io_uring: ensure finish_wait() is always called in __io_uring_task_cancel()

[linux/fpc-iii.git] / fs / nfs / super.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 *  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/addr.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/seq_file.h>
#include <linux/mount.h>
#include <linux/namei.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 <linux/nsproxy.h>
#include <linux/rcupdate.h>

#include <linux/uaccess.h>
#include <linux/nfs_ssc.h>

#include "nfs4_fs.h"
#include "callback.h"
#include "delegation.h"
#include "iostat.h"
#include "internal.h"
#include "fscache.h"
#include "nfs4session.h"
#include "pnfs.h"
#include "nfs.h"

#define NFSDBG_FACILITY         NFSDBG_VFS

const struct super_operations nfs_sops = {
        .alloc_inode    = nfs_alloc_inode,
        .free_inode     = nfs_free_inode,
        .write_inode    = nfs_write_inode,
        .drop_inode     = nfs_drop_inode,
        .statfs         = nfs_statfs,
        .evict_inode    = nfs_evict_inode,
        .umount_begin   = nfs_umount_begin,
        .show_options   = nfs_show_options,
        .show_devname   = nfs_show_devname,
        .show_path      = nfs_show_path,
        .show_stats     = nfs_show_stats,
};
EXPORT_SYMBOL_GPL(nfs_sops);

static const struct nfs_ssc_client_ops nfs_ssc_clnt_ops_tbl = {
        .sco_sb_deactive = nfs_sb_deactive,
};

#if IS_ENABLED(CONFIG_NFS_V4)
static int __init register_nfs4_fs(void)
{
        return register_filesystem(&nfs4_fs_type);
}

static void unregister_nfs4_fs(void)
{
        unregister_filesystem(&nfs4_fs_type);
}
#else
static int __init register_nfs4_fs(void)
{
        return 0;
}

static void unregister_nfs4_fs(void)
{
}
#endif

static void nfs_ssc_register_ops(void)
{
        nfs_ssc_register(&nfs_ssc_clnt_ops_tbl);
}

static void nfs_ssc_unregister_ops(void)
{
        nfs_ssc_unregister(&nfs_ssc_clnt_ops_tbl);
}

static struct shrinker acl_shrinker = {
        .count_objects  = nfs_access_cache_count,
        .scan_objects   = nfs_access_cache_scan,
        .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 = register_nfs4_fs();
        if (ret < 0)
                goto error_1;

        ret = nfs_register_sysctl();
        if (ret < 0)
                goto error_2;
        ret = register_shrinker(&acl_shrinker);
        if (ret < 0)
                goto error_3;
        nfs_ssc_register_ops();
        return 0;
error_3:
        nfs_unregister_sysctl();
error_2:
        unregister_nfs4_fs();
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);
        nfs_unregister_sysctl();
        unregister_nfs4_fs();
        nfs_ssc_unregister_ops();
        unregister_filesystem(&nfs_fs_type);
}

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

        if (!atomic_inc_not_zero(&sb->s_active))
                return false;
        if (atomic_inc_return(&server->active) != 1)
                atomic_dec(&sb->s_active);
        return true;
}
EXPORT_SYMBOL_GPL(nfs_sb_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);
}
EXPORT_SYMBOL_GPL(nfs_sb_deactive);

static int __nfs_list_for_each_server(struct list_head *head,
                int (*fn)(struct nfs_server *, void *),
                void *data)
{
        struct nfs_server *server, *last = NULL;
        int ret = 0;

        rcu_read_lock();
        list_for_each_entry_rcu(server, head, client_link) {
                if (!(server->super && nfs_sb_active(server->super)))
                        continue;
                rcu_read_unlock();
                if (last)
                        nfs_sb_deactive(last->super);
                last = server;
                ret = fn(server, data);
                if (ret)
                        goto out;
                rcu_read_lock();
        }
        rcu_read_unlock();
out:
        if (last)
                nfs_sb_deactive(last->super);
        return ret;
}

int nfs_client_for_each_server(struct nfs_client *clp,
                int (*fn)(struct nfs_server *, void *),
                void *data)
{
        return __nfs_list_for_each_server(&clp->cl_superblocks, fn, data);
}
EXPORT_SYMBOL_GPL(nfs_client_for_each_server);

/*
 * Deliver file system statistics to userspace
 */
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(d_inode(dentry));
        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);
                nfs_zap_caches(d_inode(pd_dentry));
                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;
}
EXPORT_SYMBOL_GPL(nfs_statfs);

/*
 * 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[NFS_AUTH_INFO_MAX_FLAVORS] = {
                /* update NFS_AUTH_INFO_MAX_FLAVORS when this list changes! */
                { 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;
        char *proto = NULL;

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

        if (nfss->flags & NFS_MOUNT_LEGACY_INTERFACE)
                return;

        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_puts(m, ",mountaddr=unspecified");
        }

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

        nfs_show_mountd_netid(m, nfss, showdefaults);
}

#if IS_ENABLED(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);
}
#else
static void nfs_show_nfsv4_options(struct seq_file *m, struct nfs_server *nfss,
                                    int showdefaults)
{
}
#endif

static void nfs_show_nfs_version(struct seq_file *m,
                unsigned int version,
                unsigned int minorversion)
{
        seq_printf(m, ",vers=%u", version);
        if (version == 4)
                seq_printf(m, ".%u", minorversion);
}

/*
 * 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", "" },
                { NFS_MOUNT_SOFTERR, ",softerr", "" },
                { NFS_MOUNT_SOFTREVAL, ",softreval", "" },
                { 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;
        int local_flock, local_fcntl;

        nfs_show_nfs_version(m, version, clp->cl_minorversion);
        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);
        if (!(nfss->flags & (NFS_MOUNT_SOFT|NFS_MOUNT_SOFTERR)))
                        seq_puts(m, ",hard");
        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);
        }
        rcu_read_lock();
        seq_printf(m, ",proto=%s",
                   rpc_peeraddr2str(nfss->client, RPC_DISPLAY_NETID));
        rcu_read_unlock();
        if (clp->cl_nconnect > 0)
                seq_printf(m, ",nconnect=%u", clp->cl_nconnect);
        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_puts(m, ",fsc");

        if (nfss->options & NFS_OPTION_MIGRATION)
                seq_puts(m, ",migration");

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

        local_flock = nfss->flags & NFS_MOUNT_LOCAL_FLOCK;
        local_fcntl = nfss->flags & NFS_MOUNT_LOCAL_FCNTL;

        if (!local_flock && !local_fcntl)
                seq_puts(m, ",local_lock=none");
        else if (local_flock && local_fcntl)
                seq_puts(m, ",local_lock=all");
        else if (local_flock)
                seq_puts(m, ",local_lock=flock");
        else
                seq_puts(m, ",local_lock=posix");
}

/*
 * Describe the mount options on this VFS mountpoint
 */
int nfs_show_options(struct seq_file *m, struct dentry *root)
{
        struct nfs_server *nfss = NFS_SB(root->d_sb);

        nfs_show_mount_options(m, nfss, 0);

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

        return 0;
}
EXPORT_SYMBOL_GPL(nfs_show_options);

#if IS_ENABLED(CONFIG_NFS_V4)
static void show_lease(struct seq_file *m, struct nfs_server *server)
{
        struct nfs_client *clp = server->nfs_client;
        unsigned long expire;

        seq_printf(m, ",lease_time=%ld", clp->cl_lease_time / HZ);
        expire = clp->cl_last_renewal + clp->cl_lease_time;
        seq_printf(m, ",lease_expired=%ld",
                   time_after(expire, jiffies) ?  0 : (jiffies - expire) / HZ);
}
#ifdef CONFIG_NFS_V4_1
static void show_sessions(struct seq_file *m, struct nfs_server *server)
{
        if (nfs4_has_session(server->nfs_client))
                seq_puts(m, ",sessions");
}
#else
static void show_sessions(struct seq_file *m, struct nfs_server *server) {}
#endif
#endif

#ifdef CONFIG_NFS_V4_1
static void show_pnfs(struct seq_file *m, struct nfs_server *server)
{
        seq_printf(m, ",pnfs=");
        if (server->pnfs_curr_ld)
                seq_printf(m, "%s", server->pnfs_curr_ld->name);
        else
                seq_printf(m, "not configured");
}

static void show_implementation_id(struct seq_file *m, struct nfs_server *nfss)
{
        if (nfss->nfs_client && nfss->nfs_client->cl_implid) {
                struct nfs41_impl_id *impl_id = nfss->nfs_client->cl_implid;
                seq_printf(m, "\n\timpl_id:\tname='%s',domain='%s',"
                           "date='%llu,%u'",
                           impl_id->name, impl_id->domain,
                           impl_id->date.seconds, impl_id->date.nseconds);
        }
}
#else
#if IS_ENABLED(CONFIG_NFS_V4)
static void show_pnfs(struct seq_file *m, struct nfs_server *server)
{
}
#endif
static void show_implementation_id(struct seq_file *m, struct nfs_server *nfss)
{
}
#endif

int nfs_show_devname(struct seq_file *m, struct dentry *root)
{
        char *page = (char *) __get_free_page(GFP_KERNEL);
        char *devname, *dummy;
        int err = 0;
        if (!page)
                return -ENOMEM;
        devname = nfs_path(&dummy, root, page, PAGE_SIZE, 0);
        if (IS_ERR(devname))
                err = PTR_ERR(devname);
        else
                seq_escape(m, devname, " \t\n\\");
        free_page((unsigned long)page);
        return err;
}
EXPORT_SYMBOL_GPL(nfs_show_devname);

int nfs_show_path(struct seq_file *m, struct dentry *dentry)
{
        seq_puts(m, "/");
        return 0;
}
EXPORT_SYMBOL_GPL(nfs_show_path);

/*
 * Present statistical information for this VFS mountpoint
 */
int nfs_show_stats(struct seq_file *m, struct dentry *root)
{
        int i, cpu;
        struct nfs_server *nfss = NFS_SB(root->d_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_puts(m, "\n\topts:\t");
        seq_puts(m, sb_rdonly(root->d_sb) ? "ro" : "rw");
        seq_puts(m, root->d_sb->s_flags & SB_SYNCHRONOUS ? ",sync" : "");
        seq_puts(m, root->d_sb->s_flags & SB_NOATIME ? ",noatime" : "");
        seq_puts(m, root->d_sb->s_flags & SB_NODIRATIME ? ",nodiratime" : "");
        nfs_show_mount_options(m, nfss, 1);

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

        show_implementation_id(m, nfss);

        seq_puts(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);

#if IS_ENABLED(CONFIG_NFS_V4)
        if (nfss->nfs_client->rpc_ops->version == 4) {
                seq_puts(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, ",bm2=0x%x", nfss->attr_bitmask[2]);
                seq_printf(m, ",acl=0x%x", nfss->acl_bitmask);
                show_sessions(m, nfss);
                show_pnfs(m, nfss);
                show_lease(m, nfss);
        }
#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_puts(m, "\n\tevents:\t");
        for (i = 0; i < __NFSIOS_COUNTSMAX; i++)
                seq_printf(m, "%lu ", totals.events[i]);
        seq_puts(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_puts(m, "\n\tfsc:\t");
                for (i = 0; i < __NFSIOS_FSCACHEMAX; i++)
                        seq_printf(m, "%Lu ", totals.fscache[i]);
        }
#endif
        seq_putc(m, '\n');

        rpc_clnt_show_stats(m, nfss->client);

        return 0;
}
EXPORT_SYMBOL_GPL(nfs_show_stats);

/*
 * Begin unmount by attempting to remove all automounted mountpoints we added
 * in response to xdev traversals and referrals
 */
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);
}
EXPORT_SYMBOL_GPL(nfs_umount_begin);

/*
 * Return true if 'match' is in auth_info or auth_info is empty.
 * Return false otherwise.
 */
bool nfs_auth_info_match(const struct nfs_auth_info *auth_info,
                         rpc_authflavor_t match)
{
        int i;

        if (!auth_info->flavor_len)
                return true;

        for (i = 0; i < auth_info->flavor_len; i++) {
                if (auth_info->flavors[i] == match)
                        return true;
        }
        return false;
}
EXPORT_SYMBOL_GPL(nfs_auth_info_match);

/*
 * Ensure that a specified authtype in ctx->auth_info is supported by
 * the server. Returns 0 and sets ctx->selected_flavor if it's ok, and
 * -EACCES if not.
 */
static int nfs_verify_authflavors(struct nfs_fs_context *ctx,
                                  rpc_authflavor_t *server_authlist,
                                  unsigned int count)
{
        rpc_authflavor_t flavor = RPC_AUTH_MAXFLAVOR;
        bool found_auth_null = false;
        unsigned int i;

        /*
         * If the sec= mount option is used, the specified flavor or AUTH_NULL
         * must be in the list returned by the server.
         *
         * AUTH_NULL has a special meaning when it's in the server list - it
         * means that the server will ignore the rpc creds, so any flavor
         * can be used but still use the sec= that was specified.
         *
         * Note also that the MNT procedure in MNTv1 does not return a list
         * of supported security flavors. In this case, nfs_mount() fabricates
         * a security flavor list containing just AUTH_NULL.
         */
        for (i = 0; i < count; i++) {
                flavor = server_authlist[i];

                if (nfs_auth_info_match(&ctx->auth_info, flavor))
                        goto out;

                if (flavor == RPC_AUTH_NULL)
                        found_auth_null = true;
        }

        if (found_auth_null) {
                flavor = ctx->auth_info.flavors[0];
                goto out;
        }

        dfprintk(MOUNT,
                 "NFS: specified auth flavors not supported by server\n");
        return -EACCES;

out:
        ctx->selected_flavor = flavor;
        dfprintk(MOUNT, "NFS: using auth flavor %u\n", ctx->selected_flavor);
        return 0;
}

/*
 * Use the remote server's MOUNT service to request the NFS file handle
 * corresponding to the provided path.
 */
static int nfs_request_mount(struct fs_context *fc,
                             struct nfs_fh *root_fh,
                             rpc_authflavor_t *server_authlist,
                             unsigned int *server_authlist_len)
{
        struct nfs_fs_context *ctx = nfs_fc2context(fc);
        struct nfs_mount_request request = {
                .sap            = (struct sockaddr *)
                                                &ctx->mount_server.address,
                .dirpath        = ctx->nfs_server.export_path,
                .protocol       = ctx->mount_server.protocol,
                .fh             = root_fh,
                .noresvport     = ctx->flags & NFS_MOUNT_NORESVPORT,
                .auth_flav_len  = server_authlist_len,
                .auth_flavs     = server_authlist,
                .net            = fc->net_ns,
        };
        int status;

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

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

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

        return 0;
}

static struct nfs_server *nfs_try_mount_request(struct fs_context *fc)
{
        struct nfs_fs_context *ctx = nfs_fc2context(fc);
        int status;
        unsigned int i;
        bool tried_auth_unix = false;
        bool auth_null_in_list = false;
        struct nfs_server *server = ERR_PTR(-EACCES);
        rpc_authflavor_t authlist[NFS_MAX_SECFLAVORS];
        unsigned int authlist_len = ARRAY_SIZE(authlist);

        status = nfs_request_mount(fc, ctx->mntfh, authlist, &authlist_len);
        if (status)
                return ERR_PTR(status);

        /*
         * Was a sec= authflavor specified in the options? First, verify
         * whether the server supports it, and then just try to use it if so.
         */
        if (ctx->auth_info.flavor_len > 0) {
                status = nfs_verify_authflavors(ctx, authlist, authlist_len);
                dfprintk(MOUNT, "NFS: using auth flavor %u\n",
                         ctx->selected_flavor);
                if (status)
                        return ERR_PTR(status);
                return ctx->nfs_mod->rpc_ops->create_server(fc);
        }

        /*
         * No sec= option was provided. RFC 2623, section 2.7 suggests we
         * SHOULD prefer the flavor listed first. However, some servers list
         * AUTH_NULL first. Avoid ever choosing AUTH_NULL.
         */
        for (i = 0; i < authlist_len; ++i) {
                rpc_authflavor_t flavor;
                struct rpcsec_gss_info info;

                flavor = authlist[i];
                switch (flavor) {
                case RPC_AUTH_UNIX:
                        tried_auth_unix = true;
                        break;
                case RPC_AUTH_NULL:
                        auth_null_in_list = true;
                        continue;
                default:
                        if (rpcauth_get_gssinfo(flavor, &info) != 0)
                                continue;
                        break;
                }
                dfprintk(MOUNT, "NFS: attempting to use auth flavor %u\n", flavor);
                ctx->selected_flavor = flavor;
                server = ctx->nfs_mod->rpc_ops->create_server(fc);
                if (!IS_ERR(server))
                        return server;
        }

        /*
         * Nothing we tried so far worked. At this point, give up if we've
         * already tried AUTH_UNIX or if the server's list doesn't contain
         * AUTH_NULL
         */
        if (tried_auth_unix || !auth_null_in_list)
                return server;

        /* Last chance! Try AUTH_UNIX */
        dfprintk(MOUNT, "NFS: attempting to use auth flavor %u\n", RPC_AUTH_UNIX);
        ctx->selected_flavor = RPC_AUTH_UNIX;
        return ctx->nfs_mod->rpc_ops->create_server(fc);
}

int nfs_try_get_tree(struct fs_context *fc)
{
        struct nfs_fs_context *ctx = nfs_fc2context(fc);

        if (ctx->need_mount)
                ctx->server = nfs_try_mount_request(fc);
        else
                ctx->server = ctx->nfs_mod->rpc_ops->create_server(fc);

        return nfs_get_tree_common(fc);
}
EXPORT_SYMBOL_GPL(nfs_try_get_tree);


#define NFS_REMOUNT_CMP_FLAGMASK ~(NFS_MOUNT_INTR \
                | NFS_MOUNT_SECURE \
                | NFS_MOUNT_TCP \
                | NFS_MOUNT_VER3 \
                | NFS_MOUNT_KERBEROS \
                | NFS_MOUNT_NONLM \
                | NFS_MOUNT_BROKEN_SUID \
                | NFS_MOUNT_STRICTLOCK \
                | NFS_MOUNT_LEGACY_INTERFACE)

#define NFS_MOUNT_CMP_FLAGMASK (NFS_REMOUNT_CMP_FLAGMASK & \
                ~(NFS_MOUNT_UNSHARED | NFS_MOUNT_NORESVPORT))

static int
nfs_compare_remount_data(struct nfs_server *nfss,
                         struct nfs_fs_context *ctx)
{
        if ((ctx->flags ^ nfss->flags) & NFS_REMOUNT_CMP_FLAGMASK ||
            ctx->rsize != nfss->rsize ||
            ctx->wsize != nfss->wsize ||
            ctx->version != nfss->nfs_client->rpc_ops->version ||
            ctx->minorversion != nfss->nfs_client->cl_minorversion ||
            ctx->retrans != nfss->client->cl_timeout->to_retries ||
            !nfs_auth_info_match(&ctx->auth_info, nfss->client->cl_auth->au_flavor) ||
            ctx->acregmin != nfss->acregmin / HZ ||
            ctx->acregmax != nfss->acregmax / HZ ||
            ctx->acdirmin != nfss->acdirmin / HZ ||
            ctx->acdirmax != nfss->acdirmax / HZ ||
            ctx->timeo != (10U * nfss->client->cl_timeout->to_initval / HZ) ||
            (ctx->options & NFS_OPTION_FSCACHE) != (nfss->options & NFS_OPTION_FSCACHE) ||
            ctx->nfs_server.port != nfss->port ||
            ctx->nfs_server.addrlen != nfss->nfs_client->cl_addrlen ||
            !rpc_cmp_addr((struct sockaddr *)&ctx->nfs_server.address,
                          (struct sockaddr *)&nfss->nfs_client->cl_addr))
                return -EINVAL;

        return 0;
}

int nfs_reconfigure(struct fs_context *fc)
{
        struct nfs_fs_context *ctx = nfs_fc2context(fc);
        struct super_block *sb = fc->root->d_sb;
        struct nfs_server *nfss = sb->s_fs_info;

        sync_filesystem(sb);

        /*
         * 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 (ctx->skip_reconfig_option_check)
                return 0;

        /*
         * noac is a special case. It implies -o sync, but that's not
         * necessarily reflected in the mtab options. reconfigure_super
         * will clear SB_SYNCHRONOUS if -o sync wasn't specified in the
         * remount options, so we have to explicitly reset it.
         */
        if (ctx->flags & NFS_MOUNT_NOAC) {
                fc->sb_flags |= SB_SYNCHRONOUS;
                fc->sb_flags_mask |= SB_SYNCHRONOUS;
        }

        /* compare new mount options with old ones */
        return nfs_compare_remount_data(nfss, ctx);
}
EXPORT_SYMBOL_GPL(nfs_reconfigure);

/*
 * Finish setting up an NFS superblock
 */
static void nfs_fill_super(struct super_block *sb, struct nfs_fs_context *ctx)
{
        struct nfs_server *server = NFS_SB(sb);

        sb->s_blocksize_bits = 0;
        sb->s_blocksize = 0;
        sb->s_xattr = server->nfs_client->cl_nfs_mod->xattr;
        sb->s_op = server->nfs_client->cl_nfs_mod->sops;
        if (ctx && ctx->bsize)
                sb->s_blocksize = nfs_block_size(ctx->bsize, &sb->s_blocksize_bits);

        if (server->nfs_client->rpc_ops->version != 2) {
                /* The VFS shouldn't apply the umask to mode bits. We will do
                 * so ourselves when necessary.
                 */
                sb->s_flags |= SB_POSIXACL;
                sb->s_time_gran = 1;
                sb->s_export_op = &nfs_export_ops;
        } else
                sb->s_time_gran = 1000;

        if (server->nfs_client->rpc_ops->version != 4) {
                sb->s_time_min = 0;
                sb->s_time_max = U32_MAX;
        } else {
                sb->s_time_min = S64_MIN;
                sb->s_time_max = S64_MAX;
        }

        sb->s_magic = NFS_SUPER_MAGIC;

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

        nfs_super_set_maxbytes(sb, server->maxfilesize);
}

static int nfs_compare_mount_options(const struct super_block *s, const struct nfs_server *b,
                                     const struct fs_context *fc)
{
        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_SB_MASK) != (fc->sb_flags & NFS_SB_MASK))
                goto Ebusy;
        if (a->nfs_client != b->nfs_client)
                goto Ebusy;
        if ((a->flags ^ b->flags) & NFS_MOUNT_CMP_FLAGMASK)
                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;
}

static int nfs_set_super(struct super_block *s, struct fs_context *fc)
{
        struct nfs_server *server = fc->s_fs_info;
        int ret;

        s->s_d_op = server->nfs_client->rpc_ops->dentry_ops;
        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;
        struct rpc_xprt *xprt1 = server1->client->cl_xprt;
        struct rpc_xprt *xprt2 = server2->client->cl_xprt;

        if (!net_eq(xprt1->xprt_net, xprt2->xprt_net))
                return 0;

        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_userns(const struct nfs_server *old,
                const struct nfs_server *new)
{
        const struct user_namespace *oldns = &init_user_ns;
        const struct user_namespace *newns = &init_user_ns;

        if (old->client && old->client->cl_cred)
                oldns = old->client->cl_cred->user_ns;
        if (new->client && new->client->cl_cred)
                newns = new->client->cl_cred->user_ns;
        if (oldns != newns)
                return 0;
        return 1;
}

static int nfs_compare_super(struct super_block *sb, struct fs_context *fc)
{
        struct nfs_server *server = fc->s_fs_info, *old = NFS_SB(sb);

        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;
        if (!nfs_compare_userns(old, server))
                return 0;
        return nfs_compare_mount_options(sb, server, fc);
}

#ifdef CONFIG_NFS_FSCACHE
static void nfs_get_cache_cookie(struct super_block *sb,
                                 struct nfs_fs_context *ctx)
{
        struct nfs_server *nfss = NFS_SB(sb);
        char *uniq = NULL;
        int ulen = 0;

        nfss->fscache_key = NULL;
        nfss->fscache = NULL;

        if (!ctx)
                return;

        if (ctx->clone_data.sb) {
                struct nfs_server *mnt_s = NFS_SB(ctx->clone_data.sb);
                if (!(mnt_s->options & NFS_OPTION_FSCACHE))
                        return;
                if (mnt_s->fscache_key) {
                        uniq = mnt_s->fscache_key->key.uniquifier;
                        ulen = mnt_s->fscache_key->key.uniq_len;
                }
        } else {
                if (!(ctx->options & NFS_OPTION_FSCACHE))
                        return;
                if (ctx->fscache_uniq) {
                        uniq = ctx->fscache_uniq;
                        ulen = strlen(ctx->fscache_uniq);
                }
        }

        nfs_fscache_get_super_cookie(sb, uniq, ulen);
}
#else
static void nfs_get_cache_cookie(struct super_block *sb,
                                 struct nfs_fs_context *ctx)
{
}
#endif

int nfs_get_tree_common(struct fs_context *fc)
{
        struct nfs_fs_context *ctx = nfs_fc2context(fc);
        struct super_block *s;
        int (*compare_super)(struct super_block *, struct fs_context *) = nfs_compare_super;
        struct nfs_server *server = ctx->server;
        int error;

        ctx->server = NULL;
        if (IS_ERR(server))
                return PTR_ERR(server);

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

        /* -o noac implies -o sync */
        if (server->flags & NFS_MOUNT_NOAC)
                fc->sb_flags |= SB_SYNCHRONOUS;

        if (ctx->clone_data.sb)
                if (ctx->clone_data.sb->s_flags & SB_SYNCHRONOUS)
                        fc->sb_flags |= SB_SYNCHRONOUS;

        if (server->caps & NFS_CAP_SECURITY_LABEL)
                fc->lsm_flags |= SECURITY_LSM_NATIVE_LABELS;

        /* Get a superblock - note that we may end up sharing one that already exists */
        fc->s_fs_info = server;
        s = sget_fc(fc, compare_super, nfs_set_super);
        fc->s_fs_info = NULL;
        if (IS_ERR(s)) {
                error = PTR_ERR(s);
                nfs_errorf(fc, "NFS: Couldn't get superblock");
                goto out_err_nosb;
        }

        if (s->s_fs_info != server) {
                nfs_free_server(server);
                server = NULL;
        } else {
                error = super_setup_bdi_name(s, "%u:%u", MAJOR(server->s_dev),
                                             MINOR(server->s_dev));
                if (error)
                        goto error_splat_super;
                s->s_bdi->io_pages = server->rpages;
                server->super = s;
        }

        if (!s->s_root) {
                unsigned bsize = ctx->clone_data.inherited_bsize;
                /* initial superblock/root creation */
                nfs_fill_super(s, ctx);
                if (bsize) {
                        s->s_blocksize_bits = bsize;
                        s->s_blocksize = 1U << bsize;
                }
                nfs_get_cache_cookie(s, ctx);
        }

        error = nfs_get_root(s, fc);
        if (error < 0) {
                nfs_errorf(fc, "NFS: Couldn't get root dentry");
                goto error_splat_super;
        }

        s->s_flags |= SB_ACTIVE;
        error = 0;

out:
        return error;

out_err_nosb:
        nfs_free_server(server);
        goto out;
error_splat_super:
        deactivate_locked_super(s);
        goto out;
}

/*
 * Destroy an NFS2/3 superblock
 */
void nfs_kill_super(struct super_block *s)
{
        struct nfs_server *server = NFS_SB(s);
        dev_t dev = s->s_dev;

        generic_shutdown_super(s);

        nfs_fscache_release_super_cookie(s);

        nfs_free_server(server);
        free_anon_bdev(dev);
}
EXPORT_SYMBOL_GPL(nfs_kill_super);

#if IS_ENABLED(CONFIG_NFS_V4)

/*
 * NFS v4 module parameters need to stay in the
 * NFS client for backwards compatibility
 */
unsigned int nfs_callback_set_tcpport;
unsigned short nfs_callback_nr_threads;
/* Default cache timeout is 10 minutes */
unsigned int nfs_idmap_cache_timeout = 600;
/* Turn off NFSv4 uid/gid mapping when using AUTH_SYS */
bool nfs4_disable_idmapping = true;
unsigned short max_session_slots = NFS4_DEF_SLOT_TABLE_SIZE;
unsigned short max_session_cb_slots = NFS4_DEF_CB_SLOT_TABLE_SIZE;
unsigned short send_implementation_id = 1;
char nfs4_client_id_uniquifier[NFS4_CLIENT_ID_UNIQ_LEN] = "";
bool recover_lost_locks = false;

EXPORT_SYMBOL_GPL(nfs_callback_nr_threads);
EXPORT_SYMBOL_GPL(nfs_callback_set_tcpport);
EXPORT_SYMBOL_GPL(nfs_idmap_cache_timeout);
EXPORT_SYMBOL_GPL(nfs4_disable_idmapping);
EXPORT_SYMBOL_GPL(max_session_slots);
EXPORT_SYMBOL_GPL(max_session_cb_slots);
EXPORT_SYMBOL_GPL(send_implementation_id);
EXPORT_SYMBOL_GPL(nfs4_client_id_uniquifier);
EXPORT_SYMBOL_GPL(recover_lost_locks);

#define NFS_CALLBACK_MAXPORTNR (65535U)

static int param_set_portnr(const char *val, const struct kernel_param *kp)
{
        unsigned long num;
        int ret;

        if (!val)
                return -EINVAL;
        ret = kstrtoul(val, 0, &num);
        if (ret || num > NFS_CALLBACK_MAXPORTNR)
                return -EINVAL;
        *((unsigned int *)kp->arg) = num;
        return 0;
}
static const struct kernel_param_ops param_ops_portnr = {
        .set = param_set_portnr,
        .get = param_get_uint,
};
#define param_check_portnr(name, p) __param_check(name, p, unsigned int);

module_param_named(callback_tcpport, nfs_callback_set_tcpport, portnr, 0644);
module_param_named(callback_nr_threads, nfs_callback_nr_threads, ushort, 0644);
MODULE_PARM_DESC(callback_nr_threads, "Number of threads that will be "
                "assigned to the NFSv4 callback channels.");
module_param(nfs_idmap_cache_timeout, int, 0644);
module_param(nfs4_disable_idmapping, bool, 0644);
module_param_string(nfs4_unique_id, nfs4_client_id_uniquifier,
                        NFS4_CLIENT_ID_UNIQ_LEN, 0600);
MODULE_PARM_DESC(nfs4_disable_idmapping,
                "Turn off NFSv4 idmapping when using 'sec=sys'");
module_param(max_session_slots, ushort, 0644);
MODULE_PARM_DESC(max_session_slots, "Maximum number of outstanding NFSv4.1 "
                "requests the client will negotiate");
module_param(max_session_cb_slots, ushort, 0644);
MODULE_PARM_DESC(max_session_cb_slots, "Maximum number of parallel NFSv4.1 "
                "callbacks the client will process for a given server");
module_param(send_implementation_id, ushort, 0644);
MODULE_PARM_DESC(send_implementation_id,
                "Send implementation ID with NFSv4.1 exchange_id");
MODULE_PARM_DESC(nfs4_unique_id, "nfs_client_id4 uniquifier string");

module_param(recover_lost_locks, bool, 0644);
MODULE_PARM_DESC(recover_lost_locks,
                 "If the server reports that a lock might be lost, "
                 "try to recover it risking data corruption.");


#endif /* CONFIG_NFS_V4 */