linux/fs/devpts/inode.c

577 lines
14 KiB
C
Raw Normal View History

/* -*- linux-c -*- --------------------------------------------------------- *
*
* linux/fs/devpts/inode.c
*
* Copyright 1998-2004 H. Peter Anvin -- All Rights Reserved
*
* This file is part of the Linux kernel and is made available under
* the terms of the GNU General Public License, version 2, or at your
* option, any later version, incorporated herein by reference.
*
* ------------------------------------------------------------------------- */
#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/sched.h>
#include <linux/namei.h>
#include <linux/mount.h>
#include <linux/tty.h>
#include <linux/mutex.h>
#include <linux/idr.h>
#include <linux/devpts_fs.h>
#include <linux/parser.h>
#include <linux/fsnotify.h>
#include <linux/seq_file.h>
#define DEVPTS_SUPER_MAGIC 0x1cd1
#define DEVPTS_DEFAULT_MODE 0600
Define mknod_ptmx() /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>
2009-01-02 13:42:02 +00:00
/*
* ptmx is a new node in /dev/pts and will be unused in legacy (single-
* instance) mode. To prevent surprises in user space, set permissions of
* ptmx to 0. Use 'chmod' or remount with '-o ptmxmode' to set meaningful
* permissions.
*/
#define DEVPTS_DEFAULT_PTMX_MODE 0000
#define PTMX_MINOR 2
extern int pty_limit; /* Config limit on Unix98 ptys */
static DEFINE_MUTEX(allocated_ptys_lock);
static struct vfsmount *devpts_mnt;
struct pts_mount_opts {
int setuid;
int setgid;
uid_t uid;
gid_t gid;
umode_t mode;
Define mknod_ptmx() /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>
2009-01-02 13:42:02 +00:00
umode_t ptmxmode;
Enable multiple instances of devpts To support containers, allow multiple instances of devpts filesystem, such that indices of ptys allocated in one instance are independent of ptys allocated in other instances of devpts. But to preserve backward compatibility, enable this support for multiple instances only if: - CONFIG_DEVPTS_MULTIPLE_INSTANCES is set to Y, and - '-o newinstance' mount option is specified while mounting devpts To use multi-instance mount, a container startup script could: $ ns_exec -cm /bin/bash $ umount /dev/pts $ mount -t devpts -o newinstance lxcpts /dev/pts $ mount -o bind /dev/pts/ptmx /dev/ptmx $ /usr/sbin/sshd -p 1234 where 'ns_exec -cm /bin/bash' is calls clone() with CLONE_NEWNS flag and execs /bin/bash in the child process. A pty created by the sshd is not visible in the original mount of /dev/pts. USER-SPACE-IMPACT: - See Documentation/fs/devpts.txt (included in next patch) for user- space impact in multi-instance and mixed-mode operation. TODO: - Update mount(8), pts(4) man pages. Highlight impact of not redirecting /dev/ptmx to /dev/pts/ptmx after a multi-instance mount. Changelog[v6]: - [Dave Hansen] Use new get_init_pts_sb() interface - [Serge Hallyn] Don't bother displaying 'newinstance' in show_options - [Serge Hallyn] Use macros (PARSE_REMOUNT/PARSE_MOUNT) instead of 0/1. - [Serge Hallyn] Check error return from get_sb_single() (now get_init_pts_sb()) - devpts_pty_kill(): don't dput error dentries Changelog[v5]: - Move get_sb_ref() definition to earlier patch - Move usage info to Documentation/filesystems/devpts.txt (next patch) - Make ptmx node even in init_pts_ns, now that default mode is 0000 (defined in earlier patch, enabled here). - Cache ptmx dentry and use to update mode during remount (defined in earlier patch, enabled here). - Bugfix: explicitly ignore newinstance on remount (if newinstance was specified on remount of initial mount, it would be ignored but /proc/mounts would imply that the option was set) Changelog[v4]: - Update patch description to address H. Peter Anvin's comments - Consolidate multi-instance mode code under new config token, CONFIG_DEVPTS_MULTIPLE_INSTANCE. - Move usage-details from patch description to Documentation/fs/devpts.txt Changelog[v3]: - Rename new mount option to 'newinstance' - Create ptmx nodes only in 'newinstance' mounts - Bugfix: parse_mount_options() modifies @data but since we need to parse the @data twice (once in devpts_get_sb() and once during do_remount_sb()), parse a local copy of @data in devpts_get_sb(). (restructured code in devpts_get_sb() to fix this) Changelog[v2]: - Support both single-mount and multiple-mount semantics and provide '-onewmnt' option to select the semantics. 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>
2009-01-02 13:42:27 +00:00
int newinstance;
};
enum {
Enable multiple instances of devpts To support containers, allow multiple instances of devpts filesystem, such that indices of ptys allocated in one instance are independent of ptys allocated in other instances of devpts. But to preserve backward compatibility, enable this support for multiple instances only if: - CONFIG_DEVPTS_MULTIPLE_INSTANCES is set to Y, and - '-o newinstance' mount option is specified while mounting devpts To use multi-instance mount, a container startup script could: $ ns_exec -cm /bin/bash $ umount /dev/pts $ mount -t devpts -o newinstance lxcpts /dev/pts $ mount -o bind /dev/pts/ptmx /dev/ptmx $ /usr/sbin/sshd -p 1234 where 'ns_exec -cm /bin/bash' is calls clone() with CLONE_NEWNS flag and execs /bin/bash in the child process. A pty created by the sshd is not visible in the original mount of /dev/pts. USER-SPACE-IMPACT: - See Documentation/fs/devpts.txt (included in next patch) for user- space impact in multi-instance and mixed-mode operation. TODO: - Update mount(8), pts(4) man pages. Highlight impact of not redirecting /dev/ptmx to /dev/pts/ptmx after a multi-instance mount. Changelog[v6]: - [Dave Hansen] Use new get_init_pts_sb() interface - [Serge Hallyn] Don't bother displaying 'newinstance' in show_options - [Serge Hallyn] Use macros (PARSE_REMOUNT/PARSE_MOUNT) instead of 0/1. - [Serge Hallyn] Check error return from get_sb_single() (now get_init_pts_sb()) - devpts_pty_kill(): don't dput error dentries Changelog[v5]: - Move get_sb_ref() definition to earlier patch - Move usage info to Documentation/filesystems/devpts.txt (next patch) - Make ptmx node even in init_pts_ns, now that default mode is 0000 (defined in earlier patch, enabled here). - Cache ptmx dentry and use to update mode during remount (defined in earlier patch, enabled here). - Bugfix: explicitly ignore newinstance on remount (if newinstance was specified on remount of initial mount, it would be ignored but /proc/mounts would imply that the option was set) Changelog[v4]: - Update patch description to address H. Peter Anvin's comments - Consolidate multi-instance mode code under new config token, CONFIG_DEVPTS_MULTIPLE_INSTANCE. - Move usage-details from patch description to Documentation/fs/devpts.txt Changelog[v3]: - Rename new mount option to 'newinstance' - Create ptmx nodes only in 'newinstance' mounts - Bugfix: parse_mount_options() modifies @data but since we need to parse the @data twice (once in devpts_get_sb() and once during do_remount_sb()), parse a local copy of @data in devpts_get_sb(). (restructured code in devpts_get_sb() to fix this) Changelog[v2]: - Support both single-mount and multiple-mount semantics and provide '-onewmnt' option to select the semantics. 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>
2009-01-02 13:42:27 +00:00
Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_newinstance,
Opt_err
};
static const match_table_t tokens = {
{Opt_uid, "uid=%u"},
{Opt_gid, "gid=%u"},
{Opt_mode, "mode=%o"},
Define mknod_ptmx() /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>
2009-01-02 13:42:02 +00:00
#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
{Opt_ptmxmode, "ptmxmode=%o"},
Enable multiple instances of devpts To support containers, allow multiple instances of devpts filesystem, such that indices of ptys allocated in one instance are independent of ptys allocated in other instances of devpts. But to preserve backward compatibility, enable this support for multiple instances only if: - CONFIG_DEVPTS_MULTIPLE_INSTANCES is set to Y, and - '-o newinstance' mount option is specified while mounting devpts To use multi-instance mount, a container startup script could: $ ns_exec -cm /bin/bash $ umount /dev/pts $ mount -t devpts -o newinstance lxcpts /dev/pts $ mount -o bind /dev/pts/ptmx /dev/ptmx $ /usr/sbin/sshd -p 1234 where 'ns_exec -cm /bin/bash' is calls clone() with CLONE_NEWNS flag and execs /bin/bash in the child process. A pty created by the sshd is not visible in the original mount of /dev/pts. USER-SPACE-IMPACT: - See Documentation/fs/devpts.txt (included in next patch) for user- space impact in multi-instance and mixed-mode operation. TODO: - Update mount(8), pts(4) man pages. Highlight impact of not redirecting /dev/ptmx to /dev/pts/ptmx after a multi-instance mount. Changelog[v6]: - [Dave Hansen] Use new get_init_pts_sb() interface - [Serge Hallyn] Don't bother displaying 'newinstance' in show_options - [Serge Hallyn] Use macros (PARSE_REMOUNT/PARSE_MOUNT) instead of 0/1. - [Serge Hallyn] Check error return from get_sb_single() (now get_init_pts_sb()) - devpts_pty_kill(): don't dput error dentries Changelog[v5]: - Move get_sb_ref() definition to earlier patch - Move usage info to Documentation/filesystems/devpts.txt (next patch) - Make ptmx node even in init_pts_ns, now that default mode is 0000 (defined in earlier patch, enabled here). - Cache ptmx dentry and use to update mode during remount (defined in earlier patch, enabled here). - Bugfix: explicitly ignore newinstance on remount (if newinstance was specified on remount of initial mount, it would be ignored but /proc/mounts would imply that the option was set) Changelog[v4]: - Update patch description to address H. Peter Anvin's comments - Consolidate multi-instance mode code under new config token, CONFIG_DEVPTS_MULTIPLE_INSTANCE. - Move usage-details from patch description to Documentation/fs/devpts.txt Changelog[v3]: - Rename new mount option to 'newinstance' - Create ptmx nodes only in 'newinstance' mounts - Bugfix: parse_mount_options() modifies @data but since we need to parse the @data twice (once in devpts_get_sb() and once during do_remount_sb()), parse a local copy of @data in devpts_get_sb(). (restructured code in devpts_get_sb() to fix this) Changelog[v2]: - Support both single-mount and multiple-mount semantics and provide '-onewmnt' option to select the semantics. 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>
2009-01-02 13:42:27 +00:00
{Opt_newinstance, "newinstance"},
Define mknod_ptmx() /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>
2009-01-02 13:42:02 +00:00
#endif
{Opt_err, NULL}
};
struct pts_fs_info {
struct ida allocated_ptys;
struct pts_mount_opts mount_opts;
Define mknod_ptmx() /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>
2009-01-02 13:42:02 +00:00
struct dentry *ptmx_dentry;
};
static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb)
{
return sb->s_fs_info;
}
static inline struct super_block *pts_sb_from_inode(struct inode *inode)
{
Enable multiple instances of devpts To support containers, allow multiple instances of devpts filesystem, such that indices of ptys allocated in one instance are independent of ptys allocated in other instances of devpts. But to preserve backward compatibility, enable this support for multiple instances only if: - CONFIG_DEVPTS_MULTIPLE_INSTANCES is set to Y, and - '-o newinstance' mount option is specified while mounting devpts To use multi-instance mount, a container startup script could: $ ns_exec -cm /bin/bash $ umount /dev/pts $ mount -t devpts -o newinstance lxcpts /dev/pts $ mount -o bind /dev/pts/ptmx /dev/ptmx $ /usr/sbin/sshd -p 1234 where 'ns_exec -cm /bin/bash' is calls clone() with CLONE_NEWNS flag and execs /bin/bash in the child process. A pty created by the sshd is not visible in the original mount of /dev/pts. USER-SPACE-IMPACT: - See Documentation/fs/devpts.txt (included in next patch) for user- space impact in multi-instance and mixed-mode operation. TODO: - Update mount(8), pts(4) man pages. Highlight impact of not redirecting /dev/ptmx to /dev/pts/ptmx after a multi-instance mount. Changelog[v6]: - [Dave Hansen] Use new get_init_pts_sb() interface - [Serge Hallyn] Don't bother displaying 'newinstance' in show_options - [Serge Hallyn] Use macros (PARSE_REMOUNT/PARSE_MOUNT) instead of 0/1. - [Serge Hallyn] Check error return from get_sb_single() (now get_init_pts_sb()) - devpts_pty_kill(): don't dput error dentries Changelog[v5]: - Move get_sb_ref() definition to earlier patch - Move usage info to Documentation/filesystems/devpts.txt (next patch) - Make ptmx node even in init_pts_ns, now that default mode is 0000 (defined in earlier patch, enabled here). - Cache ptmx dentry and use to update mode during remount (defined in earlier patch, enabled here). - Bugfix: explicitly ignore newinstance on remount (if newinstance was specified on remount of initial mount, it would be ignored but /proc/mounts would imply that the option was set) Changelog[v4]: - Update patch description to address H. Peter Anvin's comments - Consolidate multi-instance mode code under new config token, CONFIG_DEVPTS_MULTIPLE_INSTANCE. - Move usage-details from patch description to Documentation/fs/devpts.txt Changelog[v3]: - Rename new mount option to 'newinstance' - Create ptmx nodes only in 'newinstance' mounts - Bugfix: parse_mount_options() modifies @data but since we need to parse the @data twice (once in devpts_get_sb() and once during do_remount_sb()), parse a local copy of @data in devpts_get_sb(). (restructured code in devpts_get_sb() to fix this) Changelog[v2]: - Support both single-mount and multiple-mount semantics and provide '-onewmnt' option to select the semantics. 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>
2009-01-02 13:42:27 +00:00
#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
if (inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
return inode->i_sb;
Enable multiple instances of devpts To support containers, allow multiple instances of devpts filesystem, such that indices of ptys allocated in one instance are independent of ptys allocated in other instances of devpts. But to preserve backward compatibility, enable this support for multiple instances only if: - CONFIG_DEVPTS_MULTIPLE_INSTANCES is set to Y, and - '-o newinstance' mount option is specified while mounting devpts To use multi-instance mount, a container startup script could: $ ns_exec -cm /bin/bash $ umount /dev/pts $ mount -t devpts -o newinstance lxcpts /dev/pts $ mount -o bind /dev/pts/ptmx /dev/ptmx $ /usr/sbin/sshd -p 1234 where 'ns_exec -cm /bin/bash' is calls clone() with CLONE_NEWNS flag and execs /bin/bash in the child process. A pty created by the sshd is not visible in the original mount of /dev/pts. USER-SPACE-IMPACT: - See Documentation/fs/devpts.txt (included in next patch) for user- space impact in multi-instance and mixed-mode operation. TODO: - Update mount(8), pts(4) man pages. Highlight impact of not redirecting /dev/ptmx to /dev/pts/ptmx after a multi-instance mount. Changelog[v6]: - [Dave Hansen] Use new get_init_pts_sb() interface - [Serge Hallyn] Don't bother displaying 'newinstance' in show_options - [Serge Hallyn] Use macros (PARSE_REMOUNT/PARSE_MOUNT) instead of 0/1. - [Serge Hallyn] Check error return from get_sb_single() (now get_init_pts_sb()) - devpts_pty_kill(): don't dput error dentries Changelog[v5]: - Move get_sb_ref() definition to earlier patch - Move usage info to Documentation/filesystems/devpts.txt (next patch) - Make ptmx node even in init_pts_ns, now that default mode is 0000 (defined in earlier patch, enabled here). - Cache ptmx dentry and use to update mode during remount (defined in earlier patch, enabled here). - Bugfix: explicitly ignore newinstance on remount (if newinstance was specified on remount of initial mount, it would be ignored but /proc/mounts would imply that the option was set) Changelog[v4]: - Update patch description to address H. Peter Anvin's comments - Consolidate multi-instance mode code under new config token, CONFIG_DEVPTS_MULTIPLE_INSTANCE. - Move usage-details from patch description to Documentation/fs/devpts.txt Changelog[v3]: - Rename new mount option to 'newinstance' - Create ptmx nodes only in 'newinstance' mounts - Bugfix: parse_mount_options() modifies @data but since we need to parse the @data twice (once in devpts_get_sb() and once during do_remount_sb()), parse a local copy of @data in devpts_get_sb(). (restructured code in devpts_get_sb() to fix this) Changelog[v2]: - Support both single-mount and multiple-mount semantics and provide '-onewmnt' option to select the semantics. 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>
2009-01-02 13:42:27 +00:00
#endif
return devpts_mnt->mnt_sb;
}
Enable multiple instances of devpts To support containers, allow multiple instances of devpts filesystem, such that indices of ptys allocated in one instance are independent of ptys allocated in other instances of devpts. But to preserve backward compatibility, enable this support for multiple instances only if: - CONFIG_DEVPTS_MULTIPLE_INSTANCES is set to Y, and - '-o newinstance' mount option is specified while mounting devpts To use multi-instance mount, a container startup script could: $ ns_exec -cm /bin/bash $ umount /dev/pts $ mount -t devpts -o newinstance lxcpts /dev/pts $ mount -o bind /dev/pts/ptmx /dev/ptmx $ /usr/sbin/sshd -p 1234 where 'ns_exec -cm /bin/bash' is calls clone() with CLONE_NEWNS flag and execs /bin/bash in the child process. A pty created by the sshd is not visible in the original mount of /dev/pts. USER-SPACE-IMPACT: - See Documentation/fs/devpts.txt (included in next patch) for user- space impact in multi-instance and mixed-mode operation. TODO: - Update mount(8), pts(4) man pages. Highlight impact of not redirecting /dev/ptmx to /dev/pts/ptmx after a multi-instance mount. Changelog[v6]: - [Dave Hansen] Use new get_init_pts_sb() interface - [Serge Hallyn] Don't bother displaying 'newinstance' in show_options - [Serge Hallyn] Use macros (PARSE_REMOUNT/PARSE_MOUNT) instead of 0/1. - [Serge Hallyn] Check error return from get_sb_single() (now get_init_pts_sb()) - devpts_pty_kill(): don't dput error dentries Changelog[v5]: - Move get_sb_ref() definition to earlier patch - Move usage info to Documentation/filesystems/devpts.txt (next patch) - Make ptmx node even in init_pts_ns, now that default mode is 0000 (defined in earlier patch, enabled here). - Cache ptmx dentry and use to update mode during remount (defined in earlier patch, enabled here). - Bugfix: explicitly ignore newinstance on remount (if newinstance was specified on remount of initial mount, it would be ignored but /proc/mounts would imply that the option was set) Changelog[v4]: - Update patch description to address H. Peter Anvin's comments - Consolidate multi-instance mode code under new config token, CONFIG_DEVPTS_MULTIPLE_INSTANCE. - Move usage-details from patch description to Documentation/fs/devpts.txt Changelog[v3]: - Rename new mount option to 'newinstance' - Create ptmx nodes only in 'newinstance' mounts - Bugfix: parse_mount_options() modifies @data but since we need to parse the @data twice (once in devpts_get_sb() and once during do_remount_sb()), parse a local copy of @data in devpts_get_sb(). (restructured code in devpts_get_sb() to fix this) Changelog[v2]: - Support both single-mount and multiple-mount semantics and provide '-onewmnt' option to select the semantics. 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>
2009-01-02 13:42:27 +00:00
#define PARSE_MOUNT 0
#define PARSE_REMOUNT 1
/*
* parse_mount_options():
* Set @opts to mount options specified in @data. If an option is not
* specified in @data, set it to its default value. The exception is
* 'newinstance' option which can only be set/cleared on a mount (i.e.
* cannot be changed during remount).
*
* Note: @data may be NULL (in which case all options are set to default).
*/
Enable multiple instances of devpts To support containers, allow multiple instances of devpts filesystem, such that indices of ptys allocated in one instance are independent of ptys allocated in other instances of devpts. But to preserve backward compatibility, enable this support for multiple instances only if: - CONFIG_DEVPTS_MULTIPLE_INSTANCES is set to Y, and - '-o newinstance' mount option is specified while mounting devpts To use multi-instance mount, a container startup script could: $ ns_exec -cm /bin/bash $ umount /dev/pts $ mount -t devpts -o newinstance lxcpts /dev/pts $ mount -o bind /dev/pts/ptmx /dev/ptmx $ /usr/sbin/sshd -p 1234 where 'ns_exec -cm /bin/bash' is calls clone() with CLONE_NEWNS flag and execs /bin/bash in the child process. A pty created by the sshd is not visible in the original mount of /dev/pts. USER-SPACE-IMPACT: - See Documentation/fs/devpts.txt (included in next patch) for user- space impact in multi-instance and mixed-mode operation. TODO: - Update mount(8), pts(4) man pages. Highlight impact of not redirecting /dev/ptmx to /dev/pts/ptmx after a multi-instance mount. Changelog[v6]: - [Dave Hansen] Use new get_init_pts_sb() interface - [Serge Hallyn] Don't bother displaying 'newinstance' in show_options - [Serge Hallyn] Use macros (PARSE_REMOUNT/PARSE_MOUNT) instead of 0/1. - [Serge Hallyn] Check error return from get_sb_single() (now get_init_pts_sb()) - devpts_pty_kill(): don't dput error dentries Changelog[v5]: - Move get_sb_ref() definition to earlier patch - Move usage info to Documentation/filesystems/devpts.txt (next patch) - Make ptmx node even in init_pts_ns, now that default mode is 0000 (defined in earlier patch, enabled here). - Cache ptmx dentry and use to update mode during remount (defined in earlier patch, enabled here). - Bugfix: explicitly ignore newinstance on remount (if newinstance was specified on remount of initial mount, it would be ignored but /proc/mounts would imply that the option was set) Changelog[v4]: - Update patch description to address H. Peter Anvin's comments - Consolidate multi-instance mode code under new config token, CONFIG_DEVPTS_MULTIPLE_INSTANCE. - Move usage-details from patch description to Documentation/fs/devpts.txt Changelog[v3]: - Rename new mount option to 'newinstance' - Create ptmx nodes only in 'newinstance' mounts - Bugfix: parse_mount_options() modifies @data but since we need to parse the @data twice (once in devpts_get_sb() and once during do_remount_sb()), parse a local copy of @data in devpts_get_sb(). (restructured code in devpts_get_sb() to fix this) Changelog[v2]: - Support both single-mount and multiple-mount semantics and provide '-onewmnt' option to select the semantics. 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>
2009-01-02 13:42:27 +00:00
static int parse_mount_options(char *data, int op, struct pts_mount_opts *opts)
{
char *p;
opts->setuid = 0;
opts->setgid = 0;
opts->uid = 0;
opts->gid = 0;
opts->mode = DEVPTS_DEFAULT_MODE;
Define mknod_ptmx() /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>
2009-01-02 13:42:02 +00:00
opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
Enable multiple instances of devpts To support containers, allow multiple instances of devpts filesystem, such that indices of ptys allocated in one instance are independent of ptys allocated in other instances of devpts. But to preserve backward compatibility, enable this support for multiple instances only if: - CONFIG_DEVPTS_MULTIPLE_INSTANCES is set to Y, and - '-o newinstance' mount option is specified while mounting devpts To use multi-instance mount, a container startup script could: $ ns_exec -cm /bin/bash $ umount /dev/pts $ mount -t devpts -o newinstance lxcpts /dev/pts $ mount -o bind /dev/pts/ptmx /dev/ptmx $ /usr/sbin/sshd -p 1234 where 'ns_exec -cm /bin/bash' is calls clone() with CLONE_NEWNS flag and execs /bin/bash in the child process. A pty created by the sshd is not visible in the original mount of /dev/pts. USER-SPACE-IMPACT: - See Documentation/fs/devpts.txt (included in next patch) for user- space impact in multi-instance and mixed-mode operation. TODO: - Update mount(8), pts(4) man pages. Highlight impact of not redirecting /dev/ptmx to /dev/pts/ptmx after a multi-instance mount. Changelog[v6]: - [Dave Hansen] Use new get_init_pts_sb() interface - [Serge Hallyn] Don't bother displaying 'newinstance' in show_options - [Serge Hallyn] Use macros (PARSE_REMOUNT/PARSE_MOUNT) instead of 0/1. - [Serge Hallyn] Check error return from get_sb_single() (now get_init_pts_sb()) - devpts_pty_kill(): don't dput error dentries Changelog[v5]: - Move get_sb_ref() definition to earlier patch - Move usage info to Documentation/filesystems/devpts.txt (next patch) - Make ptmx node even in init_pts_ns, now that default mode is 0000 (defined in earlier patch, enabled here). - Cache ptmx dentry and use to update mode during remount (defined in earlier patch, enabled here). - Bugfix: explicitly ignore newinstance on remount (if newinstance was specified on remount of initial mount, it would be ignored but /proc/mounts would imply that the option was set) Changelog[v4]: - Update patch description to address H. Peter Anvin's comments - Consolidate multi-instance mode code under new config token, CONFIG_DEVPTS_MULTIPLE_INSTANCE. - Move usage-details from patch description to Documentation/fs/devpts.txt Changelog[v3]: - Rename new mount option to 'newinstance' - Create ptmx nodes only in 'newinstance' mounts - Bugfix: parse_mount_options() modifies @data but since we need to parse the @data twice (once in devpts_get_sb() and once during do_remount_sb()), parse a local copy of @data in devpts_get_sb(). (restructured code in devpts_get_sb() to fix this) Changelog[v2]: - Support both single-mount and multiple-mount semantics and provide '-onewmnt' option to select the semantics. 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>
2009-01-02 13:42:27 +00:00
/* newinstance makes sense only on initial mount */
if (op == PARSE_MOUNT)
opts->newinstance = 0;
while ((p = strsep(&data, ",")) != NULL) {
substring_t args[MAX_OPT_ARGS];
int token;
int option;
if (!*p)
continue;
token = match_token(p, tokens, args);
switch (token) {
case Opt_uid:
if (match_int(&args[0], &option))
return -EINVAL;
opts->uid = option;
opts->setuid = 1;
break;
case Opt_gid:
if (match_int(&args[0], &option))
return -EINVAL;
opts->gid = option;
opts->setgid = 1;
break;
case Opt_mode:
if (match_octal(&args[0], &option))
return -EINVAL;
opts->mode = option & S_IALLUGO;
break;
Define mknod_ptmx() /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>
2009-01-02 13:42:02 +00:00
#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
case Opt_ptmxmode:
if (match_octal(&args[0], &option))
return -EINVAL;
opts->ptmxmode = option & S_IALLUGO;
break;
Enable multiple instances of devpts To support containers, allow multiple instances of devpts filesystem, such that indices of ptys allocated in one instance are independent of ptys allocated in other instances of devpts. But to preserve backward compatibility, enable this support for multiple instances only if: - CONFIG_DEVPTS_MULTIPLE_INSTANCES is set to Y, and - '-o newinstance' mount option is specified while mounting devpts To use multi-instance mount, a container startup script could: $ ns_exec -cm /bin/bash $ umount /dev/pts $ mount -t devpts -o newinstance lxcpts /dev/pts $ mount -o bind /dev/pts/ptmx /dev/ptmx $ /usr/sbin/sshd -p 1234 where 'ns_exec -cm /bin/bash' is calls clone() with CLONE_NEWNS flag and execs /bin/bash in the child process. A pty created by the sshd is not visible in the original mount of /dev/pts. USER-SPACE-IMPACT: - See Documentation/fs/devpts.txt (included in next patch) for user- space impact in multi-instance and mixed-mode operation. TODO: - Update mount(8), pts(4) man pages. Highlight impact of not redirecting /dev/ptmx to /dev/pts/ptmx after a multi-instance mount. Changelog[v6]: - [Dave Hansen] Use new get_init_pts_sb() interface - [Serge Hallyn] Don't bother displaying 'newinstance' in show_options - [Serge Hallyn] Use macros (PARSE_REMOUNT/PARSE_MOUNT) instead of 0/1. - [Serge Hallyn] Check error return from get_sb_single() (now get_init_pts_sb()) - devpts_pty_kill(): don't dput error dentries Changelog[v5]: - Move get_sb_ref() definition to earlier patch - Move usage info to Documentation/filesystems/devpts.txt (next patch) - Make ptmx node even in init_pts_ns, now that default mode is 0000 (defined in earlier patch, enabled here). - Cache ptmx dentry and use to update mode during remount (defined in earlier patch, enabled here). - Bugfix: explicitly ignore newinstance on remount (if newinstance was specified on remount of initial mount, it would be ignored but /proc/mounts would imply that the option was set) Changelog[v4]: - Update patch description to address H. Peter Anvin's comments - Consolidate multi-instance mode code under new config token, CONFIG_DEVPTS_MULTIPLE_INSTANCE. - Move usage-details from patch description to Documentation/fs/devpts.txt Changelog[v3]: - Rename new mount option to 'newinstance' - Create ptmx nodes only in 'newinstance' mounts - Bugfix: parse_mount_options() modifies @data but since we need to parse the @data twice (once in devpts_get_sb() and once during do_remount_sb()), parse a local copy of @data in devpts_get_sb(). (restructured code in devpts_get_sb() to fix this) Changelog[v2]: - Support both single-mount and multiple-mount semantics and provide '-onewmnt' option to select the semantics. 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>
2009-01-02 13:42:27 +00:00
case Opt_newinstance:
/* newinstance makes sense only on initial mount */
if (op == PARSE_MOUNT)
opts->newinstance = 1;
break;
Define mknod_ptmx() /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>
2009-01-02 13:42:02 +00:00
#endif
default:
printk(KERN_ERR "devpts: called with bogus options\n");
return -EINVAL;
}
}
return 0;
}
Define mknod_ptmx() /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>
2009-01-02 13:42:02 +00:00
#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
static int mknod_ptmx(struct super_block *sb)
{
int mode;
int rc = -ENOMEM;
struct dentry *dentry;
struct inode *inode;
struct dentry *root = sb->s_root;
struct pts_fs_info *fsi = DEVPTS_SB(sb);
struct pts_mount_opts *opts = &fsi->mount_opts;
mutex_lock(&root->d_inode->i_mutex);
/* If we have already created ptmx node, return */
if (fsi->ptmx_dentry) {
rc = 0;
goto out;
}
dentry = d_alloc_name(root, "ptmx");
if (!dentry) {
printk(KERN_NOTICE "Unable to alloc dentry for ptmx node\n");
goto out;
}
/*
* Create a new 'ptmx' node in this mount of devpts.
*/
inode = new_inode(sb);
if (!inode) {
printk(KERN_ERR "Unable to alloc inode for ptmx node\n");
dput(dentry);
goto out;
}
inode->i_ino = 2;
inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
mode = S_IFCHR|opts->ptmxmode;
init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2));
d_add(dentry, inode);
fsi->ptmx_dentry = dentry;
rc = 0;
out:
mutex_unlock(&root->d_inode->i_mutex);
return rc;
}
static void update_ptmx_mode(struct pts_fs_info *fsi)
{
struct inode *inode;
if (fsi->ptmx_dentry) {
inode = fsi->ptmx_dentry->d_inode;
inode->i_mode = S_IFCHR|fsi->mount_opts.ptmxmode;
}
}
#else
static inline void update_ptmx_mode(struct pts_fs_info *fsi)
{
return;
}
#endif
static int devpts_remount(struct super_block *sb, int *flags, char *data)
{
Define mknod_ptmx() /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>
2009-01-02 13:42:02 +00:00
int err;
struct pts_fs_info *fsi = DEVPTS_SB(sb);
struct pts_mount_opts *opts = &fsi->mount_opts;
Enable multiple instances of devpts To support containers, allow multiple instances of devpts filesystem, such that indices of ptys allocated in one instance are independent of ptys allocated in other instances of devpts. But to preserve backward compatibility, enable this support for multiple instances only if: - CONFIG_DEVPTS_MULTIPLE_INSTANCES is set to Y, and - '-o newinstance' mount option is specified while mounting devpts To use multi-instance mount, a container startup script could: $ ns_exec -cm /bin/bash $ umount /dev/pts $ mount -t devpts -o newinstance lxcpts /dev/pts $ mount -o bind /dev/pts/ptmx /dev/ptmx $ /usr/sbin/sshd -p 1234 where 'ns_exec -cm /bin/bash' is calls clone() with CLONE_NEWNS flag and execs /bin/bash in the child process. A pty created by the sshd is not visible in the original mount of /dev/pts. USER-SPACE-IMPACT: - See Documentation/fs/devpts.txt (included in next patch) for user- space impact in multi-instance and mixed-mode operation. TODO: - Update mount(8), pts(4) man pages. Highlight impact of not redirecting /dev/ptmx to /dev/pts/ptmx after a multi-instance mount. Changelog[v6]: - [Dave Hansen] Use new get_init_pts_sb() interface - [Serge Hallyn] Don't bother displaying 'newinstance' in show_options - [Serge Hallyn] Use macros (PARSE_REMOUNT/PARSE_MOUNT) instead of 0/1. - [Serge Hallyn] Check error return from get_sb_single() (now get_init_pts_sb()) - devpts_pty_kill(): don't dput error dentries Changelog[v5]: - Move get_sb_ref() definition to earlier patch - Move usage info to Documentation/filesystems/devpts.txt (next patch) - Make ptmx node even in init_pts_ns, now that default mode is 0000 (defined in earlier patch, enabled here). - Cache ptmx dentry and use to update mode during remount (defined in earlier patch, enabled here). - Bugfix: explicitly ignore newinstance on remount (if newinstance was specified on remount of initial mount, it would be ignored but /proc/mounts would imply that the option was set) Changelog[v4]: - Update patch description to address H. Peter Anvin's comments - Consolidate multi-instance mode code under new config token, CONFIG_DEVPTS_MULTIPLE_INSTANCE. - Move usage-details from patch description to Documentation/fs/devpts.txt Changelog[v3]: - Rename new mount option to 'newinstance' - Create ptmx nodes only in 'newinstance' mounts - Bugfix: parse_mount_options() modifies @data but since we need to parse the @data twice (once in devpts_get_sb() and once during do_remount_sb()), parse a local copy of @data in devpts_get_sb(). (restructured code in devpts_get_sb() to fix this) Changelog[v2]: - Support both single-mount and multiple-mount semantics and provide '-onewmnt' option to select the semantics. 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>
2009-01-02 13:42:27 +00:00
err = parse_mount_options(data, PARSE_REMOUNT, opts);
Define mknod_ptmx() /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>
2009-01-02 13:42:02 +00:00
/*
* parse_mount_options() restores options to default values
* before parsing and may have changed ptmxmode. So, update the
* mode in the inode too. Bogus options don't fail the remount,
* so do this even on error return.
*/
update_ptmx_mode(fsi);
return err;
}
static int devpts_show_options(struct seq_file *seq, struct vfsmount *vfs)
{
struct pts_fs_info *fsi = DEVPTS_SB(vfs->mnt_sb);
struct pts_mount_opts *opts = &fsi->mount_opts;
if (opts->setuid)
seq_printf(seq, ",uid=%u", opts->uid);
if (opts->setgid)
seq_printf(seq, ",gid=%u", opts->gid);
seq_printf(seq, ",mode=%03o", opts->mode);
Define mknod_ptmx() /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>
2009-01-02 13:42:02 +00:00
#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode);
#endif
return 0;
}
static const struct super_operations devpts_sops = {
.statfs = simple_statfs,
.remount_fs = devpts_remount,
.show_options = devpts_show_options,
};
static void *new_pts_fs_info(void)
{
struct pts_fs_info *fsi;
fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL);
if (!fsi)
return NULL;
ida_init(&fsi->allocated_ptys);
fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE;
Define mknod_ptmx() /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>
2009-01-02 13:42:02 +00:00
fsi->mount_opts.ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
return fsi;
}
static int
devpts_fill_super(struct super_block *s, void *data, int silent)
{
Define mknod_ptmx() /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>
2009-01-02 13:42:02 +00:00
struct inode *inode;
s->s_blocksize = 1024;
s->s_blocksize_bits = 10;
s->s_magic = DEVPTS_SUPER_MAGIC;
s->s_op = &devpts_sops;
s->s_time_gran = 1;
s->s_fs_info = new_pts_fs_info();
if (!s->s_fs_info)
goto fail;
inode = new_inode(s);
if (!inode)
goto free_fsi;
inode->i_ino = 1;
inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR;
inode->i_op = &simple_dir_inode_operations;
inode->i_fop = &simple_dir_operations;
inode->i_nlink = 2;
s->s_root = d_alloc_root(inode);
if (s->s_root)
return 0;
Define mknod_ptmx() /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>
2009-01-02 13:42:02 +00:00
printk(KERN_ERR "devpts: get root dentry failed\n");
iput(inode);
free_fsi:
kfree(s->s_fs_info);
fail:
return -ENOMEM;
}
#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
static int compare_init_pts_sb(struct super_block *s, void *p)
{
if (devpts_mnt)
return devpts_mnt->mnt_sb == s;
Enable multiple instances of devpts To support containers, allow multiple instances of devpts filesystem, such that indices of ptys allocated in one instance are independent of ptys allocated in other instances of devpts. But to preserve backward compatibility, enable this support for multiple instances only if: - CONFIG_DEVPTS_MULTIPLE_INSTANCES is set to Y, and - '-o newinstance' mount option is specified while mounting devpts To use multi-instance mount, a container startup script could: $ ns_exec -cm /bin/bash $ umount /dev/pts $ mount -t devpts -o newinstance lxcpts /dev/pts $ mount -o bind /dev/pts/ptmx /dev/ptmx $ /usr/sbin/sshd -p 1234 where 'ns_exec -cm /bin/bash' is calls clone() with CLONE_NEWNS flag and execs /bin/bash in the child process. A pty created by the sshd is not visible in the original mount of /dev/pts. USER-SPACE-IMPACT: - See Documentation/fs/devpts.txt (included in next patch) for user- space impact in multi-instance and mixed-mode operation. TODO: - Update mount(8), pts(4) man pages. Highlight impact of not redirecting /dev/ptmx to /dev/pts/ptmx after a multi-instance mount. Changelog[v6]: - [Dave Hansen] Use new get_init_pts_sb() interface - [Serge Hallyn] Don't bother displaying 'newinstance' in show_options - [Serge Hallyn] Use macros (PARSE_REMOUNT/PARSE_MOUNT) instead of 0/1. - [Serge Hallyn] Check error return from get_sb_single() (now get_init_pts_sb()) - devpts_pty_kill(): don't dput error dentries Changelog[v5]: - Move get_sb_ref() definition to earlier patch - Move usage info to Documentation/filesystems/devpts.txt (next patch) - Make ptmx node even in init_pts_ns, now that default mode is 0000 (defined in earlier patch, enabled here). - Cache ptmx dentry and use to update mode during remount (defined in earlier patch, enabled here). - Bugfix: explicitly ignore newinstance on remount (if newinstance was specified on remount of initial mount, it would be ignored but /proc/mounts would imply that the option was set) Changelog[v4]: - Update patch description to address H. Peter Anvin's comments - Consolidate multi-instance mode code under new config token, CONFIG_DEVPTS_MULTIPLE_INSTANCE. - Move usage-details from patch description to Documentation/fs/devpts.txt Changelog[v3]: - Rename new mount option to 'newinstance' - Create ptmx nodes only in 'newinstance' mounts - Bugfix: parse_mount_options() modifies @data but since we need to parse the @data twice (once in devpts_get_sb() and once during do_remount_sb()), parse a local copy of @data in devpts_get_sb(). (restructured code in devpts_get_sb() to fix this) Changelog[v2]: - Support both single-mount and multiple-mount semantics and provide '-onewmnt' option to select the semantics. 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>
2009-01-02 13:42:27 +00:00
return 0;
}
/*
* devpts_get_sb()
*
* If the '-o newinstance' mount option was specified, mount a new
* (private) instance of devpts. PTYs created in this instance are
* independent of the PTYs in other devpts instances.
*
* If the '-o newinstance' option was not specified, mount/remount the
* initial kernel mount of devpts. This type of mount gives the
* legacy, single-instance semantics.
*
* The 'newinstance' option is needed to support multiple namespace
* semantics in devpts while preserving backward compatibility of the
* current 'single-namespace' semantics. i.e all mounts of devpts
* without the 'newinstance' mount option should bind to the initial
* kernel mount, like get_sb_single().
*
* Mounts with 'newinstance' option create a new, private namespace.
*
* NOTE:
*
* For single-mount semantics, devpts cannot use get_sb_single(),
* because get_sb_single()/sget() find and use the super-block from
* the most recent mount of devpts. But that recent mount may be a
* 'newinstance' mount and get_sb_single() would pick the newinstance
* super-block instead of the initial super-block.
*/
[PATCH] VFS: Permit filesystem to override root dentry on mount Extend the get_sb() filesystem operation to take an extra argument that permits the VFS to pass in the target vfsmount that defines the mountpoint. The filesystem is then required to manually set the superblock and root dentry pointers. For most filesystems, this should be done with simple_set_mnt() which will set the superblock pointer and then set the root dentry to the superblock's s_root (as per the old default behaviour). The get_sb() op now returns an integer as there's now no need to return the superblock pointer. This patch permits a superblock to be implicitly shared amongst several mount points, such as can be done with NFS to avoid potential inode aliasing. In such a case, simple_set_mnt() would not be called, and instead the mnt_root and mnt_sb would be set directly. The patch also makes the following changes: (*) the get_sb_*() convenience functions in the core kernel now take a vfsmount pointer argument and return an integer, so most filesystems have to change very little. (*) If one of the convenience function is not used, then get_sb() should normally call simple_set_mnt() to instantiate the vfsmount. This will always return 0, and so can be tail-called from get_sb(). (*) generic_shutdown_super() now calls shrink_dcache_sb() to clean up the dcache upon superblock destruction rather than shrink_dcache_anon(). This is required because the superblock may now have multiple trees that aren't actually bound to s_root, but that still need to be cleaned up. The currently called functions assume that the whole tree is rooted at s_root, and that anonymous dentries are not the roots of trees which results in dentries being left unculled. However, with the way NFS superblock sharing are currently set to be implemented, these assumptions are violated: the root of the filesystem is simply a dummy dentry and inode (the real inode for '/' may well be inaccessible), and all the vfsmounts are rooted on anonymous[*] dentries with child trees. [*] Anonymous until discovered from another tree. (*) The documentation has been adjusted, including the additional bit of changing ext2_* into foo_* in the documentation. [akpm@osdl.org: convert ipath_fs, do other stuff] Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Nathan Scott <nathans@sgi.com> Cc: Roland Dreier <rolandd@cisco.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23 09:02:57 +00:00
static int devpts_get_sb(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data, struct vfsmount *mnt)
{
int error;
struct pts_mount_opts opts;
struct super_block *s;
Enable multiple instances of devpts To support containers, allow multiple instances of devpts filesystem, such that indices of ptys allocated in one instance are independent of ptys allocated in other instances of devpts. But to preserve backward compatibility, enable this support for multiple instances only if: - CONFIG_DEVPTS_MULTIPLE_INSTANCES is set to Y, and - '-o newinstance' mount option is specified while mounting devpts To use multi-instance mount, a container startup script could: $ ns_exec -cm /bin/bash $ umount /dev/pts $ mount -t devpts -o newinstance lxcpts /dev/pts $ mount -o bind /dev/pts/ptmx /dev/ptmx $ /usr/sbin/sshd -p 1234 where 'ns_exec -cm /bin/bash' is calls clone() with CLONE_NEWNS flag and execs /bin/bash in the child process. A pty created by the sshd is not visible in the original mount of /dev/pts. USER-SPACE-IMPACT: - See Documentation/fs/devpts.txt (included in next patch) for user- space impact in multi-instance and mixed-mode operation. TODO: - Update mount(8), pts(4) man pages. Highlight impact of not redirecting /dev/ptmx to /dev/pts/ptmx after a multi-instance mount. Changelog[v6]: - [Dave Hansen] Use new get_init_pts_sb() interface - [Serge Hallyn] Don't bother displaying 'newinstance' in show_options - [Serge Hallyn] Use macros (PARSE_REMOUNT/PARSE_MOUNT) instead of 0/1. - [Serge Hallyn] Check error return from get_sb_single() (now get_init_pts_sb()) - devpts_pty_kill(): don't dput error dentries Changelog[v5]: - Move get_sb_ref() definition to earlier patch - Move usage info to Documentation/filesystems/devpts.txt (next patch) - Make ptmx node even in init_pts_ns, now that default mode is 0000 (defined in earlier patch, enabled here). - Cache ptmx dentry and use to update mode during remount (defined in earlier patch, enabled here). - Bugfix: explicitly ignore newinstance on remount (if newinstance was specified on remount of initial mount, it would be ignored but /proc/mounts would imply that the option was set) Changelog[v4]: - Update patch description to address H. Peter Anvin's comments - Consolidate multi-instance mode code under new config token, CONFIG_DEVPTS_MULTIPLE_INSTANCE. - Move usage-details from patch description to Documentation/fs/devpts.txt Changelog[v3]: - Rename new mount option to 'newinstance' - Create ptmx nodes only in 'newinstance' mounts - Bugfix: parse_mount_options() modifies @data but since we need to parse the @data twice (once in devpts_get_sb() and once during do_remount_sb()), parse a local copy of @data in devpts_get_sb(). (restructured code in devpts_get_sb() to fix this) Changelog[v2]: - Support both single-mount and multiple-mount semantics and provide '-onewmnt' option to select the semantics. 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>
2009-01-02 13:42:27 +00:00
error = parse_mount_options(data, PARSE_MOUNT, &opts);
if (error)
return error;
Enable multiple instances of devpts To support containers, allow multiple instances of devpts filesystem, such that indices of ptys allocated in one instance are independent of ptys allocated in other instances of devpts. But to preserve backward compatibility, enable this support for multiple instances only if: - CONFIG_DEVPTS_MULTIPLE_INSTANCES is set to Y, and - '-o newinstance' mount option is specified while mounting devpts To use multi-instance mount, a container startup script could: $ ns_exec -cm /bin/bash $ umount /dev/pts $ mount -t devpts -o newinstance lxcpts /dev/pts $ mount -o bind /dev/pts/ptmx /dev/ptmx $ /usr/sbin/sshd -p 1234 where 'ns_exec -cm /bin/bash' is calls clone() with CLONE_NEWNS flag and execs /bin/bash in the child process. A pty created by the sshd is not visible in the original mount of /dev/pts. USER-SPACE-IMPACT: - See Documentation/fs/devpts.txt (included in next patch) for user- space impact in multi-instance and mixed-mode operation. TODO: - Update mount(8), pts(4) man pages. Highlight impact of not redirecting /dev/ptmx to /dev/pts/ptmx after a multi-instance mount. Changelog[v6]: - [Dave Hansen] Use new get_init_pts_sb() interface - [Serge Hallyn] Don't bother displaying 'newinstance' in show_options - [Serge Hallyn] Use macros (PARSE_REMOUNT/PARSE_MOUNT) instead of 0/1. - [Serge Hallyn] Check error return from get_sb_single() (now get_init_pts_sb()) - devpts_pty_kill(): don't dput error dentries Changelog[v5]: - Move get_sb_ref() definition to earlier patch - Move usage info to Documentation/filesystems/devpts.txt (next patch) - Make ptmx node even in init_pts_ns, now that default mode is 0000 (defined in earlier patch, enabled here). - Cache ptmx dentry and use to update mode during remount (defined in earlier patch, enabled here). - Bugfix: explicitly ignore newinstance on remount (if newinstance was specified on remount of initial mount, it would be ignored but /proc/mounts would imply that the option was set) Changelog[v4]: - Update patch description to address H. Peter Anvin's comments - Consolidate multi-instance mode code under new config token, CONFIG_DEVPTS_MULTIPLE_INSTANCE. - Move usage-details from patch description to Documentation/fs/devpts.txt Changelog[v3]: - Rename new mount option to 'newinstance' - Create ptmx nodes only in 'newinstance' mounts - Bugfix: parse_mount_options() modifies @data but since we need to parse the @data twice (once in devpts_get_sb() and once during do_remount_sb()), parse a local copy of @data in devpts_get_sb(). (restructured code in devpts_get_sb() to fix this) Changelog[v2]: - Support both single-mount and multiple-mount semantics and provide '-onewmnt' option to select the semantics. 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>
2009-01-02 13:42:27 +00:00
if (opts.newinstance)
s = sget(fs_type, NULL, set_anon_super, NULL);
else
s = sget(fs_type, compare_init_pts_sb, set_anon_super, NULL);
if (IS_ERR(s))
return PTR_ERR(s);
if (!s->s_root) {
s->s_flags = flags;
error = devpts_fill_super(s, data, flags & MS_SILENT ? 1 : 0);
if (error)
goto out_undo_sget;
s->s_flags |= MS_ACTIVE;
}
simple_set_mnt(mnt, s);
memcpy(&(DEVPTS_SB(s))->mount_opts, &opts, sizeof(opts));
error = mknod_ptmx(s);
if (error)
goto out_dput;
return 0;
out_dput:
dput(s->s_root); /* undo dget() in simple_set_mnt() */
out_undo_sget:
deactivate_locked_super(s);
return error;
}
Enable multiple instances of devpts To support containers, allow multiple instances of devpts filesystem, such that indices of ptys allocated in one instance are independent of ptys allocated in other instances of devpts. But to preserve backward compatibility, enable this support for multiple instances only if: - CONFIG_DEVPTS_MULTIPLE_INSTANCES is set to Y, and - '-o newinstance' mount option is specified while mounting devpts To use multi-instance mount, a container startup script could: $ ns_exec -cm /bin/bash $ umount /dev/pts $ mount -t devpts -o newinstance lxcpts /dev/pts $ mount -o bind /dev/pts/ptmx /dev/ptmx $ /usr/sbin/sshd -p 1234 where 'ns_exec -cm /bin/bash' is calls clone() with CLONE_NEWNS flag and execs /bin/bash in the child process. A pty created by the sshd is not visible in the original mount of /dev/pts. USER-SPACE-IMPACT: - See Documentation/fs/devpts.txt (included in next patch) for user- space impact in multi-instance and mixed-mode operation. TODO: - Update mount(8), pts(4) man pages. Highlight impact of not redirecting /dev/ptmx to /dev/pts/ptmx after a multi-instance mount. Changelog[v6]: - [Dave Hansen] Use new get_init_pts_sb() interface - [Serge Hallyn] Don't bother displaying 'newinstance' in show_options - [Serge Hallyn] Use macros (PARSE_REMOUNT/PARSE_MOUNT) instead of 0/1. - [Serge Hallyn] Check error return from get_sb_single() (now get_init_pts_sb()) - devpts_pty_kill(): don't dput error dentries Changelog[v5]: - Move get_sb_ref() definition to earlier patch - Move usage info to Documentation/filesystems/devpts.txt (next patch) - Make ptmx node even in init_pts_ns, now that default mode is 0000 (defined in earlier patch, enabled here). - Cache ptmx dentry and use to update mode during remount (defined in earlier patch, enabled here). - Bugfix: explicitly ignore newinstance on remount (if newinstance was specified on remount of initial mount, it would be ignored but /proc/mounts would imply that the option was set) Changelog[v4]: - Update patch description to address H. Peter Anvin's comments - Consolidate multi-instance mode code under new config token, CONFIG_DEVPTS_MULTIPLE_INSTANCE. - Move usage-details from patch description to Documentation/fs/devpts.txt Changelog[v3]: - Rename new mount option to 'newinstance' - Create ptmx nodes only in 'newinstance' mounts - Bugfix: parse_mount_options() modifies @data but since we need to parse the @data twice (once in devpts_get_sb() and once during do_remount_sb()), parse a local copy of @data in devpts_get_sb(). (restructured code in devpts_get_sb() to fix this) Changelog[v2]: - Support both single-mount and multiple-mount semantics and provide '-onewmnt' option to select the semantics. 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>
2009-01-02 13:42:27 +00:00
#else
/*
* This supports only the legacy single-instance semantics (no
* multiple-instance semantics)
*/
static int devpts_get_sb(struct file_system_type *fs_type, int flags,
const char *dev_name, void *data, struct vfsmount *mnt)
{
return get_sb_single(fs_type, flags, data, devpts_fill_super, mnt);
}
#endif
static void devpts_kill_sb(struct super_block *sb)
{
struct pts_fs_info *fsi = DEVPTS_SB(sb);
kfree(fsi);
Define mknod_ptmx() /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>
2009-01-02 13:42:02 +00:00
kill_litter_super(sb);
}
static struct file_system_type devpts_fs_type = {
.owner = THIS_MODULE,
.name = "devpts",
.get_sb = devpts_get_sb,
.kill_sb = devpts_kill_sb,
};
/*
* The normal naming convention is simply /dev/pts/<number>; this conforms
* to the System V naming convention
*/
int devpts_new_index(struct inode *ptmx_inode)
{
struct super_block *sb = pts_sb_from_inode(ptmx_inode);
struct pts_fs_info *fsi = DEVPTS_SB(sb);
int index;
int ida_ret;
retry:
if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL))
return -ENOMEM;
mutex_lock(&allocated_ptys_lock);
ida_ret = ida_get_new(&fsi->allocated_ptys, &index);
if (ida_ret < 0) {
mutex_unlock(&allocated_ptys_lock);
if (ida_ret == -EAGAIN)
goto retry;
return -EIO;
}
if (index >= pty_limit) {
ida_remove(&fsi->allocated_ptys, index);
mutex_unlock(&allocated_ptys_lock);
return -EIO;
}
mutex_unlock(&allocated_ptys_lock);
return index;
}
void devpts_kill_index(struct inode *ptmx_inode, int idx)
{
struct super_block *sb = pts_sb_from_inode(ptmx_inode);
struct pts_fs_info *fsi = DEVPTS_SB(sb);
mutex_lock(&allocated_ptys_lock);
ida_remove(&fsi->allocated_ptys, idx);
mutex_unlock(&allocated_ptys_lock);
}
int devpts_pty_new(struct inode *ptmx_inode, struct tty_struct *tty)
{
/* tty layer puts index from devpts_new_index() in here */
int number = tty->index;
struct tty_driver *driver = tty->driver;
dev_t device = MKDEV(driver->major, driver->minor_start+number);
struct dentry *dentry;
struct super_block *sb = pts_sb_from_inode(ptmx_inode);
struct inode *inode = new_inode(sb);
struct dentry *root = sb->s_root;
struct pts_fs_info *fsi = DEVPTS_SB(sb);
struct pts_mount_opts *opts = &fsi->mount_opts;
char s[12];
/* We're supposed to be given the slave end of a pty */
BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY);
BUG_ON(driver->subtype != PTY_TYPE_SLAVE);
if (!inode)
return -ENOMEM;
inode->i_ino = number + 3;
inode->i_uid = opts->setuid ? opts->uid : current_fsuid();
inode->i_gid = opts->setgid ? opts->gid : current_fsgid();
inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
init_special_inode(inode, S_IFCHR|opts->mode, device);
inode->i_private = tty;
tty->driver_data = inode;
sprintf(s, "%d", number);
mutex_lock(&root->d_inode->i_mutex);
dentry = d_alloc_name(root, s);
if (!IS_ERR(dentry)) {
d_add(dentry, inode);
fsnotify_create(root->d_inode, dentry);
}
mutex_unlock(&root->d_inode->i_mutex);
return 0;
}
struct tty_struct *devpts_get_tty(struct inode *pts_inode, int number)
{
BUG_ON(pts_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
return (struct tty_struct *)pts_inode->i_private;
return NULL;
}
void devpts_pty_kill(struct tty_struct *tty)
{
struct inode *inode = tty->driver_data;
struct super_block *sb = pts_sb_from_inode(inode);
struct dentry *root = sb->s_root;
struct dentry *dentry;
BUG_ON(inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
mutex_lock(&root->d_inode->i_mutex);
dentry = d_find_alias(inode);
Enable multiple instances of devpts To support containers, allow multiple instances of devpts filesystem, such that indices of ptys allocated in one instance are independent of ptys allocated in other instances of devpts. But to preserve backward compatibility, enable this support for multiple instances only if: - CONFIG_DEVPTS_MULTIPLE_INSTANCES is set to Y, and - '-o newinstance' mount option is specified while mounting devpts To use multi-instance mount, a container startup script could: $ ns_exec -cm /bin/bash $ umount /dev/pts $ mount -t devpts -o newinstance lxcpts /dev/pts $ mount -o bind /dev/pts/ptmx /dev/ptmx $ /usr/sbin/sshd -p 1234 where 'ns_exec -cm /bin/bash' is calls clone() with CLONE_NEWNS flag and execs /bin/bash in the child process. A pty created by the sshd is not visible in the original mount of /dev/pts. USER-SPACE-IMPACT: - See Documentation/fs/devpts.txt (included in next patch) for user- space impact in multi-instance and mixed-mode operation. TODO: - Update mount(8), pts(4) man pages. Highlight impact of not redirecting /dev/ptmx to /dev/pts/ptmx after a multi-instance mount. Changelog[v6]: - [Dave Hansen] Use new get_init_pts_sb() interface - [Serge Hallyn] Don't bother displaying 'newinstance' in show_options - [Serge Hallyn] Use macros (PARSE_REMOUNT/PARSE_MOUNT) instead of 0/1. - [Serge Hallyn] Check error return from get_sb_single() (now get_init_pts_sb()) - devpts_pty_kill(): don't dput error dentries Changelog[v5]: - Move get_sb_ref() definition to earlier patch - Move usage info to Documentation/filesystems/devpts.txt (next patch) - Make ptmx node even in init_pts_ns, now that default mode is 0000 (defined in earlier patch, enabled here). - Cache ptmx dentry and use to update mode during remount (defined in earlier patch, enabled here). - Bugfix: explicitly ignore newinstance on remount (if newinstance was specified on remount of initial mount, it would be ignored but /proc/mounts would imply that the option was set) Changelog[v4]: - Update patch description to address H. Peter Anvin's comments - Consolidate multi-instance mode code under new config token, CONFIG_DEVPTS_MULTIPLE_INSTANCE. - Move usage-details from patch description to Documentation/fs/devpts.txt Changelog[v3]: - Rename new mount option to 'newinstance' - Create ptmx nodes only in 'newinstance' mounts - Bugfix: parse_mount_options() modifies @data but since we need to parse the @data twice (once in devpts_get_sb() and once during do_remount_sb()), parse a local copy of @data in devpts_get_sb(). (restructured code in devpts_get_sb() to fix this) Changelog[v2]: - Support both single-mount and multiple-mount semantics and provide '-onewmnt' option to select the semantics. 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>
2009-01-02 13:42:27 +00:00
if (IS_ERR(dentry))
goto out;
if (dentry) {
inode->i_nlink--;
d_delete(dentry);
dput(dentry); /* d_alloc_name() in devpts_pty_new() */
}
dput(dentry); /* d_find_alias above */
Enable multiple instances of devpts To support containers, allow multiple instances of devpts filesystem, such that indices of ptys allocated in one instance are independent of ptys allocated in other instances of devpts. But to preserve backward compatibility, enable this support for multiple instances only if: - CONFIG_DEVPTS_MULTIPLE_INSTANCES is set to Y, and - '-o newinstance' mount option is specified while mounting devpts To use multi-instance mount, a container startup script could: $ ns_exec -cm /bin/bash $ umount /dev/pts $ mount -t devpts -o newinstance lxcpts /dev/pts $ mount -o bind /dev/pts/ptmx /dev/ptmx $ /usr/sbin/sshd -p 1234 where 'ns_exec -cm /bin/bash' is calls clone() with CLONE_NEWNS flag and execs /bin/bash in the child process. A pty created by the sshd is not visible in the original mount of /dev/pts. USER-SPACE-IMPACT: - See Documentation/fs/devpts.txt (included in next patch) for user- space impact in multi-instance and mixed-mode operation. TODO: - Update mount(8), pts(4) man pages. Highlight impact of not redirecting /dev/ptmx to /dev/pts/ptmx after a multi-instance mount. Changelog[v6]: - [Dave Hansen] Use new get_init_pts_sb() interface - [Serge Hallyn] Don't bother displaying 'newinstance' in show_options - [Serge Hallyn] Use macros (PARSE_REMOUNT/PARSE_MOUNT) instead of 0/1. - [Serge Hallyn] Check error return from get_sb_single() (now get_init_pts_sb()) - devpts_pty_kill(): don't dput error dentries Changelog[v5]: - Move get_sb_ref() definition to earlier patch - Move usage info to Documentation/filesystems/devpts.txt (next patch) - Make ptmx node even in init_pts_ns, now that default mode is 0000 (defined in earlier patch, enabled here). - Cache ptmx dentry and use to update mode during remount (defined in earlier patch, enabled here). - Bugfix: explicitly ignore newinstance on remount (if newinstance was specified on remount of initial mount, it would be ignored but /proc/mounts would imply that the option was set) Changelog[v4]: - Update patch description to address H. Peter Anvin's comments - Consolidate multi-instance mode code under new config token, CONFIG_DEVPTS_MULTIPLE_INSTANCE. - Move usage-details from patch description to Documentation/fs/devpts.txt Changelog[v3]: - Rename new mount option to 'newinstance' - Create ptmx nodes only in 'newinstance' mounts - Bugfix: parse_mount_options() modifies @data but since we need to parse the @data twice (once in devpts_get_sb() and once during do_remount_sb()), parse a local copy of @data in devpts_get_sb(). (restructured code in devpts_get_sb() to fix this) Changelog[v2]: - Support both single-mount and multiple-mount semantics and provide '-onewmnt' option to select the semantics. 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>
2009-01-02 13:42:27 +00:00
out:
mutex_unlock(&root->d_inode->i_mutex);
}
static int __init init_devpts_fs(void)
{
int err = register_filesystem(&devpts_fs_type);
if (!err) {
devpts_mnt = kern_mount(&devpts_fs_type);
if (IS_ERR(devpts_mnt)) {
err = PTR_ERR(devpts_mnt);
unregister_filesystem(&devpts_fs_type);
}
}
return err;
}
static void __exit exit_devpts_fs(void)
{
unregister_filesystem(&devpts_fs_type);
mntput(devpts_mnt);
}
module_init(init_devpts_fs)
module_exit(exit_devpts_fs)
MODULE_LICENSE("GPL");