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[PATCH] fuse: add control filesystem

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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>
This commit is contained in:
Miklos Szeredi 2006-06-25 05:48:51 -07:00 committed by Linus Torvalds
parent 51eb01e735
commit bafa96541b
6 changed files with 331 additions and 115 deletions
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30
Documentation/filesystems/fuse.txt
View File

@ -18,6 +18,14 @@ Non-privileged mount (or user mount):
user. NOTE: this is not the same as mounts allowed with the "user"
option in /etc/fstab, which is not discussed here.
Filesystem connection:
A connection between the filesystem daemon and the kernel. The
connection exists until either the daemon dies, or the filesystem is
umounted. Note that detaching (or lazy umounting) the filesystem
does _not_ break the connection, in this case it will exist until
the last reference to the filesystem is released.
Mount owner:
The user who does the mounting.
@ -86,16 +94,20 @@ Mount options
The default is infinite. Note that the size of read requests is
limited anyway to 32 pages (which is 128kbyte on i386).
Sysfs
~~~~~
Control filesystem
~~~~~~~~~~~~~~~~~~
FUSE sets up the following hierarchy in sysfs:
There's a control filesystem for FUSE, which can be mounted by:
/sys/fs/fuse/connections/N/
mount -t fusectl none /sys/fs/fuse/connections
where N is an increasing number allocated to each new connection.
Mounting it under the '/sys/fs/fuse/connections' directory makes it
backwards compatible with earlier versions.
For each connection the following attributes are defined:
Under the fuse control filesystem each connection has a directory
named by a unique number.
For each connection the following files exist within this directory:
'waiting'
@ -110,7 +122,7 @@ For each connection the following attributes are defined:
connection. This means that all waiting requests will be aborted an
error returned for all aborted and new requests.
Only a privileged user may read or write these attributes.
Only the owner of the mount may read or write these files.
Aborting a filesystem connection
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@ -139,8 +151,8 @@ the filesystem. There are several ways to do this:
- Use forced umount (umount -f). Works in all cases but only if
filesystem is still attached (it hasn't been lazy unmounted)
- Abort filesystem through the sysfs interface. Most powerful
method, always works.
- Abort filesystem through the FUSE control filesystem. Most
powerful method, always works.
How do non-privileged mounts work?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

2
fs/fuse/Makefile
View File

@ -4,4 +4,4 @@
obj-$(CONFIG_FUSE_FS) += fuse.o
fuse-objs := dev.o dir.o file.o inode.o
fuse-objs := dev.o dir.o file.o inode.o control.o

218
fs/fuse/control.c Normal file
View File

@ -0,0 +1,218 @@
/*
FUSE: Filesystem in Userspace
Copyright (C) 2001-2006 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>
#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->f_dentry->d_inode->u.generic_ip;
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) {
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) {
struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
if (!fc)
return 0;
file->private_data=(void *)(long)atomic_read(&fc->num_waiting);
fuse_conn_put(fc);
}
size = sprintf(tmp, "%ld\n", (long)file->private_data);
return simple_read_from_buffer(buf, len, ppos, tmp, size);
}
static const struct file_operations fuse_ctl_abort_ops = {
.open = nonseekable_open,
.write = fuse_conn_abort_write,
};
static const struct file_operations fuse_ctl_waiting_ops = {
.open = nonseekable_open,
.read = fuse_conn_waiting_read,
};
static struct dentry *fuse_ctl_add_dentry(struct dentry *parent,
struct fuse_conn *fc,
const char *name,
int mode, int nlink,
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;
fc->ctl_dentry[fc->ctl_ndents++] = dentry;
inode = new_inode(fuse_control_sb);
if (!inode)
return NULL;
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;
/* setting ->i_op to NULL is not allowed */
if (iop)
inode->i_op = iop;
inode->i_fop = fop;
inode->i_nlink = nlink;
inode->u.generic_ip = fc;
d_add(dentry, inode);
return dentry;
}
/*
* Add a connection to the control filesystem (if it exists). Caller
* must host 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;
parent->d_inode->i_nlink++;
sprintf(name, "%llu", (unsigned long long) fc->id);
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))
goto err;
return 0;
err:
fuse_ctl_remove_conn(fc);
return -ENOMEM;
}
/*
* Remove a connection from the control filesystem (if it exists).
* Caller must host 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];
dentry->d_inode->u.generic_ip = NULL;
d_drop(dentry);
dput(dentry);
}
fuse_control_sb->s_root->d_inode->i_nlink--;
}
static int fuse_ctl_fill_super(struct super_block *sb, void *data, int silent)
{
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_sb(struct file_system_type *fs_type, int flags,
const char *dev_name, void *raw_data,
struct vfsmount *mnt)
{
return get_sb_single(fs_type, flags, raw_data,
fuse_ctl_fill_super, mnt);
}
static void fuse_ctl_kill_sb(struct super_block *sb)
{
mutex_lock(&fuse_mutex);
fuse_control_sb = NULL;
mutex_unlock(&fuse_mutex);
kill_litter_super(sb);
}
static struct file_system_type fuse_ctl_fs_type = {
.owner = THIS_MODULE,
.name = "fusectl",
.get_sb = fuse_ctl_get_sb,
.kill_sb = fuse_ctl_kill_sb,
};
int __init fuse_ctl_init(void)
{
return register_filesystem(&fuse_ctl_fs_type);
}
void fuse_ctl_cleanup(void)
{
unregister_filesystem(&fuse_ctl_fs_type);
}

2
fs/fuse/dev.c
View File

@ -833,7 +833,7 @@ static int fuse_dev_release(struct inode *inode, struct file *file)
end_requests(fc, &fc->processing);
spin_unlock(&fc->lock);
fasync_helper(-1, file, 0, &fc->fasync);
kobject_put(&fc->kobj);
fuse_conn_put(fc);
}
return 0;

53
fs/fuse/fuse_i.h
View File

@ -14,6 +14,7 @@
#include <linux/spinlock.h>
#include <linux/mm.h>
#include <linux/backing-dev.h>
#include <linux/mutex.h>
/** Max number of pages that can be used in a single read request */
#define FUSE_MAX_PAGES_PER_REQ 32
@ -24,6 +25,9 @@
/** It could be as large as PATH_MAX, but would that have any uses? */
#define FUSE_NAME_MAX 1024
/** Number of dentries for each connection in the control filesystem */
#define FUSE_CTL_NUM_DENTRIES 3
/** If the FUSE_DEFAULT_PERMISSIONS flag is given, the filesystem
module will check permissions based on the file mode. Otherwise no
permission checking is done in the kernel */
@ -33,6 +37,11 @@
doing the mount will be allowed to access the filesystem */
#define FUSE_ALLOW_OTHER (1 << 1)
/** List of active connections */
extern struct list_head fuse_conn_list;
/** Global mutex protecting fuse_conn_list and the control filesystem */
extern struct mutex fuse_mutex;
/** FUSE inode */
struct fuse_inode {
@ -216,6 +225,9 @@ struct fuse_conn {
/** Lock protecting accessess to members of this structure */
spinlock_t lock;
/** Refcount */
atomic_t count;
/** The user id for this mount */
uid_t user_id;
@ -310,8 +322,17 @@ struct fuse_conn {
/** Backing dev info */
struct backing_dev_info bdi;
/** kobject */
struct kobject kobj;
/** Entry on the fuse_conn_list */
struct list_head entry;
/** Unique ID */
u64 id;
/** Dentries in the control filesystem */
struct dentry *ctl_dentry[FUSE_CTL_NUM_DENTRIES];
/** number of dentries used in the above array */
int ctl_ndents;
/** O_ASYNC requests */
struct fasync_struct *fasync;
@ -327,11 +348,6 @@ static inline struct fuse_conn *get_fuse_conn(struct inode *inode)
return get_fuse_conn_super(inode->i_sb);
}
static inline struct fuse_conn *get_fuse_conn_kobj(struct kobject *obj)
{
return container_of(obj, struct fuse_conn, kobj);
}
static inline struct fuse_inode *get_fuse_inode(struct inode *inode)
{
return container_of(inode, struct fuse_inode, inode);
@ -422,6 +438,9 @@ int fuse_dev_init(void);
*/
void fuse_dev_cleanup(void);
int fuse_ctl_init(void);
void fuse_ctl_cleanup(void);
/**
* Allocate a request
*/
@ -470,3 +489,23 @@ int fuse_do_getattr(struct inode *inode);
* Invalidate inode attributes
*/
void fuse_invalidate_attr(struct inode *inode);
/**
* Acquire reference to fuse_conn
*/
struct fuse_conn *fuse_conn_get(struct fuse_conn *fc);
/**
* Release reference to fuse_conn
*/
void fuse_conn_put(struct fuse_conn *fc);
/**
* Add connection to control filesystem
*/
int fuse_ctl_add_conn(struct fuse_conn *fc);
/**
* Remove connection from control filesystem
*/
void fuse_ctl_remove_conn(struct fuse_conn *fc);

141
fs/fuse/inode.c
View File

@ -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();