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authorDennis Zhou <dennis@kernel.org>2018-11-02 00:24:10 +0300
committerJens Axboe <axboe@kernel.dk>2018-11-02 04:59:53 +0300
commitb5f2954d30c77649bce9c27e7a0a94299d9cfdf8 (patch)
treef5dd932dc087c3a60410e82c70be1daf92d350a7 /block/blk-cgroup.c
parent153fcd5f6d93b8e1e4040b1337f564a10f8d93af (diff)
downloadlinux-b5f2954d30c77649bce9c27e7a0a94299d9cfdf8.tar.xz
blkcg: revert blkcg cleanups series
This reverts a series committed earlier due to null pointer exception bug report in [1]. It seems there are edge case interactions that I did not consider and will need some time to understand what causes the adverse interactions. The original series can be found in [2] with a follow up series in [3]. [1] https://www.spinics.net/lists/cgroups/msg20719.html [2] https://lore.kernel.org/lkml/20180911184137.35897-1-dennisszhou@gmail.com/ [3] https://lore.kernel.org/lkml/20181020185612.51587-1-dennis@kernel.org/ This reverts the following commits: d459d853c2ed, b2c3fa546705, 101246ec02b5, b3b9f24f5fcc, e2b0989954ae, f0fcb3ec89f3, c839e7a03f92, bdc2491708c4, 74b7c02a9bc1, 5bf9a1f3b4ef, a7b39b4e961c, 07b05bcc3213, 49f4c2dc2b50, 27e6fa996c53 Signed-off-by: Dennis Zhou <dennis@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-cgroup.c')
-rw-r--r--block/blk-cgroup.c123
1 files changed, 38 insertions, 85 deletions
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 992da5592c6e..c630e02836a8 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -84,37 +84,6 @@ static void blkg_free(struct blkcg_gq *blkg)
kfree(blkg);
}
-static void __blkg_release(struct rcu_head *rcu)
-{
- struct blkcg_gq *blkg = container_of(rcu, struct blkcg_gq, rcu_head);
-
- percpu_ref_exit(&blkg->refcnt);
-
- /* release the blkcg and parent blkg refs this blkg has been holding */
- css_put(&blkg->blkcg->css);
- if (blkg->parent)
- blkg_put(blkg->parent);
-
- wb_congested_put(blkg->wb_congested);
-
- blkg_free(blkg);
-}
-
-/*
- * A group is RCU protected, but having an rcu lock does not mean that one
- * can access all the fields of blkg and assume these are valid. For
- * example, don't try to follow throtl_data and request queue links.
- *
- * Having a reference to blkg under an rcu allows accesses to only values
- * local to groups like group stats and group rate limits.
- */
-static void blkg_release(struct percpu_ref *ref)
-{
- struct blkcg_gq *blkg = container_of(ref, struct blkcg_gq, refcnt);
-
- call_rcu(&blkg->rcu_head, __blkg_release);
-}
-
/**
* blkg_alloc - allocate a blkg
* @blkcg: block cgroup the new blkg is associated with
@@ -141,6 +110,7 @@ static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q,
blkg->q = q;
INIT_LIST_HEAD(&blkg->q_node);
blkg->blkcg = blkcg;
+ atomic_set(&blkg->refcnt, 1);
/* root blkg uses @q->root_rl, init rl only for !root blkgs */
if (blkcg != &blkcg_root) {
@@ -247,11 +217,6 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
blkg_get(blkg->parent);
}
- ret = percpu_ref_init(&blkg->refcnt, blkg_release, 0,
- GFP_NOWAIT | __GFP_NOWARN);
- if (ret)
- goto err_cancel_ref;
-
/* invoke per-policy init */
for (i = 0; i < BLKCG_MAX_POLS; i++) {
struct blkcg_policy *pol = blkcg_policy[i];
@@ -284,8 +249,6 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
blkg_put(blkg);
return ERR_PTR(ret);
-err_cancel_ref:
- percpu_ref_exit(&blkg->refcnt);
err_put_congested:
wb_congested_put(wb_congested);
err_put_css:
@@ -296,7 +259,7 @@ err_free_blkg:
}
/**
- * __blkg_lookup_create - lookup blkg, try to create one if not there
+ * blkg_lookup_create - lookup blkg, try to create one if not there
* @blkcg: blkcg of interest
* @q: request_queue of interest
*
@@ -305,11 +268,12 @@ err_free_blkg:
* that all non-root blkg's have access to the parent blkg. This function
* should be called under RCU read lock and @q->queue_lock.
*
- * Returns the blkg or the closest blkg if blkg_create fails as it walks
- * down from root.
+ * Returns pointer to the looked up or created blkg on success, ERR_PTR()
+ * value on error. If @q is dead, returns ERR_PTR(-EINVAL). If @q is not
+ * dead and bypassing, returns ERR_PTR(-EBUSY).
*/
-struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg,
- struct request_queue *q)
+struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
+ struct request_queue *q)
{
struct blkcg_gq *blkg;
@@ -321,7 +285,7 @@ struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg,
* we shouldn't allow anything to go through for a bypassing queue.
*/
if (unlikely(blk_queue_bypass(q)))
- return q->root_blkg;
+ return ERR_PTR(blk_queue_dying(q) ? -ENODEV : -EBUSY);
blkg = __blkg_lookup(blkcg, q, true);
if (blkg)
@@ -329,58 +293,23 @@ struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg,
/*
* Create blkgs walking down from blkcg_root to @blkcg, so that all
- * non-root blkgs have access to their parents. Returns the closest
- * blkg to the intended blkg should blkg_create() fail.
+ * non-root blkgs have access to their parents.
*/
while (true) {
struct blkcg *pos = blkcg;
struct blkcg *parent = blkcg_parent(blkcg);
- struct blkcg_gq *ret_blkg = q->root_blkg;
-
- while (parent) {
- blkg = __blkg_lookup(parent, q, false);
- if (blkg) {
- /* remember closest blkg */
- ret_blkg = blkg;
- break;
- }
+
+ while (parent && !__blkg_lookup(parent, q, false)) {
pos = parent;
parent = blkcg_parent(parent);
}
blkg = blkg_create(pos, q, NULL);
- if (IS_ERR(blkg))
- return ret_blkg;
- if (pos == blkcg)
+ if (pos == blkcg || IS_ERR(blkg))
return blkg;
}
}
-/**
- * blkg_lookup_create - find or create a blkg
- * @blkcg: target block cgroup
- * @q: target request_queue
- *
- * This looks up or creates the blkg representing the unique pair
- * of the blkcg and the request_queue.
- */
-struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
- struct request_queue *q)
-{
- struct blkcg_gq *blkg = blkg_lookup(blkcg, q);
- unsigned long flags;
-
- if (unlikely(!blkg)) {
- spin_lock_irqsave(q->queue_lock, flags);
-
- blkg = __blkg_lookup_create(blkcg, q);
-
- spin_unlock_irqrestore(q->queue_lock, flags);
- }
-
- return blkg;
-}
-
static void blkg_destroy(struct blkcg_gq *blkg)
{
struct blkcg *blkcg = blkg->blkcg;
@@ -424,7 +353,7 @@ static void blkg_destroy(struct blkcg_gq *blkg)
* Put the reference taken at the time of creation so that when all
* queues are gone, group can be destroyed.
*/
- percpu_ref_kill(&blkg->refcnt);
+ blkg_put(blkg);
}
/**
@@ -452,6 +381,29 @@ static void blkg_destroy_all(struct request_queue *q)
}
/*
+ * A group is RCU protected, but having an rcu lock does not mean that one
+ * can access all the fields of blkg and assume these are valid. For
+ * example, don't try to follow throtl_data and request queue links.
+ *
+ * Having a reference to blkg under an rcu allows accesses to only values
+ * local to groups like group stats and group rate limits.
+ */
+void __blkg_release_rcu(struct rcu_head *rcu_head)
+{
+ struct blkcg_gq *blkg = container_of(rcu_head, struct blkcg_gq, rcu_head);
+
+ /* release the blkcg and parent blkg refs this blkg has been holding */
+ css_put(&blkg->blkcg->css);
+ if (blkg->parent)
+ blkg_put(blkg->parent);
+
+ wb_congested_put(blkg->wb_congested);
+
+ blkg_free(blkg);
+}
+EXPORT_SYMBOL_GPL(__blkg_release_rcu);
+
+/*
* The next function used by blk_queue_for_each_rl(). It's a bit tricky
* because the root blkg uses @q->root_rl instead of its own rl.
*/
@@ -1796,7 +1748,8 @@ void blkcg_maybe_throttle_current(void)
blkg = blkg_lookup(blkcg, q);
if (!blkg)
goto out;
- if (!blkg_tryget(blkg))
+ blkg = blkg_try_get(blkg);
+ if (!blkg)
goto out;
rcu_read_unlock();