1 files changed, 457 insertions, 0 deletions
diff --git a/block/blk-ioc.c b/block/blk-ioc.c
new file mode 100644
index 000000000..63fc02042
--- /dev/null
+++ b/block/blk-ioc.c
@@ -0,0 +1,457 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Functions related to io context handling
+ */
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/bio.h>
+#include <linux/blkdev.h>
+#include <linux/slab.h>
+#include <linux/security.h>
+#include <linux/sched/task.h>
+
+#include "blk.h"
+#include "blk-mq-sched.h"
+
+/*
+ * For io context allocations
+ */
+static struct kmem_cache *iocontext_cachep;
+
+#ifdef CONFIG_BLK_ICQ
+/**
+ * get_io_context - increment reference count to io_context
+ * @ioc: io_context to get
+ *
+ * Increment reference count to @ioc.
+ */
+static void get_io_context(struct io_context *ioc)
+{
+	BUG_ON(atomic_long_read(&ioc->refcount) <= 0);
+	atomic_long_inc(&ioc->refcount);
+}
+
+static void icq_free_icq_rcu(struct rcu_head *head)
+{
+	struct io_cq *icq = container_of(head, struct io_cq, __rcu_head);
+
+	kmem_cache_free(icq->__rcu_icq_cache, icq);
+}
+
+/*
+ * Exit an icq. Called with ioc locked for blk-mq, and with both ioc
+ * and queue locked for legacy.
+ */
+static void ioc_exit_icq(struct io_cq *icq)
+{
+	struct elevator_type *et = icq->q->elevator->type;
+
+	if (icq->flags & ICQ_EXITED)
+		return;
+
+	if (et->ops.exit_icq)
+		et->ops.exit_icq(icq);
+
+	icq->flags |= ICQ_EXITED;
+}
+
+static void ioc_exit_icqs(struct io_context *ioc)
+{
+	struct io_cq *icq;
+
+	spin_lock_irq(&ioc->lock);
+	hlist_for_each_entry(icq, &ioc->icq_list, ioc_node)
+		ioc_exit_icq(icq);
+	spin_unlock_irq(&ioc->lock);
+}
+
+/*
+ * Release an icq. Called with ioc locked for blk-mq, and with both ioc
+ * and queue locked for legacy.
+ */
+static void ioc_destroy_icq(struct io_cq *icq)
+{
+	struct io_context *ioc = icq->ioc;
+	struct request_queue *q = icq->q;
+	struct elevator_type *et = q->elevator->type;
+
+	lockdep_assert_held(&ioc->lock);
+
+	radix_tree_delete(&ioc->icq_tree, icq->q->id);
+	hlist_del_init(&icq->ioc_node);
+	list_del_init(&icq->q_node);
+
+	/*
+	 * Both setting lookup hint to and clearing it from @icq are done
+	 * under queue_lock.  If it's not pointing to @icq now, it never
+	 * will.  Hint assignment itself can race safely.
+	 */
+	if (rcu_access_pointer(ioc->icq_hint) == icq)
+		rcu_assign_pointer(ioc->icq_hint, NULL);
+
+	ioc_exit_icq(icq);
+
+	/*
+	 * @icq->q might have gone away by the time RCU callback runs
+	 * making it impossible to determine icq_cache.  Record it in @icq.
+	 */
+	icq->__rcu_icq_cache = et->icq_cache;
+	icq->flags |= ICQ_DESTROYED;
+	call_rcu(&icq->__rcu_head, icq_free_icq_rcu);
+}
+
+/*
+ * Slow path for ioc release in put_io_context().  Performs double-lock
+ * dancing to unlink all icq's and then frees ioc.
+ */
+static void ioc_release_fn(struct work_struct *work)
+{
+	struct io_context *ioc = container_of(work, struct io_context,
+					      release_work);
+	spin_lock_irq(&ioc->lock);
+
+	while (!hlist_empty(&ioc->icq_list)) {
+		struct io_cq *icq = hlist_entry(ioc->icq_list.first,
+						struct io_cq, ioc_node);
+		struct request_queue *q = icq->q;
+
+		if (spin_trylock(&q->queue_lock)) {
+			ioc_destroy_icq(icq);
+			spin_unlock(&q->queue_lock);
+		} else {
+			/* Make sure q and icq cannot be freed. */
+			rcu_read_lock();
+
+			/* Re-acquire the locks in the correct order. */
+			spin_unlock(&ioc->lock);
+			spin_lock(&q->queue_lock);
+			spin_lock(&ioc->lock);
+
+			/*
+			 * The icq may have been destroyed when the ioc lock
+			 * was released.
+			 */
+			if (!(icq->flags & ICQ_DESTROYED))
+				ioc_destroy_icq(icq);
+
+			spin_unlock(&q->queue_lock);
+			rcu_read_unlock();
+		}
+	}
+
+	spin_unlock_irq(&ioc->lock);
+
+	kmem_cache_free(iocontext_cachep, ioc);
+}
+
+/*
+ * Releasing icqs requires reverse order double locking and we may already be
+ * holding a queue_lock.  Do it asynchronously from a workqueue.
+ */
+static bool ioc_delay_free(struct io_context *ioc)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&ioc->lock, flags);
+	if (!hlist_empty(&ioc->icq_list)) {
+		queue_work(system_power_efficient_wq, &ioc->release_work);
+		spin_unlock_irqrestore(&ioc->lock, flags);
+		return true;
+	}
+	spin_unlock_irqrestore(&ioc->lock, flags);
+	return false;
+}
+
+/**
+ * ioc_clear_queue - break any ioc association with the specified queue
+ * @q: request_queue being cleared
+ *
+ * Walk @q->icq_list and exit all io_cq's.
+ */
+void ioc_clear_queue(struct request_queue *q)
+{
+	LIST_HEAD(icq_list);
+
+	spin_lock_irq(&q->queue_lock);
+	list_splice_init(&q->icq_list, &icq_list);
+	spin_unlock_irq(&q->queue_lock);
+
+	rcu_read_lock();
+	while (!list_empty(&icq_list)) {
+		struct io_cq *icq =
+			list_entry(icq_list.next, struct io_cq, q_node);
+
+		spin_lock_irq(&icq->ioc->lock);
+		if (!(icq->flags & ICQ_DESTROYED))
+			ioc_destroy_icq(icq);
+		spin_unlock_irq(&icq->ioc->lock);
+	}
+	rcu_read_unlock();
+}
+#else /* CONFIG_BLK_ICQ */
+static inline void ioc_exit_icqs(struct io_context *ioc)
+{
+}
+static inline bool ioc_delay_free(struct io_context *ioc)
+{
+	return false;
+}
+#endif /* CONFIG_BLK_ICQ */
+
+/**
+ * put_io_context - put a reference of io_context
+ * @ioc: io_context to put
+ *
+ * Decrement reference count of @ioc and release it if the count reaches
+ * zero.
+ */
+void put_io_context(struct io_context *ioc)
+{
+	BUG_ON(atomic_long_read(&ioc->refcount) <= 0);
+	if (atomic_long_dec_and_test(&ioc->refcount) && !ioc_delay_free(ioc))
+		kmem_cache_free(iocontext_cachep, ioc);
+}
+EXPORT_SYMBOL_GPL(put_io_context);
+
+/* Called by the exiting task */
+void exit_io_context(struct task_struct *task)
+{
+	struct io_context *ioc;
+
+	task_lock(task);
+	ioc = task->io_context;
+	task->io_context = NULL;
+	task_unlock(task);
+
+	if (atomic_dec_and_test(&ioc->active_ref)) {
+		ioc_exit_icqs(ioc);
+		put_io_context(ioc);
+	}
+}
+
+static struct io_context *alloc_io_context(gfp_t gfp_flags, int node)
+{
+	struct io_context *ioc;
+
+	ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags | __GFP_ZERO,
+				    node);
+	if (unlikely(!ioc))
+		return NULL;
+
+	atomic_long_set(&ioc->refcount, 1);
+	atomic_set(&ioc->active_ref, 1);
+#ifdef CONFIG_BLK_ICQ
+	spin_lock_init(&ioc->lock);
+	INIT_RADIX_TREE(&ioc->icq_tree, GFP_ATOMIC);
+	INIT_HLIST_HEAD(&ioc->icq_list);
+	INIT_WORK(&ioc->release_work, ioc_release_fn);
+#endif
+	ioc->ioprio = IOPRIO_DEFAULT;
+
+	return ioc;
+}
+
+int set_task_ioprio(struct task_struct *task, int ioprio)
+{
+	int err;
+	const struct cred *cred = current_cred(), *tcred;
+
+	rcu_read_lock();
+	tcred = __task_cred(task);
+	if (!uid_eq(tcred->uid, cred->euid) &&
+	    !uid_eq(tcred->uid, cred->uid) && !capable(CAP_SYS_NICE)) {
+		rcu_read_unlock();
+		return -EPERM;
+	}
+	rcu_read_unlock();
+
+	err = security_task_setioprio(task, ioprio);
+	if (err)
+		return err;
+
+	task_lock(task);
+	if (unlikely(!task->io_context)) {
+		struct io_context *ioc;
+
+		task_unlock(task);
+
+		ioc = alloc_io_context(GFP_ATOMIC, NUMA_NO_NODE);
+		if (!ioc)
+			return -ENOMEM;
+
+		task_lock(task);
+		if (task->flags & PF_EXITING) {
+			kmem_cache_free(iocontext_cachep, ioc);
+			goto out;
+		}
+		if (task->io_context)
+			kmem_cache_free(iocontext_cachep, ioc);
+		else
+			task->io_context = ioc;
+	}
+	task->io_context->ioprio = ioprio;
+out:
+	task_unlock(task);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(set_task_ioprio);
+
+int __copy_io(unsigned long clone_flags, struct task_struct *tsk)
+{
+	struct io_context *ioc = current->io_context;
+
+	/*
+	 * Share io context with parent, if CLONE_IO is set
+	 */
+	if (clone_flags & CLONE_IO) {
+		atomic_inc(&ioc->active_ref);
+		tsk->io_context = ioc;
+	} else if (ioprio_valid(ioc->ioprio)) {
+		tsk->io_context = alloc_io_context(GFP_KERNEL, NUMA_NO_NODE);
+		if (!tsk->io_context)
+			return -ENOMEM;
+		tsk->io_context->ioprio = ioc->ioprio;
+	}
+
+	return 0;
+}
+
+#ifdef CONFIG_BLK_ICQ
+/**
+ * ioc_lookup_icq - lookup io_cq from ioc
+ * @q: the associated request_queue
+ *
+ * Look up io_cq associated with @ioc - @q pair from @ioc.  Must be called
+ * with @q->queue_lock held.
+ */
+struct io_cq *ioc_lookup_icq(struct request_queue *q)
+{
+	struct io_context *ioc = current->io_context;
+	struct io_cq *icq;
+
+	lockdep_assert_held(&q->queue_lock);
+
+	/*
+	 * icq's are indexed from @ioc using radix tree and hint pointer,
+	 * both of which are protected with RCU.  All removals are done
+	 * holding both q and ioc locks, and we're holding q lock - if we
+	 * find a icq which points to us, it's guaranteed to be valid.
+	 */
+	rcu_read_lock();
+	icq = rcu_dereference(ioc->icq_hint);
+	if (icq && icq->q == q)
+		goto out;
+
+	icq = radix_tree_lookup(&ioc->icq_tree, q->id);
+	if (icq && icq->q == q)
+		rcu_assign_pointer(ioc->icq_hint, icq);	/* allowed to race */
+	else
+		icq = NULL;
+out:
+	rcu_read_unlock();
+	return icq;
+}
+EXPORT_SYMBOL(ioc_lookup_icq);
+
+/**
+ * ioc_create_icq - create and link io_cq
+ * @q: request_queue of interest
+ *
+ * Make sure io_cq linking @ioc and @q exists.  If icq doesn't exist, they
+ * will be created using @gfp_mask.
+ *
+ * The caller is responsible for ensuring @ioc won't go away and @q is
+ * alive and will stay alive until this function returns.
+ */
+static struct io_cq *ioc_create_icq(struct request_queue *q)
+{
+	struct io_context *ioc = current->io_context;
+	struct elevator_type *et = q->elevator->type;
+	struct io_cq *icq;
+
+	/* allocate stuff */
+	icq = kmem_cache_alloc_node(et->icq_cache, GFP_ATOMIC | __GFP_ZERO,
+				    q->node);
+	if (!icq)
+		return NULL;
+
+	if (radix_tree_maybe_preload(GFP_ATOMIC) < 0) {
+		kmem_cache_free(et->icq_cache, icq);
+		return NULL;
+	}
+
+	icq->ioc = ioc;
+	icq->q = q;
+	INIT_LIST_HEAD(&icq->q_node);
+	INIT_HLIST_NODE(&icq->ioc_node);
+
+	/* lock both q and ioc and try to link @icq */
+	spin_lock_irq(&q->queue_lock);
+	spin_lock(&ioc->lock);
+
+	if (likely(!radix_tree_insert(&ioc->icq_tree, q->id, icq))) {
+		hlist_add_head(&icq->ioc_node, &ioc->icq_list);
+		list_add(&icq->q_node, &q->icq_list);
+		if (et->ops.init_icq)
+			et->ops.init_icq(icq);
+	} else {
+		kmem_cache_free(et->icq_cache, icq);
+		icq = ioc_lookup_icq(q);
+		if (!icq)
+			printk(KERN_ERR "cfq: icq link failed!\n");
+	}
+
+	spin_unlock(&ioc->lock);
+	spin_unlock_irq(&q->queue_lock);
+	radix_tree_preload_end();
+	return icq;
+}
+
+struct io_cq *ioc_find_get_icq(struct request_queue *q)
+{
+	struct io_context *ioc = current->io_context;
+	struct io_cq *icq = NULL;
+
+	if (unlikely(!ioc)) {
+		ioc = alloc_io_context(GFP_ATOMIC, q->node);
+		if (!ioc)
+			return NULL;
+
+		task_lock(current);
+		if (current->io_context) {
+			kmem_cache_free(iocontext_cachep, ioc);
+			ioc = current->io_context;
+		} else {
+			current->io_context = ioc;
+		}
+
+		get_io_context(ioc);
+		task_unlock(current);
+	} else {
+		get_io_context(ioc);
+
+		spin_lock_irq(&q->queue_lock);
+		icq = ioc_lookup_icq(q);
+		spin_unlock_irq(&q->queue_lock);
+	}
+
+	if (!icq) {
+		icq = ioc_create_icq(q);
+		if (!icq) {
+			put_io_context(ioc);
+			return NULL;
+		}
+	}
+	return icq;
+}
+EXPORT_SYMBOL_GPL(ioc_find_get_icq);
+#endif /* CONFIG_BLK_ICQ */
+
+static int __init blk_ioc_init(void)
+{
+	iocontext_cachep = kmem_cache_create("blkdev_ioc",
+			sizeof(struct io_context), 0, SLAB_PANIC, NULL);
+	return 0;
+}
+subsys_initcall(blk_ioc_init);