blkcg: convert blkg_lookup_create to find closest blkg

[linux-2.6-microblaze.git] / block / bio.c

diff --git a/block/bio.c b/block/bio.c
index 81c05ee..bfd41e8 100644 (file)
--- a/block/bio.c
+++ b/block/bio.c
@@ -1988,34 +1988,43 @@ int bio_associate_blkcg_from_page(struct bio *bio, struct page *page)
  *
  * This function takes an extra reference of @blkcg_css which will be put
  * when @bio is released.  The caller must own @bio and is responsible for
- * synchronizing calls to this function.
+ * synchronizing calls to this function.  If @blkcg_css is NULL, a call to
+ * blkcg_get_css finds the current css from the kthread or task.
  */
 int bio_associate_blkcg(struct bio *bio, struct cgroup_subsys_state *blkcg_css)
 {
        if (unlikely(bio->bi_css))
                return -EBUSY;
-       css_get(blkcg_css);
+
+       if (blkcg_css)
+               css_get(blkcg_css);
+       else
+               blkcg_css = blkcg_get_css();
+
        bio->bi_css = blkcg_css;
        return 0;
 }
 EXPORT_SYMBOL_GPL(bio_associate_blkcg);
 
 /**
- * bio_associate_blkg - associate a bio with the specified blkg
+ * bio_associate_blkg - associate a bio with the a blkg
  * @bio: target bio
  * @blkg: the blkg to associate
  *
- * Associate @bio with the blkg specified by @blkg.  This is the queue specific
- * blkcg information associated with the @bio, a reference will be taken on the
- * @blkg and will be freed when the bio is freed.
+ * This tries to associate @bio with the specified blkg.  Association failure
+ * is handled by walking up the blkg tree.  Therefore, the blkg associated can
+ * be anything between @blkg and the root_blkg.  This situation only happens
+ * when a cgroup is dying and then the remaining bios will spill to the closest
+ * alive blkg.
+ *
+ * A reference will be taken on the @blkg and will be released when @bio is
+ * freed.
  */
 int bio_associate_blkg(struct bio *bio, struct blkcg_gq *blkg)
 {
        if (unlikely(bio->bi_blkg))
                return -EBUSY;
-       if (!blkg_try_get(blkg))
-               return -ENODEV;
-       bio->bi_blkg = blkg;
+       bio->bi_blkg = blkg_try_get_closest(blkg);
        return 0;
 }