configfs fixes for 5.3

- fix removal vs attribute read/write races (Al Viro)
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Merge tag 'configfs-for-5.3' of git://git.infradead.org/users/hch/configfs

Pull configfs fixes from Christoph Hellwig:
 "Late configfs fixes from Al that fix pretty nasty removal vs attribute
  access races"

* tag 'configfs-for-5.3' of git://git.infradead.org/users/hch/configfs:
  configfs: provide exclusion between IO and removals
  configfs: new object reprsenting tree fragments
  configfs_register_group() shouldn't be (and isn't) called in rmdirable parts
  configfs: stash the data we need into configfs_buffer at open time

fs/configfs/configfs_internal.h

@@ -20,6 +20,15 @@
 #include <linux/list.h>
 #include <linux/spinlock.h>
 
+struct configfs_fragment {
+	atomic_t frag_count;
+	struct rw_semaphore frag_sem;
+	bool frag_dead;
+};
+
+void put_fragment(struct configfs_fragment *);
+struct configfs_fragment *get_fragment(struct configfs_fragment *);
+
 struct configfs_dirent {
 	atomic_t		s_count;
 	int			s_dependent_count;
@@ -34,6 +43,7 @@ struct configfs_dirent {
 #ifdef CONFIG_LOCKDEP
 	int			s_depth;
 #endif
+	struct configfs_fragment *s_frag;
 };
 
 #define CONFIGFS_ROOT		0x0001
@@ -61,8 +71,8 @@ extern int configfs_create(struct dentry *, umode_t mode, void (*init)(struct in
 extern int configfs_create_file(struct config_item *, const struct configfs_attribute *);
 extern int configfs_create_bin_file(struct config_item *,
 				    const struct configfs_bin_attribute *);
-extern int configfs_make_dirent(struct configfs_dirent *,
-				struct dentry *, void *, umode_t, int);
+extern int configfs_make_dirent(struct configfs_dirent *, struct dentry *,
+				void *, umode_t, int, struct configfs_fragment *);
 extern int configfs_dirent_is_ready(struct configfs_dirent *);
 
 extern void configfs_hash_and_remove(struct dentry * dir, const char * name);
@@ -137,6 +147,7 @@ static inline void release_configfs_dirent(struct configfs_dirent * sd)
 {
 	if (!(sd->s_type & CONFIGFS_ROOT)) {
 		kfree(sd->s_iattr);
+		put_fragment(sd->s_frag);
 		kmem_cache_free(configfs_dir_cachep, sd);
 	}
 }

fs/configfs/dir.c

@@ -151,11 +151,38 @@ configfs_adjust_dir_dirent_depth_after_populate(struct configfs_dirent *sd)
 
 #endif /* CONFIG_LOCKDEP */
 
+static struct configfs_fragment *new_fragment(void)
+{
+	struct configfs_fragment *p;
+
+	p = kmalloc(sizeof(struct configfs_fragment), GFP_KERNEL);
+	if (p) {
+		atomic_set(&p->frag_count, 1);
+		init_rwsem(&p->frag_sem);
+		p->frag_dead = false;
+	}
+	return p;
+}
+
+void put_fragment(struct configfs_fragment *frag)
+{
+	if (frag && atomic_dec_and_test(&frag->frag_count))
+		kfree(frag);
+}
+
+struct configfs_fragment *get_fragment(struct configfs_fragment *frag)
+{
+	if (likely(frag))
+		atomic_inc(&frag->frag_count);
+	return frag;
+}
+
 /*
  * Allocates a new configfs_dirent and links it to the parent configfs_dirent
  */
 static struct configfs_dirent *configfs_new_dirent(struct configfs_dirent *parent_sd,
-						   void *element, int type)
+						   void *element, int type,
+						   struct configfs_fragment *frag)
 {
 	struct configfs_dirent * sd;
 
@@ -175,6 +202,7 @@ static struct configfs_dirent *configfs_new_dirent(struct configfs_dirent *paren
 		kmem_cache_free(configfs_dir_cachep, sd);
 		return ERR_PTR(-ENOENT);
 	}
+	sd->s_frag = get_fragment(frag);
 	list_add(&sd->s_sibling, &parent_sd->s_children);
 	spin_unlock(&configfs_dirent_lock);
 
@@ -209,11 +237,11 @@ static int configfs_dirent_exists(struct configfs_dirent *parent_sd,
 
 int configfs_make_dirent(struct configfs_dirent * parent_sd,
 			 struct dentry * dentry, void * element,
-			 umode_t mode, int type)
+			 umode_t mode, int type, struct configfs_fragment *frag)
 {
 	struct configfs_dirent * sd;
 
-	sd = configfs_new_dirent(parent_sd, element, type);
+	sd = configfs_new_dirent(parent_sd, element, type, frag);
 	if (IS_ERR(sd))
 		return PTR_ERR(sd);
 
@@ -260,7 +288,8 @@ static void init_symlink(struct inode * inode)
  *	until it is validated by configfs_dir_set_ready()
  */
 
-static int configfs_create_dir(struct config_item *item, struct dentry *dentry)
+static int configfs_create_dir(struct config_item *item, struct dentry *dentry,
+				struct configfs_fragment *frag)
 {
 	int error;
 	umode_t mode = S_IFDIR| S_IRWXU | S_IRUGO | S_IXUGO;
@@ -273,7 +302,8 @@ static int configfs_create_dir(struct config_item *item, struct dentry *dentry)
 		return error;
 
 	error = configfs_make_dirent(p->d_fsdata, dentry, item, mode,
-				     CONFIGFS_DIR | CONFIGFS_USET_CREATING);
+				     CONFIGFS_DIR | CONFIGFS_USET_CREATING,
+				     frag);
 	if (unlikely(error))
 		return error;
 
@@ -338,9 +368,10 @@ int configfs_create_link(struct configfs_symlink *sl,
 {
 	int err = 0;
 	umode_t mode = S_IFLNK | S_IRWXUGO;
+	struct configfs_dirent *p = parent->d_fsdata;
 
-	err = configfs_make_dirent(parent->d_fsdata, dentry, sl, mode,
-				   CONFIGFS_ITEM_LINK);
+	err = configfs_make_dirent(p, dentry, sl, mode,
+				   CONFIGFS_ITEM_LINK, p->s_frag);
 	if (!err) {
 		err = configfs_create(dentry, mode, init_symlink);
 		if (err) {
@@ -599,7 +630,8 @@ static int populate_attrs(struct config_item *item)
 
 static int configfs_attach_group(struct config_item *parent_item,
 				 struct config_item *item,
-				 struct dentry *dentry);
+				 struct dentry *dentry,
+				 struct configfs_fragment *frag);
 static void configfs_detach_group(struct config_item *item);
 
 static void detach_groups(struct config_group *group)
@@ -647,7 +679,8 @@ static void detach_groups(struct config_group *group)
  * try using vfs_mkdir.  Just a thought.
  */
 static int create_default_group(struct config_group *parent_group,
-				struct config_group *group)
+				struct config_group *group,
+				struct configfs_fragment *frag)
 {
 	int ret;
 	struct configfs_dirent *sd;
@@ -663,7 +696,7 @@ static int create_default_group(struct config_group *parent_group,
 		d_add(child, NULL);
 
 		ret = configfs_attach_group(&parent_group->cg_item,
-					    &group->cg_item, child);
+					    &group->cg_item, child, frag);
 		if (!ret) {
 			sd = child->d_fsdata;
 			sd->s_type |= CONFIGFS_USET_DEFAULT;
@@ -677,13 +710,14 @@ static int create_default_group(struct config_group *parent_group,
 	return ret;
 }
 
-static int populate_groups(struct config_group *group)
+static int populate_groups(struct config_group *group,
+			   struct configfs_fragment *frag)
 {
 	struct config_group *new_group;
 	int ret = 0;
 
 	list_for_each_entry(new_group, &group->default_groups, group_entry) {
-		ret = create_default_group(group, new_group);
+		ret = create_default_group(group, new_group, frag);
 		if (ret) {
 			detach_groups(group);
 			break;
@@ -797,11 +831,12 @@ static void link_group(struct config_group *parent_group, struct config_group *g
  */
 static int configfs_attach_item(struct config_item *parent_item,
 				struct config_item *item,
-				struct dentry *dentry)
+				struct dentry *dentry,
+				struct configfs_fragment *frag)
 {
 	int ret;
 
-	ret = configfs_create_dir(item, dentry);
+	ret = configfs_create_dir(item, dentry, frag);
 	if (!ret) {
 		ret = populate_attrs(item);
 		if (ret) {
@@ -831,12 +866,13 @@ static void configfs_detach_item(struct config_item *item)
 
 static int configfs_attach_group(struct config_item *parent_item,
 				 struct config_item *item,
-				 struct dentry *dentry)
+				 struct dentry *dentry,
+				 struct configfs_fragment *frag)
 {
 	int ret;
 	struct configfs_dirent *sd;
 
-	ret = configfs_attach_item(parent_item, item, dentry);
+	ret = configfs_attach_item(parent_item, item, dentry, frag);
 	if (!ret) {
 		sd = dentry->d_fsdata;
 		sd->s_type |= CONFIGFS_USET_DIR;
@@ -852,7 +888,7 @@ static int configfs_attach_group(struct config_item *parent_item,
 		 */
 		inode_lock_nested(d_inode(dentry), I_MUTEX_CHILD);
 		configfs_adjust_dir_dirent_depth_before_populate(sd);
-		ret = populate_groups(to_config_group(item));
+		ret = populate_groups(to_config_group(item), frag);
 		if (ret) {
 			configfs_detach_item(item);
 			d_inode(dentry)->i_flags |= S_DEAD;
@@ -1247,6 +1283,7 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode
 	struct configfs_dirent *sd;
 	const struct config_item_type *type;
 	struct module *subsys_owner = NULL, *new_item_owner = NULL;
+	struct configfs_fragment *frag;
 	char *name;
 
 	sd = dentry->d_parent->d_fsdata;
@@ -1265,6 +1302,12 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode
 		goto out;
 	}
 
+	frag = new_fragment();
+	if (!frag) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
 	/* Get a working ref for the duration of this function */
 	parent_item = configfs_get_config_item(dentry->d_parent);
 	type = parent_item->ci_type;
@@ -1367,9 +1410,9 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode
 	spin_unlock(&configfs_dirent_lock);
 
 	if (group)
-		ret = configfs_attach_group(parent_item, item, dentry);
+		ret = configfs_attach_group(parent_item, item, dentry, frag);
 	else
-		ret = configfs_attach_item(parent_item, item, dentry);
+		ret = configfs_attach_item(parent_item, item, dentry, frag);
 
 	spin_lock(&configfs_dirent_lock);
 	sd->s_type &= ~CONFIGFS_USET_IN_MKDIR;
@@ -1406,6 +1449,7 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode
 	 * reference.
 	 */
 	config_item_put(parent_item);
+	put_fragment(frag);
 
 out:
 	return ret;
@@ -1417,6 +1461,7 @@ static int configfs_rmdir(struct inode *dir, struct dentry *dentry)
 	struct config_item *item;
 	struct configfs_subsystem *subsys;
 	struct configfs_dirent *sd;
+	struct configfs_fragment *frag;
 	struct module *subsys_owner = NULL, *dead_item_owner = NULL;
 	int ret;
 
@@ -1474,6 +1519,16 @@ static int configfs_rmdir(struct inode *dir, struct dentry *dentry)
 		}
 	} while (ret == -EAGAIN);
 
+	frag = sd->s_frag;
+	if (down_write_killable(&frag->frag_sem)) {
+		spin_lock(&configfs_dirent_lock);
+		configfs_detach_rollback(dentry);
+		spin_unlock(&configfs_dirent_lock);
+		return -EINTR;
+	}
+	frag->frag_dead = true;
+	up_write(&frag->frag_sem);
+
 	/* Get a working ref for the duration of this function */
 	item = configfs_get_config_item(dentry);
 
@@ -1574,7 +1629,7 @@ static int configfs_dir_open(struct inode *inode, struct file *file)
 	 */
 	err = -ENOENT;
 	if (configfs_dirent_is_ready(parent_sd)) {
-		file->private_data = configfs_new_dirent(parent_sd, NULL, 0);
+		file->private_data = configfs_new_dirent(parent_sd, NULL, 0, NULL);
 		if (IS_ERR(file->private_data))
 			err = PTR_ERR(file->private_data);
 		else
@@ -1732,8 +1787,13 @@ int configfs_register_group(struct config_group *parent_group,
 {
 	struct configfs_subsystem *subsys = parent_group->cg_subsys;
 	struct dentry *parent;
+	struct configfs_fragment *frag;
 	int ret;
 
+	frag = new_fragment();
+	if (!frag)
+		return -ENOMEM;
+
 	mutex_lock(&subsys->su_mutex);
 	link_group(parent_group, group);
 	mutex_unlock(&subsys->su_mutex);
@@ -1741,7 +1801,7 @@ int configfs_register_group(struct config_group *parent_group,
 	parent = parent_group->cg_item.ci_dentry;
 
 	inode_lock_nested(d_inode(parent), I_MUTEX_PARENT);
-	ret = create_default_group(parent_group, group);
+	ret = create_default_group(parent_group, group, frag);
 	if (ret)
 		goto err_out;
 
@@ -1749,12 +1809,14 @@ int configfs_register_group(struct config_group *parent_group,
 	configfs_dir_set_ready(group->cg_item.ci_dentry->d_fsdata);
 	spin_unlock(&configfs_dirent_lock);
 	inode_unlock(d_inode(parent));
+	put_fragment(frag);
 	return 0;
 err_out:
 	inode_unlock(d_inode(parent));
 	mutex_lock(&subsys->su_mutex);
 	unlink_group(group);
 	mutex_unlock(&subsys->su_mutex);
+	put_fragment(frag);
 	return ret;
 }
 EXPORT_SYMBOL(configfs_register_group);
@@ -1770,16 +1832,12 @@ void configfs_unregister_group(struct config_group *group)
 	struct configfs_subsystem *subsys = group->cg_subsys;
 	struct dentry *dentry = group->cg_item.ci_dentry;
 	struct dentry *parent = group->cg_item.ci_parent->ci_dentry;
+	struct configfs_dirent *sd = dentry->d_fsdata;
+	struct configfs_fragment *frag = sd->s_frag;
 
-	mutex_lock(&subsys->su_mutex);
-	if (!group->cg_item.ci_parent->ci_group) {
-		/*
-		 * The parent has already been unlinked and detached
-		 * due to a rmdir.
-		 */
-		goto unlink_group;
-	}
-	mutex_unlock(&subsys->su_mutex);
+	down_write(&frag->frag_sem);
+	frag->frag_dead = true;
+	up_write(&frag->frag_sem);
 
 	inode_lock_nested(d_inode(parent), I_MUTEX_PARENT);
 	spin_lock(&configfs_dirent_lock);
@@ -1796,7 +1854,6 @@ void configfs_unregister_group(struct config_group *group)
 	dput(dentry);
 
 	mutex_lock(&subsys->su_mutex);
-unlink_group:
 	unlink_group(group);
 	mutex_unlock(&subsys->su_mutex);
 }
@@ -1853,10 +1910,17 @@ int configfs_register_subsystem(struct configfs_subsystem *subsys)
 	struct dentry *dentry;
 	struct dentry *root;
 	struct configfs_dirent *sd;
+	struct configfs_fragment *frag;
+
+	frag = new_fragment();
+	if (!frag)
+		return -ENOMEM;
 
 	root = configfs_pin_fs();
-	if (IS_ERR(root))
+	if (IS_ERR(root)) {
+		put_fragment(frag);
 		return PTR_ERR(root);
+	}
 
 	if (!group->cg_item.ci_name)
 		group->cg_item.ci_name = group->cg_item.ci_namebuf;
@@ -1872,7 +1936,7 @@ int configfs_register_subsystem(struct configfs_subsystem *subsys)
 		d_add(dentry, NULL);
 
 		err = configfs_attach_group(sd->s_element, &group->cg_item,
-					    dentry);
+					    dentry, frag);
 		if (err) {
 			BUG_ON(d_inode(dentry));
 			d_drop(dentry);
@@ -1890,6 +1954,7 @@ int configfs_register_subsystem(struct configfs_subsystem *subsys)
 		unlink_group(group);
 		configfs_release_fs();
 	}
+	put_fragment(frag);
 
 	return err;
 }
@@ -1899,12 +1964,18 @@ void configfs_unregister_subsystem(struct configfs_subsystem *subsys)
 	struct config_group *group = &subsys->su_group;
 	struct dentry *dentry = group->cg_item.ci_dentry;
 	struct dentry *root = dentry->d_sb->s_root;
+	struct configfs_dirent *sd = dentry->d_fsdata;
+	struct configfs_fragment *frag = sd->s_frag;
 
 	if (dentry->d_parent != root) {
 		pr_err("Tried to unregister non-subsystem!\n");
 		return;
 	}
 
+	down_write(&frag->frag_sem);
+	frag->frag_dead = true;
+	up_write(&frag->frag_sem);
+
 	inode_lock_nested(d_inode(root),
 			  I_MUTEX_PARENT);
 	inode_lock_nested(d_inode(dentry), I_MUTEX_CHILD);

fs/configfs/file.c

@@ -39,40 +39,44 @@ struct configfs_buffer {
 	bool			write_in_progress;
 	char			*bin_buffer;
 	int			bin_buffer_size;
+	int			cb_max_size;
+	struct config_item	*item;
+	struct module		*owner;
+	union {
+		struct configfs_attribute	*attr;
+		struct configfs_bin_attribute	*bin_attr;
+	};
 };
 
-
-/**
- *	fill_read_buffer - allocate and fill buffer from item.
- *	@dentry:	dentry pointer.
- *	@buffer:	data buffer for file.
- *
- *	Allocate @buffer->page, if it hasn't been already, then call the
- *	config_item's show() method to fill the buffer with this attribute's
- *	data.
- *	This is called only once, on the file's first read.
- */
-static int fill_read_buffer(struct dentry * dentry, struct configfs_buffer * buffer)
+static inline struct configfs_fragment *to_frag(struct file *file)
 {
-	struct configfs_attribute * attr = to_attr(dentry);
-	struct config_item * item = to_item(dentry->d_parent);
-	int ret = 0;
-	ssize_t count;
+	struct configfs_dirent *sd = file->f_path.dentry->d_fsdata;
+
+	return sd->s_frag;
+}
+
+static int fill_read_buffer(struct file *file, struct configfs_buffer *buffer)
+{
+	struct configfs_fragment *frag = to_frag(file);
+	ssize_t count = -ENOENT;
 
 	if (!buffer->page)
 		buffer->page = (char *) get_zeroed_page(GFP_KERNEL);
 	if (!buffer->page)
 		return -ENOMEM;
 
-	count = attr->show(item, buffer->page);
+	down_read(&frag->frag_sem);
+	if (!frag->frag_dead)
+		count = buffer->attr->show(buffer->item, buffer->page);
+	up_read(&frag->frag_sem);
 
-	BUG_ON(count > (ssize_t)SIMPLE_ATTR_SIZE);
-	if (count >= 0) {
-		buffer->needs_read_fill = 0;
-		buffer->count = count;
-	} else
-		ret = count;
-	return ret;
+	if (count < 0)
+		return count;
+	if (WARN_ON_ONCE(count > (ssize_t)SIMPLE_ATTR_SIZE))
+		return -EIO;
+	buffer->needs_read_fill = 0;
+	buffer->count = count;
+	return 0;
 }
 
 /**
@@ -97,12 +101,13 @@ static int fill_read_buffer(struct dentry * dentry, struct configfs_buffer * buf
 static ssize_t
 configfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 {
-	struct configfs_buffer * buffer = file->private_data;
+	struct configfs_buffer *buffer = file->private_data;
 	ssize_t retval = 0;
 
 	mutex_lock(&buffer->mutex);
 	if (buffer->needs_read_fill) {
-		if ((retval = fill_read_buffer(file->f_path.dentry,buffer)))
+		retval = fill_read_buffer(file, buffer);
+		if (retval)
 			goto out;
 	}
 	pr_debug("%s: count = %zd, ppos = %lld, buf = %s\n",
@@ -138,10 +143,8 @@ static ssize_t
 configfs_read_bin_file(struct file *file, char __user *buf,
 		       size_t count, loff_t *ppos)
 {
+	struct configfs_fragment *frag = to_frag(file);
 	struct configfs_buffer *buffer = file->private_data;
-	struct dentry *dentry = file->f_path.dentry;
-	struct config_item *item = to_item(dentry->d_parent);
-	struct configfs_bin_attribute *bin_attr = to_bin_attr(dentry);
 	ssize_t retval = 0;
 	ssize_t len = min_t(size_t, count, PAGE_SIZE);
 
@@ -156,14 +159,19 @@ configfs_read_bin_file(struct file *file, char __user *buf,
 
 	if (buffer->needs_read_fill) {
 		/* perform first read with buf == NULL to get extent */
-		len = bin_attr->read(item, NULL, 0);
+		down_read(&frag->frag_sem);
+		if (!frag->frag_dead)
+			len = buffer->bin_attr->read(buffer->item, NULL, 0);
+		else
+			len = -ENOENT;
+		up_read(&frag->frag_sem);
 		if (len <= 0) {
 			retval = len;
 			goto out;
 		}
 
 		/* do not exceed the maximum value */
-		if (bin_attr->cb_max_size && len > bin_attr->cb_max_size) {
+		if (buffer->cb_max_size && len > buffer->cb_max_size) {
 			retval = -EFBIG;
 			goto out;
 		}
@@ -176,7 +184,13 @@ configfs_read_bin_file(struct file *file, char __user *buf,
 		buffer->bin_buffer_size = len;
 
 		/* perform second read to fill buffer */
-		len = bin_attr->read(item, buffer->bin_buffer, len);
+		down_read(&frag->frag_sem);
+		if (!frag->frag_dead)
+			len = buffer->bin_attr->read(buffer->item,
+						     buffer->bin_buffer, len);
+		else
+			len = -ENOENT;
+		up_read(&frag->frag_sem);
 		if (len < 0) {
 			retval = len;
 			vfree(buffer->bin_buffer);
@@ -226,25 +240,17 @@ fill_write_buffer(struct configfs_buffer * buffer, const char __user * buf, size
 	return error ? -EFAULT : count;
 }
 
-
-/**
- *	flush_write_buffer - push buffer to config_item.
- *	@dentry:	dentry to the attribute
- *	@buffer:	data buffer for file.
- *	@count:		number of bytes
- *
- *	Get the correct pointers for the config_item and the attribute we're
- *	dealing with, then call the store() method for the attribute,
- *	passing the buffer that we acquired in fill_write_buffer().
- */
-
 static int
-flush_write_buffer(struct dentry * dentry, struct configfs_buffer * buffer, size_t count)
+flush_write_buffer(struct file *file, struct configfs_buffer *buffer, size_t count)
 {
-	struct configfs_attribute * attr = to_attr(dentry);
-	struct config_item * item = to_item(dentry->d_parent);
+	struct configfs_fragment *frag = to_frag(file);
+	int res = -ENOENT;
 
-	return attr->store(item, buffer->page, count);
+	down_read(&frag->frag_sem);
+	if (!frag->frag_dead)
+		res = buffer->attr->store(buffer->item, buffer->page, count);
+	up_read(&frag->frag_sem);
+	return res;
 }
 
 
@@ -268,13 +274,13 @@ flush_write_buffer(struct dentry * dentry, struct configfs_buffer * buffer, size
 static ssize_t
 configfs_write_file(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
 {
-	struct configfs_buffer * buffer = file->private_data;
+	struct configfs_buffer *buffer = file->private_data;
 	ssize_t len;
 
 	mutex_lock(&buffer->mutex);
 	len = fill_write_buffer(buffer, buf, count);
 	if (len > 0)
-		len = flush_write_buffer(file->f_path.dentry, buffer, len);
+		len = flush_write_buffer(file, buffer, len);
 	if (len > 0)
 		*ppos += len;
 	mutex_unlock(&buffer->mutex);
@@ -299,8 +305,6 @@ configfs_write_bin_file(struct file *file, const char __user *buf,
 			size_t count, loff_t *ppos)
 {
 	struct configfs_buffer *buffer = file->private_data;
-	struct dentry *dentry = file->f_path.dentry;
-	struct configfs_bin_attribute *bin_attr = to_bin_attr(dentry);
 	void *tbuf = NULL;
 	ssize_t len;
 
@@ -316,8 +320,8 @@ configfs_write_bin_file(struct file *file, const char __user *buf,
 	/* buffer grows? */
 	if (*ppos + count > buffer->bin_buffer_size) {
 
-		if (bin_attr->cb_max_size &&
-			*ppos + count > bin_attr->cb_max_size) {
+		if (buffer->cb_max_size &&
+			*ppos + count > buffer->cb_max_size) {
 			len = -EFBIG;
 			goto out;
 		}
@@ -349,31 +353,51 @@ configfs_write_bin_file(struct file *file, const char __user *buf,
 	return len;
 }
 
-static int check_perm(struct inode * inode, struct file * file, int type)
+static int __configfs_open_file(struct inode *inode, struct file *file, int type)
 {
-	struct config_item *item = configfs_get_config_item(file->f_path.dentry->d_parent);
-	struct configfs_attribute * attr = to_attr(file->f_path.dentry);
-	struct configfs_bin_attribute *bin_attr = NULL;
-	struct configfs_buffer * buffer;
-	struct configfs_item_operations * ops = NULL;
-	int error = 0;
+	struct dentry *dentry = file->f_path.dentry;
+	struct configfs_fragment *frag = to_frag(file);
+	struct configfs_attribute *attr;
+	struct configfs_buffer *buffer;
+	int error;
 
-	if (!item || !attr)
-		goto Einval;
+	error = -ENOMEM;
+	buffer = kzalloc(sizeof(struct configfs_buffer), GFP_KERNEL);
+	if (!buffer)
+		goto out;
 
-	if (type & CONFIGFS_ITEM_BIN_ATTR)
-		bin_attr = to_bin_attr(file->f_path.dentry);
+	error = -ENOENT;
+	down_read(&frag->frag_sem);
+	if (unlikely(frag->frag_dead))
+		goto out_free_buffer;
 
-	/* Grab the module reference for this attribute if we have one */
-	if (!try_module_get(attr->ca_owner)) {
-		error = -ENODEV;
-		goto Done;
+	error = -EINVAL;
+	buffer->item = to_item(dentry->d_parent);
+	if (!buffer->item)
+		goto out_free_buffer;
+
+	attr = to_attr(dentry);
+	if (!attr)
+		goto out_put_item;
+
+	if (type & CONFIGFS_ITEM_BIN_ATTR) {
+		buffer->bin_attr = to_bin_attr(dentry);
+		buffer->cb_max_size = buffer->bin_attr->cb_max_size;
+	} else {
+		buffer->attr = attr;
 	}
 
-	if (item->ci_type)
-		ops = item->ci_type->ct_item_ops;
-	else
-		goto Eaccess;
+	buffer->owner = attr->ca_owner;
+	/* Grab the module reference for this attribute if we have one */
+	error = -ENODEV;
+	if (!try_module_get(buffer->owner))
+		goto out_put_item;
+
+	error = -EACCES;
+	if (!buffer->item->ci_type)
+		goto out_put_module;
+
+	buffer->ops = buffer->item->ci_type->ct_item_ops;
 
 	/* File needs write support.
 	 * The inode's perms must say it's ok,
@@ -381,13 +405,11 @@ static int check_perm(struct inode * inode, struct file * file, int type)
 	 */
 	if (file->f_mode & FMODE_WRITE) {
 		if (!(inode->i_mode & S_IWUGO))
-			goto Eaccess;
-
+			goto out_put_module;
 		if ((type & CONFIGFS_ITEM_ATTR) && !attr->store)
-			goto Eaccess;
-
-		if ((type & CONFIGFS_ITEM_BIN_ATTR) && !bin_attr->write)
-			goto Eaccess;
+			goto out_put_module;
+		if ((type & CONFIGFS_ITEM_BIN_ATTR) && !buffer->bin_attr->write)
+			goto out_put_module;
 	}
 
 	/* File needs read support.
@@ -396,92 +418,72 @@ static int check_perm(struct inode * inode, struct file * file, int type)
 	 */
 	if (file->f_mode & FMODE_READ) {
 		if (!(inode->i_mode & S_IRUGO))
-			goto Eaccess;
-
+			goto out_put_module;
 		if ((type & CONFIGFS_ITEM_ATTR) && !attr->show)
-			goto Eaccess;
-
-		if ((type & CONFIGFS_ITEM_BIN_ATTR) && !bin_attr->read)
-			goto Eaccess;
+			goto out_put_module;
+		if ((type & CONFIGFS_ITEM_BIN_ATTR) && !buffer->bin_attr->read)
+			goto out_put_module;
 	}
 
-	/* No error? Great, allocate a buffer for the file, and store it
-	 * it in file->private_data for easy access.
-	 */
-	buffer = kzalloc(sizeof(struct configfs_buffer),GFP_KERNEL);
-	if (!buffer) {
-		error = -ENOMEM;
-		goto Enomem;
-	}
 	mutex_init(&buffer->mutex);
 	buffer->needs_read_fill = 1;
 	buffer->read_in_progress = false;
 	buffer->write_in_progress = false;
-	buffer->ops = ops;
 	file->private_data = buffer;
-	goto Done;
+	up_read(&frag->frag_sem);
+	return 0;
 
- Einval:
-	error = -EINVAL;
-	goto Done;
- Eaccess:
-	error = -EACCES;
- Enomem:
-	module_put(attr->ca_owner);
- Done:
-	if (error && item)
-		config_item_put(item);
+out_put_module:
+	module_put(buffer->owner);
+out_put_item:
+	config_item_put(buffer->item);
+out_free_buffer:
+	up_read(&frag->frag_sem);
+	kfree(buffer);
+out:
 	return error;
 }
 
 static int configfs_release(struct inode *inode, struct file *filp)
 {
-	struct config_item * item = to_item(filp->f_path.dentry->d_parent);
-	struct configfs_attribute * attr = to_attr(filp->f_path.dentry);
-	struct module * owner = attr->ca_owner;
-	struct configfs_buffer * buffer = filp->private_data;
+	struct configfs_buffer *buffer = filp->private_data;
 
-	if (item)
-		config_item_put(item);
-	/* After this point, attr should not be accessed. */
-	module_put(owner);
-
-	if (buffer) {
-		if (buffer->page)
-			free_page((unsigned long)buffer->page);
-		mutex_destroy(&buffer->mutex);
-		kfree(buffer);
-	}
+	module_put(buffer->owner);
+	if (buffer->page)
+		free_page((unsigned long)buffer->page);
+	mutex_destroy(&buffer->mutex);
+	kfree(buffer);
 	return 0;
 }
 
 static int configfs_open_file(struct inode *inode, struct file *filp)
 {
-	return check_perm(inode, filp, CONFIGFS_ITEM_ATTR);
+	return __configfs_open_file(inode, filp, CONFIGFS_ITEM_ATTR);
 }
 
 static int configfs_open_bin_file(struct inode *inode, struct file *filp)
 {
-	return check_perm(inode, filp, CONFIGFS_ITEM_BIN_ATTR);
+	return __configfs_open_file(inode, filp, CONFIGFS_ITEM_BIN_ATTR);
 }
 
-static int configfs_release_bin_file(struct inode *inode, struct file *filp)
+static int configfs_release_bin_file(struct inode *inode, struct file *file)
 {
-	struct configfs_buffer *buffer = filp->private_data;
-	struct dentry *dentry = filp->f_path.dentry;
-	struct config_item *item = to_item(dentry->d_parent);
-	struct configfs_bin_attribute *bin_attr = to_bin_attr(dentry);
-	ssize_t len = 0;
-	int ret;
+	struct configfs_buffer *buffer = file->private_data;
 
 	buffer->read_in_progress = false;
 
 	if (buffer->write_in_progress) {
+		struct configfs_fragment *frag = to_frag(file);
 		buffer->write_in_progress = false;
 
-		len = bin_attr->write(item, buffer->bin_buffer,
-				buffer->bin_buffer_size);
-
+		down_read(&frag->frag_sem);
+		if (!frag->frag_dead) {
+			/* result of ->release() is ignored */
+			buffer->bin_attr->write(buffer->item,
+					buffer->bin_buffer,
+					buffer->bin_buffer_size);
+		}
+		up_read(&frag->frag_sem);
 		/* vfree on NULL is safe */
 		vfree(buffer->bin_buffer);
 		buffer->bin_buffer = NULL;
@@ -489,10 +491,8 @@ static int configfs_release_bin_file(struct inode *inode, struct file *filp)
 		buffer->needs_read_fill = 1;
 	}
 
-	ret = configfs_release(inode, filp);
-	if (len < 0)
-		return len;
-	return ret;
+	configfs_release(inode, file);
+	return 0;
 }
 
 
@@ -527,7 +527,7 @@ int configfs_create_file(struct config_item * item, const struct configfs_attrib
 
 	inode_lock_nested(d_inode(dir), I_MUTEX_NORMAL);
 	error = configfs_make_dirent(parent_sd, NULL, (void *) attr, mode,
-				     CONFIGFS_ITEM_ATTR);
+				     CONFIGFS_ITEM_ATTR, parent_sd->s_frag);
 	inode_unlock(d_inode(dir));
 
 	return error;
@@ -549,7 +549,7 @@ int configfs_create_bin_file(struct config_item *item,
 
 	inode_lock_nested(dir->d_inode, I_MUTEX_NORMAL);
 	error = configfs_make_dirent(parent_sd, NULL, (void *) bin_attr, mode,
-				     CONFIGFS_ITEM_BIN_ATTR);
+				     CONFIGFS_ITEM_BIN_ATTR, parent_sd->s_frag);
 	inode_unlock(dir->d_inode);
 
 	return error;