blk-cgroup: Pre-allocate tree node on blkg_conf_prep
[ Upstream commit5.4-rM2-2.2.x-imx-squashedf255c19b3a
] Similarly to commit457e490f2b
("blkcg: allocate struct blkcg_gq outside request queue spinlock"), blkg_create can also trigger occasional -ENOMEM failures at the radix insertion because any allocation inside blkg_create has to be non-blocking, making it more likely to fail. This causes trouble for userspace tools trying to configure io weights who need to deal with this condition. This patch reduces the occurrence of -ENOMEMs on this path by preloading the radix tree element on a GFP_KERNEL context, such that we guarantee the later non-blocking insertion won't fail. A similar solution exists in blkcg_init_queue for the same situation. Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com> Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Sasha Levin <sashal@kernel.org>
parent
f77756ea66
commit
3c52715cea
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@ -855,6 +855,12 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
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goto fail;
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goto fail;
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}
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}
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if (radix_tree_preload(GFP_KERNEL)) {
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blkg_free(new_blkg);
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ret = -ENOMEM;
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goto fail;
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}
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rcu_read_lock();
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rcu_read_lock();
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spin_lock_irq(&q->queue_lock);
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spin_lock_irq(&q->queue_lock);
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@ -862,7 +868,7 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
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if (IS_ERR(blkg)) {
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if (IS_ERR(blkg)) {
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ret = PTR_ERR(blkg);
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ret = PTR_ERR(blkg);
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blkg_free(new_blkg);
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blkg_free(new_blkg);
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goto fail_unlock;
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goto fail_preloaded;
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}
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}
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if (blkg) {
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if (blkg) {
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@ -871,10 +877,12 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
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blkg = blkg_create(pos, q, new_blkg);
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blkg = blkg_create(pos, q, new_blkg);
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if (IS_ERR(blkg)) {
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if (IS_ERR(blkg)) {
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ret = PTR_ERR(blkg);
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ret = PTR_ERR(blkg);
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goto fail_unlock;
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goto fail_preloaded;
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}
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}
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}
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}
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radix_tree_preload_end();
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if (pos == blkcg)
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if (pos == blkcg)
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goto success;
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goto success;
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}
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}
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@ -884,6 +892,8 @@ success:
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ctx->body = input;
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ctx->body = input;
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return 0;
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return 0;
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fail_preloaded:
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radix_tree_preload_end();
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fail_unlock:
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fail_unlock:
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spin_unlock_irq(&q->queue_lock);
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spin_unlock_irq(&q->queue_lock);
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rcu_read_unlock();
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rcu_read_unlock();
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