[PATCH] fuse: add control filesystem

Add a control filesystem to fuse, replacing the attributes currently exported
through sysfs.  An empty directory '/sys/fs/fuse/connections' is still created
in sysfs, and mounting the control filesystem here provides backward
compatibility.

Advantages of the control filesystem over the previous solution:

  - allows the object directory and the attributes to be owned by the
    filesystem owner, hence letting unpriviled users abort the
    filesystem connection

  - does not suffer from module unload race

[akpm@osdl.org: fix this fs for recent dhowells depredations]
[akpm@osdl.org: fix 64-bit printk warnings]
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 44 insertions, 97 deletions

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 0225729..13a7e8a 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -22,13 +22,8 @@ MODULE_DESCRIPTION("Filesystem in Userspace");
 MODULE_LICENSE("GPL");
 
 static kmem_cache_t *fuse_inode_cachep;
-static struct subsystem connections_subsys;
-
-struct fuse_conn_attr {
-	struct attribute attr;
-	ssize_t (*show)(struct fuse_conn *, char *);
-	ssize_t (*store)(struct fuse_conn *, const char *, size_t);
-};
+struct list_head fuse_conn_list;
+DEFINE_MUTEX(fuse_mutex);
 
 #define FUSE_SUPER_MAGIC 0x65735546
 
@@ -211,8 +206,11 @@ static void fuse_put_super(struct super_block *sb)
 	kill_fasync(&fc->fasync, SIGIO, POLL_IN);
 	wake_up_all(&fc->waitq);
 	wake_up_all(&fc->blocked_waitq);
-	kobject_del(&fc->kobj);
-	kobject_put(&fc->kobj);
+	mutex_lock(&fuse_mutex);
+	list_del(&fc->entry);
+	fuse_ctl_remove_conn(fc);
+	mutex_unlock(&fuse_mutex);
+	fuse_conn_put(fc);
 }
 
 static void convert_fuse_statfs(struct kstatfs *stbuf, struct fuse_kstatfs *attr)
@@ -362,11 +360,6 @@ static int fuse_show_options(struct seq_file *m, struct vfsmount *mnt)
 	return 0;
 }
 
-static void fuse_conn_release(struct kobject *kobj)
-{
-	kfree(get_fuse_conn_kobj(kobj));
-}
-
 static struct fuse_conn *new_conn(void)
 {
 	struct fuse_conn *fc;
@@ -374,13 +367,12 @@ static struct fuse_conn *new_conn(void)
 	fc = kzalloc(sizeof(*fc), GFP_KERNEL);
 	if (fc) {
 		spin_lock_init(&fc->lock);
+		atomic_set(&fc->count, 1);
 		init_waitqueue_head(&fc->waitq);
 		init_waitqueue_head(&fc->blocked_waitq);
 		INIT_LIST_HEAD(&fc->pending);
 		INIT_LIST_HEAD(&fc->processing);
 		INIT_LIST_HEAD(&fc->io);
-		kobj_set_kset_s(fc, connections_subsys);
-		kobject_init(&fc->kobj);
 		atomic_set(&fc->num_waiting, 0);
 		fc->bdi.ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
 		fc->bdi.unplug_io_fn = default_unplug_io_fn;
@@ -390,6 +382,18 @@ static struct fuse_conn *new_conn(void)
 	return fc;
 }
 
+void fuse_conn_put(struct fuse_conn *fc)
+{
+	if (atomic_dec_and_test(&fc->count))
+		kfree(fc);
+}
+
+struct fuse_conn *fuse_conn_get(struct fuse_conn *fc)
+{
+	atomic_inc(&fc->count);
+	return fc;
+}
+
 static struct inode *get_root_inode(struct super_block *sb, unsigned mode)
 {
 	struct fuse_attr attr;
@@ -459,10 +463,9 @@ static void fuse_send_init(struct fuse_conn *fc, struct fuse_req *req)
 	request_send_background(fc, req);
 }
 
-static unsigned long long conn_id(void)
+static u64 conn_id(void)
 {
-	/* BKL is held for ->get_sb() */
-	static unsigned long long ctr = 1;
+	static u64 ctr = 1;
 	return ctr++;
 }
 
@@ -519,24 +522,21 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
 	if (!init_req)
 		goto err_put_root;
 
-	err = kobject_set_name(&fc->kobj, "%llu", conn_id());
-	if (err)
-		goto err_free_req;
-
-	err = kobject_add(&fc->kobj);
-	if (err)
-		goto err_free_req;
-
-	/* Setting file->private_data can't race with other mount()
-	   instances, since BKL is held for ->get_sb() */
+	mutex_lock(&fuse_mutex);
 	err = -EINVAL;
 	if (file->private_data)
-		goto err_kobject_del;
+		goto err_unlock;
 
+	fc->id = conn_id();
+	err = fuse_ctl_add_conn(fc);
+	if (err)
+		goto err_unlock;
+
+	list_add_tail(&fc->entry, &fuse_conn_list);
 	sb->s_root = root_dentry;
 	fc->connected = 1;
-	kobject_get(&fc->kobj);
-	file->private_data = fc;
+	file->private_data = fuse_conn_get(fc);
+	mutex_unlock(&fuse_mutex);
 	/*
 	 * atomic_dec_and_test() in fput() provides the necessary
 	 * memory barrier for file->private_data to be visible on all
@@ -548,15 +548,14 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
 
 	return 0;
 
- err_kobject_del:
-	kobject_del(&fc->kobj);
- err_free_req:
+ err_unlock:
+	mutex_unlock(&fuse_mutex);
 	fuse_request_free(init_req);
  err_put_root:
 	dput(root_dentry);
  err:
 	fput(file);
-	kobject_put(&fc->kobj);
+	fuse_conn_put(fc);
 	return err;
 }
 
@@ -574,68 +573,8 @@ static struct file_system_type fuse_fs_type = {
 	.kill_sb	= kill_anon_super,
 };
 
-static ssize_t fuse_conn_waiting_show(struct fuse_conn *fc, char *page)
-{
-	return sprintf(page, "%i\n", atomic_read(&fc->num_waiting));
-}
-
-static ssize_t fuse_conn_abort_store(struct fuse_conn *fc, const char *page,
-				     size_t count)
-{
-	fuse_abort_conn(fc);
-	return count;
-}
-
-static struct fuse_conn_attr fuse_conn_waiting =
-	__ATTR(waiting, 0400, fuse_conn_waiting_show, NULL);
-static struct fuse_conn_attr fuse_conn_abort =
-	__ATTR(abort, 0600, NULL, fuse_conn_abort_store);
-
-static struct attribute *fuse_conn_attrs[] = {
-	&fuse_conn_waiting.attr,
-	&fuse_conn_abort.attr,
-	NULL,
-};
-
-static ssize_t fuse_conn_attr_show(struct kobject *kobj,
-				   struct attribute *attr,
-				   char *page)
-{
-	struct fuse_conn_attr *fca =
-		container_of(attr, struct fuse_conn_attr, attr);
-
-	if (fca->show)
-		return fca->show(get_fuse_conn_kobj(kobj), page);
-	else
-		return -EACCES;
-}
-
-static ssize_t fuse_conn_attr_store(struct kobject *kobj,
-				    struct attribute *attr,
-				    const char *page, size_t count)
-{
-	struct fuse_conn_attr *fca =
-		container_of(attr, struct fuse_conn_attr, attr);
-
-	if (fca->store)
-		return fca->store(get_fuse_conn_kobj(kobj), page, count);
-	else
-		return -EACCES;
-}
-
-static struct sysfs_ops fuse_conn_sysfs_ops = {
-	.show	= &fuse_conn_attr_show,
-	.store	= &fuse_conn_attr_store,
-};
-
-static struct kobj_type ktype_fuse_conn = {
-	.release	= fuse_conn_release,
-	.sysfs_ops	= &fuse_conn_sysfs_ops,
-	.default_attrs	= fuse_conn_attrs,
-};
-
 static decl_subsys(fuse, NULL, NULL);
-static decl_subsys(connections, &ktype_fuse_conn, NULL);
+static decl_subsys(connections, NULL, NULL);
 
 static void fuse_inode_init_once(void *foo, kmem_cache_t *cachep,
 				 unsigned long flags)
@@ -709,6 +648,7 @@ static int __init fuse_init(void)
 	printk("fuse init (API version %i.%i)\n",
 	       FUSE_KERNEL_VERSION, FUSE_KERNEL_MINOR_VERSION);
 
+	INIT_LIST_HEAD(&fuse_conn_list);
 	res = fuse_fs_init();
 	if (res)
 		goto err;
@@ -721,8 +661,14 @@ static int __init fuse_init(void)
 	if (res)
 		goto err_dev_cleanup;
 
+	res = fuse_ctl_init();
+	if (res)
+		goto err_sysfs_cleanup;
+
 	return 0;
 
+ err_sysfs_cleanup:
+	fuse_sysfs_cleanup();
  err_dev_cleanup:
 	fuse_dev_cleanup();
  err_fs_cleanup:
@@ -735,6 +681,7 @@ static void __exit fuse_exit(void)
 {
 	printk(KERN_DEBUG "fuse exit\n");
 
+	fuse_ctl_cleanup();
 	fuse_sysfs_cleanup();
 	fuse_fs_cleanup();
 	fuse_dev_cleanup();