1 files changed, 252 insertions, 182 deletions

diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index 9414a7a60a9f..9adf36e6364b 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -18,25 +18,13 @@
 
 #include "kernfs-internal.h"
 
-/*
- * There's one kernfs_open_file for each open file and one kernfs_open_node
- * for each kernfs_node with one or more open files.
- *
- * kernfs_node->attr.open points to kernfs_open_node.  attr.open is
- * protected by kernfs_open_node_lock.
- *
- * filp->private_data points to seq_file whose ->private points to
- * kernfs_open_file.  kernfs_open_files are chained at
- * kernfs_open_node->files, which is protected by kernfs_open_file_mutex.
- */
-static DEFINE_SPINLOCK(kernfs_open_node_lock);
-static DEFINE_MUTEX(kernfs_open_file_mutex);
-
 struct kernfs_open_node {
-	atomic_t		refcnt;
+	struct rcu_head		rcu_head;
 	atomic_t		event;
 	wait_queue_head_t	poll;
 	struct list_head	files; /* goes through kernfs_open_file.list */
+	unsigned int		nr_mmapped;
+	unsigned int		nr_to_release;
 };
 
 /*
@@ -45,13 +33,85 @@ struct kernfs_open_node {
  * pending queue is implemented as a singly linked list of kernfs_nodes.
  * The list is terminated with the self pointer so that whether a
  * kernfs_node is on the list or not can be determined by testing the next
- * pointer for NULL.
+ * pointer for %NULL.
  */
 #define KERNFS_NOTIFY_EOL			((void *)&kernfs_notify_list)
 
 static DEFINE_SPINLOCK(kernfs_notify_lock);
 static struct kernfs_node *kernfs_notify_list = KERNFS_NOTIFY_EOL;
 
+static inline struct mutex *kernfs_open_file_mutex_ptr(struct kernfs_node *kn)
+{
+	int idx = hash_ptr(kn, NR_KERNFS_LOCK_BITS);
+
+	return &kernfs_locks->open_file_mutex[idx];
+}
+
+static inline struct mutex *kernfs_open_file_mutex_lock(struct kernfs_node *kn)
+{
+	struct mutex *lock;
+
+	lock = kernfs_open_file_mutex_ptr(kn);
+
+	mutex_lock(lock);
+
+	return lock;
+}
+
+/**
+ * of_on - Get the kernfs_open_node of the specified kernfs_open_file
+ * @of: target kernfs_open_file
+ *
+ * Return: the kernfs_open_node of the kernfs_open_file
+ */
+static struct kernfs_open_node *of_on(struct kernfs_open_file *of)
+{
+	return rcu_dereference_protected(of->kn->attr.open,
+					 !list_empty(&of->list));
+}
+
+/* Get active reference to kernfs node for an open file */
+static struct kernfs_open_file *kernfs_get_active_of(struct kernfs_open_file *of)
+{
+	/* Skip if file was already released */
+	if (unlikely(of->released))
+		return NULL;
+
+	if (!kernfs_get_active(of->kn))
+		return NULL;
+
+	return of;
+}
+
+static void kernfs_put_active_of(struct kernfs_open_file *of)
+{
+	return kernfs_put_active(of->kn);
+}
+
+/**
+ * kernfs_deref_open_node_locked - Get kernfs_open_node corresponding to @kn
+ *
+ * @kn: target kernfs_node.
+ *
+ * Fetch and return ->attr.open of @kn when caller holds the
+ * kernfs_open_file_mutex_ptr(kn).
+ *
+ * Update of ->attr.open happens under kernfs_open_file_mutex_ptr(kn). So when
+ * the caller guarantees that this mutex is being held, other updaters can't
+ * change ->attr.open and this means that we can safely deref ->attr.open
+ * outside RCU read-side critical section.
+ *
+ * The caller needs to make sure that kernfs_open_file_mutex is held.
+ *
+ * Return: @kn->attr.open when kernfs_open_file_mutex is held.
+ */
+static struct kernfs_open_node *
+kernfs_deref_open_node_locked(struct kernfs_node *kn)
+{
+	return rcu_dereference_protected(kn->attr.open,
+				lockdep_is_held(kernfs_open_file_mutex_ptr(kn)));
+}
+
 static struct kernfs_open_file *kernfs_of(struct file *file)
 {
 	return ((struct seq_file *)file->private_data)->private;
@@ -97,7 +157,7 @@ static void kernfs_seq_stop_active(struct seq_file *sf, void *v)
 
 	if (ops->seq_stop)
 		ops->seq_stop(sf, v);
-	kernfs_put_active(of->kn);
+	kernfs_put_active_of(of);
 }
 
 static void *kernfs_seq_start(struct seq_file *sf, loff_t *ppos)
@@ -110,7 +170,7 @@ static void *kernfs_seq_start(struct seq_file *sf, loff_t *ppos)
 	 * the ops aren't called concurrently for the same open file.
 	 */
 	mutex_lock(&of->mutex);
-	if (!kernfs_get_active(of->kn))
+	if (!kernfs_get_active_of(of))
 		return ERR_PTR(-ENODEV);
 
 	ops = kernfs_ops(of->kn);
@@ -120,13 +180,8 @@ static void *kernfs_seq_start(struct seq_file *sf, loff_t *ppos)
 		if (next == ERR_PTR(-ENODEV))
 			kernfs_seq_stop_active(sf, next);
 		return next;
-	} else {
-		/*
-		 * The same behavior and code as single_open().  Returns
-		 * !NULL if pos is at the beginning; otherwise, NULL.
-		 */
-		return NULL + !*ppos;
 	}
+	return single_start(sf, ppos);
 }
 
 static void *kernfs_seq_next(struct seq_file *sf, void *v, loff_t *ppos)
@@ -163,7 +218,7 @@ static int kernfs_seq_show(struct seq_file *sf, void *v)
 {
 	struct kernfs_open_file *of = sf->private;
 
-	of->event = atomic_read(&of->kn->attr.open->event);
+	of->event = atomic_read(&of_on(of)->event);
 
 	return of->kn->attr.ops->seq_show(sf, v);
 }
@@ -201,20 +256,21 @@ static ssize_t kernfs_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
 	 * the ops aren't called concurrently for the same open file.
 	 */
 	mutex_lock(&of->mutex);
-	if (!kernfs_get_active(of->kn)) {
+	if (!kernfs_get_active_of(of)) {
 		len = -ENODEV;
 		mutex_unlock(&of->mutex);
 		goto out_free;
 	}
 
-	of->event = atomic_read(&of->kn->attr.open->event);
+	of->event = atomic_read(&of_on(of)->event);
+
 	ops = kernfs_ops(of->kn);
 	if (ops->read)
 		len = ops->read(of, buf, len, iocb->ki_pos);
 	else
 		len = -EINVAL;
 
-	kernfs_put_active(of->kn);
+	kernfs_put_active_of(of);
 	mutex_unlock(&of->mutex);
 
 	if (len < 0)
@@ -249,7 +305,7 @@ static ssize_t kernfs_fop_read_iter(struct kiocb *iocb, struct iov_iter *iter)
  * There is no easy way for us to know if userspace is only doing a partial
  * write, so we don't support them. We expect the entire buffer to come on
  * the first write.  Hint: if you're writing a value, first read the file,
- * modify only the the value you're changing, then write entire buffer
+ * modify only the value you're changing, then write entire buffer
  * back.
  */
 static ssize_t kernfs_fop_write_iter(struct kiocb *iocb, struct iov_iter *iter)
@@ -285,7 +341,7 @@ static ssize_t kernfs_fop_write_iter(struct kiocb *iocb, struct iov_iter *iter)
 	 * the ops aren't called concurrently for the same open file.
 	 */
 	mutex_lock(&of->mutex);
-	if (!kernfs_get_active(of->kn)) {
+	if (!kernfs_get_active_of(of)) {
 		mutex_unlock(&of->mutex);
 		len = -ENODEV;
 		goto out_free;
@@ -297,7 +353,7 @@ static ssize_t kernfs_fop_write_iter(struct kiocb *iocb, struct iov_iter *iter)
 	else
 		len = -EINVAL;
 
-	kernfs_put_active(of->kn);
+	kernfs_put_active_of(of);
 	mutex_unlock(&of->mutex);
 
 	if (len > 0)
@@ -319,13 +375,13 @@ static void kernfs_vma_open(struct vm_area_struct *vma)
 	if (!of->vm_ops)
 		return;
 
-	if (!kernfs_get_active(of->kn))
+	if (!kernfs_get_active_of(of))
 		return;
 
 	if (of->vm_ops->open)
 		of->vm_ops->open(vma);
 
-	kernfs_put_active(of->kn);
+	kernfs_put_active_of(of);
 }
 
 static vm_fault_t kernfs_vma_fault(struct vm_fault *vmf)
@@ -337,14 +393,14 @@ static vm_fault_t kernfs_vma_fault(struct vm_fault *vmf)
 	if (!of->vm_ops)
 		return VM_FAULT_SIGBUS;
 
-	if (!kernfs_get_active(of->kn))
+	if (!kernfs_get_active_of(of))
 		return VM_FAULT_SIGBUS;
 
 	ret = VM_FAULT_SIGBUS;
 	if (of->vm_ops->fault)
 		ret = of->vm_ops->fault(vmf);
 
-	kernfs_put_active(of->kn);
+	kernfs_put_active_of(of);
 	return ret;
 }
 
@@ -357,7 +413,7 @@ static vm_fault_t kernfs_vma_page_mkwrite(struct vm_fault *vmf)
 	if (!of->vm_ops)
 		return VM_FAULT_SIGBUS;
 
-	if (!kernfs_get_active(of->kn))
+	if (!kernfs_get_active_of(of))
 		return VM_FAULT_SIGBUS;
 
 	ret = 0;
@@ -366,7 +422,7 @@ static vm_fault_t kernfs_vma_page_mkwrite(struct vm_fault *vmf)
 	else
 		file_update_time(file);
 
-	kernfs_put_active(of->kn);
+	kernfs_put_active_of(of);
 	return ret;
 }
 
@@ -380,71 +436,22 @@ static int kernfs_vma_access(struct vm_area_struct *vma, unsigned long addr,
 	if (!of->vm_ops)
 		return -EINVAL;
 
-	if (!kernfs_get_active(of->kn))
+	if (!kernfs_get_active_of(of))
 		return -EINVAL;
 
 	ret = -EINVAL;
 	if (of->vm_ops->access)
 		ret = of->vm_ops->access(vma, addr, buf, len, write);
 
-	kernfs_put_active(of->kn);
+	kernfs_put_active_of(of);
 	return ret;
 }
 
-#ifdef CONFIG_NUMA
-static int kernfs_vma_set_policy(struct vm_area_struct *vma,
-				 struct mempolicy *new)
-{
-	struct file *file = vma->vm_file;
-	struct kernfs_open_file *of = kernfs_of(file);
-	int ret;
-
-	if (!of->vm_ops)
-		return 0;
-
-	if (!kernfs_get_active(of->kn))
-		return -EINVAL;
-
-	ret = 0;
-	if (of->vm_ops->set_policy)
-		ret = of->vm_ops->set_policy(vma, new);
-
-	kernfs_put_active(of->kn);
-	return ret;
-}
-
-static struct mempolicy *kernfs_vma_get_policy(struct vm_area_struct *vma,
-					       unsigned long addr)
-{
-	struct file *file = vma->vm_file;
-	struct kernfs_open_file *of = kernfs_of(file);
-	struct mempolicy *pol;
-
-	if (!of->vm_ops)
-		return vma->vm_policy;
-
-	if (!kernfs_get_active(of->kn))
-		return vma->vm_policy;
-
-	pol = vma->vm_policy;
-	if (of->vm_ops->get_policy)
-		pol = of->vm_ops->get_policy(vma, addr);
-
-	kernfs_put_active(of->kn);
-	return pol;
-}
-
-#endif
-
 static const struct vm_operations_struct kernfs_vm_ops = {
 	.open		= kernfs_vma_open,
 	.fault		= kernfs_vma_fault,
 	.page_mkwrite	= kernfs_vma_page_mkwrite,
 	.access		= kernfs_vma_access,
-#ifdef CONFIG_NUMA
-	.set_policy	= kernfs_vma_set_policy,
-	.get_policy	= kernfs_vma_get_policy,
-#endif
 };
 
 static int kernfs_fop_mmap(struct file *file, struct vm_area_struct *vma)
@@ -458,7 +465,7 @@ static int kernfs_fop_mmap(struct file *file, struct vm_area_struct *vma)
 	 * warnings and we don't want to add spurious locking dependency
 	 * between the two.  Check whether mmap is actually implemented
 	 * without grabbing @of->mutex by testing HAS_MMAP flag.  See the
-	 * comment in kernfs_file_open() for more details.
+	 * comment in kernfs_fop_open() for more details.
 	 */
 	if (!(of->kn->flags & KERNFS_HAS_MMAP))
 		return -ENODEV;
@@ -466,7 +473,7 @@ static int kernfs_fop_mmap(struct file *file, struct vm_area_struct *vma)
 	mutex_lock(&of->mutex);
 
 	rc = -ENODEV;
-	if (!kernfs_get_active(of->kn))
+	if (!kernfs_get_active_of(of))
 		goto out_unlock;
 
 	ops = kernfs_ops(of->kn);
@@ -490,16 +497,18 @@ static int kernfs_fop_mmap(struct file *file, struct vm_area_struct *vma)
 	 * It is not possible to successfully wrap close.
 	 * So error if someone is trying to use close.
 	 */
-	rc = -EINVAL;
 	if (vma->vm_ops && vma->vm_ops->close)
 		goto out_put;
 
 	rc = 0;
-	of->mmapped = true;
-	of->vm_ops = vma->vm_ops;
+	if (!of->mmapped) {
+		of->mmapped = true;
+		of_on(of)->nr_mmapped++;
+		of->vm_ops = vma->vm_ops;
+	}
 	vma->vm_ops = &kernfs_vm_ops;
 out_put:
-	kernfs_put_active(of->kn);
+	kernfs_put_active_of(of);
 out_unlock:
 	mutex_unlock(&of->mutex);
 
@@ -514,84 +523,88 @@ out_unlock:
  *	If @kn->attr.open exists, increment its reference count; otherwise,
  *	create one.  @of is chained to the files list.
  *
- *	LOCKING:
+ *	Locking:
  *	Kernel thread context (may sleep).
  *
- *	RETURNS:
- *	0 on success, -errno on failure.
+ *	Return:
+ *	%0 on success, -errno on failure.
  */
 static int kernfs_get_open_node(struct kernfs_node *kn,
 				struct kernfs_open_file *of)
 {
-	struct kernfs_open_node *on, *new_on = NULL;
-
- retry:
-	mutex_lock(&kernfs_open_file_mutex);
-	spin_lock_irq(&kernfs_open_node_lock);
+	struct kernfs_open_node *on;
+	struct mutex *mutex;
 
-	if (!kn->attr.open && new_on) {
-		kn->attr.open = new_on;
-		new_on = NULL;
-	}
+	mutex = kernfs_open_file_mutex_lock(kn);
+	on = kernfs_deref_open_node_locked(kn);
 
-	on = kn->attr.open;
-	if (on) {
-		atomic_inc(&on->refcnt);
-		list_add_tail(&of->list, &on->files);
+	if (!on) {
+		/* not there, initialize a new one */
+		on = kzalloc(sizeof(*on), GFP_KERNEL);
+		if (!on) {
+			mutex_unlock(mutex);
+			return -ENOMEM;
+		}
+		atomic_set(&on->event, 1);
+		init_waitqueue_head(&on->poll);
+		INIT_LIST_HEAD(&on->files);
+		rcu_assign_pointer(kn->attr.open, on);
 	}
 
-	spin_unlock_irq(&kernfs_open_node_lock);
-	mutex_unlock(&kernfs_open_file_mutex);
+	list_add_tail(&of->list, &on->files);
+	if (kn->flags & KERNFS_HAS_RELEASE)
+		on->nr_to_release++;
 
-	if (on) {
-		kfree(new_on);
-		return 0;
-	}
-
-	/* not there, initialize a new one and retry */
-	new_on = kmalloc(sizeof(*new_on), GFP_KERNEL);
-	if (!new_on)
-		return -ENOMEM;
-
-	atomic_set(&new_on->refcnt, 0);
-	atomic_set(&new_on->event, 1);
-	init_waitqueue_head(&new_on->poll);
-	INIT_LIST_HEAD(&new_on->files);
-	goto retry;
+	mutex_unlock(mutex);
+	return 0;
 }
 
 /**
- *	kernfs_put_open_node - put kernfs_open_node
- *	@kn: target kernfs_nodet
+ *	kernfs_unlink_open_file - Unlink @of from @kn.
+ *
+ *	@kn: target kernfs_node
  *	@of: associated kernfs_open_file
+ *	@open_failed: ->open() failed, cancel ->release()
  *
- *	Put @kn->attr.open and unlink @of from the files list.  If
- *	reference count reaches zero, disassociate and free it.
+ *	Unlink @of from list of @kn's associated open files. If list of
+ *	associated open files becomes empty, disassociate and free
+ *	kernfs_open_node.
  *
  *	LOCKING:
  *	None.
  */
-static void kernfs_put_open_node(struct kernfs_node *kn,
-				 struct kernfs_open_file *of)
+static void kernfs_unlink_open_file(struct kernfs_node *kn,
+				    struct kernfs_open_file *of,
+				    bool open_failed)
 {
-	struct kernfs_open_node *on = kn->attr.open;
-	unsigned long flags;
+	struct kernfs_open_node *on;
+	struct mutex *mutex;
 
-	mutex_lock(&kernfs_open_file_mutex);
-	spin_lock_irqsave(&kernfs_open_node_lock, flags);
+	mutex = kernfs_open_file_mutex_lock(kn);
 
-	if (of)
-		list_del(&of->list);
+	on = kernfs_deref_open_node_locked(kn);
+	if (!on) {
+		mutex_unlock(mutex);
+		return;
+	}
 
-	if (atomic_dec_and_test(&on->refcnt))
-		kn->attr.open = NULL;
-	else
-		on = NULL;
+	if (of) {
+		if (kn->flags & KERNFS_HAS_RELEASE) {
+			WARN_ON_ONCE(of->released == open_failed);
+			if (open_failed)
+				on->nr_to_release--;
+		}
+		if (of->mmapped)
+			on->nr_mmapped--;
+		list_del(&of->list);
+	}
 
-	spin_unlock_irqrestore(&kernfs_open_node_lock, flags);
-	mutex_unlock(&kernfs_open_file_mutex);
+	if (list_empty(&on->files)) {
+		rcu_assign_pointer(kn->attr.open, NULL);
+		kfree_rcu(on, rcu_head);
+	}
 
-	kfree(on);
+	mutex_unlock(mutex);
 }
 
 static int kernfs_fop_open(struct inode *inode, struct file *file)
@@ -641,11 +654,18 @@ static int kernfs_fop_open(struct inode *inode, struct file *file)
 	 * each file a separate locking class.  Let's differentiate on
 	 * whether the file has mmap or not for now.
 	 *
-	 * Both paths of the branch look the same.  They're supposed to
+	 * For similar reasons, writable and readonly files are given different
+	 * lockdep key, because the writable file /sys/power/resume may call vfs
+	 * lookup helpers for arbitrary paths and readonly files can be read by
+	 * overlayfs from vfs helpers when sysfs is a lower layer of overalyfs.
+	 *
+	 * All three cases look the same.  They're supposed to
 	 * look that way and give @of->mutex different static lockdep keys.
 	 */
 	if (has_mmap)
 		mutex_init(&of->mutex);
+	else if (file->f_mode & FMODE_WRITE)
+		mutex_init(&of->mutex);
 	else
 		mutex_init(&of->mutex);
 
@@ -711,7 +731,7 @@ static int kernfs_fop_open(struct inode *inode, struct file *file)
 	return 0;
 
 err_put_node:
-	kernfs_put_open_node(kn, of);
+	kernfs_unlink_open_file(kn, of, true);
 err_seq_release:
 	seq_release(inode, file);
 err_free:
@@ -729,11 +749,11 @@ static void kernfs_release_file(struct kernfs_node *kn,
 	/*
 	 * @of is guaranteed to have no other file operations in flight and
 	 * we just want to synchronize release and drain paths.
-	 * @kernfs_open_file_mutex is enough.  @of->mutex can't be used
+	 * @kernfs_open_file_mutex_ptr(kn) is enough. @of->mutex can't be used
 	 * here because drain path may be called from places which can
 	 * cause circular dependency.
 	 */
-	lockdep_assert_held(&kernfs_open_file_mutex);
+	lockdep_assert_held(kernfs_open_file_mutex_ptr(kn));
 
 	if (!of->released) {
 		/*
@@ -743,6 +763,7 @@ static void kernfs_release_file(struct kernfs_node *kn,
 		 */
 		kn->attr.ops->release(of);
 		of->released = true;
+		of_on(of)->nr_to_release--;
 	}
 }
 
@@ -752,12 +773,14 @@ static int kernfs_fop_release(struct inode *inode, struct file *filp)
 	struct kernfs_open_file *of = kernfs_of(filp);
 
 	if (kn->flags & KERNFS_HAS_RELEASE) {
-		mutex_lock(&kernfs_open_file_mutex);
+		struct mutex *mutex;
+
+		mutex = kernfs_open_file_mutex_lock(kn);
 		kernfs_release_file(kn, of);
-		mutex_unlock(&kernfs_open_file_mutex);
+		mutex_unlock(mutex);
 	}
 
-	kernfs_put_open_node(kn, of);
+	kernfs_unlink_open_file(kn, of, false);
 	seq_release(inode, filp);
 	kfree(of->prealloc_buf);
 	kfree(of);
@@ -765,37 +788,54 @@ static int kernfs_fop_release(struct inode *inode, struct file *filp)
 	return 0;
 }
 
+bool kernfs_should_drain_open_files(struct kernfs_node *kn)
+{
+	struct kernfs_open_node *on;
+	bool ret;
+
+	/*
+	 * @kn being deactivated guarantees that @kn->attr.open can't change
+	 * beneath us making the lockless test below safe.
+	 * Callers post kernfs_unbreak_active_protection may be counted in
+	 * kn->active by now, do not WARN_ON because of them.
+	 */
+
+	rcu_read_lock();
+	on = rcu_dereference(kn->attr.open);
+	ret = on && (on->nr_mmapped || on->nr_to_release);
+	rcu_read_unlock();
+
+	return ret;
+}
+
 void kernfs_drain_open_files(struct kernfs_node *kn)
 {
 	struct kernfs_open_node *on;
 	struct kernfs_open_file *of;
+	struct mutex *mutex;
 
-	if (!(kn->flags & (KERNFS_HAS_MMAP | KERNFS_HAS_RELEASE)))
+	mutex = kernfs_open_file_mutex_lock(kn);
+	on = kernfs_deref_open_node_locked(kn);
+	if (!on) {
+		mutex_unlock(mutex);
 		return;
-
-	spin_lock_irq(&kernfs_open_node_lock);
-	on = kn->attr.open;
-	if (on)
-		atomic_inc(&on->refcnt);
-	spin_unlock_irq(&kernfs_open_node_lock);
-	if (!on)
-		return;
-
-	mutex_lock(&kernfs_open_file_mutex);
+	}
 
 	list_for_each_entry(of, &on->files, list) {
 		struct inode *inode = file_inode(of->file);
 
-		if (kn->flags & KERNFS_HAS_MMAP)
+		if (of->mmapped) {
 			unmap_mapping_range(inode->i_mapping, 0, 0, 1);
+			of->mmapped = false;
+			on->nr_mmapped--;
+		}
 
 		if (kn->flags & KERNFS_HAS_RELEASE)
 			kernfs_release_file(kn, of);
 	}
 
-	mutex_unlock(&kernfs_open_file_mutex);
-
-	kernfs_put_open_node(kn, NULL);
+	WARN_ON_ONCE(on->nr_mmapped || on->nr_to_release);
+	mutex_unlock(mutex);
 }
 
 /*
@@ -814,8 +854,7 @@ void kernfs_drain_open_files(struct kernfs_node *kn)
  */
 __poll_t kernfs_generic_poll(struct kernfs_open_file *of, poll_table *wait)
 {
-	struct kernfs_node *kn = kernfs_dentry_node(of->file->f_path.dentry);
-	struct kernfs_open_node *on = kn->attr.open;
+	struct kernfs_open_node *on = of_on(of);
 
 	poll_wait(of->file, &on->poll, wait);
 
@@ -831,7 +870,7 @@ static __poll_t kernfs_fop_poll(struct file *filp, poll_table *wait)
 	struct kernfs_node *kn = kernfs_dentry_node(filp->f_path.dentry);
 	__poll_t ret;
 
-	if (!kernfs_get_active(kn))
+	if (!kernfs_get_active_of(of))
 		return DEFAULT_POLLMASK|EPOLLERR|EPOLLPRI;
 
 	if (kn->attr.ops->poll)
@@ -839,7 +878,34 @@ static __poll_t kernfs_fop_poll(struct file *filp, poll_table *wait)
 	else
 		ret = kernfs_generic_poll(of, wait);
 
-	kernfs_put_active(kn);
+	kernfs_put_active_of(of);
+	return ret;
+}
+
+static loff_t kernfs_fop_llseek(struct file *file, loff_t offset, int whence)
+{
+	struct kernfs_open_file *of = kernfs_of(file);
+	const struct kernfs_ops *ops;
+	loff_t ret;
+
+	/*
+	 * @of->mutex nests outside active ref and is primarily to ensure that
+	 * the ops aren't called concurrently for the same open file.
+	 */
+	mutex_lock(&of->mutex);
+	if (!kernfs_get_active_of(of)) {
+		mutex_unlock(&of->mutex);
+		return -ENODEV;
+	}
+
+	ops = kernfs_ops(of->kn);
+	if (ops->llseek)
+		ret = ops->llseek(of, offset, whence);
+	else
+		ret = generic_file_llseek(file, offset, whence);
+
+	kernfs_put_active_of(of);
+	mutex_unlock(&of->mutex);
 	return ret;
 }
 
@@ -862,11 +928,13 @@ repeat:
 
 	root = kernfs_root(kn);
 	/* kick fsnotify */
-	down_write(&root->kernfs_rwsem);
 
+	down_read(&root->kernfs_supers_rwsem);
+	down_read(&root->kernfs_rwsem);
 	list_for_each_entry(info, &kernfs_root(kn)->supers, node) {
 		struct kernfs_node *parent;
 		struct inode *p_inode = NULL;
+		const char *kn_name;
 		struct inode *inode;
 		struct qstr name;
 
@@ -880,7 +948,8 @@ repeat:
 		if (!inode)
 			continue;
 
-		name = (struct qstr)QSTR_INIT(kn->name, strlen(kn->name));
+		kn_name = kernfs_rcu_name(kn);
+		name = QSTR(kn_name);
 		parent = kernfs_get_parent(kn);
 		if (parent) {
 			p_inode = ilookup(info->sb, kernfs_ino(parent));
@@ -900,7 +969,8 @@ repeat:
 		iput(inode);
 	}
 
-	up_write(&root->kernfs_rwsem);
+	up_read(&root->kernfs_rwsem);
+	up_read(&root->kernfs_supers_rwsem);
 	kernfs_put(kn);
 	goto repeat;
 }
@@ -922,13 +992,13 @@ void kernfs_notify(struct kernfs_node *kn)
 		return;
 
 	/* kick poll immediately */
-	spin_lock_irqsave(&kernfs_open_node_lock, flags);
-	on = kn->attr.open;
+	rcu_read_lock();
+	on = rcu_dereference(kn->attr.open);
 	if (on) {
 		atomic_inc(&on->event);
 		wake_up_interruptible(&on->poll);
 	}
-	spin_unlock_irqrestore(&kernfs_open_node_lock, flags);
+	rcu_read_unlock();
 
 	/* schedule work to kick fsnotify */
 	spin_lock_irqsave(&kernfs_notify_lock, flags);
@@ -945,13 +1015,13 @@ EXPORT_SYMBOL_GPL(kernfs_notify);
 const struct file_operations kernfs_file_fops = {
 	.read_iter	= kernfs_fop_read_iter,
 	.write_iter	= kernfs_fop_write_iter,
-	.llseek		= generic_file_llseek,
+	.llseek		= kernfs_fop_llseek,
 	.mmap		= kernfs_fop_mmap,
 	.open		= kernfs_fop_open,
 	.release	= kernfs_fop_release,
 	.poll		= kernfs_fop_poll,
 	.fsync		= noop_fsync,
-	.splice_read	= generic_file_splice_read,
+	.splice_read	= copy_splice_read,
 	.splice_write	= iter_file_splice_write,
 };
 
@@ -968,7 +1038,7 @@ const struct file_operations kernfs_file_fops = {
  * @ns: optional namespace tag of the file
  * @key: lockdep key for the file's active_ref, %NULL to disable lockdep
  *
- * Returns the created node on success, ERR_PTR() value on error.
+ * Return: the created node on success, ERR_PTR() value on error.
  */
 struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
 					 const char *name,
@@ -1002,7 +1072,7 @@ struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
 #endif
 
 	/*
-	 * kn->attr.ops is accesible only while holding active ref.  We
+	 * kn->attr.ops is accessible only while holding active ref.  We
 	 * need to know whether some ops are implemented outside active
 	 * ref.  Cache their existence in flags.
 	 */