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, 593 insertions, 0 deletions

diff --git a/fs/exportfs/Makefile b/fs/exportfs/Makefile
new file mode 100644
index 000000000..a04a8af83
--- /dev/null
+++ b/fs/exportfs/Makefile
@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Makefile for the filesystem export support routines.
+
+obj-$(CONFIG_EXPORTFS) += exportfs.o
+
+exportfs-objs := expfs.o
diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
new file mode 100644
index 000000000..ab88d33d1
--- /dev/null
+++ b/fs/exportfs/expfs.c
@@ -0,0 +1,586 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) Neil Brown 2002
+ * Copyright (C) Christoph Hellwig 2007
+ *
+ * This file contains the code mapping from inodes to NFS file handles,
+ * and for mapping back from file handles to dentries.
+ *
+ * For details on why we do all the strange and hairy things in here
+ * take a look at Documentation/filesystems/nfs/exporting.rst.
+ */
+#include <linux/exportfs.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/module.h>
+#include <linux/mount.h>
+#include <linux/namei.h>
+#include <linux/sched.h>
+#include <linux/cred.h>
+
+#define dprintk(fmt, args...) pr_debug(fmt, ##args)
+
+
+static int get_name(const struct path *path, char *name, struct dentry *child);
+
+
+static int exportfs_get_name(struct vfsmount *mnt, struct dentry *dir,
+		char *name, struct dentry *child)
+{
+	const struct export_operations *nop = dir->d_sb->s_export_op;
+	struct path path = {.mnt = mnt, .dentry = dir};
+
+	if (nop->get_name)
+		return nop->get_name(dir, name, child);
+	else
+		return get_name(&path, name, child);
+}
+
+/*
+ * Check if the dentry or any of it's aliases is acceptable.
+ */
+static struct dentry *
+find_acceptable_alias(struct dentry *result,
+		int (*acceptable)(void *context, struct dentry *dentry),
+		void *context)
+{
+	struct dentry *dentry, *toput = NULL;
+	struct inode *inode;
+
+	if (acceptable(context, result))
+		return result;
+
+	inode = result->d_inode;
+	spin_lock(&inode->i_lock);
+	hlist_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias) {
+		dget(dentry);
+		spin_unlock(&inode->i_lock);
+		if (toput)
+			dput(toput);
+		if (dentry != result && acceptable(context, dentry)) {
+			dput(result);
+			return dentry;
+		}
+		spin_lock(&inode->i_lock);
+		toput = dentry;
+	}
+	spin_unlock(&inode->i_lock);
+
+	if (toput)
+		dput(toput);
+	return NULL;
+}
+
+static bool dentry_connected(struct dentry *dentry)
+{
+	dget(dentry);
+	while (dentry->d_flags & DCACHE_DISCONNECTED) {
+		struct dentry *parent = dget_parent(dentry);
+
+		dput(dentry);
+		if (dentry == parent) {
+			dput(parent);
+			return false;
+		}
+		dentry = parent;
+	}
+	dput(dentry);
+	return true;
+}
+
+static void clear_disconnected(struct dentry *dentry)
+{
+	dget(dentry);
+	while (dentry->d_flags & DCACHE_DISCONNECTED) {
+		struct dentry *parent = dget_parent(dentry);
+
+		WARN_ON_ONCE(IS_ROOT(dentry));
+
+		spin_lock(&dentry->d_lock);
+		dentry->d_flags &= ~DCACHE_DISCONNECTED;
+		spin_unlock(&dentry->d_lock);
+
+		dput(dentry);
+		dentry = parent;
+	}
+	dput(dentry);
+}
+
+/*
+ * Reconnect a directory dentry with its parent.
+ *
+ * This can return a dentry, or NULL, or an error.
+ *
+ * In the first case the returned dentry is the parent of the given
+ * dentry, and may itself need to be reconnected to its parent.
+ *
+ * In the NULL case, a concurrent VFS operation has either renamed or
+ * removed this directory.  The concurrent operation has reconnected our
+ * dentry, so we no longer need to.
+ */
+static struct dentry *reconnect_one(struct vfsmount *mnt,
+		struct dentry *dentry, char *nbuf)
+{
+	struct dentry *parent;
+	struct dentry *tmp;
+	int err;
+
+	parent = ERR_PTR(-EACCES);
+	inode_lock(dentry->d_inode);
+	if (mnt->mnt_sb->s_export_op->get_parent)
+		parent = mnt->mnt_sb->s_export_op->get_parent(dentry);
+	inode_unlock(dentry->d_inode);
+
+	if (IS_ERR(parent)) {
+		dprintk("get_parent of %lu failed, err %ld\n",
+			dentry->d_inode->i_ino, PTR_ERR(parent));
+		return parent;
+	}
+
+	dprintk("%s: find name of %lu in %lu\n", __func__,
+		dentry->d_inode->i_ino, parent->d_inode->i_ino);
+	err = exportfs_get_name(mnt, parent, nbuf, dentry);
+	if (err == -ENOENT)
+		goto out_reconnected;
+	if (err)
+		goto out_err;
+	dprintk("%s: found name: %s\n", __func__, nbuf);
+	tmp = lookup_one_unlocked(mnt_idmap(mnt), nbuf, parent, strlen(nbuf));
+	if (IS_ERR(tmp)) {
+		dprintk("lookup failed: %ld\n", PTR_ERR(tmp));
+		err = PTR_ERR(tmp);
+		goto out_err;
+	}
+	if (tmp != dentry) {
+		/*
+		 * Somebody has renamed it since exportfs_get_name();
+		 * great, since it could've only been renamed if it
+		 * got looked up and thus connected, and it would
+		 * remain connected afterwards.  We are done.
+		 */
+		dput(tmp);
+		goto out_reconnected;
+	}
+	dput(tmp);
+	if (IS_ROOT(dentry)) {
+		err = -ESTALE;
+		goto out_err;
+	}
+	return parent;
+
+out_err:
+	dput(parent);
+	return ERR_PTR(err);
+out_reconnected:
+	dput(parent);
+	/*
+	 * Someone must have renamed our entry into another parent, in
+	 * which case it has been reconnected by the rename.
+	 *
+	 * Or someone removed it entirely, in which case filehandle
+	 * lookup will succeed but the directory is now IS_DEAD and
+	 * subsequent operations on it will fail.
+	 *
+	 * Alternatively, maybe there was no race at all, and the
+	 * filesystem is just corrupt and gave us a parent that doesn't
+	 * actually contain any entry pointing to this inode.  So,
+	 * double check that this worked and return -ESTALE if not:
+	 */
+	if (!dentry_connected(dentry))
+		return ERR_PTR(-ESTALE);
+	return NULL;
+}
+
+/*
+ * Make sure target_dir is fully connected to the dentry tree.
+ *
+ * On successful return, DCACHE_DISCONNECTED will be cleared on
+ * target_dir, and target_dir->d_parent->...->d_parent will reach the
+ * root of the filesystem.
+ *
+ * Whenever DCACHE_DISCONNECTED is unset, target_dir is fully connected.
+ * But the converse is not true: target_dir may have DCACHE_DISCONNECTED
+ * set but already be connected.  In that case we'll verify the
+ * connection to root and then clear the flag.
+ *
+ * Note that target_dir could be removed by a concurrent operation.  In
+ * that case reconnect_path may still succeed with target_dir fully
+ * connected, but further operations using the filehandle will fail when
+ * necessary (due to S_DEAD being set on the directory).
+ */
+static int
+reconnect_path(struct vfsmount *mnt, struct dentry *target_dir, char *nbuf)
+{
+	struct dentry *dentry, *parent;
+
+	dentry = dget(target_dir);
+
+	while (dentry->d_flags & DCACHE_DISCONNECTED) {
+		BUG_ON(dentry == mnt->mnt_sb->s_root);
+
+		if (IS_ROOT(dentry))
+			parent = reconnect_one(mnt, dentry, nbuf);
+		else
+			parent = dget_parent(dentry);
+
+		if (!parent)
+			break;
+		dput(dentry);
+		if (IS_ERR(parent))
+			return PTR_ERR(parent);
+		dentry = parent;
+	}
+	dput(dentry);
+	clear_disconnected(target_dir);
+	return 0;
+}
+
+struct getdents_callback {
+	struct dir_context ctx;
+	char *name;		/* name that was found. It already points to a
+				   buffer NAME_MAX+1 is size */
+	u64 ino;		/* the inum we are looking for */
+	int found;		/* inode matched? */
+	int sequence;		/* sequence counter */
+};
+
+/*
+ * A rather strange filldir function to capture
+ * the name matching the specified inode number.
+ */
+static bool filldir_one(struct dir_context *ctx, const char *name, int len,
+			loff_t pos, u64 ino, unsigned int d_type)
+{
+	struct getdents_callback *buf =
+		container_of(ctx, struct getdents_callback, ctx);
+
+	buf->sequence++;
+	if (buf->ino == ino && len <= NAME_MAX) {
+		memcpy(buf->name, name, len);
+		buf->name[len] = '\0';
+		buf->found = 1;
+		return false;	// no more
+	}
+	return true;
+}
+
+/**
+ * get_name - default export_operations->get_name function
+ * @path:   the directory in which to find a name
+ * @name:   a pointer to a %NAME_MAX+1 char buffer to store the name
+ * @child:  the dentry for the child directory.
+ *
+ * calls readdir on the parent until it finds an entry with
+ * the same inode number as the child, and returns that.
+ */
+static int get_name(const struct path *path, char *name, struct dentry *child)
+{
+	const struct cred *cred = current_cred();
+	struct inode *dir = path->dentry->d_inode;
+	int error;
+	struct file *file;
+	struct kstat stat;
+	struct path child_path = {
+		.mnt = path->mnt,
+		.dentry = child,
+	};
+	struct getdents_callback buffer = {
+		.ctx.actor = filldir_one,
+		.name = name,
+	};
+
+	error = -ENOTDIR;
+	if (!dir || !S_ISDIR(dir->i_mode))
+		goto out;
+	error = -EINVAL;
+	if (!dir->i_fop)
+		goto out;
+	/*
+	 * inode->i_ino is unsigned long, kstat->ino is u64, so the
+	 * former would be insufficient on 32-bit hosts when the
+	 * filesystem supports 64-bit inode numbers.  So we need to
+	 * actually call ->getattr, not just read i_ino:
+	 */
+	error = vfs_getattr_nosec(&child_path, &stat,
+				  STATX_INO, AT_STATX_SYNC_AS_STAT);
+	if (error)
+		return error;
+	buffer.ino = stat.ino;
+	/*
+	 * Open the directory ...
+	 */
+	file = dentry_open(path, O_RDONLY, cred);
+	error = PTR_ERR(file);
+	if (IS_ERR(file))
+		goto out;
+
+	error = -EINVAL;
+	if (!file->f_op->iterate && !file->f_op->iterate_shared)
+		goto out_close;
+
+	buffer.sequence = 0;
+	while (1) {
+		int old_seq = buffer.sequence;
+
+		error = iterate_dir(file, &buffer.ctx);
+		if (buffer.found) {
+			error = 0;
+			break;
+		}
+
+		if (error < 0)
+			break;
+
+		error = -ENOENT;
+		if (old_seq == buffer.sequence)
+			break;
+	}
+
+out_close:
+	fput(file);
+out:
+	return error;
+}
+
+/**
+ * export_encode_fh - default export_operations->encode_fh function
+ * @inode:   the object to encode
+ * @fid:     where to store the file handle fragment
+ * @max_len: maximum length to store there
+ * @parent:  parent directory inode, if wanted
+ *
+ * This default encode_fh function assumes that the 32 inode number
+ * is suitable for locating an inode, and that the generation number
+ * can be used to check that it is still valid.  It places them in the
+ * filehandle fragment where export_decode_fh expects to find them.
+ */
+static int export_encode_fh(struct inode *inode, struct fid *fid,
+		int *max_len, struct inode *parent)
+{
+	int len = *max_len;
+	int type = FILEID_INO32_GEN;
+
+	if (parent && (len < 4)) {
+		*max_len = 4;
+		return FILEID_INVALID;
+	} else if (len < 2) {
+		*max_len = 2;
+		return FILEID_INVALID;
+	}
+
+	len = 2;
+	fid->i32.ino = inode->i_ino;
+	fid->i32.gen = inode->i_generation;
+	if (parent) {
+		fid->i32.parent_ino = parent->i_ino;
+		fid->i32.parent_gen = parent->i_generation;
+		len = 4;
+		type = FILEID_INO32_GEN_PARENT;
+	}
+	*max_len = len;
+	return type;
+}
+
+int exportfs_encode_inode_fh(struct inode *inode, struct fid *fid,
+			     int *max_len, struct inode *parent)
+{
+	const struct export_operations *nop = inode->i_sb->s_export_op;
+
+	if (nop && nop->encode_fh)
+		return nop->encode_fh(inode, fid->raw, max_len, parent);
+
+	return export_encode_fh(inode, fid, max_len, parent);
+}
+EXPORT_SYMBOL_GPL(exportfs_encode_inode_fh);
+
+int exportfs_encode_fh(struct dentry *dentry, struct fid *fid, int *max_len,
+		int connectable)
+{
+	int error;
+	struct dentry *p = NULL;
+	struct inode *inode = dentry->d_inode, *parent = NULL;
+
+	if (connectable && !S_ISDIR(inode->i_mode)) {
+		p = dget_parent(dentry);
+		/*
+		 * note that while p might've ceased to be our parent already,
+		 * it's still pinned by and still positive.
+		 */
+		parent = p->d_inode;
+	}
+
+	error = exportfs_encode_inode_fh(inode, fid, max_len, parent);
+	dput(p);
+
+	return error;
+}
+EXPORT_SYMBOL_GPL(exportfs_encode_fh);
+
+struct dentry *
+exportfs_decode_fh_raw(struct vfsmount *mnt, struct fid *fid, int fh_len,
+		       int fileid_type,
+		       int (*acceptable)(void *, struct dentry *),
+		       void *context)
+{
+	const struct export_operations *nop = mnt->mnt_sb->s_export_op;
+	struct dentry *result, *alias;
+	char nbuf[NAME_MAX+1];
+	int err;
+
+	/*
+	 * Try to get any dentry for the given file handle from the filesystem.
+	 */
+	if (!nop || !nop->fh_to_dentry)
+		return ERR_PTR(-ESTALE);
+	result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type);
+	if (IS_ERR_OR_NULL(result))
+		return result;
+
+	/*
+	 * If no acceptance criteria was specified by caller, a disconnected
+	 * dentry is also accepatable. Callers may use this mode to query if
+	 * file handle is stale or to get a reference to an inode without
+	 * risking the high overhead caused by directory reconnect.
+	 */
+	if (!acceptable)
+		return result;
+
+	if (d_is_dir(result)) {
+		/*
+		 * This request is for a directory.
+		 *
+		 * On the positive side there is only one dentry for each
+		 * directory inode.  On the negative side this implies that we
+		 * to ensure our dentry is connected all the way up to the
+		 * filesystem root.
+		 */
+		if (result->d_flags & DCACHE_DISCONNECTED) {
+			err = reconnect_path(mnt, result, nbuf);
+			if (err)
+				goto err_result;
+		}
+
+		if (!acceptable(context, result)) {
+			err = -EACCES;
+			goto err_result;
+		}
+
+		return result;
+	} else {
+		/*
+		 * It's not a directory.  Life is a little more complicated.
+		 */
+		struct dentry *target_dir, *nresult;
+
+		/*
+		 * See if either the dentry we just got from the filesystem
+		 * or any alias for it is acceptable.  This is always true
+		 * if this filesystem is exported without the subtreecheck
+		 * option.  If the filesystem is exported with the subtree
+		 * check option there's a fair chance we need to look at
+		 * the parent directory in the file handle and make sure
+		 * it's connected to the filesystem root.
+		 */
+		alias = find_acceptable_alias(result, acceptable, context);
+		if (alias)
+			return alias;
+
+		/*
+		 * Try to extract a dentry for the parent directory from the
+		 * file handle.  If this fails we'll have to give up.
+		 */
+		err = -ESTALE;
+		if (!nop->fh_to_parent)
+			goto err_result;
+
+		target_dir = nop->fh_to_parent(mnt->mnt_sb, fid,
+				fh_len, fileid_type);
+		if (!target_dir)
+			goto err_result;
+		err = PTR_ERR(target_dir);
+		if (IS_ERR(target_dir))
+			goto err_result;
+
+		/*
+		 * And as usual we need to make sure the parent directory is
+		 * connected to the filesystem root.  The VFS really doesn't
+		 * like disconnected directories..
+		 */
+		err = reconnect_path(mnt, target_dir, nbuf);
+		if (err) {
+			dput(target_dir);
+			goto err_result;
+		}
+
+		/*
+		 * Now that we've got both a well-connected parent and a
+		 * dentry for the inode we're after, make sure that our
+		 * inode is actually connected to the parent.
+		 */
+		err = exportfs_get_name(mnt, target_dir, nbuf, result);
+		if (err) {
+			dput(target_dir);
+			goto err_result;
+		}
+
+		inode_lock(target_dir->d_inode);
+		nresult = lookup_one(mnt_idmap(mnt), nbuf,
+				     target_dir, strlen(nbuf));
+		if (!IS_ERR(nresult)) {
+			if (unlikely(nresult->d_inode != result->d_inode)) {
+				dput(nresult);
+				nresult = ERR_PTR(-ESTALE);
+			}
+		}
+		inode_unlock(target_dir->d_inode);
+		/*
+		 * At this point we are done with the parent, but it's pinned
+		 * by the child dentry anyway.
+		 */
+		dput(target_dir);
+
+		if (IS_ERR(nresult)) {
+			err = PTR_ERR(nresult);
+			goto err_result;
+		}
+		dput(result);
+		result = nresult;
+
+		/*
+		 * And finally make sure the dentry is actually acceptable
+		 * to NFSD.
+		 */
+		alias = find_acceptable_alias(result, acceptable, context);
+		if (!alias) {
+			err = -EACCES;
+			goto err_result;
+		}
+
+		return alias;
+	}
+
+ err_result:
+	dput(result);
+	return ERR_PTR(err);
+}
+EXPORT_SYMBOL_GPL(exportfs_decode_fh_raw);
+
+struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
+				  int fh_len, int fileid_type,
+				  int (*acceptable)(void *, struct dentry *),
+				  void *context)
+{
+	struct dentry *ret;
+
+	ret = exportfs_decode_fh_raw(mnt, fid, fh_len, fileid_type,
+				     acceptable, context);
+	if (IS_ERR_OR_NULL(ret)) {
+		if (ret == ERR_PTR(-ENOMEM))
+			return ret;
+		return ERR_PTR(-ESTALE);
+	}
+	return ret;
+}
+EXPORT_SYMBOL_GPL(exportfs_decode_fh);
+
+MODULE_LICENSE("GPL");