[EMAIL PROTECTED] wrote:
> From: Sukadev Bhattiprolu <[EMAIL PROTECTED]>
> Subject: [RFC][PATCH 3/4]: Enable multiple mounts of /dev/pts
>
> To support multiple PTY namespaces, we should be allow multiple mounts of
> /dev/pts, once within each PTY namespace.
>
> This patch removes the get_sb_single() in devpts_get_sb() and uses test and
> set sb interfaces to allow remounting /dev/pts. The patch also removes the
> globals, 'devpts_root' and uses current_pts_mnt() to access 'devpts_mnt'
>
> Changelog:
> - Version 0: Based on earlier versions from Serge Hallyn and
> Matt Helsley.
>
> Signed-off-by: Sukadev Bhattiprolu <[EMAIL PROTECTED]>
> ---
> fs/devpts/inode.c | 120
> +++++++++++++++++++++++++++++++++++++++++++++---------
> 1 file changed, 101 insertions(+), 19 deletions(-)
>
> Index: linux-2.6.24/fs/devpts/inode.c
> ===================================================================
> --- linux-2.6.24.orig/fs/devpts/inode.c 2008-02-05 17:30:52.000000000
> -0800
> +++ linux-2.6.24/fs/devpts/inode.c 2008-02-05 19:16:39.000000000 -0800
> @@ -34,7 +34,10 @@ static inline struct idr *current_pts_ns
> }
>
> static struct vfsmount *devpts_mnt;
> -static struct dentry *devpts_root;
> +static inline struct vfsmount *current_pts_ns_mnt(void)
> +{
> + return devpts_mnt;
> +}
>
> static struct {
> int setuid;
> @@ -130,7 +133,7 @@ devpts_fill_super(struct super_block *s,
> inode->i_fop = &simple_dir_operations;
> inode->i_nlink = 2;
>
> - devpts_root = s->s_root = d_alloc_root(inode);
> + s->s_root = d_alloc_root(inode);
> if (s->s_root)
> return 0;
>
> @@ -140,10 +143,53 @@ fail:
> return -ENOMEM;
> }
>
> +/*
> + * We use test and set super-block operations to help determine whether we
> + * need a new super-block for this namespace. get_sb() walks the list of
> + * existing devpts supers, comparing them with the @data ptr. Since we
> + * passed 'current's namespace as the @data pointer we can compare the
> + * namespace pointer in the super-block's 's_fs_info'. If the test is
> + * TRUE then get_sb() returns a new active reference to the super block.
> + * Otherwise, it helps us build an active reference to a new one.
> + */
> +
> +static int devpts_test_sb(struct super_block *sb, void *data)
> +{
> + return sb->s_fs_info == data;
> +}
> +
> +static int devpts_set_sb(struct super_block *sb, void *data)
> +{
> + sb->s_fs_info = data;
> + return set_anon_super(sb, NULL);
> +}
> +
> static int devpts_get_sb(struct file_system_type *fs_type,
> int flags, const char *dev_name, void *data, struct vfsmount *mnt)
> {
> - return get_sb_single(fs_type, flags, data, devpts_fill_super, mnt);
> + struct super_block *sb;
> + int err;
> +
> + /* hereafter we're very simlar to get_sb_nodev */
> + sb = sget(fs_type, devpts_test_sb, devpts_set_sb, data);
> + if (IS_ERR(sb))
> + return PTR_ERR(sb);
> +
> + if (sb->s_root)
> + return simple_set_mnt(mnt, sb);
> +
> + sb->s_flags = flags;
> + err = devpts_fill_super(sb, data, flags & MS_SILENT ? 1 : 0);
> + if (err) {
> + up_write(&sb->s_umount);
> + deactivate_super(sb);
> + return err;
> + }
> +
That stuff becomes very very similar to that in proc :)
Makes sense to consolidate. Maybe...
> + sb->s_flags |= MS_ACTIVE;
> + devpts_mnt = mnt;
> +
> + return simple_set_mnt(mnt, sb);
> }
>
> static struct file_system_type devpts_fs_type = {
> @@ -158,10 +204,9 @@ static struct file_system_type devpts_fs
> * to the System V naming convention
> */
>
> -static struct dentry *get_node(int num)
> +static struct dentry *get_node(struct dentry *root, int num)
> {
> char s[12];
> - struct dentry *root = devpts_root;
> mutex_lock(&root->d_inode->i_mutex);
> return lookup_one_len(s, root, sprintf(s, "%d", num));
> }
> @@ -207,12 +252,28 @@ int devpts_pty_new(struct tty_struct *tt
> struct tty_driver *driver = tty->driver;
> dev_t device = MKDEV(driver->major, driver->minor_start+number);
> struct dentry *dentry;
> - struct inode *inode = new_inode(devpts_mnt->mnt_sb);
> + struct dentry *root;
> + struct vfsmount *mnt;
> + struct inode *inode;
> +
>
> /* 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);
>
> + mnt = current_pts_ns_mnt();
> + if (!mnt)
> + return -ENOSYS;
> + root = mnt->mnt_root;
> +
> + mutex_lock(&root->d_inode->i_mutex);
> + inode = idr_find(current_pts_ns_allocated_ptys(), number);
> + mutex_unlock(&root->d_inode->i_mutex);
> +
> + if (inode && !IS_ERR(inode))
> + return -EEXIST;
> +
> + inode = new_inode(mnt->mnt_sb);
> if (!inode)
> return -ENOMEM;
>
> @@ -222,23 +283,31 @@ int devpts_pty_new(struct tty_struct *tt
> inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
> init_special_inode(inode, S_IFCHR|config.mode, device);
> inode->i_private = tty;
> + idr_replace(current_pts_ns_allocated_ptys(), inode, number);
>
> - dentry = get_node(number);
> + dentry = get_node(root, number);
> if (!IS_ERR(dentry) && !dentry->d_inode) {
> d_instantiate(dentry, inode);
> - fsnotify_create(devpts_root->d_inode, dentry);
> + fsnotify_create(root->d_inode, dentry);
> }
>
> - mutex_unlock(&devpts_root->d_inode->i_mutex);
> + mutex_unlock(&root->d_inode->i_mutex);
>
> return 0;
> }
>
> struct tty_struct *devpts_get_tty(int number)
> {
> - struct dentry *dentry = get_node(number);
> + struct vfsmount *mnt;
> + struct dentry *dentry;
> struct tty_struct *tty;
>
> + mnt = current_pts_ns_mnt();
> + if (!mnt)
> + return NULL;
> +
> + dentry = get_node(mnt->mnt_root, number);
> +
> tty = NULL;
> if (!IS_ERR(dentry)) {
> if (dentry->d_inode)
> @@ -246,14 +315,21 @@ struct tty_struct *devpts_get_tty(int nu
> dput(dentry);
> }
>
> - mutex_unlock(&devpts_root->d_inode->i_mutex);
> + mutex_unlock(&mnt->mnt_root->d_inode->i_mutex);
>
> return tty;
> }
>
> void devpts_pty_kill(int number)
> {
> - struct dentry *dentry = get_node(number);
> + struct dentry *dentry;
> + struct dentry *root;
> + struct vfsmount *mnt;
> +
> + mnt = current_pts_ns_mnt();
> + root = mnt->mnt_root;
> +
> + dentry = get_node(root, number);
>
> if (!IS_ERR(dentry)) {
> struct inode *inode = dentry->d_inode;
> @@ -264,17 +340,23 @@ void devpts_pty_kill(int number)
> }
> dput(dentry);
> }
> - mutex_unlock(&devpts_root->d_inode->i_mutex);
> + 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);
> - }
> + struct vfsmount *mnt;
> + int err;
> +
> + err = register_filesystem(&devpts_fs_type);
> + if (err)
> + return err;
> +
> + mnt = kern_mount_data(&devpts_fs_type, NULL);
> + if (IS_ERR(mnt))
> + err = PTR_ERR(mnt);
> + else
> + devpts_mnt = mnt;
> return err;
> }
>
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