linux/fs/devpts/inode.c

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/* -*- linux-c -*- --------------------------------------------------------- *
*
* linux/fs/devpts/inode.c
*
* Copyright 1998-2004 H. Peter Anvin -- All Rights Reserved
*
* This file is part of the Linux kernel and is made available under
* the terms of the GNU General Public License, version 2, or at your
* option, any later version, incorporated herein by reference.
*
* ------------------------------------------------------------------------- */
#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/sched.h>
#include <linux/namei.h>
#include <linux/mount.h>
#include <linux/tty.h>
#include <linux/mutex.h>
#include <linux/idr.h>
#include <linux/devpts_fs.h>
#include <linux/parser.h>
#include <linux/fsnotify.h>
#include <linux/seq_file.h>
#define DEVPTS_SUPER_MAGIC 0x1cd1
#define DEVPTS_DEFAULT_MODE 0600
#define PTMX_MINOR 2
extern int pty_limit; /* Config limit on Unix98 ptys */
static DEFINE_MUTEX(allocated_ptys_lock);
static struct vfsmount *devpts_mnt;
static struct {
int setuid;
int setgid;
uid_t uid;
gid_t gid;
umode_t mode;
} config = {.mode = DEVPTS_DEFAULT_MODE};
enum {
Opt_uid, Opt_gid, Opt_mode,
Opt_err
};
static const match_table_t tokens = {
{Opt_uid, "uid=%u"},
{Opt_gid, "gid=%u"},
{Opt_mode, "mode=%o"},
{Opt_err, NULL}
};
struct pts_fs_info {
struct ida allocated_ptys;
};
static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb)
{
return sb->s_fs_info;
}
static inline struct super_block *pts_sb_from_inode(struct inode *inode)
{
if (inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
return inode->i_sb;
return devpts_mnt->mnt_sb;
}
static int devpts_remount(struct super_block *sb, int *flags, char *data)
{
char *p;
config.setuid = 0;
config.setgid = 0;
config.uid = 0;
config.gid = 0;
config.mode = DEVPTS_DEFAULT_MODE;
while ((p = strsep(&data, ",")) != NULL) {
substring_t args[MAX_OPT_ARGS];
int token;
int option;
if (!*p)
continue;
token = match_token(p, tokens, args);
switch (token) {
case Opt_uid:
if (match_int(&args[0], &option))
return -EINVAL;
config.uid = option;
config.setuid = 1;
break;
case Opt_gid:
if (match_int(&args[0], &option))
return -EINVAL;
config.gid = option;
config.setgid = 1;
break;
case Opt_mode:
if (match_octal(&args[0], &option))
return -EINVAL;
config.mode = option & S_IALLUGO;
break;
default:
printk(KERN_ERR "devpts: called with bogus options\n");
return -EINVAL;
}
}
return 0;
}
static int devpts_show_options(struct seq_file *seq, struct vfsmount *vfs)
{
if (config.setuid)
seq_printf(seq, ",uid=%u", config.uid);
if (config.setgid)
seq_printf(seq, ",gid=%u", config.gid);
seq_printf(seq, ",mode=%03o", config.mode);
return 0;
}
static const struct super_operations devpts_sops = {
.statfs = simple_statfs,
.remount_fs = devpts_remount,
.show_options = devpts_show_options,
};
static void *new_pts_fs_info(void)
{
struct pts_fs_info *fsi;
fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL);
if (!fsi)
return NULL;
ida_init(&fsi->allocated_ptys);
return fsi;
}
static int
devpts_fill_super(struct super_block *s, void *data, int silent)
{
struct inode * inode;
s->s_blocksize = 1024;
s->s_blocksize_bits = 10;
s->s_magic = DEVPTS_SUPER_MAGIC;
s->s_op = &devpts_sops;
s->s_time_gran = 1;
s->s_fs_info = new_pts_fs_info();
if (!s->s_fs_info)
goto fail;
inode = new_inode(s);
if (!inode)
goto free_fsi;
inode->i_ino = 1;
inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
inode->i_blocks = 0;
inode->i_uid = inode->i_gid = 0;
inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR;
inode->i_op = &simple_dir_inode_operations;
inode->i_fop = &simple_dir_operations;
inode->i_nlink = 2;
s->s_root = d_alloc_root(inode);
if (s->s_root)
return 0;
printk("devpts: get root dentry failed\n");
iput(inode);
free_fsi:
kfree(s->s_fs_info);
fail:
return -ENOMEM;
}
[PATCH] VFS: Permit filesystem to override root dentry on mount Extend the get_sb() filesystem operation to take an extra argument that permits the VFS to pass in the target vfsmount that defines the mountpoint. The filesystem is then required to manually set the superblock and root dentry pointers. For most filesystems, this should be done with simple_set_mnt() which will set the superblock pointer and then set the root dentry to the superblock's s_root (as per the old default behaviour). The get_sb() op now returns an integer as there's now no need to return the superblock pointer. This patch permits a superblock to be implicitly shared amongst several mount points, such as can be done with NFS to avoid potential inode aliasing. In such a case, simple_set_mnt() would not be called, and instead the mnt_root and mnt_sb would be set directly. The patch also makes the following changes: (*) the get_sb_*() convenience functions in the core kernel now take a vfsmount pointer argument and return an integer, so most filesystems have to change very little. (*) If one of the convenience function is not used, then get_sb() should normally call simple_set_mnt() to instantiate the vfsmount. This will always return 0, and so can be tail-called from get_sb(). (*) generic_shutdown_super() now calls shrink_dcache_sb() to clean up the dcache upon superblock destruction rather than shrink_dcache_anon(). This is required because the superblock may now have multiple trees that aren't actually bound to s_root, but that still need to be cleaned up. The currently called functions assume that the whole tree is rooted at s_root, and that anonymous dentries are not the roots of trees which results in dentries being left unculled. However, with the way NFS superblock sharing are currently set to be implemented, these assumptions are violated: the root of the filesystem is simply a dummy dentry and inode (the real inode for '/' may well be inaccessible), and all the vfsmounts are rooted on anonymous[*] dentries with child trees. [*] Anonymous until discovered from another tree. (*) The documentation has been adjusted, including the additional bit of changing ext2_* into foo_* in the documentation. [akpm@osdl.org: convert ipath_fs, do other stuff] Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Nathan Scott <nathans@sgi.com> Cc: Roland Dreier <rolandd@cisco.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23 09:02:57 +00:00
static int devpts_get_sb(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data, struct vfsmount *mnt)
{
[PATCH] VFS: Permit filesystem to override root dentry on mount Extend the get_sb() filesystem operation to take an extra argument that permits the VFS to pass in the target vfsmount that defines the mountpoint. The filesystem is then required to manually set the superblock and root dentry pointers. For most filesystems, this should be done with simple_set_mnt() which will set the superblock pointer and then set the root dentry to the superblock's s_root (as per the old default behaviour). The get_sb() op now returns an integer as there's now no need to return the superblock pointer. This patch permits a superblock to be implicitly shared amongst several mount points, such as can be done with NFS to avoid potential inode aliasing. In such a case, simple_set_mnt() would not be called, and instead the mnt_root and mnt_sb would be set directly. The patch also makes the following changes: (*) the get_sb_*() convenience functions in the core kernel now take a vfsmount pointer argument and return an integer, so most filesystems have to change very little. (*) If one of the convenience function is not used, then get_sb() should normally call simple_set_mnt() to instantiate the vfsmount. This will always return 0, and so can be tail-called from get_sb(). (*) generic_shutdown_super() now calls shrink_dcache_sb() to clean up the dcache upon superblock destruction rather than shrink_dcache_anon(). This is required because the superblock may now have multiple trees that aren't actually bound to s_root, but that still need to be cleaned up. The currently called functions assume that the whole tree is rooted at s_root, and that anonymous dentries are not the roots of trees which results in dentries being left unculled. However, with the way NFS superblock sharing are currently set to be implemented, these assumptions are violated: the root of the filesystem is simply a dummy dentry and inode (the real inode for '/' may well be inaccessible), and all the vfsmounts are rooted on anonymous[*] dentries with child trees. [*] Anonymous until discovered from another tree. (*) The documentation has been adjusted, including the additional bit of changing ext2_* into foo_* in the documentation. [akpm@osdl.org: convert ipath_fs, do other stuff] Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Nathan Scott <nathans@sgi.com> Cc: Roland Dreier <rolandd@cisco.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23 09:02:57 +00:00
return get_sb_single(fs_type, flags, data, devpts_fill_super, mnt);
}
static void devpts_kill_sb(struct super_block *sb)
{
struct pts_fs_info *fsi = DEVPTS_SB(sb);
kfree(fsi);
kill_anon_super(sb);
}
static struct file_system_type devpts_fs_type = {
.owner = THIS_MODULE,
.name = "devpts",
.get_sb = devpts_get_sb,
.kill_sb = devpts_kill_sb,
};
/*
* The normal naming convention is simply /dev/pts/<number>; this conforms
* to the System V naming convention
*/
int devpts_new_index(struct inode *ptmx_inode)
{
struct super_block *sb = pts_sb_from_inode(ptmx_inode);
struct pts_fs_info *fsi = DEVPTS_SB(sb);
int index;
int ida_ret;
retry:
if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL)) {
return -ENOMEM;
}
mutex_lock(&allocated_ptys_lock);
ida_ret = ida_get_new(&fsi->allocated_ptys, &index);
if (ida_ret < 0) {
mutex_unlock(&allocated_ptys_lock);
if (ida_ret == -EAGAIN)
goto retry;
return -EIO;
}
if (index >= pty_limit) {
ida_remove(&fsi->allocated_ptys, index);
mutex_unlock(&allocated_ptys_lock);
return -EIO;
}
mutex_unlock(&allocated_ptys_lock);
return index;
}
void devpts_kill_index(struct inode *ptmx_inode, int idx)
{
struct super_block *sb = pts_sb_from_inode(ptmx_inode);
struct pts_fs_info *fsi = DEVPTS_SB(sb);
mutex_lock(&allocated_ptys_lock);
ida_remove(&fsi->allocated_ptys, idx);
mutex_unlock(&allocated_ptys_lock);
}
int devpts_pty_new(struct inode *ptmx_inode, struct tty_struct *tty)
{
int number = tty->index; /* tty layer puts index from devpts_new_index() in here */
struct tty_driver *driver = tty->driver;
dev_t device = MKDEV(driver->major, driver->minor_start+number);
struct dentry *dentry;
struct super_block *sb = pts_sb_from_inode(ptmx_inode);
struct inode *inode = new_inode(sb);
struct dentry *root = sb->s_root;
char s[12];
/* We're supposed to be given the slave end of a pty */
BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY);
BUG_ON(driver->subtype != PTY_TYPE_SLAVE);
if (!inode)
return -ENOMEM;
inode->i_ino = number+2;
inode->i_uid = config.setuid ? config.uid : current_fsuid();
inode->i_gid = config.setgid ? config.gid : current_fsgid();
inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
init_special_inode(inode, S_IFCHR|config.mode, device);
inode->i_private = tty;
tty->driver_data = inode;
sprintf(s, "%d", number);
mutex_lock(&root->d_inode->i_mutex);
dentry = d_alloc_name(root, s);
if (!IS_ERR(dentry)) {
d_add(dentry, inode);
fsnotify_create(root->d_inode, dentry);
}
mutex_unlock(&root->d_inode->i_mutex);
return 0;
}
struct tty_struct *devpts_get_tty(struct inode *pts_inode, int number)
{
BUG_ON(pts_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
return (struct tty_struct *)pts_inode->i_private;
return NULL;
}
void devpts_pty_kill(struct tty_struct *tty)
{
struct inode *inode = tty->driver_data;
struct super_block *sb = pts_sb_from_inode(inode);
struct dentry *root = sb->s_root;
struct dentry *dentry;
BUG_ON(inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
mutex_lock(&root->d_inode->i_mutex);
dentry = d_find_alias(inode);
if (dentry && !IS_ERR(dentry)) {
inode->i_nlink--;
d_delete(dentry);
dput(dentry);
}
mutex_unlock(&root->d_inode->i_mutex);
}
static int __init init_devpts_fs(void)
{
int err = register_filesystem(&devpts_fs_type);
if (!err) {
devpts_mnt = kern_mount(&devpts_fs_type);
if (IS_ERR(devpts_mnt))
err = PTR_ERR(devpts_mnt);
}
return err;
}
static void __exit exit_devpts_fs(void)
{
unregister_filesystem(&devpts_fs_type);
mntput(devpts_mnt);
}
module_init(init_devpts_fs)
module_exit(exit_devpts_fs)
MODULE_LICENSE("GPL");