From: Sukadev Bhattiprolu <sukadev@xxxxxxxxxx> 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 <sukadev@xxxxxxxxxx> --- 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; + } + + 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; } _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers