3 files changed, 73 insertions, 16 deletions

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index cf4c636ff4da..db5900aaa55a 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -41,6 +41,9 @@ static bool kernfs_lockdep(struct kernfs_node *kn)
 
 static int kernfs_name_locked(struct kernfs_node *kn, char *buf, size_t buflen)
 {
+	if (!kn)
+		return strlcpy(buf, "(null)", buflen);
+
 	return strlcpy(buf, kn->parent ? kn->name : "/", buflen);
 }
 
@@ -110,6 +113,8 @@ static struct kernfs_node *kernfs_common_ancestor(struct kernfs_node *a,
  * kn_to:   /n1/n2/n3         [depth=3]
  * result:  /../..
  *
+ * [3] when @kn_to is NULL result will be "(null)"
+ *
  * Returns the length of the full path.  If the full length is equal to or
  * greater than @buflen, @buf contains the truncated path with the trailing
  * '\0'.  On error, -errno is returned.
@@ -123,6 +128,9 @@ static int kernfs_path_from_node_locked(struct kernfs_node *kn_to,
 	size_t depth_from, depth_to, len = 0;
 	int i, j;
 
+	if (!kn_to)
+		return strlcpy(buf, "(null)", buflen);
+
 	if (!kn_from)
 		kn_from = kernfs_root(kn_to)->kn;
 
@@ -166,6 +174,8 @@ static int kernfs_path_from_node_locked(struct kernfs_node *kn_to,
  * similar to strlcpy().  It returns the length of @kn's name and if @buf
  * isn't long enough, it's filled upto @buflen-1 and nul terminated.
  *
+ * Fills buffer with "(null)" if @kn is NULL.
+ *
  * This function can be called from any context.
  */
 int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen)
@@ -468,7 +478,7 @@ static void kernfs_drain(struct kernfs_node *kn)
 		rwsem_release(&kn->dep_map, 1, _RET_IP_);
 	}
 
-	kernfs_unmap_bin_file(kn);
+	kernfs_drain_open_files(kn);
 
 	mutex_lock(&kernfs_mutex);
 }
diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index 78219d5644e9..35043a8c4529 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -348,9 +348,9 @@ static void kernfs_vma_open(struct vm_area_struct *vma)
 	kernfs_put_active(of->kn);
 }
 
-static int kernfs_vma_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
+static int kernfs_vma_fault(struct vm_fault *vmf)
 {
-	struct file *file = vma->vm_file;
+	struct file *file = vmf->vma->vm_file;
 	struct kernfs_open_file *of = kernfs_of(file);
 	int ret;
 
@@ -362,16 +362,15 @@ static int kernfs_vma_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 
 	ret = VM_FAULT_SIGBUS;
 	if (of->vm_ops->fault)
-		ret = of->vm_ops->fault(vma, vmf);
+		ret = of->vm_ops->fault(vmf);
 
 	kernfs_put_active(of->kn);
 	return ret;
 }
 
-static int kernfs_vma_page_mkwrite(struct vm_area_struct *vma,
-				   struct vm_fault *vmf)
+static int kernfs_vma_page_mkwrite(struct vm_fault *vmf)
 {
-	struct file *file = vma->vm_file;
+	struct file *file = vmf->vma->vm_file;
 	struct kernfs_open_file *of = kernfs_of(file);
 	int ret;
 
@@ -383,7 +382,7 @@ static int kernfs_vma_page_mkwrite(struct vm_area_struct *vma,
 
 	ret = 0;
 	if (of->vm_ops->page_mkwrite)
-		ret = of->vm_ops->page_mkwrite(vma, vmf);
+		ret = of->vm_ops->page_mkwrite(vmf);
 	else
 		file_update_time(file);
 
@@ -516,7 +515,7 @@ static int kernfs_fop_mmap(struct file *file, struct vm_area_struct *vma)
 		goto out_put;
 
 	rc = 0;
-	of->mmapped = 1;
+	of->mmapped = true;
 	of->vm_ops = vma->vm_ops;
 	vma->vm_ops = &kernfs_vm_ops;
 out_put:
@@ -708,7 +707,8 @@ static int kernfs_fop_open(struct inode *inode, struct file *file)
 	if (error)
 		goto err_free;
 
-	((struct seq_file *)file->private_data)->private = of;
+	of->seq_file = file->private_data;
+	of->seq_file->private = of;
 
 	/* seq_file clears PWRITE unconditionally, restore it if WRITE */
 	if (file->f_mode & FMODE_WRITE)
@@ -717,13 +717,22 @@ static int kernfs_fop_open(struct inode *inode, struct file *file)
 	/* make sure we have open node struct */
 	error = kernfs_get_open_node(kn, of);
 	if (error)
-		goto err_close;
+		goto err_seq_release;
+
+	if (ops->open) {
+		/* nobody has access to @of yet, skip @of->mutex */
+		error = ops->open(of);
+		if (error)
+			goto err_put_node;
+	}
 
 	/* open succeeded, put active references */
 	kernfs_put_active(kn);
 	return 0;
 
-err_close:
+err_put_node:
+	kernfs_put_open_node(kn, of);
+err_seq_release:
 	seq_release(inode, file);
 err_free:
 	kfree(of->prealloc_buf);
@@ -733,11 +742,41 @@ err_out:
 	return error;
 }
 
+/* used from release/drain to ensure that ->release() is called exactly once */
+static void kernfs_release_file(struct kernfs_node *kn,
+				struct kernfs_open_file *of)
+{
+	/*
+	 * @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
+	 * here because drain path may be called from places which can
+	 * cause circular dependency.
+	 */
+	lockdep_assert_held(&kernfs_open_file_mutex);
+
+	if (!of->released) {
+		/*
+		 * A file is never detached without being released and we
+		 * need to be able to release files which are deactivated
+		 * and being drained.  Don't use kernfs_ops().
+		 */
+		kn->attr.ops->release(of);
+		of->released = true;
+	}
+}
+
 static int kernfs_fop_release(struct inode *inode, struct file *filp)
 {
 	struct kernfs_node *kn = filp->f_path.dentry->d_fsdata;
 	struct kernfs_open_file *of = kernfs_of(filp);
 
+	if (kn->flags & KERNFS_HAS_RELEASE) {
+		mutex_lock(&kernfs_open_file_mutex);
+		kernfs_release_file(kn, of);
+		mutex_unlock(&kernfs_open_file_mutex);
+	}
+
 	kernfs_put_open_node(kn, of);
 	seq_release(inode, filp);
 	kfree(of->prealloc_buf);
@@ -746,12 +785,12 @@ static int kernfs_fop_release(struct inode *inode, struct file *filp)
 	return 0;
 }
 
-void kernfs_unmap_bin_file(struct kernfs_node *kn)
+void kernfs_drain_open_files(struct kernfs_node *kn)
 {
 	struct kernfs_open_node *on;
 	struct kernfs_open_file *of;
 
-	if (!(kn->flags & KERNFS_HAS_MMAP))
+	if (!(kn->flags & (KERNFS_HAS_MMAP | KERNFS_HAS_RELEASE)))
 		return;
 
 	spin_lock_irq(&kernfs_open_node_lock);
@@ -763,10 +802,16 @@ void kernfs_unmap_bin_file(struct kernfs_node *kn)
 		return;
 
 	mutex_lock(&kernfs_open_file_mutex);
+
 	list_for_each_entry(of, &on->files, list) {
 		struct inode *inode = file_inode(of->file);
-		unmap_mapping_range(inode->i_mapping, 0, 0, 1);
+
+		if (kn->flags & KERNFS_HAS_MMAP)
+			unmap_mapping_range(inode->i_mapping, 0, 0, 1);
+
+		kernfs_release_file(kn, of);
 	}
+
 	mutex_unlock(&kernfs_open_file_mutex);
 
 	kernfs_put_open_node(kn, NULL);
@@ -965,6 +1010,8 @@ struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
 		kn->flags |= KERNFS_HAS_SEQ_SHOW;
 	if (ops->mmap)
 		kn->flags |= KERNFS_HAS_MMAP;
+	if (ops->release)
+		kn->flags |= KERNFS_HAS_RELEASE;
 
 	rc = kernfs_add_one(kn);
 	if (rc) {
diff --git a/fs/kernfs/kernfs-internal.h b/fs/kernfs/kernfs-internal.h
index bfd551bbf231..3100987cf8ba 100644
--- a/fs/kernfs/kernfs-internal.h
+++ b/fs/kernfs/kernfs-internal.h
@@ -104,7 +104,7 @@ struct kernfs_node *kernfs_new_node(struct kernfs_node *parent,
  */
 extern const struct file_operations kernfs_file_fops;
 
-void kernfs_unmap_bin_file(struct kernfs_node *kn);
+void kernfs_drain_open_files(struct kernfs_node *kn);
 
 /*
  * symlink.c