[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>
diff --git a/fs/fuse/control.c b/fs/fuse/control.c
new file mode 100644
index 0000000..a3bce3a
--- /dev/null
+++ b/fs/fuse/control.c
@@ -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);
+}