[PATCH 5/7]: Determine pts_ns from a pty's inode.
sukadev at us.ibm.com
sukadev at us.ibm.com
Mon Mar 24 21:25:41 PDT 2008
From: Sukadev Bhattiprolu <sukadev at us.ibm.com>
Subject: [PATCH 5/7]: Determine pts_ns from a pty's inode.
The devpts interfaces currently operate on a specific pts namespace
which they get from the 'current' task.
With implementation of containers and cloning of PTS namespaces, we want
to be able to access PTYs in a child-pts-ns from a parent-pts-ns. For
instance we could bind-mount and pivot-root the child container on
'/vserver/vserver1' and then access the "pts/0" of 'vserver1' using
$ echo foo > /vserver/vserver1/dev/pts/0
The task doing the above 'echo' could be in parent-pts-ns. So we find
the 'pts-ns' of the above file from the inode representing the above
file rather than from the 'current' task.
Note that we need to find and hold a reference to the pts_ns to prevent
the pts_ns from being freed while it is being accessed from 'outside'.
This patch implements, 'pts_ns_from_inode()' which returns the pts_ns
using 'inode->i_sb->s_fs_info'.
Since, the 'inode' information is not visible inside devpts code itself,
this patch modifies the tty driver code to determine the pts_ns and passes
it into devpts.
TODO:
What is the expected behavior when '/dev/tty' or '/dev/ptmx' are
accessed from parent-pts-ns. i.e:
$ echo "foobar" > /vserver/vserver1/dev/tty)
This patch currently ignores the '/vserver/vserver1' part (that
seemed to be the easiest to do :-). So opening /dev/ptmx from
even the child pts-ns will create a pty in the _PARENT_ pts-ns.
Signed-off-by: Sukadev Bhattiprolu <sukadev at us.ibm.com>
---
drivers/char/pty.c | 2 -
drivers/char/tty_io.c | 86 +++++++++++++++++++++++++++++++++++++++-------
fs/devpts/inode.c | 19 +++-------
include/linux/devpts_fs.h | 42 +++++++++++++++++++---
4 files changed, 119 insertions(+), 30 deletions(-)
Index: 2.6.25-rc5-mm1/include/linux/devpts_fs.h
===================================================================
--- 2.6.25-rc5-mm1.orig/include/linux/devpts_fs.h 2008-03-24 20:05:05.000000000 -0700
+++ 2.6.25-rc5-mm1/include/linux/devpts_fs.h 2008-03-24 20:08:33.000000000 -0700
@@ -17,6 +17,7 @@
#include <linux/nsproxy.h>
#include <linux/kref.h>
#include <linux/idr.h>
+#include <linux/fs.h>
struct pts_namespace {
struct kref kref;
@@ -26,12 +27,43 @@ struct pts_namespace {
extern struct pts_namespace init_pts_ns;
+#define DEVPTS_SUPER_MAGIC 0x1cd1
+static inline struct pts_namespace *pts_ns_from_inode(struct inode *inode)
+{
+ /*
+ * Need this bug-on for now to catch any cases in tty_open()
+ * or release_dev() I may have missed.
+ */
+ BUG_ON(inode->i_sb->s_magic != DEVPTS_SUPER_MAGIC);
+
+ /*
+ * If we have a valid inode, we already have a reference to
+ * mount-point. Since there is a single super-block for the
+ * devpts mount, i_sb->s_fs_info cannot go to NULL. So we
+ * should not need a lock here.
+ */
+
+ return (struct pts_namespace *)inode->i_sb->s_fs_info;
+}
+
+static inline struct pts_namespace *current_pts_ns(void)
+{
+ return &init_pts_ns;
+}
+
+
#ifdef CONFIG_UNIX98_PTYS
-int devpts_new_index(void);
-void devpts_kill_index(int idx);
-int devpts_pty_new(struct tty_struct *tty); /* mknod in devpts */
-struct tty_struct *devpts_get_tty(int number); /* get tty structure */
-void devpts_pty_kill(int number); /* unlink */
+int devpts_new_index(struct pts_namespace *pts_ns);
+void devpts_kill_index(struct pts_namespace *pts_ns, int idx);
+
+/* mknod in devpts */
+int devpts_pty_new(struct pts_namespace *pts_ns, struct tty_struct *tty);
+
+/* get tty structure */
+struct tty_struct *devpts_get_tty(struct pts_namespace *pts_ns, int number);
+
+/* unlink */
+void devpts_pty_kill(struct pts_namespace *pts_ns, int number);
static inline void free_pts_ns(struct kref *ns_kref) { }
Index: 2.6.25-rc5-mm1/drivers/char/tty_io.c
===================================================================
--- 2.6.25-rc5-mm1.orig/drivers/char/tty_io.c 2008-03-24 20:04:26.000000000 -0700
+++ 2.6.25-rc5-mm1/drivers/char/tty_io.c 2008-03-24 20:08:15.000000000 -0700
@@ -2064,8 +2064,8 @@ static void tty_line_name(struct tty_dri
* relaxed for the (most common) case of reopening a tty.
*/
-static int init_dev(struct tty_driver *driver, int idx,
- struct tty_struct **ret_tty)
+static int init_dev(struct tty_driver *driver, struct pts_namespace *pts_ns,
+ int idx, struct tty_struct **ret_tty)
{
struct tty_struct *tty, *o_tty;
struct ktermios *tp, **tp_loc, *o_tp, **o_tp_loc;
@@ -2074,7 +2074,7 @@ static int init_dev(struct tty_driver *d
/* check whether we're reopening an existing tty */
if (driver->flags & TTY_DRIVER_DEVPTS_MEM) {
- tty = devpts_get_tty(idx);
+ tty = devpts_get_tty(pts_ns, idx);
/*
* If we don't have a tty here on a slave open, it's because
* the master already started the close process and there's
@@ -2361,6 +2361,43 @@ static void release_tty(struct tty_struc
}
/*
+ * When opening /dev/tty and /dev/ptmx, use the pts-ns of the calling
+ * process. For any other pts device, use the pts-ns, in which the
+ * device was created. This latter case is needed when the pty is
+ * being accessed from a parent container.
+ *
+ * Eg: Suppose the user used bind-mount and pivot-root to mount a
+ * child- container's root on /vs/vs1. Then "/vs/vs1/dev/pts/0"
+ * in parent container and "/dev/pts/0" in child container would
+ * refer to the same device.
+ *
+ * When parent-container opens, "/vs/vs1/dev/pts/0" we find and
+ * grab/drop reference to child container's pts-ns (using @filp).
+ */
+struct pts_namespace *pty_pts_ns(struct tty_driver *driver, struct inode *inode)
+{
+
+ int devpts;
+ int pty_master;
+ dev_t dev;
+ struct pts_namespace *pts_ns;
+
+ devpts = (driver->flags & TTY_DRIVER_DEVPTS_MEM) != 0;
+ pty_master = (driver->type == TTY_DRIVER_TYPE_PTY &&
+ driver->subtype == PTY_TYPE_MASTER);
+
+ pts_ns = NULL;
+ if (devpts) {
+ dev = inode->i_rdev;
+ if (pty_master || dev == MKDEV(TTYAUX_MAJOR, 0))
+ pts_ns = current_pts_ns();
+ else
+ pts_ns = pts_ns_from_inode(inode);
+ }
+ return pts_ns;
+}
+
+/*
* Even releasing the tty structures is a tricky business.. We have
* to be very careful that the structures are all released at the
* same time, as interrupts might otherwise get the wrong pointers.
@@ -2376,10 +2413,12 @@ static void release_dev(struct file *fil
int idx;
char buf[64];
unsigned long flags;
+ struct pts_namespace *pts_ns;
+ struct inode *inode;
+ inode = filp->f_path.dentry->d_inode;
tty = (struct tty_struct *)filp->private_data;
- if (tty_paranoia_check(tty, filp->f_path.dentry->d_inode,
- "release_dev"))
+ if (tty_paranoia_check(tty, inode, "release_dev"))
return;
check_tty_count(tty, "release_dev");
@@ -2391,6 +2430,7 @@ static void release_dev(struct file *fil
tty->driver->subtype == PTY_TYPE_MASTER);
devpts = (tty->driver->flags & TTY_DRIVER_DEVPTS_MEM) != 0;
o_tty = tty->link;
+ pts_ns = pty_pts_ns(tty->driver, inode);
#ifdef TTY_PARANOIA_CHECK
if (idx < 0 || idx >= tty->driver->num) {
@@ -2633,8 +2673,13 @@ static void release_dev(struct file *fil
release_tty(tty, idx);
/* Make this pty number available for reallocation */
- if (devpts)
- devpts_kill_index(idx);
+ if (devpts) {
+ devpts_kill_index(pts_ns, idx);
+ /*
+ * Drop reference got in init_dev()
+ */
+ put_pts_ns(pts_ns);
+ }
}
/**
@@ -2666,6 +2711,7 @@ static int tty_open(struct inode *inode,
int index;
dev_t device = inode->i_rdev;
unsigned short saved_flags = filp->f_flags;
+ struct pts_namespace *pts_ns;
nonseekable_open(inode, filp);
@@ -2715,7 +2761,20 @@ retry_open:
return -ENODEV;
}
got_driver:
- retval = init_dev(driver, index, &tty);
+
+ /*
+ * What pts-ns do we want to use when opening "/dev/tty" ?
+ * Sounds like current_pts_ns(), but what should happen
+ * if parent pts ns does:
+ *
+ * echo foo > /vs/vs1/dev/tty
+ *
+ * (See Serge's setupvs1 script for the /vs/vs1...)
+ */
+ pts_ns = pty_pts_ns(driver, inode);
+ get_pts_ns(pts_ns);
+
+ retval = init_dev(driver, pts_ns, index, &tty);
mutex_unlock(&tty_mutex);
if (retval)
return retval;
@@ -2790,16 +2849,19 @@ static int ptmx_open(struct inode *inode
struct tty_struct *tty;
int retval;
int index;
+ struct pts_namespace *pts_ns;
nonseekable_open(inode, filp);
+ pts_ns = current_pts_ns();
+
/* find a device that is not in use. */
- index = devpts_new_index();
+ index = devpts_new_index(pts_ns);
if (index < 0)
return index;
mutex_lock(&tty_mutex);
- retval = init_dev(ptm_driver, index, &tty);
+ retval = init_dev(ptm_driver, pts_ns, index, &tty);
mutex_unlock(&tty_mutex);
if (retval)
@@ -2809,7 +2871,7 @@ static int ptmx_open(struct inode *inode
filp->private_data = tty;
file_move(filp, &tty->tty_files);
- retval = devpts_pty_new(tty->link);
+ retval = devpts_pty_new(pts_ns, tty->link);
if (retval)
goto out1;
@@ -2821,7 +2883,7 @@ out1:
release_dev(filp);
return retval;
out:
- devpts_kill_index(index);
+ devpts_kill_index(pts_ns, index);
return retval;
}
#endif
Index: 2.6.25-rc5-mm1/fs/devpts/inode.c
===================================================================
--- 2.6.25-rc5-mm1.orig/fs/devpts/inode.c 2008-03-24 20:04:31.000000000 -0700
+++ 2.6.25-rc5-mm1/fs/devpts/inode.c 2008-03-24 20:08:33.000000000 -0700
@@ -23,8 +23,6 @@
#include <linux/fsnotify.h>
#include <linux/seq_file.h>
-#define DEVPTS_SUPER_MAGIC 0x1cd1
-
#define DEVPTS_DEFAULT_MODE 0600
extern int pty_limit; /* Config limit on Unix98 ptys */
@@ -245,11 +243,10 @@ static struct dentry *get_node(struct de
return lookup_one_len(s, root, sprintf(s, "%d", num));
}
-int devpts_new_index(void)
+int devpts_new_index(struct pts_namespace *pts_ns)
{
int index;
int idr_ret;
- struct pts_namespace *pts_ns = &init_pts_ns;
retry:
if (!idr_pre_get(&pts_ns->allocated_ptys, GFP_KERNEL)) {
@@ -274,16 +271,15 @@ retry:
return index;
}
-void devpts_kill_index(int idx)
+void devpts_kill_index(struct pts_namespace *pts_ns, int idx)
{
- struct pts_namespace *pts_ns = &init_pts_ns;
down(&allocated_ptys_lock);
idr_remove(&pts_ns->allocated_ptys, idx);
up(&allocated_ptys_lock);
}
-int devpts_pty_new(struct tty_struct *tty)
+int devpts_pty_new( struct pts_namespace *pts_ns, struct tty_struct *tty)
{
int number = tty->index; /* tty layer puts index from devpts_new_index() in here */
struct tty_driver *driver = tty->driver;
@@ -292,7 +288,6 @@ int devpts_pty_new(struct tty_struct *tt
struct dentry *root;
struct vfsmount *mnt;
struct inode *inode;
- struct pts_namespace *pts_ns = &init_pts_ns;
/* We're supposed to be given the slave end of a pty */
BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY);
@@ -331,13 +326,13 @@ int devpts_pty_new(struct tty_struct *tt
return 0;
}
-struct tty_struct *devpts_get_tty(int number)
+struct tty_struct *devpts_get_tty(struct pts_namespace *pts_ns, int number)
{
struct vfsmount *mnt;
struct dentry *dentry;
struct tty_struct *tty;
- mnt = init_pts_ns.mnt;
+ mnt = pts_ns->mnt;
dentry = get_node(mnt->mnt_root, number);
@@ -353,12 +348,12 @@ struct tty_struct *devpts_get_tty(int nu
return tty;
}
-void devpts_pty_kill(int number)
+void devpts_pty_kill(struct pts_namespace *pts_ns, int number)
{
struct dentry *dentry;
struct dentry *root;
- root = init_pts_ns.mnt->mnt_root;
+ root = pts_ns->mnt->mnt_root;
dentry = get_node(root, number);
Index: 2.6.25-rc5-mm1/drivers/char/pty.c
===================================================================
--- 2.6.25-rc5-mm1.orig/drivers/char/pty.c 2008-03-24 20:02:57.000000000 -0700
+++ 2.6.25-rc5-mm1/drivers/char/pty.c 2008-03-24 20:08:15.000000000 -0700
@@ -59,7 +59,7 @@ static void pty_close(struct tty_struct
set_bit(TTY_OTHER_CLOSED, &tty->flags);
#ifdef CONFIG_UNIX98_PTYS
if (tty->driver == ptm_driver)
- devpts_pty_kill(tty->index);
+ devpts_pty_kill(current_pts_ns(), tty->index);
#endif
tty_vhangup(tty->link);
}
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