/*
 *  linux/fs/nfs/super.c
 *
 *  Copyright (C) 1992  Rick Sladkey
 *
 *  nfs superblock handling functions
 *
 *  Modularised by Alan Cox <alan@lxorguk.ukuu.org.uk>, while hacking some
 *  experimental NFS changes. Modularisation taken straight from SYS5 fs.
 *
 *  Change to nfs_read_super() to permit NFS mounts to multi-homed hosts.
 *  J.S.Peatfield@damtp.cam.ac.uk
 *
 *  Split from inode.c by David Howells <dhowells@redhat.com>
 *
 * - superblocks are indexed on server only - all inodes, dentries, etc. associated with a
 *   particular server are held in the same superblock
 * - NFS superblocks can have several effective roots to the dentry tree
 * - directory type roots are spliced into the tree when a path from one root reaches the root
 *   of another (see nfs_lookup())
 */

#include <linux/module.h>
#include <linux/init.h>

#include <linux/time.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/stat.h>
#include <linux/errno.h>
#include <linux/unistd.h>
#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/stats.h>
#include <linux/sunrpc/metrics.h>
#include <linux/sunrpc/xprtsock.h>
#include <linux/sunrpc/xprtrdma.h>
#include <linux/nfs_fs.h>
#include <linux/nfs_mount.h>
#include <linux/nfs4_mount.h>
#include <linux/lockd/bind.h>
#include <linux/smp_lock.h>
#include <linux/seq_file.h>
#include <linux/mount.h>
#include <linux/mnt_namespace.h>
#include <linux/namei.h>
#include <linux/nfs_idmap.h>
#include <linux/vfs.h>
#include <linux/inet.h>
#include <linux/in6.h>
#include <linux/slab.h>
#include <net/ipv6.h>
#include <linux/netdevice.h>
#include <linux/nfs_xdr.h>
#include <linux/magic.h>
#include <linux/parser.h>

#include <asm/system.h>
#include <asm/uaccess.h>

#include "nfs4_fs.h"
#include "callback.h"
#include "delegation.h"
#include "iostat.h"
#include "internal.h"
#include "fscache.h"

#define NFSDBG_FACILITY         NFSDBG_VFS

enum {
        /* Mount options that take no arguments */
        Opt_soft, Opt_hard,
        Opt_posix, Opt_noposix,
        Opt_cto, Opt_nocto,
        Opt_ac, Opt_noac,
        Opt_lock, Opt_nolock,
        Opt_v2, Opt_v3, Opt_v4,
        Opt_udp, Opt_tcp, Opt_rdma,
        Opt_acl, Opt_noacl,
        Opt_rdirplus, Opt_nordirplus,
        Opt_sharecache, Opt_nosharecache,
        Opt_resvport, Opt_noresvport,
        Opt_fscache, Opt_nofscache,

        /* Mount options that take integer arguments */
        Opt_port,
        Opt_rsize, Opt_wsize, Opt_bsize,
        Opt_timeo, Opt_retrans,
        Opt_acregmin, Opt_acregmax,
        Opt_acdirmin, Opt_acdirmax,
        Opt_actimeo,
        Opt_namelen,
        Opt_mountport,
        Opt_mountvers,
        Opt_nfsvers,
        Opt_minorversion,

        /* Mount options that take string arguments */
        Opt_sec, Opt_proto, Opt_mountproto, Opt_mounthost,
        Opt_addr, Opt_mountaddr, Opt_clientaddr,
        Opt_lookupcache,
        Opt_fscache_uniq,

        /* Special mount options */
        Opt_userspace, Opt_deprecated, Opt_sloppy,

        Opt_err
};

static const match_table_t nfs_mount_option_tokens = {
        { Opt_userspace, "bg" },
        { Opt_userspace, "fg" },
        { Opt_userspace, "retry=%s" },

        { Opt_sloppy, "sloppy" },

        { Opt_soft, "soft" },
        { Opt_hard, "hard" },
        { Opt_deprecated, "intr" },
        { Opt_deprecated, "nointr" },
        { Opt_posix, "posix" },
        { Opt_noposix, "noposix" },
        { Opt_cto, "cto" },
        { Opt_nocto, "nocto" },
        { Opt_ac, "ac" },
        { Opt_noac, "noac" },
        { Opt_lock, "lock" },
        { Opt_nolock, "nolock" },
        { Opt_v2, "v2" },
        { Opt_v3, "v3" },
        { Opt_v4, "v4" },
        { Opt_udp, "udp" },
        { Opt_tcp, "tcp" },
        { Opt_rdma, "rdma" },
        { Opt_acl, "acl" },
        { Opt_noacl, "noacl" },
        { Opt_rdirplus, "rdirplus" },
        { Opt_nordirplus, "nordirplus" },
        { Opt_sharecache, "sharecache" },
        { Opt_nosharecache, "nosharecache" },
        { Opt_resvport, "resvport" },
        { Opt_noresvport, "noresvport" },
        { Opt_fscache, "fsc" },
        { Opt_nofscache, "nofsc" },

        { Opt_port, "port=%s" },
        { Opt_rsize, "rsize=%s" },
        { Opt_wsize, "wsize=%s" },
        { Opt_bsize, "bsize=%s" },
        { Opt_timeo, "timeo=%s" },
        { Opt_retrans, "retrans=%s" },
        { Opt_acregmin, "acregmin=%s" },
        { Opt_acregmax, "acregmax=%s" },
        { Opt_acdirmin, "acdirmin=%s" },
        { Opt_acdirmax, "acdirmax=%s" },
        { Opt_actimeo, "actimeo=%s" },
        { Opt_namelen, "namlen=%s" },
        { Opt_mountport, "mountport=%s" },
        { Opt_mountvers, "mountvers=%s" },
        { Opt_nfsvers, "nfsvers=%s" },
        { Opt_nfsvers, "vers=%s" },
        { Opt_minorversion, "minorversion=%s" },

        { Opt_sec, "sec=%s" },
        { Opt_proto, "proto=%s" },
        { Opt_mountproto, "mountproto=%s" },
        { Opt_addr, "addr=%s" },
        { Opt_clientaddr, "clientaddr=%s" },
        { Opt_mounthost, "mounthost=%s" },
        { Opt_mountaddr, "mountaddr=%s" },

        { Opt_lookupcache, "lookupcache=%s" },
        { Opt_fscache_uniq, "fsc=%s" },

        { Opt_err, NULL }
};

enum {
        Opt_xprt_udp, Opt_xprt_udp6, Opt_xprt_tcp, Opt_xprt_tcp6, Opt_xprt_rdma,

        Opt_xprt_err
};

static const match_table_t nfs_xprt_protocol_tokens = {
        { Opt_xprt_udp, "udp" },
        { Opt_xprt_udp6, "udp6" },
        { Opt_xprt_tcp, "tcp" },
        { Opt_xprt_tcp6, "tcp6" },
        { Opt_xprt_rdma, "rdma" },

        { Opt_xprt_err, NULL }
};

enum {
        Opt_sec_none, Opt_sec_sys,
        Opt_sec_krb5, Opt_sec_krb5i, Opt_sec_krb5p,
        Opt_sec_lkey, Opt_sec_lkeyi, Opt_sec_lkeyp,
        Opt_sec_spkm, Opt_sec_spkmi, Opt_sec_spkmp,

        Opt_sec_err
};

static const match_table_t nfs_secflavor_tokens = {
        { Opt_sec_none, "none" },
        { Opt_sec_none, "null" },
        { Opt_sec_sys, "sys" },

        { Opt_sec_krb5, "krb5" },
        { Opt_sec_krb5i, "krb5i" },
        { Opt_sec_krb5p, "krb5p" },

        { Opt_sec_lkey, "lkey" },
        { Opt_sec_lkeyi, "lkeyi" },
        { Opt_sec_lkeyp, "lkeyp" },

        { Opt_sec_spkm, "spkm3" },
        { Opt_sec_spkmi, "spkm3i" },
        { Opt_sec_spkmp, "spkm3p" },

        { Opt_sec_err, NULL }
};

enum {
        Opt_lookupcache_all, Opt_lookupcache_positive,
        Opt_lookupcache_none,

        Opt_lookupcache_err
};

static match_table_t nfs_lookupcache_tokens = {
        { Opt_lookupcache_all, "all" },
        { Opt_lookupcache_positive, "pos" },
        { Opt_lookupcache_positive, "positive" },
        { Opt_lookupcache_none, "none" },

        { Opt_lookupcache_err, NULL }
};


static void nfs_umount_begin(struct super_block *);
static int  nfs_statfs(struct dentry *, struct kstatfs *);
static int  nfs_show_options(struct seq_file *, struct vfsmount *);
static int  nfs_show_stats(struct seq_file *, struct vfsmount *);
static int nfs_get_sb(struct file_system_type *, int, const char *, void *, struct vfsmount *);
static int nfs_xdev_get_sb(struct file_system_type *fs_type,
                int flags, const char *dev_name, void *raw_data, struct vfsmount *mnt);
static void nfs_put_super(struct super_block *);
static void nfs_kill_super(struct super_block *);
static int nfs_remount(struct super_block *sb, int *flags, char *raw_data);

static struct file_system_type nfs_fs_type = {
        .owner          = THIS_MODULE,
        .name           = "nfs",
        .get_sb         = nfs_get_sb,
        .kill_sb        = nfs_kill_super,
        .fs_flags       = FS_RENAME_DOES_D_MOVE|FS_REVAL_DOT|FS_BINARY_MOUNTDATA,
};

struct file_system_type nfs_xdev_fs_type = {
        .owner          = THIS_MODULE,
        .name           = "nfs",
        .get_sb         = nfs_xdev_get_sb,
        .kill_sb        = nfs_kill_super,
        .fs_flags       = FS_RENAME_DOES_D_MOVE|FS_REVAL_DOT|FS_BINARY_MOUNTDATA,
};

static const struct super_operations nfs_sops = {
        .alloc_inode    = nfs_alloc_inode,
        .destroy_inode  = nfs_destroy_inode,
        .write_inode    = nfs_write_inode,
        .put_super      = nfs_put_super,
        .statfs         = nfs_statfs,
        .clear_inode    = nfs_clear_inode,
        .umount_begin   = nfs_umount_begin,
        .show_options   = nfs_show_options,
        .show_stats     = nfs_show_stats,
        .remount_fs     = nfs_remount,
};

#ifdef CONFIG_NFS_V4
static int nfs4_validate_text_mount_data(void *options,
        struct nfs_parsed_mount_data *args, const char *dev_name);
static int nfs4_try_mount(int flags, const char *dev_name,
        struct nfs_parsed_mount_data *data, struct vfsmount *mnt);
static int nfs4_get_sb(struct file_system_type *fs_type,
        int flags, const char *dev_name, void *raw_data, struct vfsmount *mnt);
static int nfs4_remote_get_sb(struct file_system_type *fs_type,
        int flags, const char *dev_name, void *raw_data, struct vfsmount *mnt);
static int nfs4_xdev_get_sb(struct file_system_type *fs_type,
        int flags, const char *dev_name, void *raw_data, struct vfsmount *mnt);
static int nfs4_referral_get_sb(struct file_system_type *fs_type,
        int flags, const char *dev_name, void *raw_data, struct vfsmount *mnt);
static int nfs4_remote_referral_get_sb(struct file_system_type *fs_type,
        int flags, const char *dev_name, void *raw_data, struct vfsmount *mnt);
static void nfs4_kill_super(struct super_block *sb);

static struct file_system_type nfs4_fs_type = {
        .owner          = THIS_MODULE,
        .name           = "nfs4",
        .get_sb         = nfs4_get_sb,
        .kill_sb        = nfs4_kill_super,
        .fs_flags       = FS_RENAME_DOES_D_MOVE|FS_REVAL_DOT|FS_BINARY_MOUNTDATA,
};

static struct file_system_type nfs4_remote_fs_type = {
        .owner          = THIS_MODULE,
        .name           = "nfs4",
        .get_sb         = nfs4_remote_get_sb,
        .kill_sb        = nfs4_kill_super,
        .fs_flags       = FS_RENAME_DOES_D_MOVE|FS_REVAL_DOT|FS_BINARY_MOUNTDATA,
};

struct file_system_type nfs4_xdev_fs_type = {
        .owner          = THIS_MODULE,
        .name           = "nfs4",
        .get_sb         = nfs4_xdev_get_sb,
        .kill_sb        = nfs4_kill_super,
        .fs_flags       = FS_RENAME_DOES_D_MOVE|FS_REVAL_DOT|FS_BINARY_MOUNTDATA,
};

static struct file_system_type nfs4_remote_referral_fs_type = {
        .owner          = THIS_MODULE,
        .name           = "nfs4",
        .get_sb         = nfs4_remote_referral_get_sb,
        .kill_sb        = nfs4_kill_super,
        .fs_flags       = FS_RENAME_DOES_D_MOVE|FS_REVAL_DOT|FS_BINARY_MOUNTDATA,
};

struct file_system_type nfs4_referral_fs_type = {
        .owner          = THIS_MODULE,
        .name           = "nfs4",
        .get_sb         = nfs4_referral_get_sb,
        .kill_sb        = nfs4_kill_super,
        .fs_flags       = FS_RENAME_DOES_D_MOVE|FS_REVAL_DOT|FS_BINARY_MOUNTDATA,
};

static const struct super_operations nfs4_sops = {
        .alloc_inode    = nfs_alloc_inode,
        .destroy_inode  = nfs_destroy_inode,
        .write_inode    = nfs_write_inode,
        .put_super      = nfs_put_super,
        .statfs         = nfs_statfs,
        .clear_inode    = nfs4_clear_inode,
        .umount_begin   = nfs_umount_begin,
        .show_options   = nfs_show_options,
        .show_stats     = nfs_show_stats,
        .remount_fs     = nfs_remount,
};
#endif

static struct shrinker acl_shrinker = {
        .shrink         = nfs_access_cache_shrinker,
        .seeks          = DEFAULT_SEEKS,
};

/*
 * Register the NFS filesystems
 */
int __init register_nfs_fs(void)
{
        int ret;

        ret = register_filesystem(&nfs_fs_type);
        if (ret < 0)
                goto error_0;

        ret = nfs_register_sysctl();
        if (ret < 0)
                goto error_1;
#ifdef CONFIG_NFS_V4
        ret = register_filesystem(&nfs4_fs_type);
        if (ret < 0)
                goto error_2;
#endif
        register_shrinker(&acl_shrinker);
        return 0;

#ifdef CONFIG_NFS_V4
error_2:
        nfs_unregister_sysctl();
#endif
error_1:
        unregister_filesystem(&nfs_fs_type);
error_0:
        return ret;
}

/*
 * Unregister the NFS filesystems
 */
void __exit unregister_nfs_fs(void)
{
        unregister_shrinker(&acl_shrinker);
#ifdef CONFIG_NFS_V4
        unregister_filesystem(&nfs4_fs_type);
#endif
        nfs_unregister_sysctl();
        unregister_filesystem(&nfs_fs_type);
}

void nfs_sb_active(struct super_block *sb)
{
        struct nfs_server *server = NFS_SB(sb);

        if (atomic_inc_return(&server->active) == 1)
                atomic_inc(&sb->s_active);
}

void nfs_sb_deactive(struct super_block *sb)
{
        struct nfs_server *server = NFS_SB(sb);

        if (atomic_dec_and_test(&server->active))
                deactivate_super(sb);
}

/*
 * Deliver file system statistics to userspace
 */
static int nfs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
        struct nfs_server *server = NFS_SB(dentry->d_sb);
        unsigned char blockbits;
        unsigned long blockres;
        struct nfs_fh *fh = NFS_FH(dentry->d_inode);
        struct nfs_fsstat res;
        int error = -ENOMEM;

        res.fattr = nfs_alloc_fattr();
        if (res.fattr == NULL)
                goto out_err;

        error = server->nfs_client->rpc_ops->statfs(server, fh, &res);
        if (unlikely(error == -ESTALE)) {
                struct dentry *pd_dentry;

                pd_dentry = dget_parent(dentry);
                if (pd_dentry != NULL) {
                        nfs_zap_caches(pd_dentry->d_inode);
                        dput(pd_dentry);
                }
        }
        nfs_free_fattr(res.fattr);
        if (error < 0)
                goto out_err;

        buf->f_type = NFS_SUPER_MAGIC;

        /*
         * Current versions of glibc do not correctly handle the
         * case where f_frsize != f_bsize.  Eventually we want to
         * report the value of wtmult in this field.
         */
        buf->f_frsize = dentry->d_sb->s_blocksize;

        /*
         * On most *nix systems, f_blocks, f_bfree, and f_bavail
         * are reported in units of f_frsize.  Linux hasn't had
         * an f_frsize field in its statfs struct until recently,
         * thus historically Linux's sys_statfs reports these
         * fields in units of f_bsize.
         */
        buf->f_bsize = dentry->d_sb->s_blocksize;
        blockbits = dentry->d_sb->s_blocksize_bits;
        blockres = (1 << blockbits) - 1;
        buf->f_blocks = (res.tbytes + blockres) >> blockbits;
        buf->f_bfree = (res.fbytes + blockres) >> blockbits;
        buf->f_bavail = (res.abytes + blockres) >> blockbits;

        buf->f_files = res.tfiles;
        buf->f_ffree = res.afiles;

        buf->f_namelen = server->namelen;

        return 0;

 out_err:
        dprintk("%s: statfs error = %d\n", __func__, -error);
        return error;
}

/*
 * Map the security flavour number to a name
 */
static const char *nfs_pseudoflavour_to_name(rpc_authflavor_t flavour)
{
        static const struct {
                rpc_authflavor_t flavour;
                const char *str;
        } sec_flavours[] = {
                { RPC_AUTH_NULL, "null" },
                { RPC_AUTH_UNIX, "sys" },
                { RPC_AUTH_GSS_KRB5, "krb5" },
                { RPC_AUTH_GSS_KRB5I, "krb5i" },
                { RPC_AUTH_GSS_KRB5P, "krb5p" },
                { RPC_AUTH_GSS_LKEY, "lkey" },
                { RPC_AUTH_GSS_LKEYI, "lkeyi" },
                { RPC_AUTH_GSS_LKEYP, "lkeyp" },
                { RPC_AUTH_GSS_SPKM, "spkm" },
                { RPC_AUTH_GSS_SPKMI, "spkmi" },
                { RPC_AUTH_GSS_SPKMP, "spkmp" },
                { UINT_MAX, "unknown" }
        };
        int i;

        for (i = 0; sec_flavours[i].flavour != UINT_MAX; i++) {
                if (sec_flavours[i].flavour == flavour)
                        break;
        }
        return sec_flavours[i].str;
}

static void nfs_show_mountd_netid(struct seq_file *m, struct nfs_server *nfss,
                                  int showdefaults)
{
        struct sockaddr *sap = (struct sockaddr *) &nfss->mountd_address;

        seq_printf(m, ",mountproto=");
        switch (sap->sa_family) {
        case AF_INET:
                switch (nfss->mountd_protocol) {
                case IPPROTO_UDP:
                        seq_printf(m, RPCBIND_NETID_UDP);
                        break;
                case IPPROTO_TCP:
                        seq_printf(m, RPCBIND_NETID_TCP);
                        break;
                default:
                        if (showdefaults)
                                seq_printf(m, "auto");
                }
                break;
        case AF_INET6:
                switch (nfss->mountd_protocol) {
                case IPPROTO_UDP:
                        seq_printf(m, RPCBIND_NETID_UDP6);
                        break;
                case IPPROTO_TCP:
                        seq_printf(m, RPCBIND_NETID_TCP6);
                        break;
                default:
                        if (showdefaults)
                                seq_printf(m, "auto");
                }
                break;
        default:
                if (showdefaults)
                        seq_printf(m, "auto");
        }
}

static void nfs_show_mountd_options(struct seq_file *m, struct nfs_server *nfss,
                                    int showdefaults)
{
        struct sockaddr *sap = (struct sockaddr *)&nfss->mountd_address;

        switch (sap->sa_family) {
        case AF_INET: {
                struct sockaddr_in *sin = (struct sockaddr_in *)sap;
                seq_printf(m, ",mountaddr=%pI4", &sin->sin_addr.s_addr);
                break;
        }
        case AF_INET6: {
                struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)sap;
                seq_printf(m, ",mountaddr=%pI6c", &sin6->sin6_addr);
                break;
        }
        default:
                if (showdefaults)
                        seq_printf(m, ",mountaddr=unspecified");
        }

        if (nfss->mountd_version || showdefaults)
                seq_printf(m, ",mountvers=%u", nfss->mountd_version);
        if (nfss->mountd_port || showdefaults)
                seq_printf(m, ",mountport=%u", nfss->mountd_port);

        nfs_show_mountd_netid(m, nfss, showdefaults);
}

#ifdef CONFIG_NFS_V4
static void nfs_show_nfsv4_options(struct seq_file *m, struct nfs_server *nfss,
                                    int showdefaults)
{
        struct nfs_client *clp = nfss->nfs_client;

        seq_printf(m, ",clientaddr=%s", clp->cl_ipaddr);
        seq_printf(m, ",minorversion=%u", clp->cl_minorversion);
}
#else
static void nfs_show_nfsv4_options(struct seq_file *m, struct nfs_server *nfss,
                                    int showdefaults)
{
}
#endif

/*
 * Describe the mount options in force on this server representation
 */
static void nfs_show_mount_options(struct seq_file *m, struct nfs_server *nfss,
                                   int showdefaults)
{
        static const struct proc_nfs_info {
                int flag;
                const char *str;
                const char *nostr;
        } nfs_info[] = {
                { NFS_MOUNT_SOFT, ",soft", ",hard" },
                { NFS_MOUNT_POSIX, ",posix", "" },
                { NFS_MOUNT_NOCTO, ",nocto", "" },
                { NFS_MOUNT_NOAC, ",noac", "" },
                { NFS_MOUNT_NONLM, ",nolock", "" },
                { NFS_MOUNT_NOACL, ",noacl", "" },
                { NFS_MOUNT_NORDIRPLUS, ",nordirplus", "" },
                { NFS_MOUNT_UNSHARED, ",nosharecache", "" },
                { NFS_MOUNT_NORESVPORT, ",noresvport", "" },
                { 0, NULL, NULL }
        };
        const struct proc_nfs_info *nfs_infop;
        struct nfs_client *clp = nfss->nfs_client;
        u32 version = clp->rpc_ops->version;

        seq_printf(m, ",vers=%u", version);
        seq_printf(m, ",rsize=%u", nfss->rsize);
        seq_printf(m, ",wsize=%u", nfss->wsize);
        if (nfss->bsize != 0)
                seq_printf(m, ",bsize=%u", nfss->bsize);
        seq_printf(m, ",namlen=%u", nfss->namelen);
        if (nfss->acregmin != NFS_DEF_ACREGMIN*HZ || showdefaults)
                seq_printf(m, ",acregmin=%u", nfss->acregmin/HZ);
        if (nfss->acregmax != NFS_DEF_ACREGMAX*HZ || showdefaults)
                seq_printf(m, ",acregmax=%u", nfss->acregmax/HZ);
        if (nfss->acdirmin != NFS_DEF_ACDIRMIN*HZ || showdefaults)
                seq_printf(m, ",acdirmin=%u", nfss->acdirmin/HZ);
        if (nfss->acdirmax != NFS_DEF_ACDIRMAX*HZ || showdefaults)
                seq_printf(m, ",acdirmax=%u", nfss->acdirmax/HZ);
        for (nfs_infop = nfs_info; nfs_infop->flag; nfs_infop++) {
                if (nfss->flags & nfs_infop->flag)
                        seq_puts(m, nfs_infop->str);
                else
                        seq_puts(m, nfs_infop->nostr);
        }
        seq_printf(m, ",proto=%s",
                   rpc_peeraddr2str(nfss->client, RPC_DISPLAY_NETID));
        if (version == 4) {
                if (nfss->port != NFS_PORT)
                        seq_printf(m, ",port=%u", nfss->port);
        } else
                if (nfss->port)
                        seq_printf(m, ",port=%u", nfss->port);

        seq_printf(m, ",timeo=%lu", 10U * nfss->client->cl_timeout->to_initval / HZ);
        seq_printf(m, ",retrans=%u", nfss->client->cl_timeout->to_retries);
        seq_printf(m, ",sec=%s", nfs_pseudoflavour_to_name(nfss->client->cl_auth->au_flavor));

        if (version != 4)
                nfs_show_mountd_options(m, nfss, showdefaults);
        else
                nfs_show_nfsv4_options(m, nfss, showdefaults);

        if (nfss->options & NFS_OPTION_FSCACHE)
                seq_printf(m, ",fsc");

        if (nfss->flags & NFS_MOUNT_LOOKUP_CACHE_NONEG) {
                if (nfss->flags & NFS_MOUNT_LOOKUP_CACHE_NONE)
                        seq_printf(m, ",lookupcache=none");
                else
                        seq_printf(m, ",lookupcache=pos");
        }
}

/*
 * Describe the mount options on this VFS mountpoint
 */
static int nfs_show_options(struct seq_file *m, struct vfsmount *mnt)
{
        struct nfs_server *nfss = NFS_SB(mnt->mnt_sb);

        nfs_show_mount_options(m, nfss, 0);

        seq_printf(m, ",addr=%s",
                        rpc_peeraddr2str(nfss->nfs_client->cl_rpcclient,
                                                        RPC_DISPLAY_ADDR));

        return 0;
}

/*
 * Present statistical information for this VFS mountpoint
 */
static int nfs_show_stats(struct seq_file *m, struct vfsmount *mnt)
{
        int i, cpu;
        struct nfs_server *nfss = NFS_SB(mnt->mnt_sb);
        struct rpc_auth *auth = nfss->client->cl_auth;
        struct nfs_iostats totals = { };

        seq_printf(m, "statvers=%s", NFS_IOSTAT_VERS);

        /*
         * Display all mount option settings
         */
        seq_printf(m, "\n\topts:\t");
        seq_puts(m, mnt->mnt_sb->s_flags & MS_RDONLY ? "ro" : "rw");
        seq_puts(m, mnt->mnt_sb->s_flags & MS_SYNCHRONOUS ? ",sync" : "");
        seq_puts(m, mnt->mnt_sb->s_flags & MS_NOATIME ? ",noatime" : "");
        seq_puts(m, mnt->mnt_sb->s_flags & MS_NODIRATIME ? ",nodiratime" : "");
        nfs_show_mount_options(m, nfss, 1);

        seq_printf(m, "\n\tage:\t%lu", (jiffies - nfss->mount_time) / HZ);

        seq_printf(m, "\n\tcaps:\t");
        seq_printf(m, "caps=0x%x", nfss->caps);
        seq_printf(m, ",wtmult=%u", nfss->wtmult);
        seq_printf(m, ",dtsize=%u", nfss->dtsize);
        seq_printf(m, ",bsize=%u", nfss->bsize);
        seq_printf(m, ",namlen=%u", nfss->namelen);

#ifdef CONFIG_NFS_V4
        if (nfss->nfs_client->rpc_ops->version == 4) {
                seq_printf(m, "\n\tnfsv4:\t");
                seq_printf(m, "bm0=0x%x", nfss->attr_bitmask[0]);
                seq_printf(m, ",bm1=0x%x", nfss->attr_bitmask[1]);
                seq_printf(m, ",acl=0x%x", nfss->acl_bitmask);
        }
#endif

        /*
         * Display security flavor in effect for this mount
         */
        seq_printf(m, "\n\tsec:\tflavor=%u", auth->au_ops->au_flavor);
        if (auth->au_flavor)
                seq_printf(m, ",pseudoflavor=%u", auth->au_flavor);

        /*
         * Display superblock I/O counters
         */
        for_each_possible_cpu(cpu) {
                struct nfs_iostats *stats;

                preempt_disable();
                stats = per_cpu_ptr(nfss->io_stats, cpu);

                for (i = 0; i < __NFSIOS_COUNTSMAX; i++)
                        totals.events[i] += stats->events[i];
                for (i = 0; i < __NFSIOS_BYTESMAX; i++)
                        totals.bytes[i] += stats->bytes[i];
#ifdef CONFIG_NFS_FSCACHE
                for (i = 0; i < __NFSIOS_FSCACHEMAX; i++)
                        totals.fscache[i] += stats->fscache[i];
#endif

                preempt_enable();
        }

        seq_printf(m, "\n\tevents:\t");
        for (i = 0; i < __NFSIOS_COUNTSMAX; i++)
                seq_printf(m, "%lu ", totals.events[i]);
        seq_printf(m, "\n\tbytes:\t");
        for (i = 0; i < __NFSIOS_BYTESMAX; i++)
                seq_printf(m, "%Lu ", totals.bytes[i]);
#ifdef CONFIG_NFS_FSCACHE
        if (nfss->options & NFS_OPTION_FSCACHE) {
                seq_printf(m, "\n\tfsc:\t");
                for (i = 0; i < __NFSIOS_FSCACHEMAX; i++)
                        seq_printf(m, "%Lu ", totals.bytes[i]);
        }
#endif
        seq_printf(m, "\n");

        rpc_print_iostats(m, nfss->client);

        return 0;
}

/*
 * Begin unmount by attempting to remove all automounted mountpoints we added
 * in response to xdev traversals and referrals
 */
static void nfs_umount_begin(struct super_block *sb)
{
        struct nfs_server *server;
        struct rpc_clnt *rpc;

        server = NFS_SB(sb);
        /* -EIO all pending I/O */
        rpc = server->client_acl;
        if (!IS_ERR(rpc))
                rpc_killall_tasks(rpc);
        rpc = server->client;
        if (!IS_ERR(rpc))
                rpc_killall_tasks(rpc);
}

static struct nfs_parsed_mount_data *nfs_alloc_parsed_mount_data(unsigned int version)
{
        struct nfs_parsed_mount_data *data;

        data = kzalloc(sizeof(*data), GFP_KERNEL);
        if (data) {
                data->acregmin          = NFS_DEF_ACREGMIN;
                data->acregmax          = NFS_DEF_ACREGMAX;
                data->acdirmin          = NFS_DEF_ACDIRMIN;
                data->acdirmax          = NFS_DEF_ACDIRMAX;
                data->mount_server.port = NFS_UNSPEC_PORT;
                data->nfs_server.port   = NFS_UNSPEC_PORT;
                data->nfs_server.protocol = XPRT_TRANSPORT_TCP;
                data->auth_flavors[0]   = RPC_AUTH_UNIX;
                data->auth_flavor_len   = 1;
                data->version           = version;
                data->minorversion      = 0;
        }
        return data;
}

/*
 * Sanity-check a server address provided by the mount command.
 *
 * Address family must be initialized, and address must not be
 * the ANY address for that family.
 */
static int nfs_verify_server_address(struct sockaddr *addr)
{
        switch (addr->sa_family) {
        case AF_INET: {
                struct sockaddr_in *sa = (struct sockaddr_in *)addr;
                return sa->sin_addr.s_addr != htonl(INADDR_ANY);
        }
        case AF_INET6: {
                struct in6_addr *sa = &((struct sockaddr_in6 *)addr)->sin6_addr;
                return !ipv6_addr_any(sa);
        }
        }

        dfprintk(MOUNT, "NFS: Invalid IP address specified\n");
        return 0;
}

/*
 * Select between a default port value and a user-specified port value.
 * If a zero value is set, then autobind will be used.
 */
static void nfs_set_port(struct sockaddr *sap, int *port,
                                 const unsigned short default_port)
{
        if (*port == NFS_UNSPEC_PORT)
                *port = default_port;

        rpc_set_port(sap, *port);
}

/*
 * Sanity check the NFS transport protocol.
 *
 */
static void nfs_validate_transport_protocol(struct nfs_parsed_mount_data *mnt)
{
        switch (mnt->nfs_server.protocol) {
        case XPRT_TRANSPORT_UDP:
        case XPRT_TRANSPORT_TCP:
        case XPRT_TRANSPORT_RDMA:
                break;
        default:
                mnt->nfs_server.protocol = XPRT_TRANSPORT_TCP;
        }
}

/*
 * For text based NFSv2/v3 mounts, the mount protocol transport default
 * settings should depend upon the specified NFS transport.
 */
static void nfs_set_mount_transport_protocol(struct nfs_parsed_mount_data *mnt)
{
        nfs_validate_transport_protocol(mnt);

        if (mnt->mount_server.protocol == XPRT_TRANSPORT_UDP ||
            mnt->mount_server.protocol == XPRT_TRANSPORT_TCP)
                        return;
        switch (mnt->nfs_server.protocol) {
        case XPRT_TRANSPORT_UDP:
                mnt->mount_server.protocol = XPRT_TRANSPORT_UDP;
                break;
        case XPRT_TRANSPORT_TCP:
        case XPRT_TRANSPORT_RDMA:
                mnt->mount_server.protocol = XPRT_TRANSPORT_TCP;
        }
}

/*
 * Parse the value of the 'sec=' option.
 */
static int nfs_parse_security_flavors(char *value,
                                      struct nfs_parsed_mount_data *mnt)
{
        substring_t args[MAX_OPT_ARGS];

        dfprintk(MOUNT, "NFS: parsing sec=%s option\n", value);

        switch (match_token(value, nfs_secflavor_tokens, args)) {
        case Opt_sec_none:
                mnt->auth_flavors[0] = RPC_AUTH_NULL;
                break;
        case Opt_sec_sys:
                mnt->auth_flavors[0] = RPC_AUTH_UNIX;
                break;
        case Opt_sec_krb5:
                mnt->auth_flavors[0] = RPC_AUTH_GSS_KRB5;
                break;
        case Opt_sec_krb5i:
                mnt->auth_flavors[0] = RPC_AUTH_GSS_KRB5I;
                break;
        case Opt_sec_krb5p:
                mnt->auth_flavors[0] = RPC_AUTH_GSS_KRB5P;
                break;
        case Opt_sec_lkey:
                mnt->auth_flavors[0] = RPC_AUTH_GSS_LKEY;
                break;
        case Opt_sec_lkeyi:
                mnt->auth_flavors[0] = RPC_AUTH_GSS_LKEYI;
                break;
        case Opt_sec_lkeyp:
                mnt->auth_flavors[0] = RPC_AUTH_GSS_LKEYP;
                break;
        case Opt_sec_spkm:
                mnt->auth_flavors[0] = RPC_AUTH_GSS_SPKM;
                break;
        case Opt_sec_spkmi:
                mnt->auth_flavors[0] = RPC_AUTH_GSS_SPKMI;
                break;
        case Opt_sec_spkmp:
                mnt->auth_flavors[0] = RPC_AUTH_GSS_SPKMP;
                break;
        default:
                return 0;
        }

        mnt->auth_flavor_len = 1;
        return 1;
}

/*
 * Error-check and convert a string of mount options from user space into
 * a data structure.  The whole mount string is processed; bad options are
 * skipped as they are encountered.  If there were no errors, return 1;
 * otherwise return 0 (zero).
 */
static int nfs_parse_mount_options(char *raw,
                                   struct nfs_parsed_mount_data *mnt)
{
        char *p, *string, *secdata;
        int rc, sloppy = 0, invalid_option = 0;
        unsigned short protofamily = AF_UNSPEC;
        unsigned short mountfamily = AF_UNSPEC;

        if (!raw) {
                dfprintk(MOUNT, "NFS: mount options string was NULL.\n");
                return 1;
        }
        dfprintk(MOUNT, "NFS: nfs mount opts='%s'\n", raw);

        secdata = alloc_secdata();
        if (!secdata)
                goto out_nomem;

        rc = security_sb_copy_data(raw, secdata);
        if (rc)
                goto out_security_failure;

        rc = security_sb_parse_opts_str(secdata, &mnt->lsm_opts);
        if (rc)
                goto out_security_failure;

        free_secdata(secdata);

        while ((p = strsep(&raw, ",")) != NULL) {
                substring_t args[MAX_OPT_ARGS];
                unsigned long option;
                int token;

                if (!*p)
                        continue;

                dfprintk(MOUNT, "NFS:   parsing nfs mount option '%s'\n", p);

                token = match_token(p, nfs_mount_option_tokens, args);
                switch (token) {

                /*
                 * boolean options:  foo/nofoo
                 */
                case Opt_soft:
                        mnt->flags |= NFS_MOUNT_SOFT;
                        break;
                case Opt_hard:
                        mnt->flags &= ~NFS_MOUNT_SOFT;
                        break;
                case Opt_posix:
                        mnt->flags |= NFS_MOUNT_POSIX;
                        break;
                case Opt_noposix:

                        mnt->flags &= ~NFS_MOUNT_POSIX;
                        break;
                case Opt_cto:
                        mnt->flags &= ~NFS_MOUNT_NOCTO;
                        break;
                case Opt_nocto:
                        mnt->flags |= NFS_MOUNT_NOCTO;
                        break;
                case Opt_ac:
                        mnt->flags &= ~NFS_MOUNT_NOAC;
                        break;
                case Opt_noac:
                        mnt->flags |= NFS_MOUNT_NOAC;
                        break;
                case Opt_lock:
                        mnt->flags &= ~NFS_MOUNT_NONLM;
                        break;
                case Opt_nolock:
                        mnt->flags |= NFS_MOUNT_NONLM;
                        break;
                case Opt_v2:
                        mnt->flags &= ~NFS_MOUNT_VER3;
                        mnt->version = 2;
                        break;
                case Opt_v3:
                        mnt->flags |= NFS_MOUNT_VER3;
                        mnt->version = 3;
                        break;
#ifdef CONFIG_NFS_V4
                case Opt_v4:
                        mnt->flags &= ~NFS_MOUNT_VER3;
                        mnt->version = 4;
                        break;
#endif
                case Opt_udp:
                        mnt->flags &= ~NFS_MOUNT_TCP;
                        mnt->nfs_server.protocol = XPRT_TRANSPORT_UDP;
                        break;
                case Opt_tcp:
                        mnt->flags |= NFS_MOUNT_TCP;
                        mnt->nfs_server.protocol = XPRT_TRANSPORT_TCP;
                        break;
                case Opt_rdma:
                        mnt->flags |= NFS_MOUNT_TCP; /* for side protocols */
                        mnt->nfs_server.protocol = XPRT_TRANSPORT_RDMA;
                        xprt_load_transport(p);
                        break;
                case Opt_acl:
                        mnt->flags &= ~NFS_MOUNT_NOACL;
                        break;
                case Opt_noacl:
                        mnt->flags |= NFS_MOUNT_NOACL;
                        break;
                case Opt_rdirplus:
                        mnt->flags &= ~NFS_MOUNT_NORDIRPLUS;
                        break;
                case Opt_nordirplus:
                        mnt->flags |= NFS_MOUNT_NORDIRPLUS;
                        break;
                case Opt_sharecache:
                        mnt->flags &= ~NFS_MOUNT_UNSHARED;
                        break;
                case Opt_nosharecache:
                        mnt->flags |= NFS_MOUNT_UNSHARED;
                        break;
                case Opt_resvport:
                        mnt->flags &= ~NFS_MOUNT_NORESVPORT;
                        break;
                case Opt_noresvport:
                        mnt->flags |= NFS_MOUNT_NORESVPORT;
                        break;
                case Opt_fscache:
                        mnt->options |= NFS_OPTION_FSCACHE;
                        kfree(mnt->fscache_uniq);
                        mnt->fscache_uniq = NULL;
                        break;
                case Opt_nofscache:
                        mnt->options &= ~NFS_OPTION_FSCACHE;
                        kfree(mnt->fscache_uniq);
                        mnt->fscache_uniq = NULL;
                        break;

                /*
                 * options that take numeric values
                 */
                case Opt_port:
                        string = match_strdup(args);
                        if (string == NULL)
                                goto out_nomem;
                        rc = strict_strtoul(string, 10, &option);
                        kfree(string);
                        if (rc != 0 || option > USHRT_MAX)
                                goto out_invalid_value;
                        mnt->nfs_server.port = option;
                        break;
                case Opt_rsize:
                        string = match_strdup(args);
                        if (string == NULL)
                                goto out_nomem;
                        rc = strict_strtoul(string, 10, &option);
                        kfree(string);
                        if (rc != 0)
                                goto out_invalid_value;
                        mnt->rsize = option;
                        break;
                case Opt_wsize:
                        string = match_strdup(args);
                        if (string == NULL)
                                goto out_nomem;
                        rc = strict_strtoul(string, 10, &option);
                        kfree(string);
                        if (rc != 0)
                                goto out_invalid_value;
                        mnt->wsize = option;
                        break;
                case Opt_bsize:
                        string = match_strdup(args);
                        if (string == NULL)
                                goto out_nomem;
                        rc = strict_strtoul(string, 10, &option);
                        kfree(string);
                        if (rc != 0)
                                goto out_invalid_value;
                        mnt->bsize = option;
                        break;
                case Opt_timeo:
                        string = match_strdup(args);
                        if (string == NULL)
                                goto out_nomem;
                        rc = strict_strtoul(string, 10, &option);
                        kfree(string);
                        if (rc != 0 || option == 0)
                                goto out_invalid_value;
                        mnt->timeo = option;
                        break;
                case Opt_retrans:
                        string = match_strdup(args);
                        if (string == NULL)
                                goto out_nomem;
                        rc = strict_strtoul(string, 10, &option);
                        kfree(string);
                        if (rc != 0 || option == 0)
                                goto out_invalid_value;
                        mnt->retrans = option;
                        break;
                case Opt_acregmin:
                        string = match_strdup(args);
                        if (string == NULL)
                                goto out_nomem;
                        rc = strict_strtoul(string, 10, &option);
                        kfree(string);
                        if (rc != 0)
                                goto out_invalid_value;
                        mnt->acregmin = option;
                        break;
                case Opt_acregmax:
                        string = match_strdup(args);
                        if (string == NULL)
                                goto out_nomem;
                        rc = strict_strtoul(string, 10, &option);
                        kfree(string);
                        if (rc != 0)
                                goto out_invalid_value;
                        mnt->acregmax = option;
                        break;
                case Opt_acdirmin:
                        string = match_strdup(args);
                        if (string == NULL)
                                goto out_nomem;
                        rc = strict_strtoul(string, 10, &option);
                        kfree(string);
                        if (rc != 0)
                                goto out_invalid_value;
                        mnt->acdirmin = option;
                        break;
                case Opt_acdirmax:
                        string = match_strdup(args);
                        if (string == NULL)
                                goto out_nomem;
                        rc = strict_strtoul(string, 10, &option);
                        kfree(string);
                        if (rc != 0)
                                goto out_invalid_value;
                        mnt->acdirmax = option;
                        break;
                case Opt_actimeo:
                        string = match_strdup(args);
                        if (string == NULL)
                                goto out_nomem;
                        rc = strict_strtoul(string, 10, &option);
                        kfree(string);
                        if (rc != 0)
                                goto out_invalid_value;
                        mnt->acregmin = mnt->acregmax =
                        mnt->acdirmin = mnt->acdirmax = option;
                        break;
                case Opt_namelen:
                        string = match_strdup(args);
                        if (string == NULL)
                                goto out_nomem;
                        rc = strict_strtoul(string, 10, &option);
                        kfree(string);
                        if (rc != 0)
                                goto out_invalid_value;
                        mnt->namlen = option;
                        break;
                case Opt_mountport:
                        string = match_strdup(args);
                        if (string == NULL)
                                goto out_nomem;
                        rc = strict_strtoul(string, 10, &option);
                        kfree(string);
                        if (rc != 0 || option > USHRT_MAX)
                                goto out_invalid_value;
                        mnt->mount_server.port = option;
                        break;
                case Opt_mountvers:
                        string = match_strdup(args);
                        if (string == NULL)
                                goto out_nomem;
                        rc = strict_strtoul(string, 10, &option);
                        kfree(string);
                        if (rc != 0 ||
                            option < NFS_MNT_VERSION ||
                            option > NFS_MNT3_VERSION)
                                goto out_invalid_value;
                        mnt->mount_server.version = option;
                        break;
                case Opt_nfsvers:
                        string = match_strdup(args);
                        if (string == NULL)
                                goto out_nomem;
                        rc = strict_strtoul(string, 10, &option);
                        kfree(string);
                        if (rc != 0)
                                goto out_invalid_value;
                        switch (option) {
                        case NFS2_VERSION:
                                mnt->flags &= ~NFS_MOUNT_VER3;
                                mnt->version = 2;
                                break;
                        case NFS3_VERSION:
                                mnt->flags |= NFS_MOUNT_VER3;
                                mnt->version = 3;
                                break;
#ifdef CONFIG_NFS_V4
                        case NFS4_VERSION:
                                mnt->flags &= ~NFS_MOUNT_VER3;
                                mnt->version = 4;
                                break;
#endif
                        default:
                                goto out_invalid_value;
                        }
                        break;
                case Opt_minorversion:
                        string = match_strdup(args);
                        if (string == NULL)
                                goto out_nomem;
                        rc = strict_strtoul(string, 10, &option);
                        kfree(string);
                        if (rc != 0)
                                goto out_invalid_value;
                        if (option > NFS4_MAX_MINOR_VERSION)
                                goto out_invalid_value;
                        mnt->minorversion = option;
                        break;

                /*
                 * options that take text values
                 */
                case Opt_sec:
                        string = match_strdup(args);
                        if (string == NULL)
                                goto out_nomem;
                        rc = nfs_parse_security_flavors(string, mnt);
                        kfree(string);
                        if (!rc) {
                                dfprintk(MOUNT, "NFS:   unrecognized "
                                                "security flavor\n");
                                return 0;
                        }
                        break;
                case Opt_proto:
                        string = match_strdup(args);
                        if (string == NULL)
                                goto out_nomem;
                        token = match_token(string,
                                            nfs_xprt_protocol_tokens, args);

                        protofamily = AF_INET;
                        switch (token) {
                        case Opt_xprt_udp6:
                                protofamily = AF_INET6;
                        case Opt_xprt_udp:
                                mnt->flags &= ~NFS_MOUNT_TCP;
                                mnt->nfs_server.protocol = XPRT_TRANSPORT_UDP;
                                kfree(string);
                                break;
                        case Opt_xprt_tcp6:
                                protofamily = AF_INET6;
                        case Opt_xprt_tcp:
                                mnt->flags |= NFS_MOUNT_TCP;
                                mnt->nfs_server.protocol = XPRT_TRANSPORT_TCP;
                                kfree(string);
                                break;
                        case Opt_xprt_rdma:
                                /* vector side protocols to TCP */
                                mnt->flags |= NFS_MOUNT_TCP;
                                mnt->nfs_server.protocol = XPRT_TRANSPORT_RDMA;
                                xprt_load_transport(string);
                                kfree(string);
                                break;
                        default:
                                dfprintk(MOUNT, "NFS:   unrecognized "
                                                "transport protocol\n");
                                kfree(string);
                                return 0;
                        }
                        break;
                case Opt_mountproto:
                        string = match_strdup(args);
                        if (string == NULL)
                                goto out_nomem;
                        token = match_token(string,
                                            nfs_xprt_protocol_tokens, args);
                        kfree(string);

                        mountfamily = AF_INET;
                        switch (token) {
                        case Opt_xprt_udp6:
                                mountfamily = AF_INET6;
                        case Opt_xprt_udp:
                                mnt->mount_server.protocol = XPRT_TRANSPORT_UDP;
                                break;
                        case Opt_xprt_tcp6:
                                mountfamily = AF_INET6;
                        case Opt_xprt_tcp:
                                mnt->mount_server.protocol = XPRT_TRANSPORT_TCP;
                                break;
                        case Opt_xprt_rdma: /* not used for side protocols */
                        default:
                                dfprintk(MOUNT, "NFS:   unrecognized "
                                                "transport protocol\n");
                                return 0;
                        }
                        break;
                case Opt_addr:
                        string = match_strdup(args);
                        if (string == NULL)
                                goto out_nomem;
                        mnt->nfs_server.addrlen =
                                rpc_pton(string, strlen(string),
                                        (struct sockaddr *)
                                        &mnt->nfs_server.address,
                                        sizeof(mnt->nfs_server.address));
                        kfree(string);
                        if (mnt->nfs_server.addrlen == 0)
                                goto out_invalid_address;
                        break;
                case Opt_clientaddr:
                        string = match_strdup(args);
                        if (string == NULL)
                                goto out_nomem;
                        kfree(mnt->client_address);
                        mnt->client_address = string;
                        break;
                case Opt_mounthost:
                        string = match_strdup(args);
                        if (string == NULL)
                                goto out_nomem;
                        kfree(mnt->mount_server.hostname);
                        mnt->mount_server.hostname = string;
                        break;
                case Opt_mountaddr:
                        string = match_strdup(args);
                        if (string == NULL)
                                goto out_nomem;
                        mnt->mount_server.addrlen =
                                rpc_pton(string, strlen(string),
                                        (struct sockaddr *)
                                        &mnt->mount_server.address,
                                        sizeof(mnt->mount_server.address));
                        kfree(string);
                        if (mnt->mount_server.addrlen == 0)
                                goto out_invalid_address;
                        break;
                case Opt_lookupcache:
                        string = match_strdup(args);
                        if (string == NULL)
                                goto out_nomem;
                        token = match_token(string,
                                        nfs_lookupcache_tokens, args);
                        kfree(string);
                        switch (token) {
                                case Opt_lookupcache_all:
                                        mnt->flags &= ~(NFS_MOUNT_LOOKUP_CACHE_NONEG|NFS_MOUNT_LOOKUP_CACHE_NONE);
                                        break;
                                case Opt_lookupcache_positive:
                                        mnt->flags &= ~NFS_MOUNT_LOOKUP_CACHE_NONE;
                                        mnt->flags |= NFS_MOUNT_LOOKUP_CACHE_NONEG;
                                        break;
                                case Opt_lookupcache_none:
                                        mnt->flags |= NFS_MOUNT_LOOKUP_CACHE_NONEG|NFS_MOUNT_LOOKUP_CACHE_NONE;
                                        break;
                                default:
                                        dfprintk(MOUNT, "NFS:   invalid "
                                                        "lookupcache argument\n");
                                        return 0;
                        };
                        break;
                case Opt_fscache_uniq:
                        string = match_strdup(args);
                        if (string == NULL)
                                goto out_nomem;
                        kfree(mnt->fscache_uniq);
                        mnt->fscache_uniq = string;
                        mnt->options |= NFS_OPTION_FSCACHE;
                        break;

                /*
                 * Special options
                 */
                case Opt_sloppy:
                        sloppy = 1;
                        dfprintk(MOUNT, "NFS:   relaxing parsing rules\n");
                        break;
                case Opt_userspace:
                case Opt_deprecated:
                        dfprintk(MOUNT, "NFS:   ignoring mount option "
                                        "'%s'\n", p);
                        break;

                default:
                        invalid_option = 1;
                        dfprintk(MOUNT, "NFS:   unrecognized mount option "
                                        "'%s'\n", p);
                }
        }

        if (!sloppy && invalid_option)
                return 0;

        /*
         * verify that any proto=/mountproto= options match the address
         * familiies in the addr=/mountaddr= options.
         */
        if (protofamily != AF_UNSPEC &&
            protofamily != mnt->nfs_server.address.ss_family)
                goto out_proto_mismatch;

        if (mountfamily != AF_UNSPEC) {
                if (mnt->mount_server.addrlen) {
                        if (mountfamily != mnt->mount_server.address.ss_family)
                                goto out_mountproto_mismatch;
                } else {
                        if (mountfamily != mnt->nfs_server.address.ss_family)
                                goto out_mountproto_mismatch;
                }
        }

        return 1;

out_mountproto_mismatch:
        printk(KERN_INFO "NFS: mount server address does not match mountproto= "
                         "option\n");
        return 0;
out_proto_mismatch:
        printk(KERN_INFO "NFS: server address does not match proto= option\n");
        return 0;
out_invalid_address:
        printk(KERN_INFO "NFS: bad IP address specified: %s\n", p);
        return 0;
out_invalid_value:
        printk(KERN_INFO "NFS: bad mount option value specified: %s\n", p);
        return 0;
out_nomem:
        printk(KERN_INFO "NFS: not enough memory to parse option\n");
        return 0;
out_security_failure:
        free_secdata(secdata);
        printk(KERN_INFO "NFS: security options invalid: %d\n", rc);
        return 0;
}

/*
 * Match the requested auth flavors with the list returned by
 * the server.  Returns zero and sets the mount's authentication
 * flavor on success; returns -EACCES if server does not support
 * the requested flavor.
 */
static int nfs_walk_authlist(struct nfs_parsed_mount_data *args,
                             struct nfs_mount_request *request)
{
        unsigned int i, j, server_authlist_len = *(request->auth_flav_len);

        /*
         * Certain releases of Linux's mountd return an empty
         * flavor list.  To prevent behavioral regression with
         * these servers (ie. rejecting mounts that used to
         * succeed), revert to pre-2.6.32 behavior (no checking)
         * if the returned flavor list is empty.
         */
        if (server_authlist_len == 0)
                return 0;

        /*
         * We avoid sophisticated negotiating here, as there are
         * plenty of cases where we can get it wrong, providing
         * either too little or too much security.
         *
         * RFC 2623, section 2.7 suggests we SHOULD prefer the
         * flavor listed first.  However, some servers list
         * AUTH_NULL first.  Our caller plants AUTH_SYS, the
         * preferred default, in args->auth_flavors[0] if user
         * didn't specify sec= mount option.
         */
        for (i = 0; i < args->auth_flavor_len; i++)
                for (j = 0; j < server_authlist_len; j++)
                        if (args->auth_flavors[i] == request->auth_flavs[j]) {
                                dfprintk(MOUNT, "NFS: using auth flavor %d\n",
                                        request->auth_flavs[j]);
                                args->auth_flavors[0] = request->auth_flavs[j];
                                return 0;
                        }

        dfprintk(MOUNT, "NFS: server does not support requested auth flavor\n");
        nfs_umount(request);
        return -EACCES;
}

/*
 * Use the remote server's MOUNT service to request the NFS file handle
 * corresponding to the provided path.
 */
static int nfs_try_mount(struct nfs_parsed_mount_data *args,
                         struct nfs_fh *root_fh)
{
        rpc_authflavor_t server_authlist[NFS_MAX_SECFLAVORS];
        unsigned int server_authlist_len = ARRAY_SIZE(server_authlist);
        struct nfs_mount_request request = {
                .sap            = (struct sockaddr *)
                                                &args->mount_server.address,
                .dirpath        = args->nfs_server.export_path,
                .protocol       = args->mount_server.protocol,
                .fh             = root_fh,
                .noresvport     = args->flags & NFS_MOUNT_NORESVPORT,
                .auth_flav_len  = &server_authlist_len,
                .auth_flavs     = server_authlist,
        };
        int status;

        if (args->mount_server.version == 0) {
                switch (args->version) {
                        default:
                                args->mount_server.version = NFS_MNT3_VERSION;
                                break;
                        case 2:
                                args->mount_server.version = NFS_MNT_VERSION;
                }
        }
        request.version = args->mount_server.version;

        if (args->mount_server.hostname)
                request.hostname = args->mount_server.hostname;
        else
                request.hostname = args->nfs_server.hostname;

        /*
         * Construct the mount server's address.
         */
        if (args->mount_server.address.ss_family == AF_UNSPEC) {
                memcpy(request.sap, &args->nfs_server.address,
                       args->nfs_server.addrlen);
                args->mount_server.addrlen = args->nfs_server.addrlen;
        }
        request.salen = args->mount_server.addrlen;
        nfs_set_port(request.sap, &args->mount_server.port, 0);

        /*
         * Now ask the mount server to map our export path
         * to a file handle.
         */
        status = nfs_mount(&request);
        if (status != 0) {
                dfprintk(MOUNT, "NFS: unable to mount server %s, error %d\n",
                                request.hostname, status);
                return status;
        }

        /*
         * MNTv1 (NFSv2) does not support auth flavor negotiation.
         */
        if (args->mount_server.version != NFS_MNT3_VERSION)
                return 0;
        return nfs_walk_authlist(args, &request);
}

static int nfs_parse_simple_hostname(const char *dev_name,
                                     char **hostname, size_t maxnamlen,
                                     char **export_path, size_t maxpathlen)
{
        size_t len;
        char *colon, *comma;

        colon = strchr(dev_name, ':');
        if (colon == NULL)
                goto out_bad_devname;

        len = colon - dev_name;
        if (len > maxnamlen)
                goto out_hostname;

        /* N.B. caller will free nfs_server.hostname in all cases */
        *hostname = kstrndup(dev_name, len, GFP_KERNEL);
        if (!*hostname)
                goto out_nomem;

        /* kill possible hostname list: not supported */
        comma = strchr(*hostname, ',');
        if (comma != NULL) {
                if (comma == *hostname)
                        goto out_bad_devname;
                *comma = '\0';
        }

        colon++;
        len = strlen(colon);
        if (len > maxpathlen)
                goto out_path;
        *export_path = kstrndup(colon, len, GFP_KERNEL);
        if (!*export_path)
                goto out_nomem;

        dfprintk(MOUNT, "NFS: MNTPATH: '%s'\n", *export_path);
        return 0;

out_bad_devname:
        dfprintk(MOUNT, "NFS: device name not in host:path format\n");
        return -EINVAL;

out_nomem:
        dfprintk(MOUNT, "NFS: not enough memory to parse device name\n");
        return -ENOMEM;

out_hostname:
        dfprintk(MOUNT, "NFS: server hostname too long\n");
        return -ENAMETOOLONG;

out_path:
        dfprintk(MOUNT, "NFS: export pathname too long\n");
        return -ENAMETOOLONG;
}

/*
 * Hostname has square brackets around it because it contains one or
 * more colons.  We look for the first closing square bracket, and a
 * colon must follow it.
 */
static int nfs_parse_protected_hostname(const char *dev_name,
                                        char **hostname, size_t maxnamlen,
                                        char **export_path, size_t maxpathlen)
{
        size_t len;
        char *start, *end;

        start = (char *)(dev_name + 1);

        end = strchr(start, ']');
        if (end == NULL)
                goto out_bad_devname;
        if (*(end + 1) != ':')
                goto out_bad_devname;

        len = end - start;
        if (len > maxnamlen)
                goto out_hostname;

        /* N.B. caller will free nfs_server.hostname in all cases */
        *hostname = kstrndup(start, len, GFP_KERNEL);
        if (*hostname == NULL)
                goto out_nomem;

        end += 2;
        len = strlen(end);
        if (len > maxpathlen)
                goto out_path;
        *export_path = kstrndup(end, len, GFP_KERNEL);
        if (!*export_path)
                goto out_nomem;

        return 0;

out_bad_devname:
        dfprintk(MOUNT, "NFS: device name not in host:path format\n");
        return -EINVAL;

out_nomem:
        dfprintk(MOUNT, "NFS: not enough memory to parse device name\n");
        return -ENOMEM;

out_hostname:
        dfprintk(MOUNT, "NFS: server hostname too long\n");
        return -ENAMETOOLONG;

out_path:
        dfprintk(MOUNT, "NFS: export pathname too long\n");
        return -ENAMETOOLONG;
}

/*
 * Split "dev_name" into "hostname:export_path".
 *
 * The leftmost colon demarks the split between the server's hostname
 * and the export path.  If the hostname starts with a left square
 * bracket, then it may contain colons.
 *
 * Note: caller frees hostname and export path, even on error.
 */
static int nfs_parse_devname(const char *dev_name,
                             char **hostname, size_t maxnamlen,
                             char **export_path, size_t maxpathlen)
{
        if (*dev_name == '[')
                return nfs_parse_protected_hostname(dev_name,
                                                    hostname, maxnamlen,
                                                    export_path, maxpathlen);

        return nfs_parse_simple_hostname(dev_name,
                                         hostname, maxnamlen,
                                         export_path, maxpathlen);
}

/*
 * Validate the NFS2/NFS3 mount data
 * - fills in the mount root filehandle
 *
 * For option strings, user space handles the following behaviors:
 *
 * + DNS: mapping server host name to IP address ("addr=" option)
 *
 * + failure mode: how to behave if a mount request can't be handled
 *   immediately ("fg/bg" option)
 *
 * + retry: how often to retry a mount request ("retry=" option)
 *
 * + breaking back: trying proto=udp after proto=tcp, v2 after v3,
 *   mountproto=tcp after mountproto=udp, and so on
 */
static int nfs_validate_mount_data(void *options,
                                   struct nfs_parsed_mount_data *args,
                                   struct nfs_fh *mntfh,
                                   const char *dev_name)
{
        struct nfs_mount_data *data = (struct nfs_mount_data *)options;
        struct sockaddr *sap = (struct sockaddr *)&args->nfs_server.address;

        if (data == NULL)
                goto out_no_data;

        switch (data->version) {
        case 1:
                data->namlen = 0;
        case 2:
                data->bsize = 0;
        case 3:
                if (data->flags & NFS_MOUNT_VER3)
                        goto out_no_v3;
                data->root.size = NFS2_FHSIZE;
                memcpy(data->root.data, data->old_root.data, NFS2_FHSIZE);
        case 4:
                if (data->flags & NFS_MOUNT_SECFLAVOUR)
                        goto out_no_sec;
        case 5:
                memset(data->context, 0, sizeof(data->context));
        case 6:
                if (data->flags & NFS_MOUNT_VER3) {
                        if (data->root.size > NFS3_FHSIZE || data->root.size == 0)
                                goto out_invalid_fh;
                        mntfh->size = data->root.size;
                        args->version = 3;
                } else {
                        mntfh->size = NFS2_FHSIZE;
                        args->version = 2;
                }


                memcpy(mntfh->data, data->root.data, mntfh->size);
                if (mntfh->size < sizeof(mntfh->data))
                        memset(mntfh->data + mntfh->size, 0,
                               sizeof(mntfh->data) - mntfh->size);

                /*
                 * Translate to nfs_parsed_mount_data, which nfs_fill_super
                 * can deal with.
                 */
                args->flags             = data->flags & NFS_MOUNT_FLAGMASK;
                args->rsize             = data->rsize;
                args->wsize             = data->wsize;
                args->timeo             = data->timeo;
                args->retrans           = data->retrans;
                args->acregmin          = data->acregmin;
                args->acregmax          = data->acregmax;
                args->acdirmin          = data->acdirmin;
                args->acdirmax          = data->acdirmax;

                memcpy(sap, &data->addr, sizeof(data->addr));
                args->nfs_server.addrlen = sizeof(data->addr);
                if (!nfs_verify_server_address(sap))
                        goto out_no_address;

                if (!(data->flags & NFS_MOUNT_TCP))
                        args->nfs_server.protocol = XPRT_TRANSPORT_UDP;
                /* N.B. caller will free nfs_server.hostname in all cases */
                args->nfs_server.hostname = kstrdup(data->hostname, GFP_KERNEL);
                args->namlen            = data->namlen;
                args->bsize             = data->bsize;

                if (data->flags & NFS_MOUNT_SECFLAVOUR)
                        args->auth_flavors[0] = data->pseudoflavor;
                if (!args->nfs_server.hostname)
                        goto out_nomem;

                /*
                 * The legacy version 6 binary mount data from userspace has a
                 * field used only to transport selinux information into the
                 * the kernel.  To continue to support that functionality we
                 * have a touch of selinux knowledge here in the NFS code. The
                 * userspace code converted context=blah to just blah so we are
                 * converting back to the full string selinux understands.
                 */
                if (data->context[0]){
#ifdef CONFIG_SECURITY_SELINUX
                        int rc;
                        char *opts_str = kmalloc(sizeof(data->context) + 8, GFP_KERNEL);
                        if (!opts_str)
                                return -ENOMEM;
                        strcpy(opts_str, "context=");
                        data->context[NFS_MAX_CONTEXT_LEN] = '\0';
                        strcat(opts_str, &data->context[0]);
                        rc = security_sb_parse_opts_str(opts_str, &args->lsm_opts);
                        kfree(opts_str);
                        if (rc)
                                return rc;
#else
                        return -EINVAL;
#endif
                }

                break;
        default: {
                int status;

                if (nfs_parse_mount_options((char *)options, args) == 0)
                        return -EINVAL;

                if (!nfs_verify_server_address(sap))
                        goto out_no_address;

                if (args->version == 4)
#ifdef CONFIG_NFS_V4
                        return nfs4_validate_text_mount_data(options,
                                                             args, dev_name);
#else
                        goto out_v4_not_compiled;
#endif

                nfs_set_port(sap, &args->nfs_server.port, 0);

                nfs_set_mount_transport_protocol(args);

                status = nfs_parse_devname(dev_name,
                                           &args->nfs_server.hostname,
                                           PAGE_SIZE,
                                           &args->nfs_server.export_path,
                                           NFS_MAXPATHLEN);
                if (!status)
                        status = nfs_try_mount(args, mntfh);

                kfree(args->nfs_server.export_path);
                args->nfs_server.export_path = NULL;

                if (status)
                        return status;

                break;
                }
        }

#ifndef CONFIG_NFS_V3
        if (args->version == 3)
                goto out_v3_not_compiled;
#endif /* !CONFIG_NFS_V3 */

        return 0;

out_no_data:
        dfprintk(MOUNT, "NFS: mount program didn't pass any mount data\n");
        return -EINVAL;

out_no_v3:
        dfprintk(MOUNT, "NFS: nfs_mount_data version %d does not support v3\n",
                 data->version);
        return -EINVAL;

out_no_sec:
        dfprintk(MOUNT, "NFS: nfs_mount_data version supports only AUTH_SYS\n");
        return -EINVAL;

#ifndef CONFIG_NFS_V3
out_v3_not_compiled:
        dfprintk(MOUNT, "NFS: NFSv3 is not compiled into kernel\n");
        return -EPROTONOSUPPORT;
#endif /* !CONFIG_NFS_V3 */

#ifndef CONFIG_NFS_V4
out_v4_not_compiled:
        dfprintk(MOUNT, "NFS: NFSv4 is not compiled into kernel\n");
        return -EPROTONOSUPPORT;
#endif /* !CONFIG_NFS_V4 */

out_nomem:
        dfprintk(MOUNT, "NFS: not enough memory to handle mount options\n");
        return -ENOMEM;

out_no_address:
        dfprintk(MOUNT, "NFS: mount program didn't pass remote address\n");
        return -EINVAL;

out_invalid_fh:
        dfprintk(MOUNT, "NFS: invalid root filehandle\n");
        return -EINVAL;
}

static int
nfs_compare_remount_data(struct nfs_server *nfss,
                         struct nfs_parsed_mount_data *data)
{
        if (data->flags != nfss->flags ||
            data->rsize != nfss->rsize ||
            data->wsize != nfss->wsize ||
            data->retrans != nfss->client->cl_timeout->to_retries ||
            data->auth_flavors[0] != nfss->client->cl_auth->au_flavor ||
            data->acregmin != nfss->acregmin / HZ ||
            data->acregmax != nfss->acregmax / HZ ||
            data->acdirmin != nfss->acdirmin / HZ ||
            data->acdirmax != nfss->acdirmax / HZ ||
            data->timeo != (10U * nfss->client->cl_timeout->to_initval / HZ) ||
            data->nfs_server.port != nfss->port ||
            data->nfs_server.addrlen != nfss->nfs_client->cl_addrlen ||
            !rpc_cmp_addr((struct sockaddr *)&data->nfs_server.address,
                          (struct sockaddr *)&nfss->nfs_client->cl_addr))
                return -EINVAL;

        return 0;
}

static int
nfs_remount(struct super_block *sb, int *flags, char *raw_data)
{
        int error;
        struct nfs_server *nfss = sb->s_fs_info;
        struct nfs_parsed_mount_data *data;
        struct nfs_mount_data *options = (struct nfs_mount_data *)raw_data;
        struct nfs4_mount_data *options4 = (struct nfs4_mount_data *)raw_data;
        u32 nfsvers = nfss->nfs_client->rpc_ops->version;

        /*
         * Userspace mount programs that send binary options generally send
         * them populated with default values. We have no way to know which
         * ones were explicitly specified. Fall back to legacy behavior and
         * just return success.
         */
        if ((nfsvers == 4 && (!options4 || options4->version == 1)) ||
            (nfsvers <= 3 && (!options || (options->version >= 1 &&
                                           options->version <= 6))))
                return 0;

        data = kzalloc(sizeof(*data), GFP_KERNEL);
        if (data == NULL)
                return -ENOMEM;

        /* fill out struct with values from existing mount */
        data->flags = nfss->flags;
        data->rsize = nfss->rsize;
        data->wsize = nfss->wsize;
        data->retrans = nfss->client->cl_timeout->to_retries;
        data->auth_flavors[0] = nfss->client->cl_auth->au_flavor;
        data->acregmin = nfss->acregmin / HZ;
        data->acregmax = nfss->acregmax / HZ;
        data->acdirmin = nfss->acdirmin / HZ;
        data->acdirmax = nfss->acdirmax / HZ;
        data->timeo = 10U * nfss->client->cl_timeout->to_initval / HZ;
        data->nfs_server.port = nfss->port;
        data->nfs_server.addrlen = nfss->nfs_client->cl_addrlen;
        memcpy(&data->nfs_server.address, &nfss->nfs_client->cl_addr,
                data->nfs_server.addrlen);

        /* overwrite those values with any that were specified */
        error = nfs_parse_mount_options((char *)options, data);

        if (error < 0)
                goto out;

        /* compare new mount options with old ones */
        error = nfs_compare_remount_data(nfss, data);
out:
        kfree(data);
        return error;
}

/*
 * Initialise the common bits of the superblock
 */
static inline void nfs_initialise_sb(struct super_block *sb)
{
        struct nfs_server *server = NFS_SB(sb);

        sb->s_magic = NFS_SUPER_MAGIC;

        /* We probably want something more informative here */
        snprintf(sb->s_id, sizeof(sb->s_id),
                 "%x:%x", MAJOR(sb->s_dev), MINOR(sb->s_dev));

        if (sb->s_blocksize == 0)
                sb->s_blocksize = nfs_block_bits(server->wsize,
                                                 &sb->s_blocksize_bits);

        if (server->flags & NFS_MOUNT_NOAC)
                sb->s_flags |= MS_SYNCHRONOUS;

        sb->s_bdi = &server->backing_dev_info;

        nfs_super_set_maxbytes(sb, server->maxfilesize);
}

/*
 * Finish setting up an NFS2/3 superblock
 */
static void nfs_fill_super(struct super_block *sb,
                           struct nfs_parsed_mount_data *data)
{
        struct nfs_server *server = NFS_SB(sb);

        sb->s_blocksize_bits = 0;
        sb->s_blocksize = 0;
        if (data->bsize)
                sb->s_blocksize = nfs_block_size(data->bsize, &sb->s_blocksize_bits);

        if (server->nfs_client->rpc_ops->version == 3) {
                /* The VFS shouldn't apply the umask to mode bits. We will do
                 * so ourselves when necessary.
                 */
                sb->s_flags |= MS_POSIXACL;
                sb->s_time_gran = 1;
        }

        sb->s_op = &nfs_sops;
        nfs_initialise_sb(sb);
}

/*
 * Finish setting up a cloned NFS2/3 superblock
 */
static void nfs_clone_super(struct super_block *sb,
                            const struct super_block *old_sb)
{
        struct nfs_server *server = NFS_SB(sb);

        sb->s_blocksize_bits = old_sb->s_blocksize_bits;
        sb->s_blocksize = old_sb->s_blocksize;
        sb->s_maxbytes = old_sb->s_maxbytes;

        if (server->nfs_client->rpc_ops->version == 3) {
                /* The VFS shouldn't apply the umask to mode bits. We will do
                 * so ourselves when necessary.
                 */
                sb->s_flags |= MS_POSIXACL;
                sb->s_time_gran = 1;
        }

        sb->s_op = old_sb->s_op;
        nfs_initialise_sb(sb);
}

static int nfs_compare_mount_options(const struct super_block *s, const struct nfs_server *b, int flags)
{
        const struct nfs_server *a = s->s_fs_info;
        const struct rpc_clnt *clnt_a = a->client;
        const struct rpc_clnt *clnt_b = b->client;

        if ((s->s_flags & NFS_MS_MASK) != (flags & NFS_MS_MASK))
                goto Ebusy;
        if (a->nfs_client != b->nfs_client)
                goto Ebusy;
        if (a->flags != b->flags)
                goto Ebusy;
        if (a->wsize != b->wsize)
                goto Ebusy;
        if (a->rsize != b->rsize)
                goto Ebusy;
        if (a->acregmin != b->acregmin)
                goto Ebusy;
        if (a->acregmax != b->acregmax)
                goto Ebusy;
        if (a->acdirmin != b->acdirmin)
                goto Ebusy;
        if (a->acdirmax != b->acdirmax)
                goto Ebusy;
        if (clnt_a->cl_auth->au_flavor != clnt_b->cl_auth->au_flavor)
                goto Ebusy;
        return 1;
Ebusy:
        return 0;
}

struct nfs_sb_mountdata {
        struct nfs_server *server;
        int mntflags;
};

static int nfs_set_super(struct super_block *s, void *data)
{
        struct nfs_sb_mountdata *sb_mntdata = data;
        struct nfs_server *server = sb_mntdata->server;
        int ret;

        s->s_flags = sb_mntdata->mntflags;
        s->s_fs_info = server;
        ret = set_anon_super(s, server);
        if (ret == 0)
                server->s_dev = s->s_dev;
        return ret;
}

static int nfs_compare_super_address(struct nfs_server *server1,
                                     struct nfs_server *server2)
{
        struct sockaddr *sap1, *sap2;

        sap1 = (struct sockaddr *)&server1->nfs_client->cl_addr;
        sap2 = (struct sockaddr *)&server2->nfs_client->cl_addr;

        if (sap1->sa_family != sap2->sa_family)
                return 0;

        switch (sap1->sa_family) {
        case AF_INET: {
                struct sockaddr_in *sin1 = (struct sockaddr_in *)sap1;
                struct sockaddr_in *sin2 = (struct sockaddr_in *)sap2;
                if (sin1->sin_addr.s_addr != sin2->sin_addr.s_addr)
                        return 0;
                if (sin1->sin_port != sin2->sin_port)
                        return 0;
                break;
        }
        case AF_INET6: {
                struct sockaddr_in6 *sin1 = (struct sockaddr_in6 *)sap1;
                struct sockaddr_in6 *sin2 = (struct sockaddr_in6 *)sap2;
                if (!ipv6_addr_equal(&sin1->sin6_addr, &sin2->sin6_addr))
                        return 0;
                if (sin1->sin6_port != sin2->sin6_port)
                        return 0;
                break;
        }
        default:
                return 0;
        }

        return 1;
}

static int nfs_compare_super(struct super_block *sb, void *data)
{
        struct nfs_sb_mountdata *sb_mntdata = data;
        struct nfs_server *server = sb_mntdata->server, *old = NFS_SB(sb);
        int mntflags = sb_mntdata->mntflags;

        if (!nfs_compare_super_address(old, server))
                return 0;
        /* Note: NFS_MOUNT_UNSHARED == NFS4_MOUNT_UNSHARED */
        if (old->flags & NFS_MOUNT_UNSHARED)
                return 0;
        if (memcmp(&old->fsid, &server->fsid, sizeof(old->fsid)) != 0)
                return 0;
        return nfs_compare_mount_options(sb, server, mntflags);
}

static int nfs_bdi_register(struct nfs_server *server)
{
        return bdi_register_dev(&server->backing_dev_info, server->s_dev);
}

static int nfs_get_sb(struct file_system_type *fs_type,
        int flags, const char *dev_name, void *raw_data, struct vfsmount *mnt)
{
        struct nfs_server *server = NULL;
        struct super_block *s;
        struct nfs_parsed_mount_data *data;
        struct nfs_fh *mntfh;
        struct dentry *mntroot;
        int (*compare_super)(struct super_block *, void *) = nfs_compare_super;
        struct nfs_sb_mountdata sb_mntdata = {
                .mntflags = flags,
        };
        int error = -ENOMEM;

        data = nfs_alloc_parsed_mount_data(3);
        mntfh = nfs_alloc_fhandle();
        if (data == NULL || mntfh == NULL)
                goto out_free_fh;

        security_init_mnt_opts(&data->lsm_opts);

        /* Validate the mount data */
        error = nfs_validate_mount_data(raw_data, data, mntfh, dev_name);
        if (error < 0)
                goto out;

#ifdef CONFIG_NFS_V4
        if (data->version == 4) {
                error = nfs4_try_mount(flags, dev_name, data, mnt);
                kfree(data->client_address);
                kfree(data->nfs_server.export_path);
                goto out;
        }
#endif  /* CONFIG_NFS_V4 */

        /* Get a volume representation */
        server = nfs_create_server(data, mntfh);
        if (IS_ERR(server)) {
                error = PTR_ERR(server);
                goto out;
        }
        sb_mntdata.server = server;

        if (server->flags & NFS_MOUNT_UNSHARED)
                compare_super = NULL;

        /* Get a superblock - note that we may end up sharing one that already exists */
        s = sget(fs_type, compare_super, nfs_set_super, &sb_mntdata);
        if (IS_ERR(s)) {
                error = PTR_ERR(s);
                goto out_err_nosb;
        }

        if (s->s_fs_info != server) {
                nfs_free_server(server);
                server = NULL;
        } else {
                error = nfs_bdi_register(server);
                if (error)
                        goto error_splat_bdi;
        }

        if (!s->s_root) {
                /* initial superblock/root creation */
                nfs_fill_super(s, data);
                nfs_fscache_get_super_cookie(
                        s, data ? data->fscache_uniq : NULL, NULL);
        }

        mntroot = nfs_get_root(s, mntfh);
        if (IS_ERR(mntroot)) {
                error = PTR_ERR(mntroot);
                goto error_splat_super;
        }

        error = security_sb_set_mnt_opts(s, &data->lsm_opts);
        if (error)
                goto error_splat_root;

        s->s_flags |= MS_ACTIVE;
        mnt->mnt_sb = s;
        mnt->mnt_root = mntroot;
        error = 0;

out:
        kfree(data->nfs_server.hostname);
        kfree(data->mount_server.hostname);
        kfree(data->fscache_uniq);
        security_free_mnt_opts(&data->lsm_opts);
out_free_fh:
        nfs_free_fhandle(mntfh);
        kfree(data);
        return error;

out_err_nosb:
        nfs_free_server(server);
        goto out;

error_splat_root:
        dput(mntroot);
error_splat_super:
        if (server && !s->s_root)
                bdi_unregister(&server->backing_dev_info);
error_splat_bdi:
        deactivate_locked_super(s);
        goto out;
}

/*
 * Ensure that we unregister the bdi before kill_anon_super
 * releases the device name
 */
static void nfs_put_super(struct super_block *s)
{
        struct nfs_server *server = NFS_SB(s);

        bdi_unregister(&server->backing_dev_info);
}

/*
 * Destroy an NFS2/3 superblock
 */
static void nfs_kill_super(struct super_block *s)
{
        struct nfs_server *server = NFS_SB(s);

        kill_anon_super(s);
        nfs_fscache_release_super_cookie(s);
        nfs_free_server(server);
}

/*
 * Clone an NFS2/3 server record on xdev traversal (FSID-change)
 */
static int nfs_xdev_get_sb(struct file_system_type *fs_type, int flags,
                           const char *dev_name, void *raw_data,
                           struct vfsmount *mnt)
{
        struct nfs_clone_mount *data = raw_data;
        struct super_block *s;
        struct nfs_server *server;
        struct dentry *mntroot;
        int (*compare_super)(struct super_block *, void *) = nfs_compare_super;
        struct nfs_sb_mountdata sb_mntdata = {
                .mntflags = flags,
        };
        int error;

        dprintk("--> nfs_xdev_get_sb()\n");

        /* create a new volume representation */
        server = nfs_clone_server(NFS_SB(data->sb), data->fh, data->fattr);
        if (IS_ERR(server)) {
                error = PTR_ERR(server);
                goto out_err_noserver;
        }
        sb_mntdata.server = server;

        if (server->flags & NFS_MOUNT_UNSHARED)
                compare_super = NULL;

        /* Get a superblock - note that we may end up sharing one that already exists */
        s = sget(&nfs_fs_type, compare_super, nfs_set_super, &sb_mntdata);
        if (IS_ERR(s)) {
                error = PTR_ERR(s);
                goto out_err_nosb;
        }

        if (s->s_fs_info != server) {
                nfs_free_server(server);
                server = NULL;
        } else {
                error = nfs_bdi_register(server);
                if (error)
                        goto error_splat_bdi;
        }

        if (!s->s_root) {
                /* initial superblock/root creation */
                nfs_clone_super(s, data->sb);
                nfs_fscache_get_super_cookie(s, NULL, data);
        }

        mntroot = nfs_get_root(s, data->fh);
        if (IS_ERR(mntroot)) {
                error = PTR_ERR(mntroot);
                goto error_splat_super;
        }
        if (mntroot->d_inode->i_op != NFS_SB(s)->nfs_client->rpc_ops->dir_inode_ops) {
                dput(mntroot);
                error = -ESTALE;
                goto error_splat_super;
        }

        s->s_flags |= MS_ACTIVE;
        mnt->mnt_sb = s;
        mnt->mnt_root = mntroot;

        /* clone any lsm security options from the parent to the new sb */
        security_sb_clone_mnt_opts(data->sb, s);

        dprintk("<-- nfs_xdev_get_sb() = 0\n");
        return 0;

out_err_nosb:
        nfs_free_server(server);
out_err_noserver:
        dprintk("<-- nfs_xdev_get_sb() = %d [error]\n", error);
        return error;

error_splat_super:
        if (server && !s->s_root)
                bdi_unregister(&server->backing_dev_info);
error_splat_bdi:
        deactivate_locked_super(s);
        dprintk("<-- nfs_xdev_get_sb() = %d [splat]\n", error);
        return error;
}

#ifdef CONFIG_NFS_V4

/*
 * Finish setting up a cloned NFS4 superblock
 */
static void nfs4_clone_super(struct super_block *sb,
                            const struct super_block *old_sb)
{
        sb->s_blocksize_bits = old_sb->s_blocksize_bits;
        sb->s_blocksize = old_sb->s_blocksize;
        sb->s_maxbytes = old_sb->s_maxbytes;
        sb->s_time_gran = 1;
        sb->s_op = old_sb->s_op;
        nfs_initialise_sb(sb);
}

/*
 * Set up an NFS4 superblock
 */
static void nfs4_fill_super(struct super_block *sb)
{
        sb->s_time_gran = 1;
        sb->s_op = &nfs4_sops;
        nfs_initialise_sb(sb);
}

static void nfs4_validate_mount_flags(struct nfs_parsed_mount_data *args)
{
        args->flags &= ~(NFS_MOUNT_NONLM|NFS_MOUNT_NOACL|NFS_MOUNT_VER3);
}

static int nfs4_validate_text_mount_data(void *options,
                                         struct nfs_parsed_mount_data *args,
                                         const char *dev_name)
{
        struct sockaddr *sap = (struct sockaddr *)&args->nfs_server.address;

        nfs_set_port(sap, &args->nfs_server.port, NFS_PORT);

        nfs_validate_transport_protocol(args);

        nfs4_validate_mount_flags(args);

        if (args->version != 4) {
                dfprintk(MOUNT,
                         "NFS4: Illegal mount version\n");
                return -EINVAL;
        }

        if (args->auth_flavor_len > 1) {
                dfprintk(MOUNT,
                         "NFS4: Too many RPC auth flavours specified\n");
                return -EINVAL;
        }

        if (args->client_address == NULL) {
                dfprintk(MOUNT,
                         "NFS4: mount program didn't pass callback address\n");
                return -EINVAL;
        }

        return nfs_parse_devname(dev_name,
                                   &args->nfs_server.hostname,
                                   NFS4_MAXNAMLEN,
                                   &args->nfs_server.export_path,
                                   NFS4_MAXPATHLEN);
}

/*
 * Validate NFSv4 mount options
 */
static int nfs4_validate_mount_data(void *options,
                                    struct nfs_parsed_mount_data *args,
                                    const char *dev_name)
{
        struct sockaddr *sap = (struct sockaddr *)&args->nfs_server.address;
        struct nfs4_mount_data *data = (struct nfs4_mount_data *)options;
        char *c;

        if (data == NULL)
                goto out_no_data;

        switch (data->version) {
        case 1:
                if (data->host_addrlen > sizeof(args->nfs_server.address))
                        goto out_no_address;
                if (data->host_addrlen == 0)
                        goto out_no_address;
                args->nfs_server.addrlen = data->host_addrlen;
                if (copy_from_user(sap, data->host_addr, data->host_addrlen))
                        return -EFAULT;
                if (!nfs_verify_server_address(sap))
                        goto out_no_address;

                if (data->auth_flavourlen) {
                        if (data->auth_flavourlen > 1)
                                goto out_inval_auth;
                        if (copy_from_user(&args->auth_flavors[0],
                                           data->auth_flavours,
                                           sizeof(args->auth_flavors[0])))
                                return -EFAULT;
                }

                c = strndup_user(data->hostname.data, NFS4_MAXNAMLEN);
                if (IS_ERR(c))
                        return PTR_ERR(c);
                args->nfs_server.hostname = c;

                c = strndup_user(data->mnt_path.data, NFS4_MAXPATHLEN);
                if (IS_ERR(c))
                        return PTR_ERR(c);
                args->nfs_server.export_path = c;
                dfprintk(MOUNT, "NFS: MNTPATH: '%s'\n", c);

                c = strndup_user(data->client_addr.data, 16);
                if (IS_ERR(c))
                        return PTR_ERR(c);
                args->client_address = c;

                /*
                 * Translate to nfs_parsed_mount_data, which nfs4_fill_super
                 * can deal with.
                 */

                args->flags     = data->flags & NFS4_MOUNT_FLAGMASK;
                args->rsize     = data->rsize;
                args->wsize     = data->wsize;
                args->timeo     = data->timeo;
                args->retrans   = data->retrans;
                args->acregmin  = data->acregmin;
                args->acregmax  = data->acregmax;
                args->acdirmin  = data->acdirmin;
                args->acdirmax  = data->acdirmax;
                args->nfs_server.protocol = data->proto;
                nfs_validate_transport_protocol(args);

                break;
        default:
                if (nfs_parse_mount_options((char *)options, args) == 0)
                        return -EINVAL;

                if (!nfs_verify_server_address(sap))
                        return -EINVAL;

                return nfs4_validate_text_mount_data(options, args, dev_name);
        }

        return 0;

out_no_data:
        dfprintk(MOUNT, "NFS4: mount program didn't pass any mount data\n");
        return -EINVAL;

out_inval_auth:
        dfprintk(MOUNT, "NFS4: Invalid number of RPC auth flavours %d\n",
                 data->auth_flavourlen);
        return -EINVAL;

out_no_address:
        dfprintk(MOUNT, "NFS4: mount program didn't pass remote address\n");
        return -EINVAL;
}

/*
 * Get the superblock for the NFS4 root partition
 */
static int nfs4_remote_get_sb(struct file_system_type *fs_type,
        int flags, const char *dev_name, void *raw_data, struct vfsmount *mnt)
{
        struct nfs_parsed_mount_data *data = raw_data;
        struct super_block *s;
        struct nfs_server *server;
        struct nfs_fh *mntfh;
        struct dentry *mntroot;
        int (*compare_super)(struct super_block *, void *) = nfs_compare_super;
        struct nfs_sb_mountdata sb_mntdata = {
                .mntflags = flags,
        };
        int error = -ENOMEM;

        mntfh = nfs_alloc_fhandle();
        if (data == NULL || mntfh == NULL)
                goto out_free_fh;

        security_init_mnt_opts(&data->lsm_opts);

        /* Get a volume representation */
        server = nfs4_create_server(data, mntfh);
        if (IS_ERR(server)) {
                error = PTR_ERR(server);
                goto out;
        }
        sb_mntdata.server = server;

        if (server->flags & NFS4_MOUNT_UNSHARED)
                compare_super = NULL;

        /* Get a superblock - note that we may end up sharing one that already exists */
        s = sget(&nfs4_fs_type, compare_super, nfs_set_super, &sb_mntdata);
        if (IS_ERR(s)) {
                error = PTR_ERR(s);
                goto out_free;
        }

        if (s->s_fs_info != server) {
                nfs_free_server(server);
                server = NULL;
        } else {
                error = nfs_bdi_register(server);
                if (error)
                        goto error_splat_bdi;
        }

        if (!s->s_root) {
                /* initial superblock/root creation */
                nfs4_fill_super(s);
                nfs_fscache_get_super_cookie(
                        s, data ? data->fscache_uniq : NULL, NULL);
        }

        mntroot = nfs4_get_root(s, mntfh);
        if (IS_ERR(mntroot)) {
                error = PTR_ERR(mntroot);
                goto error_splat_super;
        }

        error = security_sb_set_mnt_opts(s, &data->lsm_opts);
        if (error)
                goto error_splat_root;

        s->s_flags |= MS_ACTIVE;
        mnt->mnt_sb = s;
        mnt->mnt_root = mntroot;
        error = 0;

out:
        security_free_mnt_opts(&data->lsm_opts);
out_free_fh:
        nfs_free_fhandle(mntfh);
        return error;

out_free:
        nfs_free_server(server);
        goto out;

error_splat_root:
        dput(mntroot);
error_splat_super:
        if (server && !s->s_root)
                bdi_unregister(&server->backing_dev_info);
error_splat_bdi:
        deactivate_locked_super(s);
        goto out;
}

static struct vfsmount *nfs_do_root_mount(struct file_system_type *fs_type,
                int flags, void *data, const char *hostname)
{
        struct vfsmount *root_mnt;
        char *root_devname;
        size_t len;

        len = strlen(hostname) + 3;
        root_devname = kmalloc(len, GFP_KERNEL);
        if (root_devname == NULL)
                return ERR_PTR(-ENOMEM);
        snprintf(root_devname, len, "%s:/", hostname);
        root_mnt = vfs_kern_mount(fs_type, flags, root_devname, data);
        kfree(root_devname);
        return root_mnt;
}

static void nfs_fix_devname(const struct path *path, struct vfsmount *mnt)
{
        char *page = (char *) __get_free_page(GFP_KERNEL);
        char *devname, *tmp;

        if (page == NULL)
                return;
        devname = nfs_path(path->mnt->mnt_devname,
                        path->mnt->mnt_root, path->dentry,
                        page, PAGE_SIZE);
        if (IS_ERR(devname))
                goto out_freepage;
        tmp = kstrdup(devname, GFP_KERNEL);
        if (tmp == NULL)
                goto out_freepage;
        kfree(mnt->mnt_devname);
        mnt->mnt_devname = tmp;
out_freepage:
        free_page((unsigned long)page);
}

struct nfs_referral_count {
        struct list_head list;
        const struct task_struct *task;
        unsigned int referral_count;
};

static LIST_HEAD(nfs_referral_count_list);
static DEFINE_SPINLOCK(nfs_referral_count_list_lock);

static struct nfs_referral_count *nfs_find_referral_count(void)
{
        struct nfs_referral_count *p;

        list_for_each_entry(p, &nfs_referral_count_list, list) {
                if (p->task == current)
                        return p;
        }
        return NULL;
}

#define NFS_MAX_NESTED_REFERRALS 2

static int nfs_referral_loop_protect(void)
{
        struct nfs_referral_count *p, *new;
        int ret = -ENOMEM;

        new = kmalloc(sizeof(*new), GFP_KERNEL);
        if (!new)
                goto out;
        new->task = current;
        new->referral_count = 1;

        ret = 0;
        spin_lock(&nfs_referral_count_list_lock);
        p = nfs_find_referral_count();
        if (p != NULL) {
                if (p->referral_count >= NFS_MAX_NESTED_REFERRALS)
                        ret = -ELOOP;
                else
                        p->referral_count++;
        } else {
                list_add(&new->list, &nfs_referral_count_list);
                new = NULL;
        }
        spin_unlock(&nfs_referral_count_list_lock);
        kfree(new);
out:
        return ret;
}

static void nfs_referral_loop_unprotect(void)
{
        struct nfs_referral_count *p;

        spin_lock(&nfs_referral_count_list_lock);
        p = nfs_find_referral_count();
        p->referral_count--;
        if (p->referral_count == 0)
                list_del(&p->list);
        else
                p = NULL;
        spin_unlock(&nfs_referral_count_list_lock);
        kfree(p);
}

static int nfs_follow_remote_path(struct vfsmount *root_mnt,
                const char *export_path, struct vfsmount *mnt_target)
{
        struct nameidata *nd = NULL;
        struct mnt_namespace *ns_private;
        struct super_block *s;
        int ret;

        nd = kmalloc(sizeof(*nd), GFP_KERNEL);
        if (nd == NULL)
                return -ENOMEM;

        ns_private = create_mnt_ns(root_mnt);
        ret = PTR_ERR(ns_private);
        if (IS_ERR(ns_private))
                goto out_mntput;

        ret = nfs_referral_loop_protect();
        if (ret != 0)
                goto out_put_mnt_ns;

        ret = vfs_path_lookup(root_mnt->mnt_root, root_mnt,
                        export_path, LOOKUP_FOLLOW, nd);

        nfs_referral_loop_unprotect();
        put_mnt_ns(ns_private);

        if (ret != 0)
                goto out_err;

        s = nd->path.mnt->mnt_sb;
        atomic_inc(&s->s_active);
        mnt_target->mnt_sb = s;
        mnt_target->mnt_root = dget(nd->path.dentry);

        /* Correct the device pathname */
        nfs_fix_devname(&nd->path, mnt_target);

        path_put(&nd->path);
        kfree(nd);
        down_write(&s->s_umount);
        return 0;
out_put_mnt_ns:
        put_mnt_ns(ns_private);
out_mntput:
        mntput(root_mnt);
out_err:
        kfree(nd);
        return ret;
}

static int nfs4_try_mount(int flags, const char *dev_name,
                         struct nfs_parsed_mount_data *data,
                         struct vfsmount *mnt)
{
        char *export_path;
        struct vfsmount *root_mnt;
        int error;

        dfprintk(MOUNT, "--> nfs4_try_mount()\n");

        export_path = data->nfs_server.export_path;
        data->nfs_server.export_path = "/";
        root_mnt = nfs_do_root_mount(&nfs4_remote_fs_type, flags, data,
                        data->nfs_server.hostname);
        data->nfs_server.export_path = export_path;

        error = PTR_ERR(root_mnt);
        if (IS_ERR(root_mnt))
                goto out;

        error = nfs_follow_remote_path(root_mnt, export_path, mnt);

out:
        dfprintk(MOUNT, "<-- nfs4_try_mount() = %d%s\n", error,
                        error != 0 ? " [error]" : "");
        return error;
}

/*
 * Get the superblock for an NFS4 mountpoint
 */
static int nfs4_get_sb(struct file_system_type *fs_type,
        int flags, const char *dev_name, void *raw_data, struct vfsmount *mnt)
{
        struct nfs_parsed_mount_data *data;
        int error = -ENOMEM;

        data = nfs_alloc_parsed_mount_data(4);
        if (data == NULL)
                goto out_free_data;

        /* Validate the mount data */
        error = nfs4_validate_mount_data(raw_data, data, dev_name);
        if (error < 0)
                goto out;

        error = nfs4_try_mount(flags, dev_name, data, mnt);

out:
        kfree(data->client_address);
        kfree(data->nfs_server.export_path);
        kfree(data->nfs_server.hostname);
        kfree(data->fscache_uniq);
out_free_data:
        kfree(data);
        dprintk("<-- nfs4_get_sb() = %d%s\n", error,
                        error != 0 ? " [error]" : "");
        return error;
}

static void nfs4_kill_super(struct super_block *sb)
{
        struct nfs_server *server = NFS_SB(sb);

        dprintk("--> %s\n", __func__);
        nfs_super_return_all_delegations(sb);
        kill_anon_super(sb);
        nfs_fscache_release_super_cookie(sb);
        nfs_free_server(server);
        dprintk("<-- %s\n", __func__);
}

/*
 * Clone an NFS4 server record on xdev traversal (FSID-change)
 */
static int nfs4_xdev_get_sb(struct file_system_type *fs_type, int flags,
                            const char *dev_name, void *raw_data,
                            struct vfsmount *mnt)
{
        struct nfs_clone_mount *data = raw_data;
        struct super_block *s;
        struct nfs_server *server;
        struct dentry *mntroot;
        int (*compare_super)(struct super_block *, void *) = nfs_compare_super;
        struct nfs_sb_mountdata sb_mntdata = {
                .mntflags = flags,
        };
        int error;

        dprintk("--> nfs4_xdev_get_sb()\n");

        /* create a new volume representation */
        server = nfs_clone_server(NFS_SB(data->sb), data->fh, data->fattr);
        if (IS_ERR(server)) {
                error = PTR_ERR(server);
                goto out_err_noserver;
        }
        sb_mntdata.server = server;

        if (server->flags & NFS4_MOUNT_UNSHARED)
                compare_super = NULL;

        /* Get a superblock - note that we may end up sharing one that already exists */
        s = sget(&nfs4_fs_type, compare_super, nfs_set_super, &sb_mntdata);
        if (IS_ERR(s)) {
                error = PTR_ERR(s);
                goto out_err_nosb;
        }

        if (s->s_fs_info != server) {
                nfs_free_server(server);
                server = NULL;
        } else {
                error = nfs_bdi_register(server);
                if (error)
                        goto error_splat_bdi;
        }

        if (!s->s_root) {
                /* initial superblock/root creation */
                nfs4_clone_super(s, data->sb);
                nfs_fscache_get_super_cookie(s, NULL, data);
        }

        mntroot = nfs4_get_root(s, data->fh);
        if (IS_ERR(mntroot)) {
                error = PTR_ERR(mntroot);
                goto error_splat_super;
        }
        if (mntroot->d_inode->i_op != NFS_SB(s)->nfs_client->rpc_ops->dir_inode_ops) {
                dput(mntroot);
                error = -ESTALE;
                goto error_splat_super;
        }

        s->s_flags |= MS_ACTIVE;
        mnt->mnt_sb = s;
        mnt->mnt_root = mntroot;

        security_sb_clone_mnt_opts(data->sb, s);

        dprintk("<-- nfs4_xdev_get_sb() = 0\n");
        return 0;

out_err_nosb:
        nfs_free_server(server);
out_err_noserver:
        dprintk("<-- nfs4_xdev_get_sb() = %d [error]\n", error);
        return error;

error_splat_super:
        if (server && !s->s_root)
                bdi_unregister(&server->backing_dev_info);
error_splat_bdi:
        deactivate_locked_super(s);
        dprintk("<-- nfs4_xdev_get_sb() = %d [splat]\n", error);
        return error;
}

static int nfs4_remote_referral_get_sb(struct file_system_type *fs_type,
                int flags, const char *dev_name, void *raw_data,
                struct vfsmount *mnt)
{
        struct nfs_clone_mount *data = raw_data;
        struct super_block *s;
        struct nfs_server *server;
        struct dentry *mntroot;
        struct nfs_fh *mntfh;
        int (*compare_super)(struct super_block *, void *) = nfs_compare_super;
        struct nfs_sb_mountdata sb_mntdata = {
                .mntflags = flags,
        };
        int error = -ENOMEM;

        dprintk("--> nfs4_referral_get_sb()\n");

        mntfh = nfs_alloc_fhandle();
        if (mntfh == NULL)
                goto out_err_nofh;