_td() is added.  A service_queue is always associated with a
  throtl_data.  This function finds the associated td and returns it.

* throtl_log() is updated to take throtl_service_queue instead of
  throtl_data.  If the service_queue is one embedded in throtl_grp, it
  prints the same header as throtl_log_tg() did.  If it's one embedded
  in throtl_data, it behaves the same as before.  This renders
  throtl_log_tg() unnecessary.  Removed.

This change is necessary for hierarchy support as we're gonna be using
the same code paths to dispatch bios to intermediate service_queues
embedded in throtl_grps and the top-level service_queue embedded in
throtl_data.

This patch doesn't make any behavior changes.

v2: throtl_log() didn't print a space after blkg path.  Updated so
    that it prints a space after throtl_grp path.  Spotted by Vivek.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>

1 files changed, 81 insertions, 29 deletions

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 00cfdd05f98f..2875ff66e1b9 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -151,16 +151,65 @@ static inline struct throtl_grp *td_root_tg(struct throtl_data *td)
         return blkg_to_tg(td->queue->root_blkg);
 }
 
-#define throtl_log_tg(tg, fmt, args...) do {                            \
-        char __pbuf[128];                                               \
+/**
+ * sq_to_tg - return the throl_grp the specified service queue belongs to
+ * @sq: the throtl_service_queue of interest
+ *
+ * Return the throtl_grp @sq belongs to.  If @sq is the top-level one
+ * embedded in throtl_data, %NULL is returned.
+ */
+static struct throtl_grp *sq_to_tg(struct throtl_service_queue *sq)
+{
+        if (sq && sq->parent_sq)
+                return container_of(sq, struct throtl_grp, service_queue);
+        else
+                return NULL;
+}
+
+/**
+ * sq_to_td - return throtl_data the specified service queue belongs to
+ * @sq: the throtl_service_queue of interest
+ *
+ * A service_queue can be embeded in either a throtl_grp or throtl_data.
+ * Determine the associated throtl_data accordingly and return it.
+ */
+static struct throtl_data *sq_to_td(struct throtl_service_queue *sq)
+{
+        struct throtl_grp *tg = sq_to_tg(sq);
+
+        if (tg)
+                return tg->td;
+        else
+                return container_of(sq, struct throtl_data, service_queue);
+}
+
+/**
+ * throtl_log - log debug message via blktrace
+ * @sq: the service_queue being reported
+ * @fmt: printf format string
+ * @args: printf args
+ *
+ * The messages are prefixed with "throtl BLKG_NAME" if @sq belongs to a
+ * throtl_grp; otherwise, just "throtl".
+ *
+ * TODO: this should be made a function and name formatting should happen
+ * after testing whether blktrace is enabled.
+ */
+#define throtl_log(sq, fmt, args...)    do {                            \
+        struct throtl_grp *__tg = sq_to_tg((sq));                       \
+        struct throtl_data *__td = sq_to_td((sq));                      \
+                                                                        \
+        (void)__td;                                                     \
+        if ((__tg)) {                                                   \
+                char __pbuf[128];                                       \
                                                                         \
-        blkg_path(tg_to_blkg(tg), __pbuf, sizeof(__pbuf));              \
-        blk_add_trace_msg((tg)->td->queue, "throtl %s " fmt, __pbuf, ##args); \
+                blkg_path(tg_to_blkg(__tg), __pbuf, sizeof(__pbuf));    \
+                blk_add_trace_msg(__td->queue, "throtl %s " fmt, __pbuf, ##args); \
+        } else {                                                        \
+                blk_add_trace_msg(__td->queue, "throtl " fmt, ##args);  \
+        }                                                               \
 } while (0)
 
-#define throtl_log(td, fmt, args...)    \
-        blk_add_trace_msg((td)->queue, "throtl " fmt, ##args)
-
 /*
  * Worker for allocating per cpu stat for tgs. This is scheduled on the
  * system_wq once there are some groups on the alloc_list waiting for
@@ -402,9 +451,10 @@ static void throtl_schedule_delayed_work(struct throtl_data *td,
                                          unsigned long delay)
 {
         struct delayed_work *dwork = &td->dispatch_work;
+        struct throtl_service_queue *sq = &td->service_queue;
 
         mod_delayed_work(kthrotld_workqueue, dwork, delay);
-        throtl_log(td, "schedule work. delay=%lu jiffies=%lu", delay, jiffies);
+        throtl_log(sq, "schedule work. delay=%lu jiffies=%lu", delay, jiffies);
 }
 
 static void throtl_schedule_next_dispatch(struct throtl_data *td)
@@ -429,9 +479,10 @@ static inline void throtl_start_new_slice(struct throtl_grp *tg, bool rw)
         tg->io_disp[rw] = 0;
         tg->slice_start[rw] = jiffies;
         tg->slice_end[rw] = jiffies + throtl_slice;
-        throtl_log_tg(tg, "[%c] new slice start=%lu end=%lu jiffies=%lu",
-                        rw == READ ? 'R' : 'W', tg->slice_start[rw],
-                        tg->slice_end[rw], jiffies);
+        throtl_log(&tg->service_queue,
+                   "[%c] new slice start=%lu end=%lu jiffies=%lu",
+                   rw == READ ? 'R' : 'W', tg->slice_start[rw],
+                   tg->slice_end[rw], jiffies);
 }
 
 static inline void throtl_set_slice_end(struct throtl_grp *tg, bool rw,
@@ -444,9 +495,10 @@ static inline void throtl_extend_slice(struct throtl_grp *tg, bool rw,
                                        unsigned long jiffy_end)
 {
         tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
-        throtl_log_tg(tg, "[%c] extend slice start=%lu end=%lu jiffies=%lu",
-                        rw == READ ? 'R' : 'W', tg->slice_start[rw],
-                        tg->slice_end[rw], jiffies);
+        throtl_log(&tg->service_queue,
+                   "[%c] extend slice start=%lu end=%lu jiffies=%lu",
+                   rw == READ ? 'R' : 'W', tg->slice_start[rw],
+                   tg->slice_end[rw], jiffies);
 }
 
 /* Determine if previously allocated or extended slice is complete or not */
@@ -511,10 +563,10 @@ static inline void throtl_trim_slice(struct throtl_grp *tg, bool rw)
 
         tg->slice_start[rw] += nr_slices * throtl_slice;
 
-        throtl_log_tg(tg, "[%c] trim slice nr=%lu bytes=%llu io=%lu"
-                        " start=%lu end=%lu jiffies=%lu",
-                        rw == READ ? 'R' : 'W', nr_slices, bytes_trim, io_trim,
-                        tg->slice_start[rw], tg->slice_end[rw], jiffies);
+        throtl_log(&tg->service_queue,
+                   "[%c] trim slice nr=%lu bytes=%llu io=%lu start=%lu end=%lu jiffies=%lu",
+                   rw == READ ? 'R' : 'W', nr_slices, bytes_trim, io_trim,
+                   tg->slice_start[rw], tg->slice_end[rw], jiffies);
 }
 
 static bool tg_with_in_iops_limit(struct throtl_grp *tg, struct bio *bio,
@@ -852,7 +904,7 @@ void blk_throtl_dispatch_work_fn(struct work_struct *work)
 
         bio_list_init(&bio_list_on_stack);
 
-        throtl_log(td, "dispatch nr_queued=%u read=%u write=%u",
+        throtl_log(sq, "dispatch nr_queued=%u read=%u write=%u",
                    td->nr_queued[READ] + td->nr_queued[WRITE],
                    td->nr_queued[READ], td->nr_queued[WRITE]);
 
@@ -863,7 +915,7 @@ void blk_throtl_dispatch_work_fn(struct work_struct *work)
                         bio_list_merge(&bio_list_on_stack, &sq->bio_lists[rw]);
                         bio_list_init(&sq->bio_lists[rw]);
                 }
-                throtl_log(td, "bios disp=%u", nr_disp);
+                throtl_log(sq, "bios disp=%u", nr_disp);
         }
 
         throtl_schedule_next_dispatch(td);
@@ -972,9 +1024,10 @@ static int tg_set_conf(struct cgroup *cgrp, struct cftype *cft, const char *buf,
         else
                 *(unsigned int *)((void *)tg + cft->private) = ctx.v;
 
-        throtl_log_tg(tg, "limit change rbps=%llu wbps=%llu riops=%u wiops=%u",
-                      tg->bps[READ], tg->bps[WRITE],
-                      tg->iops[READ], tg->iops[WRITE]);
+        throtl_log(&tg->service_queue,
+                   "limit change rbps=%llu wbps=%llu riops=%u wiops=%u",
+                   tg->bps[READ], tg->bps[WRITE],
+                   tg->iops[READ], tg->iops[WRITE]);
 
         /*
          * We're already holding queue_lock and know @tg is valid.  Let's
@@ -1131,12 +1184,11 @@ bool blk_throtl_bio(struct request_queue *q, struct bio *bio)
         }
 
 queue_bio:
-        throtl_log_tg(tg, "[%c] bio. bdisp=%llu sz=%u bps=%llu"
-                        " iodisp=%u iops=%u queued=%d/%d",
-                        rw == READ ? 'R' : 'W',
-                        tg->bytes_disp[rw], bio->bi_size, tg->bps[rw],
-                        tg->io_disp[rw], tg->iops[rw],
-                        sq->nr_queued[READ], sq->nr_queued[WRITE]);
+        throtl_log(sq, "[%c] bio. bdisp=%llu sz=%u bps=%llu iodisp=%u iops=%u queued=%d/%d",
+                   rw == READ ? 'R' : 'W',
+                   tg->bytes_disp[rw], bio->bi_size, tg->bps[rw],
+                   tg->io_disp[rw], tg->iops[rw],
+                   sq->nr_queued[READ], sq->nr_queued[WRITE]);
 
         bio_associate_current(bio);
         throtl_add_bio_tg(bio, tg);