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
Signed-off-by: Miklos Szeredi <[email protected]>
---
Index: linux/fs/fuse/control.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux/fs/fuse/control.c 2006-06-12 14:09:57.000000000 +0200
@@ -0,0 +1,204 @@
+/*
+ FUSE: Filesystem in Userspace
+ Copyright (C) 2001-2006 Miklos Szeredi <[email protected]>
+
+ 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
+
+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 *) atomic_read(&fc->num_waiting);
+ fuse_conn_put(fc);
+ }
+ size = sprintf(tmp, "%i\n", (int) 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;
+ 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;
+}
+
+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;
+}
+
+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 struct super_block *fuse_ctl_get_sb(struct file_system_type *fs_type,
+ int flags, const char *dev_name,
+ void *raw_data)
+{
+ return get_sb_single(fs_type, flags, raw_data, fuse_ctl_fill_super);
+}
+
+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);
+}
Index: linux/fs/fuse/inode.c
===================================================================
--- linux.orig/fs/fuse/inode.c 2006-06-12 14:09:56.000000000 +0200
+++ linux/fs/fuse/inode.c 2006-06-12 14:09:57.000000000 +0200
@@ -22,13 +22,8 @@ MODULE_DESCRIPTION("Filesystem in Usersp
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
@@ -212,8 +207,11 @@ static void fuse_put_super(struct super_
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_
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_c
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_
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_
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_t
.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();
Index: linux/fs/fuse/Makefile
===================================================================
--- linux.orig/fs/fuse/Makefile 2006-06-12 14:09:21.000000000 +0200
+++ linux/fs/fuse/Makefile 2006-06-12 14:09:57.000000000 +0200
@@ -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
Index: linux/fs/fuse/dev.c
===================================================================
--- linux.orig/fs/fuse/dev.c 2006-06-12 14:09:56.000000000 +0200
+++ linux/fs/fuse/dev.c 2006-06-12 14:09:57.000000000 +0200
@@ -833,7 +833,7 @@ static int fuse_dev_release(struct inode
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;
Index: linux/fs/fuse/fuse_i.h
===================================================================
--- linux.orig/fs/fuse/fuse_i.h 2006-06-12 14:09:56.000000000 +0200
+++ linux/fs/fuse/fuse_i.h 2006-06-12 14:09:57.000000000 +0200
@@ -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
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);
Index: linux/Documentation/filesystems/fuse.txt
===================================================================
--- linux.orig/Documentation/filesystems/fuse.txt 2006-06-12 14:09:56.000000000 +0200
+++ linux/Documentation/filesystems/fuse.txt 2006-06-12 14:09:57.000000000 +0200
@@ -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
+~~~~~~~~~~~~~~~~~~
+
+There's a control filesystem for FUSE, which can be mounted by:
-FUSE sets up the following hierarchy in sysfs:
+ mount -t fusectl none /sys/fs/fuse/connections
- /sys/fs/fuse/connections/N/
+Mounting it under the '/sys/fs/fuse/connections' directory makes it
+backwards compatible with earlier versions.
-where N is an increasing number allocated to each new connection.
+Under the fuse control filesystem each connection has a directory
+named by a unique number.
-For each connection the following attributes are defined:
+For each connection the following files exist within this directory:
'waiting'
@@ -110,7 +122,7 @@ For each connection the following attrib
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
- 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?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
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