blkcg: remove blkio_group->path[]

blkio_group->path[] stores the path of the associated cgroup and is
used only for debug messages.  Just format the path from blkg->cgroup
when printing debug messages.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

4 files changed, 37 insertions, 15 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index b1807d4ecedb..63337024e4d7 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -114,7 +114,6 @@ static struct blkio_group *blkg_alloc(struct blkio_cgroup *blkcg,
         INIT_LIST_HEAD(&blkg->q_node);
         blkg->blkcg = blkcg;
         blkg->refcnt = 1;
-        cgroup_path(blkcg->css.cgroup, blkg->path, sizeof(blkg->path));
 
         for (i = 0; i < BLKCG_MAX_POLS; i++) {
                 struct blkio_policy_type *pol = blkio_policy[i];
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index ef6550a67a69..c524267e4f7f 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -77,8 +77,6 @@ struct blkio_group {
         struct list_head q_node;
         struct hlist_node blkcg_node;
         struct blkio_cgroup *blkcg;
-        /* Store cgroup path */
-        char path[128];
         /* reference count */
         int refcnt;
 
@@ -167,9 +165,24 @@ static inline struct blkio_group *pdata_to_blkg(void *pdata)
         return NULL;
 }
 
-static inline char *blkg_path(struct blkio_group *blkg)
+/**
+ * blkg_path - format cgroup path of blkg
+ * @blkg: blkg of interest
+ * @buf: target buffer
+ * @buflen: target buffer length
+ *
+ * Format the path of the cgroup of @blkg into @buf.
+ */
+static inline int blkg_path(struct blkio_group *blkg, char *buf, int buflen)
 {
-        return blkg->path;
+        int ret;
+
+        rcu_read_lock();
+        ret = cgroup_path(blkg->blkcg->css.cgroup, buf, buflen);
+        rcu_read_unlock();
+        if (ret)
+                strncpy(buf, "<unavailable>", buflen);
+        return ret;
 }
 
 /**
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index e2aaf27e1f10..e9b7a47f6da0 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -155,9 +155,12 @@ static inline int throtl_tg_##name(const struct throtl_grp *tg)		\
 
 THROTL_TG_FNS(on_rr);
 
-#define throtl_log_tg(td, tg, fmt, args...)                             \
-        blk_add_trace_msg((td)->queue, "throtl %s " fmt,                \
-                          blkg_path(tg_to_blkg(tg)), ##args);           \
+#define throtl_log_tg(td, tg, fmt, args...)     do {                    \
+        char __pbuf[128];                                               \
+                                                                        \
+        blkg_path(tg_to_blkg(tg), __pbuf, sizeof(__pbuf));              \
+        blk_add_trace_msg((td)->queue, "throtl %s " fmt, __pbuf, ##args); \
+} while (0)
 
 #define throtl_log(td, fmt, args...)    \
         blk_add_trace_msg((td)->queue, "throtl " fmt, ##args)
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index eb07eb64e85b..901286b5f5cb 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -573,14 +573,21 @@ static inline void cfqg_put(struct cfq_group *cfqg)
         return blkg_put(cfqg_to_blkg(cfqg));
 }
 
-#define cfq_log_cfqq(cfqd, cfqq, fmt, args...)  \
+#define cfq_log_cfqq(cfqd, cfqq, fmt, args...)  do {                    \
+        char __pbuf[128];                                               \
+                                                                        \
+        blkg_path(cfqg_to_blkg((cfqq)->cfqg), __pbuf, sizeof(__pbuf));  \
         blk_add_trace_msg((cfqd)->queue, "cfq%d%c %s " fmt, (cfqq)->pid, \
-                        cfq_cfqq_sync((cfqq)) ? 'S' : 'A', \
-                        blkg_path(cfqg_to_blkg((cfqq)->cfqg)), ##args)
-
-#define cfq_log_cfqg(cfqd, cfqg, fmt, args...)                          \
-        blk_add_trace_msg((cfqd)->queue, "%s " fmt,                     \
-                        blkg_path(cfqg_to_blkg((cfqg))), ##args)        \
+                          cfq_cfqq_sync((cfqq)) ? 'S' : 'A',            \
+                          __pbuf, ##args);                              \
+} while (0)
+
+#define cfq_log_cfqg(cfqd, cfqg, fmt, args...)  do {                    \
+        char __pbuf[128];                                               \
+                                                                        \
+        blkg_path(cfqg_to_blkg(cfqg), __pbuf, sizeof(__pbuf));          \
+        blk_add_trace_msg((cfqd)->queue, "%s " fmt, __pbuf, ##args);    \
+} while (0)
 
 static inline void cfqg_stats_update_io_add(struct cfq_group *cfqg,
                                             struct cfq_group *curr_cfqg, int rw)