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-rw-r--r--block/bio.c62
1 files changed, 36 insertions, 26 deletions
diff --git a/block/bio.c b/block/bio.c
index 71cfe3720ea7..c39251e69447 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1978,18 +1978,30 @@ int bio_associate_blkg(struct bio *bio, struct blkcg_gq *blkg)
return 0;
}
+/**
+ * __bio_associate_blkg_from_css - internal blkg association function
+ *
+ * This in the core association function that all association paths rely on.
+ * A blkg reference is taken which is released upon freeing of the bio.
+ */
static int __bio_associate_blkg_from_css(struct bio *bio,
struct cgroup_subsys_state *css)
{
+ struct request_queue *q = bio->bi_disk->queue;
struct blkcg_gq *blkg;
+ int ret;
rcu_read_lock();
- blkg = blkg_lookup_create(css_to_blkcg(css), bio->bi_disk->queue);
+ if (!css || !css->parent)
+ blkg = q->root_blkg;
+ else
+ blkg = blkg_lookup_create(css_to_blkcg(css), q);
- rcu_read_unlock();
+ ret = bio_associate_blkg(bio, blkg);
- return bio_associate_blkg(bio, blkg);
+ rcu_read_unlock();
+ return ret;
}
/**
@@ -1998,13 +2010,14 @@ static int __bio_associate_blkg_from_css(struct bio *bio,
* @css: target css
*
* Associate @bio with the blkg found by combining the css's blkg and the
- * request_queue of the @bio. This takes a reference on the css that will
- * be put upon freeing of @bio.
+ * request_queue of the @bio. This falls back to the queue's root_blkg if
+ * the association fails with the css.
*/
int bio_associate_blkg_from_css(struct bio *bio,
struct cgroup_subsys_state *css)
{
- css_get(css);
+ if (unlikely(bio->bi_blkg))
+ return -EBUSY;
return __bio_associate_blkg_from_css(bio, css);
}
EXPORT_SYMBOL_GPL(bio_associate_blkg_from_css);
@@ -2016,22 +2029,29 @@ EXPORT_SYMBOL_GPL(bio_associate_blkg_from_css);
* @page: the page to lookup the blkcg from
*
* Associate @bio with the blkg from @page's owning memcg and the respective
- * request_queue. This works like every other associate function wrt
- * references.
+ * request_queue. If cgroup_e_css returns NULL, fall back to the queue's
+ * root_blkg.
*
* Note: this must be called after bio has an associated device.
*/
int bio_associate_blkg_from_page(struct bio *bio, struct page *page)
{
struct cgroup_subsys_state *css;
+ int ret;
if (unlikely(bio->bi_blkg))
return -EBUSY;
if (!page->mem_cgroup)
return 0;
- css = cgroup_get_e_css(page->mem_cgroup->css.cgroup, &io_cgrp_subsys);
- return __bio_associate_blkg_from_css(bio, css);
+ rcu_read_lock();
+
+ css = cgroup_e_css(page->mem_cgroup->css.cgroup, &io_cgrp_subsys);
+
+ ret = __bio_associate_blkg_from_css(bio, css);
+
+ rcu_read_unlock();
+ return ret;
}
#endif /* CONFIG_MEMCG */
@@ -2041,12 +2061,12 @@ int bio_associate_blkg_from_page(struct bio *bio, struct page *page)
* @bio: target bio
*
* Associate @bio with the blkg found from the bio's css and the request_queue.
- * If one is not found, bio_lookup_blkg creates the blkg.
+ * If one is not found, bio_lookup_blkg creates the blkg. This falls back to
+ * the queue's root_blkg if association fails.
*/
int bio_associate_create_blkg(struct request_queue *q, struct bio *bio)
{
- struct blkcg *blkcg;
- struct blkcg_gq *blkg;
+ struct cgroup_subsys_state *css;
int ret = 0;
/* someone has already associated this bio with a blkg */
@@ -2055,15 +2075,9 @@ int bio_associate_create_blkg(struct request_queue *q, struct bio *bio)
rcu_read_lock();
- blkcg = css_to_blkcg(blkcg_get_css());
+ css = blkcg_css();
- if (!blkcg->css.parent) {
- ret = bio_associate_blkg(bio, q->root_blkg);
- } else {
- blkg = blkg_lookup_create(blkcg, q);
-
- ret = bio_associate_blkg(bio, blkg);
- }
+ ret = __bio_associate_blkg_from_css(bio, css);
rcu_read_unlock();
return ret;
@@ -2080,8 +2094,6 @@ void bio_disassociate_task(struct bio *bio)
bio->bi_ioc = NULL;
}
if (bio->bi_blkg) {
- /* a ref is always taken on css */
- css_put(&bio_blkcg(bio)->css);
blkg_put(bio->bi_blkg);
bio->bi_blkg = NULL;
}
@@ -2094,10 +2106,8 @@ void bio_disassociate_task(struct bio *bio)
*/
void bio_clone_blkg_association(struct bio *dst, struct bio *src)
{
- if (src->bi_blkg) {
- css_get(&bio_blkcg(src)->css);
+ if (src->bi_blkg)
bio_associate_blkg(dst, src->bi_blkg);
- }
}
EXPORT_SYMBOL_GPL(bio_clone_blkg_association);
#endif /* CONFIG_BLK_CGROUP */