Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-nextgrafted

Pull networking updates from Jakub Kicinski:
 "Core:

   - Add dedicated kmem_cache for typical/small skb->head, avoid having
     to access struct page at kfree time, and improve memory use.

   - Introduce sysctl to set default RPS configuration for new netdevs.

   - Define Netlink protocol specification format which can be used to
     describe messages used by each family and auto-generate parsers.
     Add tools for generating kernel data structures and uAPI headers.

   - Expose all net/core sysctls inside netns.

   - Remove 4s sleep in netpoll if carrier is instantly detected on
     boot.

   - Add configurable limit of MDB entries per port, and port-vlan.

   - Continue populating drop reasons throughout the stack.

   - Retire a handful of legacy Qdiscs and classifiers.

  Protocols:

   - Support IPv4 big TCP (TSO frames larger than 64kB).

   - Add IP_LOCAL_PORT_RANGE socket option, to control local port range
     on socket by socket basis.

   - Track and report in procfs number of MPTCP sockets used.

   - Support mixing IPv4 and IPv6 flows in the in-kernel MPTCP path
     manager.

   - IPv6: don't check net.ipv6.route.max_size and rely on garbage
     collection to free memory (similarly to IPv4).

   - Support Penultimate Segment Pop (PSP) flavor in SRv6 (RFC8986).

   - ICMP: add per-rate limit counters.

   - Add support for user scanning requests in ieee802154.

   - Remove static WEP support.

   - Support minimal Wi-Fi 7 Extremely High Throughput (EHT) rate
     reporting.

   - WiFi 7 EHT channel puncturing support (client & AP).

  BPF:

   - Add a rbtree data structure following the "next-gen data structure"
     precedent set by recently added linked list, that is, by using
     kfunc + kptr instead of adding a new BPF map type.

   - Expose XDP hints via kfuncs with initial support for RX hash and
     timestamp metadata.

   - Add BPF_F_NO_TUNNEL_KEY extension to bpf_skb_set_tunnel_key to
     better support decap on GRE tunnel devices not operating in collect
     metadata.

   - Improve x86 JIT's codegen for PROBE_MEM runtime error checks.

   - Remove the need for trace_printk_lock for bpf_trace_printk and
     bpf_trace_vprintk helpers.

   - Extend libbpf's bpf_tracing.h support for tracing arguments of
     kprobes/uprobes and syscall as a special case.

   - Significantly reduce the search time for module symbols by
     livepatch and BPF.

   - Enable cpumasks to be used as kptrs, which is useful for tracing
     programs tracking which tasks end up running on which CPUs in
     different time intervals.

   - Add support for BPF trampoline on s390x and riscv64.

   - Add capability to export the XDP features supported by the NIC.

   - Add __bpf_kfunc tag for marking kernel functions as kfuncs.

   - Add cgroup.memory=nobpf kernel parameter option to disable BPF
     memory accounting for container environments.

  Netfilter:

   - Remove the CLUSTERIP target. It has been marked as obsolete for
     years, and we still have WARN splats wrt races of the out-of-band
     /proc interface installed by this target.

   - Add 'destroy' commands to nf_tables. They are identical to the
     existing 'delete' commands, but do not return an error if the
     referenced object (set, chain, rule...) did not exist.

  Driver API:

   - Improve cpumask_local_spread() locality to help NICs set the right
     IRQ affinity on AMD platforms.

   - Separate C22 and C45 MDIO bus transactions more clearly.

   - Introduce new DCB table to control DSCP rewrite on egress.

   - Support configuration of Physical Layer Collision Avoidance (PLCA)
     Reconciliation Sublayer (RS) (802.3cg-2019). Modern version of
     shared medium Ethernet.

   - Support for MAC Merge layer (IEEE 802.3-2018 clause 99). Allowing
     preemption of low priority frames by high priority frames.

   - Add support for controlling MACSec offload using netlink SET.

   - Rework devlink instance refcounts to allow registration and
     de-registration under the instance lock. Split the code into
     multiple files, drop some of the unnecessarily granular locks and
     factor out common parts of netlink operation handling.

   - Add TX frame aggregation parameters (for USB drivers).

   - Add a new attr TCA_EXT_WARN_MSG to report TC (offload) warning
     messages with notifications for debug.

   - Allow offloading of UDP NEW connections via act_ct.

   - Add support for per action HW stats in TC.

   - Support hardware miss to TC action (continue processing in SW from
     a specific point in the action chain).

   - Warn if old Wireless Extension user space interface is used with
     modern cfg80211/mac80211 drivers. Do not support Wireless
     Extensions for Wi-Fi 7 devices at all. Everyone should switch to
     using nl80211 interface instead.

   - Improve the CAN bit timing configuration. Use extack to return
     error messages directly to user space, update the SJW handling,
     including the definition of a new default value that will benefit
     CAN-FD controllers, by increasing their oscillator tolerance.

  New hardware / drivers:

   - Ethernet:
      - nVidia BlueField-3 support (control traffic driver)
      - Ethernet support for imx93 SoCs
      - Motorcomm yt8531 gigabit Ethernet PHY
      - onsemi NCN26000 10BASE-T1S PHY (with support for PLCA)
      - Microchip LAN8841 PHY (incl. cable diagnostics and PTP)
      - Amlogic gxl MDIO mux

   - WiFi:
      - RealTek RTL8188EU (rtl8xxxu)
      - Qualcomm Wi-Fi 7 devices (ath12k)

   - CAN:
      - Renesas R-Car V4H

  Drivers:

   - Bluetooth:
      - Set Per Platform Antenna Gain (PPAG) for Intel controllers.

   - Ethernet NICs:
      - Intel (1G, igc):
         - support TSN / Qbv / packet scheduling features of i226 model
      - Intel (100G, ice):
         - use GNSS subsystem instead of TTY
         - multi-buffer XDP support
         - extend support for GPIO pins to E823 devices
      - nVidia/Mellanox:
         - update the shared buffer configuration on PFC commands
         - implement PTP adjphase function for HW offset control
         - TC support for Geneve and GRE with VF tunnel offload
         - more efficient crypto key management method
         - multi-port eswitch support
      - Netronome/Corigine:
         - add DCB IEEE support
         - support IPsec offloading for NFP3800
      - Freescale/NXP (enetc):
         - support XDP_REDIRECT for XDP non-linear buffers
         - improve reconfig, avoid link flap and waiting for idle
         - support MAC Merge layer
      - Other NICs:
         - sfc/ef100: add basic devlink support for ef100
         - ionic: rx_push mode operation (writing descriptors via MMIO)
         - bnxt: use the auxiliary bus abstraction for RDMA
         - r8169: disable ASPM and reset bus in case of tx timeout
         - cpsw: support QSGMII mode for J721e CPSW9G
         - cpts: support pulse-per-second output
         - ngbe: add an mdio bus driver
         - usbnet: optimize usbnet_bh() by avoiding unnecessary queuing
         - r8152: handle devices with FW with NCM support
         - amd-xgbe: support 10Mbps, 2.5GbE speeds and rx-adaptation
         - virtio-net: support multi buffer XDP
         - virtio/vsock: replace virtio_vsock_pkt with sk_buff
         - tsnep: XDP support

   - Ethernet high-speed switches:
      - nVidia/Mellanox (mlxsw):
         - add support for latency TLV (in FW control messages)
      - Microchip (sparx5):
         - separate explicit and implicit traffic forwarding rules, make
           the implicit rules always active
         - add support for egress DSCP rewrite
         - IS0 VCAP support (Ingress Classification)
         - IS2 VCAP filters (protos, L3 addrs, L4 ports, flags, ToS
           etc.)
         - ES2 VCAP support (Egress Access Control)
         - support for Per-Stream Filtering and Policing (802.1Q,
           8.6.5.1)

   - Ethernet embedded switches:
      - Marvell (mv88e6xxx):
         - add MAB (port auth) offload support
         - enable PTP receive for mv88e6390
      - NXP (ocelot):
         - support MAC Merge layer
         - support for the the vsc7512 internal copper phys
      - Microchip:
         - lan9303: convert to PHYLINK
         - lan966x: support TC flower filter statistics
         - lan937x: PTP support for KSZ9563/KSZ8563 and LAN937x
         - lan937x: support Credit Based Shaper configuration
         - ksz9477: support Energy Efficient Ethernet
      - other:
         - qca8k: convert to regmap read/write API, use bulk operations
         - rswitch: Improve TX timestamp accuracy

   - Intel WiFi (iwlwifi):
      - EHT (Wi-Fi 7) rate reporting
      - STEP equalizer support: transfer some STEP (connection to radio
        on platforms with integrated wifi) related parameters from the
        BIOS to the firmware.

   - Qualcomm 802.11ax WiFi (ath11k):
      - IPQ5018 support
      - Fine Timing Measurement (FTM) responder role support
      - channel 177 support

   - MediaTek WiFi (mt76):
      - per-PHY LED support
      - mt7996: EHT (Wi-Fi 7) support
      - Wireless Ethernet Dispatch (WED) reset support
      - switch to using page pool allocator

   - RealTek WiFi (rtw89):
      - support new version of Bluetooth co-existance

   - Mobile:
      - rmnet: support TX aggregation"

* tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1872 commits)
  page_pool: add a comment explaining the fragment counter usage
  net: ethtool: fix __ethtool_dev_mm_supported() implementation
  ethtool: pse-pd: Fix double word in comments
  xsk: add linux/vmalloc.h to xsk.c
  sefltests: netdevsim: wait for devlink instance after netns removal
  selftest: fib_tests: Always cleanup before exit
  net/mlx5e: Align IPsec ASO result memory to be as required by hardware
  net/mlx5e: TC, Set CT miss to the specific ct action instance
  net/mlx5e: Rename CHAIN_TO_REG to MAPPED_OBJ_TO_REG
  net/mlx5: Refactor tc miss handling to a single function
  net/mlx5: Kconfig: Make tc offload depend on tc skb extension
  net/sched: flower: Support hardware miss to tc action
  net/sched: flower: Move filter handle initialization earlier
  net/sched: cls_api: Support hardware miss to tc action
  net/sched: Rename user cookie and act cookie
  sfc: fix builds without CONFIG_RTC_LIB
  sfc: clean up some inconsistent indentings
  net/mlx4_en: Introduce flexible array to silence overflow warning
  net: lan966x: Fix possible deadlock inside PTP
  net/ulp: Remove redundant ->clone() test in inet_clone_ulp().
  ...

2 files changed, 645 insertions, 0 deletions

diff --git a/fs/devpts/Makefile b/fs/devpts/Makefile
new file mode 100644
index 000000000..66064c8fc
--- /dev/null
+++ b/fs/devpts/Makefile
@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Makefile for the Linux /dev/pts virtual filesystem.
+#
+
+obj-$(CONFIG_UNIX98_PTYS)		+= devpts.o
+
+devpts-$(CONFIG_UNIX98_PTYS)		:= inode.o
diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c
new file mode 100644
index 000000000..4f25015aa
--- /dev/null
+++ b/fs/devpts/inode.c
@@ -0,0 +1,637 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* -*- linux-c -*- --------------------------------------------------------- *
+ *
+ * linux/fs/devpts/inode.c
+ *
+ *  Copyright 1998-2004 H. Peter Anvin -- All Rights Reserved
+ *
+ * ------------------------------------------------------------------------- */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/fs.h>
+#include <linux/sched.h>
+#include <linux/namei.h>
+#include <linux/slab.h>
+#include <linux/mount.h>
+#include <linux/tty.h>
+#include <linux/mutex.h>
+#include <linux/magic.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_DEFAULT_MODE 0600
+/*
+ * 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
+
+/*
+ * sysctl support for setting limits on the number of Unix98 ptys allocated.
+ * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly.
+ */
+static int pty_limit = NR_UNIX98_PTY_DEFAULT;
+static int pty_reserve = NR_UNIX98_PTY_RESERVE;
+static int pty_limit_min;
+static int pty_limit_max = INT_MAX;
+static atomic_t pty_count = ATOMIC_INIT(0);
+
+static struct ctl_table pty_table[] = {
+	{
+		.procname	= "max",
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.data		= &pty_limit,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &pty_limit_min,
+		.extra2		= &pty_limit_max,
+	}, {
+		.procname	= "reserve",
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.data		= &pty_reserve,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &pty_limit_min,
+		.extra2		= &pty_limit_max,
+	}, {
+		.procname	= "nr",
+		.maxlen		= sizeof(int),
+		.mode		= 0444,
+		.data		= &pty_count,
+		.proc_handler	= proc_dointvec,
+	},
+	{}
+};
+
+static struct ctl_table pty_kern_table[] = {
+	{
+		.procname	= "pty",
+		.mode		= 0555,
+		.child		= pty_table,
+	},
+	{}
+};
+
+static struct ctl_table pty_root_table[] = {
+	{
+		.procname	= "kernel",
+		.mode		= 0555,
+		.child		= pty_kern_table,
+	},
+	{}
+};
+
+struct pts_mount_opts {
+	int setuid;
+	int setgid;
+	kuid_t   uid;
+	kgid_t   gid;
+	umode_t mode;
+	umode_t ptmxmode;
+	int reserve;
+	int max;
+};
+
+enum {
+	Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_newinstance,  Opt_max,
+	Opt_err
+};
+
+static const match_table_t tokens = {
+	{Opt_uid, "uid=%u"},
+	{Opt_gid, "gid=%u"},
+	{Opt_mode, "mode=%o"},
+	{Opt_ptmxmode, "ptmxmode=%o"},
+	{Opt_newinstance, "newinstance"},
+	{Opt_max, "max=%d"},
+	{Opt_err, NULL}
+};
+
+struct pts_fs_info {
+	struct ida allocated_ptys;
+	struct pts_mount_opts mount_opts;
+	struct super_block *sb;
+	struct dentry *ptmx_dentry;
+};
+
+static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb)
+{
+	return sb->s_fs_info;
+}
+
+static int devpts_ptmx_path(struct path *path)
+{
+	struct super_block *sb;
+	int err;
+
+	/* Is a devpts filesystem at "pts" in the same directory? */
+	err = path_pts(path);
+	if (err)
+		return err;
+
+	/* Is the path the root of a devpts filesystem? */
+	sb = path->mnt->mnt_sb;
+	if ((sb->s_magic != DEVPTS_SUPER_MAGIC) ||
+	    (path->mnt->mnt_root != sb->s_root))
+		return -ENODEV;
+
+	return 0;
+}
+
+/*
+ * Try to find a suitable devpts filesystem. We support the following
+ * scenarios:
+ * - The ptmx device node is located in the same directory as the devpts
+ *   mount where the pts device nodes are located.
+ *   This is e.g. the case when calling open on the /dev/pts/ptmx device
+ *   node when the devpts filesystem is mounted at /dev/pts.
+ * - The ptmx device node is located outside the devpts filesystem mount
+ *   where the pts device nodes are located. For example, the ptmx device
+ *   is a symlink, separate device node, or bind-mount.
+ *   A supported scenario is bind-mounting /dev/pts/ptmx to /dev/ptmx and
+ *   then calling open on /dev/ptmx. In this case a suitable pts
+ *   subdirectory can be found in the common parent directory /dev of the
+ *   devpts mount and the ptmx bind-mount, after resolving the /dev/ptmx
+ *   bind-mount.
+ *   If no suitable pts subdirectory can be found this function will fail.
+ *   This is e.g. the case when bind-mounting /dev/pts/ptmx to /ptmx.
+ */
+struct vfsmount *devpts_mntget(struct file *filp, struct pts_fs_info *fsi)
+{
+	struct path path;
+	int err = 0;
+
+	path = filp->f_path;
+	path_get(&path);
+
+	/* Walk upward while the start point is a bind mount of
+	 * a single file.
+	 */
+	while (path.mnt->mnt_root == path.dentry)
+		if (follow_up(&path) == 0)
+			break;
+
+	/* devpts_ptmx_path() finds a devpts fs or returns an error. */
+	if ((path.mnt->mnt_sb->s_magic != DEVPTS_SUPER_MAGIC) ||
+	    (DEVPTS_SB(path.mnt->mnt_sb) != fsi))
+		err = devpts_ptmx_path(&path);
+	dput(path.dentry);
+	if (!err) {
+		if (DEVPTS_SB(path.mnt->mnt_sb) == fsi)
+			return path.mnt;
+
+		err = -ENODEV;
+	}
+
+	mntput(path.mnt);
+	return ERR_PTR(err);
+}
+
+struct pts_fs_info *devpts_acquire(struct file *filp)
+{
+	struct pts_fs_info *result;
+	struct path path;
+	struct super_block *sb;
+
+	path = filp->f_path;
+	path_get(&path);
+
+	/* Has the devpts filesystem already been found? */
+	if (path.mnt->mnt_sb->s_magic != DEVPTS_SUPER_MAGIC) {
+		int err;
+
+		err = devpts_ptmx_path(&path);
+		if (err) {
+			result = ERR_PTR(err);
+			goto out;
+		}
+	}
+
+	/*
+	 * pty code needs to hold extra references in case of last /dev/tty close
+	 */
+	sb = path.mnt->mnt_sb;
+	atomic_inc(&sb->s_active);
+	result = DEVPTS_SB(sb);
+
+out:
+	path_put(&path);
+	return result;
+}
+
+void devpts_release(struct pts_fs_info *fsi)
+{
+	deactivate_super(fsi->sb);
+}
+
+#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.
+ *
+ * Note: @data may be NULL (in which case all options are set to default).
+ */
+static int parse_mount_options(char *data, int op, struct pts_mount_opts *opts)
+{
+	char *p;
+	kuid_t uid;
+	kgid_t gid;
+
+	opts->setuid  = 0;
+	opts->setgid  = 0;
+	opts->uid     = GLOBAL_ROOT_UID;
+	opts->gid     = GLOBAL_ROOT_GID;
+	opts->mode    = DEVPTS_DEFAULT_MODE;
+	opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
+	opts->max     = NR_UNIX98_PTY_MAX;
+
+	/* Only allow instances mounted from the initial mount
+	 * namespace to tap the reserve pool of ptys.
+	 */
+	if (op == PARSE_MOUNT)
+		opts->reserve =
+			(current->nsproxy->mnt_ns == init_task.nsproxy->mnt_ns);
+
+	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;
+			uid = make_kuid(current_user_ns(), option);
+			if (!uid_valid(uid))
+				return -EINVAL;
+			opts->uid = uid;
+			opts->setuid = 1;
+			break;
+		case Opt_gid:
+			if (match_int(&args[0], &option))
+				return -EINVAL;
+			gid = make_kgid(current_user_ns(), option);
+			if (!gid_valid(gid))
+				return -EINVAL;
+			opts->gid = gid;
+			opts->setgid = 1;
+			break;
+		case Opt_mode:
+			if (match_octal(&args[0], &option))
+				return -EINVAL;
+			opts->mode = option & S_IALLUGO;
+			break;
+		case Opt_ptmxmode:
+			if (match_octal(&args[0], &option))
+				return -EINVAL;
+			opts->ptmxmode = option & S_IALLUGO;
+			break;
+		case Opt_newinstance:
+			break;
+		case Opt_max:
+			if (match_int(&args[0], &option) ||
+			    option < 0 || option > NR_UNIX98_PTY_MAX)
+				return -EINVAL;
+			opts->max = option;
+			break;
+		default:
+			pr_err("called with bogus options\n");
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
+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;
+	kuid_t ptmx_uid = current_fsuid();
+	kgid_t ptmx_gid = current_fsgid();
+
+	inode_lock(d_inode(root));
+
+	/* If we have already created ptmx node, return */
+	if (fsi->ptmx_dentry) {
+		rc = 0;
+		goto out;
+	}
+
+	dentry = d_alloc_name(root, "ptmx");
+	if (!dentry) {
+		pr_err("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) {
+		pr_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(inode);
+
+	mode = S_IFCHR|opts->ptmxmode;
+	init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2));
+	inode->i_uid = ptmx_uid;
+	inode->i_gid = ptmx_gid;
+
+	d_add(dentry, inode);
+
+	fsi->ptmx_dentry = dentry;
+	rc = 0;
+out:
+	inode_unlock(d_inode(root));
+	return rc;
+}
+
+static void update_ptmx_mode(struct pts_fs_info *fsi)
+{
+	struct inode *inode;
+	if (fsi->ptmx_dentry) {
+		inode = d_inode(fsi->ptmx_dentry);
+		inode->i_mode = S_IFCHR|fsi->mount_opts.ptmxmode;
+	}
+}
+
+static int devpts_remount(struct super_block *sb, int *flags, char *data)
+{
+	int err;
+	struct pts_fs_info *fsi = DEVPTS_SB(sb);
+	struct pts_mount_opts *opts = &fsi->mount_opts;
+
+	err = parse_mount_options(data, PARSE_REMOUNT, opts);
+
+	/*
+	 * 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 dentry *root)
+{
+	struct pts_fs_info *fsi = DEVPTS_SB(root->d_sb);
+	struct pts_mount_opts *opts = &fsi->mount_opts;
+
+	if (opts->setuid)
+		seq_printf(seq, ",uid=%u",
+			   from_kuid_munged(&init_user_ns, opts->uid));
+	if (opts->setgid)
+		seq_printf(seq, ",gid=%u",
+			   from_kgid_munged(&init_user_ns, opts->gid));
+	seq_printf(seq, ",mode=%03o", opts->mode);
+	seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode);
+	if (opts->max < NR_UNIX98_PTY_MAX)
+		seq_printf(seq, ",max=%d", opts->max);
+
+	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(struct super_block *sb)
+{
+	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;
+	fsi->mount_opts.ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
+	fsi->sb = sb;
+
+	return fsi;
+}
+
+static int
+devpts_fill_super(struct super_block *s, void *data, int silent)
+{
+	struct inode *inode;
+	int error;
+
+	s->s_iflags &= ~SB_I_NODEV;
+	s->s_blocksize = 1024;
+	s->s_blocksize_bits = 10;
+	s->s_magic = DEVPTS_SUPER_MAGIC;
+	s->s_op = &devpts_sops;
+	s->s_d_op = &simple_dentry_operations;
+	s->s_time_gran = 1;
+
+	error = -ENOMEM;
+	s->s_fs_info = new_pts_fs_info(s);
+	if (!s->s_fs_info)
+		goto fail;
+
+	error = parse_mount_options(data, PARSE_MOUNT, &DEVPTS_SB(s)->mount_opts);
+	if (error)
+		goto fail;
+
+	error = -ENOMEM;
+	inode = new_inode(s);
+	if (!inode)
+		goto fail;
+	inode->i_ino = 1;
+	inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
+	inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR;
+	inode->i_op = &simple_dir_inode_operations;
+	inode->i_fop = &simple_dir_operations;
+	set_nlink(inode, 2);
+
+	s->s_root = d_make_root(inode);
+	if (!s->s_root) {
+		pr_err("get root dentry failed\n");
+		goto fail;
+	}
+
+	error = mknod_ptmx(s);
+	if (error)
+		goto fail_dput;
+
+	return 0;
+fail_dput:
+	dput(s->s_root);
+	s->s_root = NULL;
+fail:
+	return error;
+}
+
+/*
+ * devpts_mount()
+ *
+ *     Mount a new (private) instance of devpts.  PTYs created in this
+ *     instance are independent of the PTYs in other devpts instances.
+ */
+static struct dentry *devpts_mount(struct file_system_type *fs_type,
+	int flags, const char *dev_name, void *data)
+{
+	return mount_nodev(fs_type, flags, data, devpts_fill_super);
+}
+
+static void devpts_kill_sb(struct super_block *sb)
+{
+	struct pts_fs_info *fsi = DEVPTS_SB(sb);
+
+	if (fsi)
+		ida_destroy(&fsi->allocated_ptys);
+	kfree(fsi);
+	kill_litter_super(sb);
+}
+
+static struct file_system_type devpts_fs_type = {
+	.name		= "devpts",
+	.mount		= devpts_mount,
+	.kill_sb	= devpts_kill_sb,
+	.fs_flags	= FS_USERNS_MOUNT,
+};
+
+/*
+ * The normal naming convention is simply /dev/pts/<number>; this conforms
+ * to the System V naming convention
+ */
+
+int devpts_new_index(struct pts_fs_info *fsi)
+{
+	int index = -ENOSPC;
+
+	if (atomic_inc_return(&pty_count) >= (pty_limit -
+			  (fsi->mount_opts.reserve ? 0 : pty_reserve)))
+		goto out;
+
+	index = ida_alloc_max(&fsi->allocated_ptys, fsi->mount_opts.max - 1,
+			GFP_KERNEL);
+
+out:
+	if (index < 0)
+		atomic_dec(&pty_count);
+	return index;
+}
+
+void devpts_kill_index(struct pts_fs_info *fsi, int idx)
+{
+	ida_free(&fsi->allocated_ptys, idx);
+	atomic_dec(&pty_count);
+}
+
+/**
+ * devpts_pty_new -- create a new inode in /dev/pts/
+ * @ptmx_inode: inode of the master
+ * @device: major+minor of the node to be created
+ * @index: used as a name of the node
+ * @priv: what's given back by devpts_get_priv
+ *
+ * The created inode is returned. Remove it from /dev/pts/ by devpts_pty_kill.
+ */
+struct dentry *devpts_pty_new(struct pts_fs_info *fsi, int index, void *priv)
+{
+	struct dentry *dentry;
+	struct super_block *sb = fsi->sb;
+	struct inode *inode;
+	struct dentry *root;
+	struct pts_mount_opts *opts;
+	char s[12];
+
+	root = sb->s_root;
+	opts = &fsi->mount_opts;
+
+	inode = new_inode(sb);
+	if (!inode)
+		return ERR_PTR(-ENOMEM);
+
+	inode->i_ino = index + 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(inode);
+	init_special_inode(inode, S_IFCHR|opts->mode, MKDEV(UNIX98_PTY_SLAVE_MAJOR, index));
+
+	sprintf(s, "%d", index);
+
+	dentry = d_alloc_name(root, s);
+	if (dentry) {
+		dentry->d_fsdata = priv;
+		d_add(dentry, inode);
+		fsnotify_create(d_inode(root), dentry);
+	} else {
+		iput(inode);
+		dentry = ERR_PTR(-ENOMEM);
+	}
+
+	return dentry;
+}
+
+/**
+ * devpts_get_priv -- get private data for a slave
+ * @pts_inode: inode of the slave
+ *
+ * Returns whatever was passed as priv in devpts_pty_new for a given inode.
+ */
+void *devpts_get_priv(struct dentry *dentry)
+{
+	if (dentry->d_sb->s_magic != DEVPTS_SUPER_MAGIC)
+		return NULL;
+	return dentry->d_fsdata;
+}
+
+/**
+ * devpts_pty_kill -- remove inode form /dev/pts/
+ * @inode: inode of the slave to be removed
+ *
+ * This is an inverse operation of devpts_pty_new.
+ */
+void devpts_pty_kill(struct dentry *dentry)
+{
+	WARN_ON_ONCE(dentry->d_sb->s_magic != DEVPTS_SUPER_MAGIC);
+
+	dentry->d_fsdata = NULL;
+	drop_nlink(dentry->d_inode);
+	d_drop(dentry);
+	fsnotify_unlink(d_inode(dentry->d_parent), dentry);
+	dput(dentry);	/* d_alloc_name() in devpts_pty_new() */
+}
+
+static int __init init_devpts_fs(void)
+{
+	int err = register_filesystem(&devpts_fs_type);
+	if (!err) {
+		register_sysctl_table(pty_root_table);
+	}
+	return err;
+}
+module_init(init_devpts_fs)