fs/fuse/control.c - linux - Git at Google

 /*
   FUSE: Filesystem in Userspace
   Copyright (C) 2001-2008  Miklos Szeredi <miklos@szeredi.hu>

   This program can be distributed under the terms of the GNU GPL.
   See the file COPYING.
 */

 #include "fuse_i.h"

 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/fs_context.h>

 #define FUSE_CTL_SUPER_MAGIC 0x65735543

 /*
  * This is non-NULL when the single instance of the control filesystem
  * exists.  Protected by fuse_mutex
  */
 static struct super_block *fuse_control_sb;

 static struct fuse_conn *fuse_ctl_file_conn_get(struct file *file)
 {
 	struct fuse_conn *fc;
 	mutex_lock(&fuse_mutex);
 	fc = file_inode(file)->i_private;
 	if (fc)
 		fc = fuse_conn_get(fc);
 	mutex_unlock(&fuse_mutex);
 	return fc;
 }

 static ssize_t fuse_conn_abort_write(struct file *file, const char __user *buf,
 				     size_t count, loff_t *ppos)
 {
 	struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
 	if (fc) {
 		if (fc->abort_err)
 			fc->aborted = true;
 		fuse_abort_conn(fc);
 		fuse_conn_put(fc);
 	}
 	return count;
 }

 static ssize_t fuse_conn_waiting_read(struct file *file, char __user *buf,
 				      size_t len, loff_t *ppos)
 {
 	char tmp[32];
 	size_t size;

 	if (!*ppos) {
 		long value;
 		struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
 		if (!fc)
 			return 0;

 		value = atomic_read(&fc->num_waiting);
 		file->private_data = (void *)value;
 		fuse_conn_put(fc);
 	}
 	size = sprintf(tmp, "%ld\n", (long)file->private_data);
 	return simple_read_from_buffer(buf, len, ppos, tmp, size);
 }

 static ssize_t fuse_conn_limit_read(struct file *file, char __user *buf,
 				    size_t len, loff_t *ppos, unsigned val)
 {
 	char tmp[32];
 	size_t size = sprintf(tmp, "%u\n", val);

 	return simple_read_from_buffer(buf, len, ppos, tmp, size);
 }

 static ssize_t fuse_conn_limit_write(struct file *file, const char __user *buf,
 				     size_t count, loff_t *ppos, unsigned *val,
 				     unsigned global_limit)
 {
 	unsigned long t;
 	unsigned limit = (1 << 16) - 1;
 	int err;

 	if (*ppos)
 		return -EINVAL;

 	err = kstrtoul_from_user(buf, count, 0, &t);
 	if (err)
 		return err;

 	if (!capable(CAP_SYS_ADMIN))
 		limit = min(limit, global_limit);

 	if (t > limit)
 		return -EINVAL;

 	*val = t;

 	return count;
 }

 static ssize_t fuse_conn_max_background_read(struct file *file,
 					     char __user *buf, size_t len,
 					     loff_t *ppos)
 {
 	struct fuse_conn *fc;
 	unsigned val;

 	fc = fuse_ctl_file_conn_get(file);
 	if (!fc)
 		return 0;

 	val = READ_ONCE(fc->max_background);
 	fuse_conn_put(fc);

 	return fuse_conn_limit_read(file, buf, len, ppos, val);
 }

 static ssize_t fuse_conn_max_background_write(struct file *file,
 					      const char __user *buf,
 					      size_t count, loff_t *ppos)
 {
 	unsigned val;
 	ssize_t ret;

 	ret = fuse_conn_limit_write(file, buf, count, ppos, &val,
 				    max_user_bgreq);
 	if (ret > 0) {
 		struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
 		if (fc) {
 			spin_lock(&fc->bg_lock);
 			fc->max_background = val;
 			fc->blocked = fc->num_background >= fc->max_background;
 			if (!fc->blocked)
 				wake_up(&fc->blocked_waitq);
 			spin_unlock(&fc->bg_lock);
 			fuse_conn_put(fc);
 		}
 	}

 	return ret;
 }

 static ssize_t fuse_conn_congestion_threshold_read(struct file *file,
 						   char __user *buf, size_t len,
 						   loff_t *ppos)
 {
 	struct fuse_conn *fc;
 	unsigned val;

 	fc = fuse_ctl_file_conn_get(file);
 	if (!fc)
 		return 0;

 	val = READ_ONCE(fc->congestion_threshold);
 	fuse_conn_put(fc);

 	return fuse_conn_limit_read(file, buf, len, ppos, val);
 }

 static ssize_t fuse_conn_congestion_threshold_write(struct file *file,
 						    const char __user *buf,
 						    size_t count, loff_t *ppos)
 {
 	unsigned val;
 	struct fuse_conn *fc;
 	ssize_t ret;

 	ret = fuse_conn_limit_write(file, buf, count, ppos, &val,
 				    max_user_congthresh);
 	if (ret <= 0)
 		goto out;
 	fc = fuse_ctl_file_conn_get(file);
 	if (!fc)
 		goto out;

 	down_read(&fc->killsb);
 	spin_lock(&fc->bg_lock);
 	fc->congestion_threshold = val;
 	spin_unlock(&fc->bg_lock);
 	up_read(&fc->killsb);
 	fuse_conn_put(fc);
 out:
 	return ret;
 }

 static const struct file_operations fuse_ctl_abort_ops = {
 	.open = nonseekable_open,
 	.write = fuse_conn_abort_write,
 	.llseek = no_llseek,
 };

 static const struct file_operations fuse_ctl_waiting_ops = {
 	.open = nonseekable_open,
 	.read = fuse_conn_waiting_read,
 	.llseek = no_llseek,
 };

 static const struct file_operations fuse_conn_max_background_ops = {
 	.open = nonseekable_open,
 	.read = fuse_conn_max_background_read,
 	.write = fuse_conn_max_background_write,
 	.llseek = no_llseek,
 };

 static const struct file_operations fuse_conn_congestion_threshold_ops = {
 	.open = nonseekable_open,
 	.read = fuse_conn_congestion_threshold_read,
 	.write = fuse_conn_congestion_threshold_write,
 	.llseek = no_llseek,
 };

 static struct dentry *fuse_ctl_add_dentry(struct dentry *parent,
 					  struct fuse_conn *fc,
 					  const char *name,
 					  int mode, int nlink,
 					  const struct inode_operations *iop,
 					  const struct file_operations *fop)
 {
 	struct dentry *dentry;
 	struct inode *inode;

 	BUG_ON(fc->ctl_ndents >= FUSE_CTL_NUM_DENTRIES);
 	dentry = d_alloc_name(parent, name);
 	if (!dentry)
 		return NULL;

 	inode = new_inode(fuse_control_sb);
 	if (!inode) {
 		dput(dentry);
 		return NULL;
 	}

 	inode->i_ino = get_next_ino();
 	inode->i_mode = mode;
 	inode->i_uid = fc->user_id;
 	inode->i_gid = fc->group_id;
 	inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
 	/* setting ->i_op to NULL is not allowed */
 	if (iop)
 		inode->i_op = iop;
 	inode->i_fop = fop;
 	set_nlink(inode, nlink);
 	inode->i_private = fc;
 	d_add(dentry, inode);

 	fc->ctl_dentry[fc->ctl_ndents++] = dentry;

 	return dentry;
 }

 /*
  * Add a connection to the control filesystem (if it exists).  Caller
  * must hold fuse_mutex
  */
 int fuse_ctl_add_conn(struct fuse_conn *fc)
 {
 	struct dentry *parent;
 	char name[32];

 	if (!fuse_control_sb)
 		return 0;

 	parent = fuse_control_sb->s_root;
 	inc_nlink(d_inode(parent));
 	sprintf(name, "%u", fc->dev);
 	parent = fuse_ctl_add_dentry(parent, fc, name, S_IFDIR | 0500, 2,
 				     &simple_dir_inode_operations,
 				     &simple_dir_operations);
 	if (!parent)
 		goto err;

 	if (!fuse_ctl_add_dentry(parent, fc, "waiting", S_IFREG | 0400, 1,
 				 NULL, &fuse_ctl_waiting_ops) ||
 	    !fuse_ctl_add_dentry(parent, fc, "abort", S_IFREG | 0200, 1,
 				 NULL, &fuse_ctl_abort_ops) ||
 	    !fuse_ctl_add_dentry(parent, fc, "max_background", S_IFREG | 0600,
 				 1, NULL, &fuse_conn_max_background_ops) ||
 	    !fuse_ctl_add_dentry(parent, fc, "congestion_threshold",
 				 S_IFREG | 0600, 1, NULL,
 				 &fuse_conn_congestion_threshold_ops))
 		goto err;

 	return 0;

  err:
 	fuse_ctl_remove_conn(fc);
 	return -ENOMEM;
 }

 /*
  * Remove a connection from the control filesystem (if it exists).
  * Caller must hold fuse_mutex
  */
 void fuse_ctl_remove_conn(struct fuse_conn *fc)
 {
 	int i;

 	if (!fuse_control_sb)
 		return;

 	for (i = fc->ctl_ndents - 1; i >= 0; i--) {
 		struct dentry *dentry = fc->ctl_dentry[i];
 		d_inode(dentry)->i_private = NULL;
 		if (!i) {
 			/* Get rid of submounts: */
 			d_invalidate(dentry);
 		}
 		dput(dentry);
 	}
 	drop_nlink(d_inode(fuse_control_sb->s_root));
 }

 static int fuse_ctl_fill_super(struct super_block *sb, struct fs_context *fsc)
 {
 	static const struct tree_descr empty_descr = {""};
 	struct fuse_conn *fc;
 	int err;

 	err = simple_fill_super(sb, FUSE_CTL_SUPER_MAGIC, &empty_descr);
 	if (err)
 		return err;

 	mutex_lock(&fuse_mutex);
 	BUG_ON(fuse_control_sb);
 	fuse_control_sb = sb;
 	list_for_each_entry(fc, &fuse_conn_list, entry) {
 		err = fuse_ctl_add_conn(fc);
 		if (err) {
 			fuse_control_sb = NULL;
 			mutex_unlock(&fuse_mutex);
 			return err;
 		}
 	}
 	mutex_unlock(&fuse_mutex);

 	return 0;
 }

 static int fuse_ctl_get_tree(struct fs_context *fsc)
 {
 	return get_tree_single(fsc, fuse_ctl_fill_super);
 }

 static const struct fs_context_operations fuse_ctl_context_ops = {
 	.get_tree	= fuse_ctl_get_tree,
 };

 static int fuse_ctl_init_fs_context(struct fs_context *fsc)
 {
 	fsc->ops = &fuse_ctl_context_ops;
 	return 0;
 }

 static void fuse_ctl_kill_sb(struct super_block *sb)
 {
 	struct fuse_conn *fc;

 	mutex_lock(&fuse_mutex);
 	fuse_control_sb = NULL;
 	list_for_each_entry(fc, &fuse_conn_list, entry)
 		fc->ctl_ndents = 0;
 	mutex_unlock(&fuse_mutex);

 	kill_litter_super(sb);
 }

 static struct file_system_type fuse_ctl_fs_type = {
 	.owner		= THIS_MODULE,
 	.name		= "fusectl",
 	.init_fs_context = fuse_ctl_init_fs_context,
 	.kill_sb	= fuse_ctl_kill_sb,
 };
 MODULE_ALIAS_FS("fusectl");

 int __init fuse_ctl_init(void)
 {
 	return register_filesystem(&fuse_ctl_fs_type);
 }

 void __exit fuse_ctl_cleanup(void)
 {
 	unregister_filesystem(&fuse_ctl_fs_type);
 }
	/*
	FUSE: Filesystem in Userspace
	Copyright (C) 2001-2008 Miklos Szeredi <miklos@szeredi.hu>

	This program can be distributed under the terms of the GNU GPL.
	See the file COPYING.
	*/

	#include "fuse_i.h"

	#include <linux/init.h>
	#include <linux/module.h>
	#include <linux/fs_context.h>

	#define FUSE_CTL_SUPER_MAGIC 0x65735543

	/*
	* This is non-NULL when the single instance of the control filesystem
	* exists. Protected by fuse_mutex
	*/
	static struct super_block *fuse_control_sb;

	static struct fuse_conn fuse_ctl_file_conn_get(struct file file)
	{
	struct fuse_conn *fc;
	mutex_lock(&fuse_mutex);
	fc = file_inode(file)->i_private;
	if (fc)
	fc = fuse_conn_get(fc);
	mutex_unlock(&fuse_mutex);
	return fc;
	}

	static ssize_t fuse_conn_abort_write(struct file file, const char __user buf,
	size_t count, loff_t *ppos)
	{
	struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
	if (fc) {
	if (fc->abort_err)
	fc->aborted = true;
	fuse_abort_conn(fc);
	fuse_conn_put(fc);
	}
	return count;
	}

	static ssize_t fuse_conn_waiting_read(struct file file, char __user buf,
	size_t len, loff_t *ppos)
	{
	char tmp[32];
	size_t size;

	if (!*ppos) {
	long value;
	struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
	if (!fc)
	return 0;

	value = atomic_read(&fc->num_waiting);
	file->private_data = (void *)value;
	fuse_conn_put(fc);
	}
	size = sprintf(tmp, "%ld\n", (long)file->private_data);
	return simple_read_from_buffer(buf, len, ppos, tmp, size);
	}

	static ssize_t fuse_conn_limit_read(struct file file, char __user buf,
	size_t len, loff_t *ppos, unsigned val)
	{
	char tmp[32];
	size_t size = sprintf(tmp, "%u\n", val);

	return simple_read_from_buffer(buf, len, ppos, tmp, size);
	}

	static ssize_t fuse_conn_limit_write(struct file file, const char __user buf,
	size_t count, loff_t ppos, unsigned val,
	unsigned global_limit)
	{
	unsigned long t;
	unsigned limit = (1 << 16) - 1;
	int err;

	if (*ppos)
	return -EINVAL;

	err = kstrtoul_from_user(buf, count, 0, &t);
	if (err)
	return err;

	if (!capable(CAP_SYS_ADMIN))
	limit = min(limit, global_limit);

	if (t > limit)
	return -EINVAL;

	*val = t;

	return count;
	}

	static ssize_t fuse_conn_max_background_read(struct file *file,
	char __user *buf, size_t len,
	loff_t *ppos)
	{
	struct fuse_conn *fc;
	unsigned val;

	fc = fuse_ctl_file_conn_get(file);
	if (!fc)
	return 0;

	val = READ_ONCE(fc->max_background);
	fuse_conn_put(fc);

	return fuse_conn_limit_read(file, buf, len, ppos, val);
	}

	static ssize_t fuse_conn_max_background_write(struct file *file,
	const char __user *buf,
	size_t count, loff_t *ppos)
	{
	unsigned val;
	ssize_t ret;

	ret = fuse_conn_limit_write(file, buf, count, ppos, &val,
	max_user_bgreq);
	if (ret > 0) {
	struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
	if (fc) {
	spin_lock(&fc->bg_lock);
	fc->max_background = val;
	fc->blocked = fc->num_background >= fc->max_background;
	if (!fc->blocked)
	wake_up(&fc->blocked_waitq);
	spin_unlock(&fc->bg_lock);
	fuse_conn_put(fc);
	}
	}

	return ret;
	}

	static ssize_t fuse_conn_congestion_threshold_read(struct file *file,
	char __user *buf, size_t len,
	loff_t *ppos)
	{
	struct fuse_conn *fc;
	unsigned val;

	fc = fuse_ctl_file_conn_get(file);
	if (!fc)
	return 0;

	val = READ_ONCE(fc->congestion_threshold);
	fuse_conn_put(fc);

	return fuse_conn_limit_read(file, buf, len, ppos, val);
	}

	static ssize_t fuse_conn_congestion_threshold_write(struct file *file,
	const char __user *buf,
	size_t count, loff_t *ppos)
	{
	unsigned val;
	struct fuse_conn *fc;
	ssize_t ret;

	ret = fuse_conn_limit_write(file, buf, count, ppos, &val,
	max_user_congthresh);
	if (ret <= 0)
	goto out;
	fc = fuse_ctl_file_conn_get(file);
	if (!fc)
	goto out;

	down_read(&fc->killsb);
	spin_lock(&fc->bg_lock);
	fc->congestion_threshold = val;
	spin_unlock(&fc->bg_lock);
	up_read(&fc->killsb);
	fuse_conn_put(fc);
	out:
	return ret;
	}

	static const struct file_operations fuse_ctl_abort_ops = {
	.open = nonseekable_open,
	.write = fuse_conn_abort_write,
	.llseek = no_llseek,
	};

	static const struct file_operations fuse_ctl_waiting_ops = {
	.open = nonseekable_open,
	.read = fuse_conn_waiting_read,
	.llseek = no_llseek,
	};

	static const struct file_operations fuse_conn_max_background_ops = {
	.open = nonseekable_open,
	.read = fuse_conn_max_background_read,
	.write = fuse_conn_max_background_write,
	.llseek = no_llseek,
	};

	static const struct file_operations fuse_conn_congestion_threshold_ops = {
	.open = nonseekable_open,
	.read = fuse_conn_congestion_threshold_read,
	.write = fuse_conn_congestion_threshold_write,
	.llseek = no_llseek,
	};

	static struct dentry fuse_ctl_add_dentry(struct dentry parent,
	struct fuse_conn *fc,
	const char *name,
	int mode, int nlink,
	const struct inode_operations *iop,
	const struct file_operations *fop)
	{
	struct dentry *dentry;
	struct inode *inode;

	BUG_ON(fc->ctl_ndents >= FUSE_CTL_NUM_DENTRIES);
	dentry = d_alloc_name(parent, name);
	if (!dentry)
	return NULL;

	inode = new_inode(fuse_control_sb);
	if (!inode) {
	dput(dentry);
	return NULL;
	}

	inode->i_ino = get_next_ino();
	inode->i_mode = mode;
	inode->i_uid = fc->user_id;
	inode->i_gid = fc->group_id;
	inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
	/* setting ->i_op to NULL is not allowed */
	if (iop)
	inode->i_op = iop;
	inode->i_fop = fop;
	set_nlink(inode, nlink);
	inode->i_private = fc;
	d_add(dentry, inode);

	fc->ctl_dentry[fc->ctl_ndents++] = dentry;

	return dentry;
	}

	/*
	* Add a connection to the control filesystem (if it exists). Caller
	* must hold fuse_mutex
	*/
	int fuse_ctl_add_conn(struct fuse_conn *fc)
	{
	struct dentry *parent;
	char name[32];

	if (!fuse_control_sb)
	return 0;

	parent = fuse_control_sb->s_root;
	inc_nlink(d_inode(parent));
	sprintf(name, "%u", fc->dev);
	parent = fuse_ctl_add_dentry(parent, fc, name, S_IFDIR \| 0500, 2,
	&simple_dir_inode_operations,
	&simple_dir_operations);
	if (!parent)
	goto err;

	if (!fuse_ctl_add_dentry(parent, fc, "waiting", S_IFREG \| 0400, 1,
	NULL, &fuse_ctl_waiting_ops) \|\|
	!fuse_ctl_add_dentry(parent, fc, "abort", S_IFREG \| 0200, 1,
	NULL, &fuse_ctl_abort_ops) \|\|
	!fuse_ctl_add_dentry(parent, fc, "max_background", S_IFREG \| 0600,
	1, NULL, &fuse_conn_max_background_ops) \|\|
	!fuse_ctl_add_dentry(parent, fc, "congestion_threshold",
	S_IFREG \| 0600, 1, NULL,
	&fuse_conn_congestion_threshold_ops))
	goto err;

	return 0;

	err:
	fuse_ctl_remove_conn(fc);
	return -ENOMEM;
	}

	/*
	* Remove a connection from the control filesystem (if it exists).
	* Caller must hold fuse_mutex
	*/
	void fuse_ctl_remove_conn(struct fuse_conn *fc)
	{
	int i;

	if (!fuse_control_sb)
	return;

	for (i = fc->ctl_ndents - 1; i >= 0; i--) {
	struct dentry *dentry = fc->ctl_dentry[i];
	d_inode(dentry)->i_private = NULL;
	if (!i) {
	/* Get rid of submounts: */
	d_invalidate(dentry);
	}
	dput(dentry);
	}
	drop_nlink(d_inode(fuse_control_sb->s_root));
	}

	static int fuse_ctl_fill_super(struct super_block sb, struct fs_context fsc)
	{
	static const struct tree_descr empty_descr = {""};
	struct fuse_conn *fc;
	int err;

	err = simple_fill_super(sb, FUSE_CTL_SUPER_MAGIC, &empty_descr);
	if (err)
	return err;

	mutex_lock(&fuse_mutex);
	BUG_ON(fuse_control_sb);
	fuse_control_sb = sb;
	list_for_each_entry(fc, &fuse_conn_list, entry) {
	err = fuse_ctl_add_conn(fc);
	if (err) {
	fuse_control_sb = NULL;
	mutex_unlock(&fuse_mutex);
	return err;
	}
	}
	mutex_unlock(&fuse_mutex);

	return 0;
	}

	static int fuse_ctl_get_tree(struct fs_context *fsc)
	{
	return get_tree_single(fsc, fuse_ctl_fill_super);
	}

	static const struct fs_context_operations fuse_ctl_context_ops = {
	.get_tree = fuse_ctl_get_tree,
	};

	static int fuse_ctl_init_fs_context(struct fs_context *fsc)
	{
	fsc->ops = &fuse_ctl_context_ops;
	return 0;
	}

	static void fuse_ctl_kill_sb(struct super_block *sb)
	{
	struct fuse_conn *fc;

	mutex_lock(&fuse_mutex);
	fuse_control_sb = NULL;
	list_for_each_entry(fc, &fuse_conn_list, entry)
	fc->ctl_ndents = 0;
	mutex_unlock(&fuse_mutex);

	kill_litter_super(sb);
	}

	static struct file_system_type fuse_ctl_fs_type = {
	.owner = THIS_MODULE,
	.name = "fusectl",
	.init_fs_context = fuse_ctl_init_fs_context,
	.kill_sb = fuse_ctl_kill_sb,
	};
	MODULE_ALIAS_FS("fusectl");

	int __init fuse_ctl_init(void)
	{
	return register_filesystem(&fuse_ctl_fs_type);
	}

	void __exit fuse_ctl_cleanup(void)
	{
	unregister_filesystem(&fuse_ctl_fs_type);
	}