path: root/drivers/tty/pty.c
diff options
authorEric W. Biederman <ebiederm@xmission.com>2016-06-02 10:29:47 -0500
committerLinus Torvalds <torvalds@linux-foundation.org>2016-06-05 10:36:01 -0700
commiteedf265aa003b4781de24cfed40a655a664457e6 (patch)
tree0e37f0a0c6fd15f7528aa3d3bfaec5685f083282 /drivers/tty/pty.c
parent049ec1b5a76d34a6980cccdb7c0baeb4eed7a993 (diff)
devpts: Make each mount of devpts an independent filesystem.
The /dev/ptmx device node is changed to lookup the directory entry "pts" in the same directory as the /dev/ptmx device node was opened in. If there is a "pts" entry and that entry is a devpts filesystem /dev/ptmx uses that filesystem. Otherwise the open of /dev/ptmx fails. The DEVPTS_MULTIPLE_INSTANCES configuration option is removed, so that userspace can now safely depend on each mount of devpts creating a new instance of the filesystem. Each mount of devpts is now a separate and equal filesystem. Reserved ttys are now available to all instances of devpts where the mounter is in the initial mount namespace. A new vfs helper path_pts is introduced that finds a directory entry named "pts" in the directory of the passed in path, and changes the passed in path to point to it. The helper path_pts uses a function path_parent_directory that was factored out of follow_dotdot. In the implementation of devpts: - devpts_mnt is killed as it is no longer meaningful if all mounts of devpts are equal. - pts_sb_from_inode is replaced by just inode->i_sb as all cached inodes in the tty layer are now from the devpts filesystem. - devpts_add_ref is rolled into the new function devpts_ptmx. And the unnecessary inode hold is removed. - devpts_del_ref is renamed devpts_release and reduced to just a deacrivate_super. - The newinstance mount option continues to be accepted but is now ignored. In devpts_fs.h definitions for when !CONFIG_UNIX98_PTYS are removed as they are never used. Documentation/filesystems/devices.txt is updated to describe the current situation. This has been verified to work properly on openwrt-15.05, centos5, centos6, centos7, debian-6.0.2, debian-7.9, debian-8.2, ubuntu-14.04.3, ubuntu-15.10, fedora23, magia-5, mint-17.3, opensuse-42.1, slackware-14.1, gentoo-20151225 (13.0?), archlinux-2015-12-01. With the caveat that on centos6 and on slackware-14.1 that there wind up being two instances of the devpts filesystem mounted on /dev/pts, the lower copy does not end up getting used. Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Greg KH <greg@kroah.com> Cc: Peter Hurley <peter@hurleysoftware.com> Cc: Peter Anvin <hpa@zytor.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Serge Hallyn <serge.hallyn@ubuntu.com> Cc: Willy Tarreau <w@1wt.eu> Cc: Aurelien Jarno <aurelien@aurel32.net> Cc: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> Cc: Jann Horn <jann@thejh.net> Cc: Jiri Slaby <jslaby@suse.com> Cc: Florian Weimer <fw@deneb.enyo.de> Cc: Konstantin Khlebnikov <koct9i@gmail.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/tty/pty.c')
1 files changed, 8 insertions, 7 deletions
diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index dd4b8417e7f4..f856c4544eea 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -668,7 +668,7 @@ static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
fsi = tty->link->driver_data;
devpts_kill_index(fsi, tty->index);
- devpts_put_ref(fsi);
+ devpts_release(fsi);
static const struct tty_operations ptm_unix98_ops = {
@@ -733,10 +733,11 @@ static int ptmx_open(struct inode *inode, struct file *filp)
if (retval)
return retval;
- fsi = devpts_get_ref(inode, filp);
- retval = -ENODEV;
- if (!fsi)
+ fsi = devpts_acquire(filp);
+ if (IS_ERR(fsi)) {
+ retval = PTR_ERR(fsi);
goto out_free_file;
+ }
/* find a device that is not in use. */
@@ -745,7 +746,7 @@ static int ptmx_open(struct inode *inode, struct file *filp)
retval = index;
if (index < 0)
- goto out_put_ref;
+ goto out_put_fsi;
@@ -789,8 +790,8 @@ err_release:
return retval;
devpts_kill_index(fsi, index);
- devpts_put_ref(fsi);
+ devpts_release(fsi);
return retval;

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