1f8f1e2965
/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 instancs of devpts filesystem, during an open of /dev/ptmx we would be unable to determine which instance of the devpts is being accessed. So we move the 'ptmx' node into /dev/pts and use the inode of the 'ptmx' node to identify the superblock and hence the devpts instance. This patch adds ability for the kernel to internally create the [ptmx, c, 5:2] device when mounting devpts filesystem. Since the ptmx node in devpts is new and may surprise some userspace scripts, the default permissions for the new node is 0000. These permissions can be changed either using chmod or by remounting with the new '-o ptmxmode=0666' mount option. Changelog[v5]: - [Serge Hallyn bugfix]: Letting new_inode() assign inode number to ptmx can collide with hand-assigning inode numbers to ptys. So, hand-assign specific inode number to ptmx node also. - [Serge Hallyn]: Maybe safer to grab root dentry mutex while creating ptmx node - [Bugfix with Serge Hallyn] Replace lookup_one_len() in mknod_ptmx() wih d_alloc_name() (lookup during ->get_sb() locks up system). To simplify patchset, fold the ptmx_dentry patch into this. Changelog[v4]: - Change default permissions of pts/ptmx node to 0000. - Move code for ptmxmode under #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES. Changelog[v3]: - Rename ptmx_mode to ptmxmode (for consistency with 'newinstance') Changelog[v2]: - [H. Peter Anvin] Remove mknod() system call support and create the ptmx node internally. Changelog[v1]: - 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. Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> Signed-off-by: Alan Cox <alan@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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| inode.c | ||
| Makefile | ||