From: Sukadev Bhattiprolu <sukadev@xxxxxxxxxx> 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@xxxxxxxxxx> --- 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); } _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers