blk-throttle: Introduce a helper function to fill in device details

A helper function for the code which is used at 2-3 places. Makes reading
code little easier.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 68f2ac3..97ea7f8 100644 (file)
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -188,16 +188,34 @@ throtl_add_group_to_td_list(struct throtl_data *td, struct throtl_grp *tg)
        td->nr_undestroyed_grps++;
 }
 
-static void throtl_init_add_tg_lists(struct throtl_data *td,
-                       struct throtl_grp *tg, struct blkio_cgroup *blkcg)
+static void
+__throtl_tg_fill_dev_details(struct throtl_data *td, struct throtl_grp *tg)
 {
        struct backing_dev_info *bdi = &td->queue->backing_dev_info;
        unsigned int major, minor;
 
+       if (!tg || tg->blkg.dev)
+               return;
+
+       /*
+        * Fill in device details for a group which might not have been
+        * filled at group creation time as queue was being instantiated
+        * and driver had not attached a device yet
+        */
+       if (bdi->dev && dev_name(bdi->dev)) {
+               sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
+               tg->blkg.dev = MKDEV(major, minor);
+       }
+}
+
+static void throtl_init_add_tg_lists(struct throtl_data *td,
+                       struct throtl_grp *tg, struct blkio_cgroup *blkcg)
+{
+       __throtl_tg_fill_dev_details(td, tg);
+
        /* Add group onto cgroup list */
-       sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
        blkiocg_add_blkio_group(blkcg, &tg->blkg, (void *)td,
-                               MKDEV(major, minor), BLKIO_POLICY_THROTL);
+                               tg->blkg.dev, BLKIO_POLICY_THROTL);
 
        tg->bps[READ] = blkcg_get_read_bps(blkcg, tg->blkg.dev);
        tg->bps[WRITE] = blkcg_get_write_bps(blkcg, tg->blkg.dev);
@@ -225,8 +243,6 @@ throtl_grp *throtl_find_tg(struct throtl_data *td, struct blkio_cgroup *blkcg)
 {
        struct throtl_grp *tg = NULL;
        void *key = td;
-       struct backing_dev_info *bdi = &td->queue->backing_dev_info;
-       unsigned int major, minor;
 
        /*
         * This is the common case when there are no blkio cgroups.
@@ -237,12 +253,7 @@ throtl_grp *throtl_find_tg(struct throtl_data *td, struct blkio_cgroup *blkcg)
        else
                tg = tg_of_blkg(blkiocg_lookup_group(blkcg, key));
 
-       /* Fill in device details for root group */
-       if (tg && !tg->blkg.dev && bdi->dev && dev_name(bdi->dev)) {
-               sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
-               tg->blkg.dev = MKDEV(major, minor);
-       }
-
+       __throtl_tg_fill_dev_details(td, tg);
        return tg;
 }