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authorLinus Torvalds <torvalds@linux-foundation.org>2016-04-17 01:16:07 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2016-04-18 23:43:02 +0300
commit67245ff332064c01b760afa7a384ccda024bfd24 (patch)
treebf77d422b16306ba9fdcf2f7e1f340a409f8a0f6 /include
parent2e572599139d27db3aaf540b0d34f0a4f58dfca1 (diff)
downloadlinux-67245ff332064c01b760afa7a384ccda024bfd24.tar.xz
devpts: clean up interface to pty drivers
This gets rid of the horrible notion of having that struct inode *ptmx_inode be the linchpin of the interface between the pty code and devpts. By de-emphasizing the ptmx inode, a lot of things actually get cleaner, and we will have a much saner way forward. In particular, this will allow us to associate with any particular devpts instance at open-time, and not be artificially tied to one particular ptmx inode. The patch itself is actually fairly straightforward, and apart from some locking and return path cleanups it's pretty mechanical: - the interfaces that devpts exposes all take "struct pts_fs_info *" instead of "struct inode *ptmx_inode" now. NOTE! The "struct pts_fs_info" thing is a completely opaque structure as far as the pty driver is concerned: it's still declared entirely internally to devpts. So the pty code can't actually access it in any way, just pass it as a "cookie" to the devpts code. - the "look up the pts fs info" is now a single clear operation, that also does the reference count increment on the pts superblock. So "devpts_add/del_ref()" is gone, and replaced by a "lookup and get ref" operation (devpts_get_ref(inode)), along with a "put ref" op (devpts_put_ref()). - the pty master "tty->driver_data" field now contains the pts_fs_info, not the ptmx inode. - because we don't care about the ptmx inode any more as some kind of base index, the ref counting can now drop the inode games - it just gets the ref on the superblock. - the pts_fs_info now has a back-pointer to the super_block. That's so that we can easily look up the information we actually need. Although quite often, the pts fs info was actually all we wanted, and not having to look it up based on some magical inode makes things more straightforward. In particular, now that "devpts_get_ref(inode)" operation should really be the *only* place we need to look up what devpts instance we're associated with, and we do it exactly once, at ptmx_open() time. The other side of this is that one ptmx node could now be associated with multiple different devpts instances - you could have a single /dev/ptmx node, and then have multiple mount namespaces with their own instances of devpts mounted on /dev/pts/. And that's all perfectly sane in a model where we just look up the pts instance at open time. This will eventually allow us to get rid of our odd single-vs-multiple pts instance model, but this patch in itself changes no semantics, only an internal binding model. Cc: Eric Biederman <ebiederm@xmission.com> Cc: Peter Anvin <hpa@zytor.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Peter Hurley <peter@hurleysoftware.com> Cc: Serge Hallyn <serge.hallyn@ubuntu.com> Cc: Willy Tarreau <w@1wt.eu> Cc: Aurelien Jarno <aurelien@aurel32.net> Cc: Alan Cox <gnomes@lxorguk.ukuu.org.uk> Cc: Jann Horn <jann@thejh.net> Cc: Greg KH <greg@kroah.com> Cc: Jiri Slaby <jslaby@suse.com> Cc: Florian Weimer <fw@deneb.enyo.de> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/devpts_fs.h34
1 files changed, 10 insertions, 24 deletions
diff --git a/include/linux/devpts_fs.h b/include/linux/devpts_fs.h
index e0ee0b3000b2..358a4db72a27 100644
--- a/include/linux/devpts_fs.h
+++ b/include/linux/devpts_fs.h
@@ -15,38 +15,24 @@
#include <linux/errno.h>
+struct pts_fs_info;
+
#ifdef CONFIG_UNIX98_PTYS
-int devpts_new_index(struct inode *ptmx_inode);
-void devpts_kill_index(struct inode *ptmx_inode, int idx);
-void devpts_add_ref(struct inode *ptmx_inode);
-void devpts_del_ref(struct inode *ptmx_inode);
+/* Look up a pts fs info and get a ref to it */
+struct pts_fs_info *devpts_get_ref(struct inode *, struct file *);
+void devpts_put_ref(struct pts_fs_info *);
+
+int devpts_new_index(struct pts_fs_info *);
+void devpts_kill_index(struct pts_fs_info *, int);
+
/* mknod in devpts */
-struct inode *devpts_pty_new(struct inode *ptmx_inode, dev_t device, int index,
- void *priv);
+struct inode *devpts_pty_new(struct pts_fs_info *, dev_t, int, void *);
/* get private structure */
void *devpts_get_priv(struct inode *pts_inode);
/* unlink */
void devpts_pty_kill(struct inode *inode);
-#else
-
-/* Dummy stubs in the no-pty case */
-static inline int devpts_new_index(struct inode *ptmx_inode) { return -EINVAL; }
-static inline void devpts_kill_index(struct inode *ptmx_inode, int idx) { }
-static inline void devpts_add_ref(struct inode *ptmx_inode) { }
-static inline void devpts_del_ref(struct inode *ptmx_inode) { }
-static inline struct inode *devpts_pty_new(struct inode *ptmx_inode,
- dev_t device, int index, void *priv)
-{
- return ERR_PTR(-EINVAL);
-}
-static inline void *devpts_get_priv(struct inode *pts_inode)
-{
- return NULL;
-}
-static inline void devpts_pty_kill(struct inode *inode) { }
-
#endif