From: Sukadev Bhattiprolu <sukadev@xxxxxxxxxx> Subject: [RFC][PATCH 4/6]: Allow mknod of ptmx in devpts /dev/ptmx is closely tied to the devpts filesystem. An open of /dev/ptmx, allocates the next pty index and the associated device shows up in the devpts fs as /dev/pts/n. Wih multiple mounts of devpts filesystem, an open of /dev/ptmx would be unable to determine which instance of the devpts is being accessed. One solution for this would be to create make /dev/ptmx a symlink to /dev/pts/ptmx and create the device node, ptmx, in each instance of devpts. When /dev/ptmx is opened, we can use the inode of /dev/pts/ptmx to identify the specific devpts instance. (This solution has an impact on the 'startup scripts', and that is being discussed separately). This patch merely enables creating the [c, 5:2] (ptmx) device in devpts filesystem. TODO: - Ability to unlink the /dev/pts/ptmx - Remove traces of '/dev/pts/tty' node Changelog: - Earlier version of this patch enabled creating /dev/pts/tty as well. As pointed out by Al Viro and H. Peter Anvin, that is not really necessary. --- fs/devpts/inode.c | 56 +++++++++++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 53 insertions(+), 3 deletions(-) Index: linux-2.6.26-rc8-mm1/fs/devpts/inode.c =================================================================== --- linux-2.6.26-rc8-mm1.orig/fs/devpts/inode.c 2008-08-04 02:08:50.000000000 -0700 +++ linux-2.6.26-rc8-mm1/fs/devpts/inode.c 2008-08-04 17:26:26.000000000 -0700 @@ -141,6 +141,56 @@ static void *new_pts_fs_info(void) } + +static int devpts_mknod(struct inode *dir, struct dentry *dentry, + int mode, dev_t rdev) +{ + int inum; + struct inode *inode; + struct super_block *sb = dir->i_sb; + + if (dentry->d_inode) + return -EEXIST; + + if (!S_ISCHR(mode)) + return -EPERM; + + if (rdev == MKDEV(TTYAUX_MAJOR, 2)) + inum = 2; +#if 0 + else if (rdev == MKDEV(TTYAUX_MAJOR, 0)) + inum = 3; +#endif + else + return -EPERM; + + inode = new_inode(sb); + if (!inode) + return -ENOMEM; + + inode->i_ino = inum; + inode->i_uid = inode->i_gid = 0; + inode->i_blocks = 0; + inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME; + + init_special_inode(inode, mode, rdev); + + d_instantiate(dentry, inode); + /* + * Get a reference to the dentry so the device-nodes persist + * even when there are no active references to them. We use + * kill_litter_super() to remove this entry when unmounting + * devpts. + */ + dget(dentry); + return 0; +} + +const struct inode_operations devpts_dir_inode_operations = { + .lookup = simple_lookup, + .mknod = devpts_mknod, +}; + static int devpts_fill_super(struct super_block *s, void *data, int silent) { @@ -164,7 +214,7 @@ devpts_fill_super(struct super_block *s, 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_op = &devpts_dir_inode_operations; inode->i_fop = &simple_dir_operations; inode->i_nlink = 2; @@ -195,7 +245,7 @@ static void devpts_kill_sb(struct super_ //idr_destroy(&fsi->allocated_ptys); kfree(fsi); - kill_anon_super(sb); + kill_litter_super(sb); } static struct file_system_type devpts_fs_type = { @@ -274,7 +324,7 @@ int devpts_pty_new(struct inode *ptmx_in if (!inode) return -ENOMEM; - inode->i_ino = number+2; + inode->i_ino = number+4; 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; _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers