blkcg: refine error codes returned during blkcg configuration

blkcg currently returns -EINVAL for most errors which can be pretty
confusing given that the failure modes are quite varied.  Update the
error returns so that

* -EINVAL only for syntactic errors.
* -ERANGE if the value is out of range.
* -ENODEV if the target device can't be found.
* -EOPNOTSUPP if the policy is not enabled on the target device.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index c82c5dbf91876948bc574b9b2a00c74487a13597..0af3bff198ed659d54dc001b059b42792dfc9a02 100644 (file)
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -179,7 +179,7 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
 
        /* blkg holds a reference to blkcg */
        if (!css_tryget_online(&blkcg->css)) {
-               ret = -EINVAL;
+               ret = -ENODEV;
                goto err_free_blkg;
        }
 
@@ -205,7 +205,7 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
        if (blkcg_parent(blkcg)) {
                blkg->parent = __blkg_lookup(blkcg_parent(blkcg), q, false);
                if (WARN_ON_ONCE(!blkg->parent)) {
-                       ret = -EINVAL;
+                       ret = -ENODEV;
                        goto err_put_congested;
                }
                blkg_get(blkg->parent);
@@ -279,7 +279,7 @@ 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 ERR_PTR(blk_queue_dying(q) ? -EINVAL : -EBUSY);
+               return ERR_PTR(blk_queue_dying(q) ? -ENODEV : -EBUSY);
 
        blkg = __blkg_lookup(blkcg, q, true);
        if (blkg)
@@ -792,10 +792,10 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
 
        disk = get_gendisk(MKDEV(major, minor), &part);
        if (!disk)
-               return -EINVAL;
+               return -ENODEV;
        if (part) {
                put_disk(disk);
-               return -EINVAL;
+               return -ENODEV;
        }
 
        rcu_read_lock();
@@ -804,7 +804,7 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
        if (blkcg_policy_enabled(disk->queue, pol))
                blkg = blkg_lookup_create(blkcg, disk->queue);
        else
-               blkg = ERR_PTR(-EINVAL);
+               blkg = ERR_PTR(-EOPNOTSUPP);
 
        if (IS_ERR(blkg)) {
                ret = PTR_ERR(blkg);

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index bcf40266bd0a617dbc4c3c3d550b2829defe6d40..38277e3ce28611fcb849db5e1649fa7851ca99ec 100644 (file)
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1755,7 +1755,7 @@ static ssize_t __cfqg_set_weight_device(struct kernfs_open_file *of,
        cfqg = blkg_to_cfqg(ctx.blkg);
        cfqgd = blkcg_to_cfqgd(blkcg);
 
-       ret = -EINVAL;
+       ret = -ERANGE;
        if (!ctx.v || (ctx.v >= CFQ_WEIGHT_MIN && ctx.v <= CFQ_WEIGHT_MAX)) {
                if (!is_leaf_weight) {
                        cfqg->dev_weight = ctx.v;