// SPDX-License-Identifier: GPL-2.0
/*
 * NFS exporting and validation.
 *
 * We maintain a list of clients, each of which has a list of
 * exports. To export an fs to a given client, you first have
 * to create the client entry with NFSCTL_ADDCLIENT, which
 * creates a client control block and adds it to the hash
 * table. Then, you call NFSCTL_EXPORT for each fs.
 *
 *
 * Copyright (C) 1995, 1996 Olaf Kirch, <okir@monad.swb.de>
 */

#include <linux/slab.h>
#include <linux/namei.h>
#include <linux/module.h>
#include <linux/exportfs.h>
#include <linux/sunrpc/svc_xprt.h>

#include "nfsd.h"
#include "nfsfh.h"
#include "netns.h"
#include "pnfs.h"
#include "filecache.h"
#include "trace.h"

#define NFSDDBG_FACILITY        NFSDDBG_EXPORT

/*
 * We have two caches.
 * One maps client+vfsmnt+dentry to export options - the export map
 * The other maps client+filehandle-fragment to export options. - the expkey map
 *
 * The export options are actually stored in the first map, and the
 * second map contains a reference to the entry in the first map.
 */

static struct workqueue_struct *nfsd_export_wq;

#define EXPKEY_HASHBITS         8
#define EXPKEY_HASHMAX          (1 << EXPKEY_HASHBITS)
#define EXPKEY_HASHMASK         (EXPKEY_HASHMAX -1)

static void expkey_release(struct work_struct *work)
{
        struct svc_expkey *key = container_of(to_rcu_work(work),
                                              struct svc_expkey, ek_rwork);

        if (test_bit(CACHE_VALID, &key->h.flags) &&
            !test_bit(CACHE_NEGATIVE, &key->h.flags))
                path_put(&key->ek_path);
        auth_domain_put(key->ek_client);
        kfree(key);
}

static void expkey_put(struct kref *ref)
{
        struct svc_expkey *key = container_of(ref, struct svc_expkey, h.ref);

        INIT_RCU_WORK(&key->ek_rwork, expkey_release);
        queue_rcu_work(nfsd_export_wq, &key->ek_rwork);
}

static int expkey_upcall(struct cache_detail *cd, struct cache_head *h)
{
        return sunrpc_cache_pipe_upcall(cd, h);
}

static void expkey_request(struct cache_detail *cd,
                           struct cache_head *h,
                           char **bpp, int *blen)
{
        /* client fsidtype \xfsid */
        struct svc_expkey *ek = container_of(h, struct svc_expkey, h);
        char type[5];

        qword_add(bpp, blen, ek->ek_client->name);
        snprintf(type, 5, "%d", ek->ek_fsidtype);
        qword_add(bpp, blen, type);
        qword_addhex(bpp, blen, (char*)ek->ek_fsid, key_len(ek->ek_fsidtype));
        (*bpp)[-1] = '\n';
}

static struct svc_expkey *svc_expkey_update(struct cache_detail *cd, struct svc_expkey *new,
                                            struct svc_expkey *old);
static struct svc_expkey *svc_expkey_lookup(struct cache_detail *cd, struct svc_expkey *);

static int expkey_parse(struct cache_detail *cd, char *mesg, int mlen)
{
        /* client fsidtype fsid expiry [path] */
        char *buf;
        int len;
        struct auth_domain *dom = NULL;
        int err;
        u8 fsidtype;
        struct svc_expkey key;
        struct svc_expkey *ek = NULL;

        if (mesg[mlen - 1] != '\n')
                return -EINVAL;
        mesg[mlen-1] = 0;

        buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
        err = -ENOMEM;
        if (!buf)
                goto out;

        err = -EINVAL;
        if (qword_get(&mesg, buf, PAGE_SIZE) <= 0)
                goto out;

        err = -ENOENT;
        dom = auth_domain_find(buf);
        if (!dom)
                goto out;
        dprintk("found domain %s\n", buf);

        err = -EINVAL;
        if (qword_get(&mesg, buf, PAGE_SIZE) <= 0)
                goto out;
        if (kstrtou8(buf, 10, &fsidtype))
                goto out;
        dprintk("found fsidtype %u\n", fsidtype);
        if (key_len(fsidtype)==0) /* invalid type */
                goto out;
        if ((len=qword_get(&mesg, buf, PAGE_SIZE)) <= 0)
                goto out;
        dprintk("found fsid length %d\n", len);
        if (len != key_len(fsidtype))
                goto out;

        /* OK, we seem to have a valid key */
        key.h.flags = 0;
        err = get_expiry(&mesg, &key.h.expiry_time);
        if (err)
                goto out;

        key.ek_client = dom;
        key.ek_fsidtype = fsidtype;
        memcpy(key.ek_fsid, buf, len);

        ek = svc_expkey_lookup(cd, &key);
        err = -ENOMEM;
        if (!ek)
                goto out;

        /* now we want a pathname, or empty meaning NEGATIVE  */
        err = -EINVAL;
        len = qword_get(&mesg, buf, PAGE_SIZE);
        if (len < 0)
                goto out;
        dprintk("Path seems to be <%s>\n", buf);
        err = 0;
        if (len == 0) {
                set_bit(CACHE_NEGATIVE, &key.h.flags);
                ek = svc_expkey_update(cd, &key, ek);
                if (ek)
                        trace_nfsd_expkey_update(ek, NULL);
                else
                        err = -ENOMEM;
        } else {
                err = kern_path(buf, 0, &key.ek_path);
                if (err)
                        goto out;

                dprintk("Found the path %s\n", buf);

                ek = svc_expkey_update(cd, &key, ek);
                if (ek)
                        trace_nfsd_expkey_update(ek, buf);
                else
                        err = -ENOMEM;
                path_put(&key.ek_path);
        }
        cache_flush();
 out:
        if (ek)
                cache_put(&ek->h, cd);
        if (dom)
                auth_domain_put(dom);
        kfree(buf);
        return err;
}

static int expkey_show(struct seq_file *m,
                       struct cache_detail *cd,
                       struct cache_head *h)
{
        struct svc_expkey *ek ;
        int i;

        if (h ==NULL) {
                seq_puts(m, "#domain fsidtype fsid [path]\n");
                return 0;
        }
        ek = container_of(h, struct svc_expkey, h);
        seq_printf(m, "%s %d 0x", ek->ek_client->name,
                   ek->ek_fsidtype);
        for (i=0; i < key_len(ek->ek_fsidtype)/4; i++)
                seq_printf(m, "%08x", ek->ek_fsid[i]);
        if (test_bit(CACHE_VALID, &h->flags) && 
            !test_bit(CACHE_NEGATIVE, &h->flags)) {
                seq_printf(m, " ");
                seq_path(m, &ek->ek_path, "\\ \t\n");
        }
        seq_printf(m, "\n");
        return 0;
}

static inline int expkey_match (struct cache_head *a, struct cache_head *b)
{
        struct svc_expkey *orig = container_of(a, struct svc_expkey, h);
        struct svc_expkey *new = container_of(b, struct svc_expkey, h);

        if (orig->ek_fsidtype != new->ek_fsidtype ||
            orig->ek_client != new->ek_client ||
            memcmp(orig->ek_fsid, new->ek_fsid, key_len(orig->ek_fsidtype)) != 0)
                return 0;
        return 1;
}

static inline void expkey_init(struct cache_head *cnew,
                                   struct cache_head *citem)
{
        struct svc_expkey *new = container_of(cnew, struct svc_expkey, h);
        struct svc_expkey *item = container_of(citem, struct svc_expkey, h);

        kref_get(&item->ek_client->ref);
        new->ek_client = item->ek_client;
        new->ek_fsidtype = item->ek_fsidtype;

        memcpy(new->ek_fsid, item->ek_fsid, sizeof(new->ek_fsid));
}

static inline void expkey_update(struct cache_head *cnew,
                                   struct cache_head *citem)
{
        struct svc_expkey *new = container_of(cnew, struct svc_expkey, h);
        struct svc_expkey *item = container_of(citem, struct svc_expkey, h);

        new->ek_path = item->ek_path;
        path_get(&item->ek_path);
}

static struct cache_head *expkey_alloc(void)
{
        struct svc_expkey *i = kmalloc_obj(*i);
        if (i)
                return &i->h;
        else
                return NULL;
}

static void expkey_flush(void)
{
        /*
         * Take the nfsd_mutex here to ensure that the file cache is not
         * destroyed while we're in the middle of flushing.
         */
        mutex_lock(&nfsd_mutex);
        nfsd_file_cache_purge(current->nsproxy->net_ns);
        mutex_unlock(&nfsd_mutex);
}

static const struct cache_detail svc_expkey_cache_template = {
        .owner          = THIS_MODULE,
        .hash_size      = EXPKEY_HASHMAX,
        .name           = "nfsd.fh",
        .cache_put      = expkey_put,
        .cache_upcall   = expkey_upcall,
        .cache_request  = expkey_request,
        .cache_parse    = expkey_parse,
        .cache_show     = expkey_show,
        .match          = expkey_match,
        .init           = expkey_init,
        .update         = expkey_update,
        .alloc          = expkey_alloc,
        .flush          = expkey_flush,
};

static int
svc_expkey_hash(struct svc_expkey *item)
{
        int hash = item->ek_fsidtype;
        char * cp = (char*)item->ek_fsid;
        int len = key_len(item->ek_fsidtype);

        hash ^= hash_mem(cp, len, EXPKEY_HASHBITS);
        hash ^= hash_ptr(item->ek_client, EXPKEY_HASHBITS);
        hash &= EXPKEY_HASHMASK;
        return hash;
}

static struct svc_expkey *
svc_expkey_lookup(struct cache_detail *cd, struct svc_expkey *item)
{
        struct cache_head *ch;
        int hash = svc_expkey_hash(item);

        ch = sunrpc_cache_lookup_rcu(cd, &item->h, hash);
        if (ch)
                return container_of(ch, struct svc_expkey, h);
        else
                return NULL;
}

static struct svc_expkey *
svc_expkey_update(struct cache_detail *cd, struct svc_expkey *new,
                  struct svc_expkey *old)
{
        struct cache_head *ch;
        int hash = svc_expkey_hash(new);

        ch = sunrpc_cache_update(cd, &new->h, &old->h, hash);
        if (ch)
                return container_of(ch, struct svc_expkey, h);
        else
                return NULL;
}


#define EXPORT_HASHBITS         8
#define EXPORT_HASHMAX          (1<< EXPORT_HASHBITS)

static void nfsd4_fslocs_free(struct nfsd4_fs_locations *fsloc)
{
        struct nfsd4_fs_location *locations = fsloc->locations;
        int i;

        if (!locations)
                return;

        for (i = 0; i < fsloc->locations_count; i++) {
                kfree(locations[i].path);
                kfree(locations[i].hosts);
        }

        kfree(locations);
        fsloc->locations = NULL;
}

static int export_stats_init(struct export_stats *stats)
{
        stats->start_time = ktime_get_seconds();
        return percpu_counter_init_many(stats->counter, 0, GFP_KERNEL,
                                        EXP_STATS_COUNTERS_NUM);
}

static void export_stats_reset(struct export_stats *stats)
{
        if (stats) {
                int i;

                for (i = 0; i < EXP_STATS_COUNTERS_NUM; i++)
                        percpu_counter_set(&stats->counter[i], 0);
        }
}

static void export_stats_destroy(struct export_stats *stats)
{
        if (stats)
                percpu_counter_destroy_many(stats->counter,
                                            EXP_STATS_COUNTERS_NUM);
}

static void svc_export_release(struct work_struct *work)
{
        struct svc_export *exp = container_of(to_rcu_work(work),
                                              struct svc_export, ex_rwork);

        path_put(&exp->ex_path);
        auth_domain_put(exp->ex_client);
        nfsd4_fslocs_free(&exp->ex_fslocs);
        export_stats_destroy(exp->ex_stats);
        kfree(exp->ex_stats);
        kfree(exp->ex_uuid);
        kfree(exp);
}

static void svc_export_put(struct kref *ref)
{
        struct svc_export *exp = container_of(ref, struct svc_export, h.ref);

        INIT_RCU_WORK(&exp->ex_rwork, svc_export_release);
        queue_rcu_work(nfsd_export_wq, &exp->ex_rwork);
}

static int svc_export_upcall(struct cache_detail *cd, struct cache_head *h)
{
        return sunrpc_cache_pipe_upcall(cd, h);
}

static void svc_export_request(struct cache_detail *cd,
                               struct cache_head *h,
                               char **bpp, int *blen)
{
        /*  client path */
        struct svc_export *exp = container_of(h, struct svc_export, h);
        char *pth;

        qword_add(bpp, blen, exp->ex_client->name);
        pth = d_path(&exp->ex_path, *bpp, *blen);
        if (IS_ERR(pth)) {
                /* is this correct? */
                (*bpp)[0] = '\n';
                return;
        }
        qword_add(bpp, blen, pth);
        (*bpp)[-1] = '\n';
}

static struct svc_export *svc_export_update(struct svc_export *new,
                                            struct svc_export *old);
static struct svc_export *svc_export_lookup(struct svc_export *);

static int check_export(const struct path *path, int *flags, unsigned char *uuid)
{
        struct inode *inode = d_inode(path->dentry);

        /*
         * We currently export only dirs, regular files, and (for v4
         * pseudoroot) symlinks.
         */
        if (!S_ISDIR(inode->i_mode) &&
            !S_ISLNK(inode->i_mode) &&
            !S_ISREG(inode->i_mode))
                return -ENOTDIR;

        /*
         * Mountd should never pass down a writeable V4ROOT export, but,
         * just to make sure:
         */
        if (*flags & NFSEXP_V4ROOT)
                *flags |= NFSEXP_READONLY;

        /* There are two requirements on a filesystem to be exportable.
         * 1:  We must be able to identify the filesystem from a number.
         *       either a device number (so FS_REQUIRES_DEV needed)
         *       or an FSID number (so NFSEXP_FSID or ->uuid is needed).
         * 2:  We must be able to find an inode from a filehandle.
         *       This means that s_export_op must be set and comply with
         *       the requirements for remote filesystem export.
         * 3: We must not currently be on an idmapped mount.
         */
        if (!(inode->i_sb->s_type->fs_flags & FS_REQUIRES_DEV) &&
            !(*flags & NFSEXP_FSID) &&
            uuid == NULL) {
                dprintk("exp_export: export of non-dev fs without fsid\n");
                return -EINVAL;
        }

        if (!exportfs_may_export(inode->i_sb->s_export_op)) {
                dprintk("exp_export: export of invalid fs type (%s).\n",
                        inode->i_sb->s_type->name);
                return -EINVAL;
        }

        if (is_idmapped_mnt(path->mnt)) {
                dprintk("exp_export: export of idmapped mounts not yet supported.\n");
                return -EINVAL;
        }

        if (inode->i_sb->s_export_op->flags & EXPORT_OP_NOSUBTREECHK &&
            !(*flags & NFSEXP_NOSUBTREECHECK)) {
                dprintk("%s: %s does not support subtree checking!\n",
                        __func__, inode->i_sb->s_type->name);
                return -EINVAL;
        }
        return 0;
}

#ifdef CONFIG_NFSD_V4

static int
fsloc_parse(char **mesg, char *buf, struct nfsd4_fs_locations *fsloc)
{
        int len;
        int migrated, i, err;

        /* more than one fsloc */
        if (fsloc->locations)
                return -EINVAL;

        /* listsize */
        err = get_uint(mesg, &fsloc->locations_count);
        if (err)
                return err;
        if (fsloc->locations_count > MAX_FS_LOCATIONS)
                return -EINVAL;
        if (fsloc->locations_count == 0)
                return 0;

        fsloc->locations = kzalloc_objs(struct nfsd4_fs_location,
                                        fsloc->locations_count);
        if (!fsloc->locations)
                return -ENOMEM;
        for (i=0; i < fsloc->locations_count; i++) {
                /* colon separated host list */
                err = -EINVAL;
                len = qword_get(mesg, buf, PAGE_SIZE);
                if (len <= 0)
                        goto out_free_all;
                err = -ENOMEM;
                fsloc->locations[i].hosts = kstrdup(buf, GFP_KERNEL);
                if (!fsloc->locations[i].hosts)
                        goto out_free_all;
                err = -EINVAL;
                /* slash separated path component list */
                len = qword_get(mesg, buf, PAGE_SIZE);
                if (len <= 0)
                        goto out_free_all;
                err = -ENOMEM;
                fsloc->locations[i].path = kstrdup(buf, GFP_KERNEL);
                if (!fsloc->locations[i].path)
                        goto out_free_all;
        }
        /* migrated */
        err = get_int(mesg, &migrated);
        if (err)
                goto out_free_all;
        err = -EINVAL;
        if (migrated < 0 || migrated > 1)
                goto out_free_all;
        fsloc->migrated = migrated;
        return 0;
out_free_all:
        nfsd4_fslocs_free(fsloc);
        return err;
}

static int secinfo_parse(char **mesg, char *buf, struct svc_export *exp)
{
        struct exp_flavor_info *f;
        u32 listsize;
        int err;

        /* more than one secinfo */
        if (exp->ex_nflavors)
                return -EINVAL;

        err = get_uint(mesg, &listsize);
        if (err)
                return err;
        if (listsize > MAX_SECINFO_LIST)
                return -EINVAL;

        for (f = exp->ex_flavors; f < exp->ex_flavors + listsize; f++) {
                err = get_uint(mesg, &f->pseudoflavor);
                if (err)
                        return err;
                /*
                 * XXX: It would be nice to also check whether this
                 * pseudoflavor is supported, so we can discover the
                 * problem at export time instead of when a client fails
                 * to authenticate.
                 */
                err = get_uint(mesg, &f->flags);
                if (err)
                        return err;
                /* Only some flags are allowed to differ between flavors: */
                if (~NFSEXP_SECINFO_FLAGS & (f->flags ^ exp->ex_flags))
                        return -EINVAL;
        }
        exp->ex_nflavors = listsize;
        return 0;
}

#else /* CONFIG_NFSD_V4 */
static inline int
fsloc_parse(char **mesg, char *buf, struct nfsd4_fs_locations *fsloc){return 0;}
static inline int
secinfo_parse(char **mesg, char *buf, struct svc_export *exp) { return 0; }
#endif

static int xprtsec_parse(char **mesg, char *buf, struct svc_export *exp)
{
        unsigned int i, mode, listsize;
        int err;

        err = get_uint(mesg, &listsize);
        if (err)
                return err;
        if (listsize > NFSEXP_XPRTSEC_NUM)
                return -EINVAL;

        exp->ex_xprtsec_modes = 0;
        for (i = 0; i < listsize; i++) {
                err = get_uint(mesg, &mode);
                if (err)
                        return err;
                if (mode > NFSEXP_XPRTSEC_MTLS)
                        return -EINVAL;
                exp->ex_xprtsec_modes |= mode;
        }
        return 0;
}

static inline int
nfsd_uuid_parse(char **mesg, char *buf, unsigned char **puuid)
{
        int len;

        /* more than one uuid */
        if (*puuid)
                return -EINVAL;

        /* expect a 16 byte uuid encoded as \xXXXX... */
        len = qword_get(mesg, buf, PAGE_SIZE);
        if (len != EX_UUID_LEN)
                return -EINVAL;

        *puuid = kmemdup(buf, EX_UUID_LEN, GFP_KERNEL);
        if (*puuid == NULL)
                return -ENOMEM;

        return 0;
}

static int svc_export_parse(struct cache_detail *cd, char *mesg, int mlen)
{
        /* client path expiry [flags anonuid anongid fsid] */
        char *buf;
        int err;
        struct auth_domain *dom = NULL;
        struct svc_export exp = {}, *expp;
        int an_int;

        if (mesg[mlen-1] != '\n')
                return -EINVAL;
        mesg[mlen-1] = 0;

        buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
        if (!buf)
                return -ENOMEM;

        /* client */
        err = -EINVAL;
        if (qword_get(&mesg, buf, PAGE_SIZE) <= 0)
                goto out;

        err = -ENOENT;
        dom = auth_domain_find(buf);
        if (!dom)
                goto out;

        /* path */
        err = -EINVAL;
        if (qword_get(&mesg, buf, PAGE_SIZE) <= 0)
                goto out1;

        err = kern_path(buf, 0, &exp.ex_path);
        if (err)
                goto out1;

        exp.ex_client = dom;
        exp.cd = cd;
        exp.ex_devid_map = NULL;
        exp.ex_xprtsec_modes = NFSEXP_XPRTSEC_ALL;

        /* expiry */
        err = get_expiry(&mesg, &exp.h.expiry_time);
        if (err)
                goto out3;

        /* flags */
        err = get_int(&mesg, &an_int);
        if (err == -ENOENT) {
                err = 0;
                set_bit(CACHE_NEGATIVE, &exp.h.flags);
        } else {
                if (err || an_int < 0)
                        goto out3;
                exp.ex_flags= an_int;

                /* anon uid */
                err = get_int(&mesg, &an_int);
                if (err)
                        goto out3;
                exp.ex_anon_uid= make_kuid(current_user_ns(), an_int);

                /* anon gid */
                err = get_int(&mesg, &an_int);
                if (err)
                        goto out3;
                exp.ex_anon_gid= make_kgid(current_user_ns(), an_int);

                /* fsid */
                err = get_int(&mesg, &an_int);
                if (err)
                        goto out3;
                exp.ex_fsid = an_int;

                while (qword_get(&mesg, buf, PAGE_SIZE) > 0) {
                        if (strcmp(buf, "fsloc") == 0)
                                err = fsloc_parse(&mesg, buf, &exp.ex_fslocs);
                        else if (strcmp(buf, "uuid") == 0)
                                err = nfsd_uuid_parse(&mesg, buf, &exp.ex_uuid);
                        else if (strcmp(buf, "secinfo") == 0)
                                err = secinfo_parse(&mesg, buf, &exp);
                        else if (strcmp(buf, "xprtsec") == 0)
                                err = xprtsec_parse(&mesg, buf, &exp);
                        else
                                /* quietly ignore unknown words and anything
                                 * following. Newer user-space can try to set
                                 * new values, then see what the result was.
                                 */
                                break;
                        if (err)
                                goto out4;
                }

                err = check_export(&exp.ex_path, &exp.ex_flags, exp.ex_uuid);
                if (err)
                        goto out4;

                /*
                 * No point caching this if it would immediately expire.
                 * Also, this protects exportfs's dummy export from the
                 * anon_uid/anon_gid checks:
                 */
                if (exp.h.expiry_time < seconds_since_boot())
                        goto out4;
                /*
                 * For some reason exportfs has been passing down an
                 * invalid (-1) uid & gid on the "dummy" export which it
                 * uses to test export support.  To make sure exportfs
                 * sees errors from check_export we therefore need to
                 * delay these checks till after check_export:
                 */
                err = -EINVAL;
                if (!uid_valid(exp.ex_anon_uid))
                        goto out4;
                if (!gid_valid(exp.ex_anon_gid))
                        goto out4;
                err = 0;

                nfsd4_setup_layout_type(&exp);
        }

        expp = svc_export_lookup(&exp);
        if (!expp) {
                err = -ENOMEM;
                goto out4;
        }
        expp = svc_export_update(&exp, expp);
        if (expp) {
                trace_nfsd_export_update(expp);
                cache_flush();
                exp_put(expp);
        } else
                err = -ENOMEM;
out4:
        nfsd4_fslocs_free(&exp.ex_fslocs);
        kfree(exp.ex_uuid);
out3:
        path_put(&exp.ex_path);
out1:
        auth_domain_put(dom);
out:
        kfree(buf);
        return err;
}

static void exp_flags(struct seq_file *m, int flag, int fsid,
                kuid_t anonu, kgid_t anong, struct nfsd4_fs_locations *fslocs);
static void show_secinfo(struct seq_file *m, struct svc_export *exp);

static int is_export_stats_file(struct seq_file *m)
{
        /*
         * The export_stats file uses the same ops as the exports file.
         * We use the file's name to determine the reported info per export.
         * There is no rename in nsfdfs, so d_name.name is stable.
         */
        return !strcmp(m->file->f_path.dentry->d_name.name, "export_stats");
}

static int svc_export_show(struct seq_file *m,
                           struct cache_detail *cd,
                           struct cache_head *h)
{
        struct svc_export *exp;
        bool export_stats = is_export_stats_file(m);

        if (h == NULL) {
                if (export_stats)
                        seq_puts(m, "#path domain start-time\n#\tstats\n");
                else
                        seq_puts(m, "#path domain(flags)\n");
                return 0;
        }
        exp = container_of(h, struct svc_export, h);
        seq_path(m, &exp->ex_path, " \t\n\\");
        seq_putc(m, '\t');
        seq_escape(m, exp->ex_client->name, " \t\n\\");
        if (export_stats) {
                struct percpu_counter *counter = exp->ex_stats->counter;

                seq_printf(m, "\t%lld\n", exp->ex_stats->start_time);
                seq_printf(m, "\tfh_stale: %lld\n",
                           percpu_counter_sum_positive(&counter[EXP_STATS_FH_STALE]));
                seq_printf(m, "\tio_read: %lld\n",
                           percpu_counter_sum_positive(&counter[EXP_STATS_IO_READ]));
                seq_printf(m, "\tio_write: %lld\n",
                           percpu_counter_sum_positive(&counter[EXP_STATS_IO_WRITE]));
                seq_putc(m, '\n');
                return 0;
        }
        seq_putc(m, '(');
        if (test_bit(CACHE_VALID, &h->flags) &&
            !test_bit(CACHE_NEGATIVE, &h->flags)) {
                exp_flags(m, exp->ex_flags, exp->ex_fsid,
                          exp->ex_anon_uid, exp->ex_anon_gid, &exp->ex_fslocs);
                if (exp->ex_uuid) {
                        int i;
                        seq_puts(m, ",uuid=");
                        for (i = 0; i < EX_UUID_LEN; i++) {
                                if ((i&3) == 0 && i)
                                        seq_putc(m, ':');
                                seq_printf(m, "%02x", exp->ex_uuid[i]);
                        }
                }
                show_secinfo(m, exp);
        }
        seq_puts(m, ")\n");
        return 0;
}
static int svc_export_match(struct cache_head *a, struct cache_head *b)
{
        struct svc_export *orig = container_of(a, struct svc_export, h);
        struct svc_export *new = container_of(b, struct svc_export, h);
        return orig->ex_client == new->ex_client &&
                path_equal(&orig->ex_path, &new->ex_path);
}

static void svc_export_init(struct cache_head *cnew, struct cache_head *citem)
{
        struct svc_export *new = container_of(cnew, struct svc_export, h);
        struct svc_export *item = container_of(citem, struct svc_export, h);

        kref_get(&item->ex_client->ref);
        new->ex_client = item->ex_client;
        new->ex_path = item->ex_path;
        path_get(&item->ex_path);
        new->ex_fslocs.locations = NULL;
        new->ex_fslocs.locations_count = 0;
        new->ex_fslocs.migrated = 0;
        new->ex_layout_types = 0;
        new->ex_uuid = NULL;
        new->cd = item->cd;
        export_stats_reset(new->ex_stats);
}

static void export_update(struct cache_head *cnew, struct cache_head *citem)
{
        struct svc_export *new = container_of(cnew, struct svc_export, h);
        struct svc_export *item = container_of(citem, struct svc_export, h);
        int i;

        new->ex_flags = item->ex_flags;
        new->ex_anon_uid = item->ex_anon_uid;
        new->ex_anon_gid = item->ex_anon_gid;
        new->ex_fsid = item->ex_fsid;
        new->ex_devid_map = item->ex_devid_map;
        item->ex_devid_map = NULL;
        new->ex_uuid = item->ex_uuid;
        item->ex_uuid = NULL;
        new->ex_fslocs.locations = item->ex_fslocs.locations;
        item->ex_fslocs.locations = NULL;
        new->ex_fslocs.locations_count = item->ex_fslocs.locations_count;
        item->ex_fslocs.locations_count = 0;
        new->ex_fslocs.migrated = item->ex_fslocs.migrated;
        item->ex_fslocs.migrated = 0;
        new->ex_layout_types = item->ex_layout_types;
        new->ex_nflavors = item->ex_nflavors;
        for (i = 0; i < MAX_SECINFO_LIST; i++) {
                new->ex_flavors[i] = item->ex_flavors[i];
        }
        new->ex_xprtsec_modes = item->ex_xprtsec_modes;
}

static struct cache_head *svc_export_alloc(void)
{
        struct svc_export *i = kmalloc_obj(*i);
        if (!i)
                return NULL;

        i->ex_stats = kmalloc_obj(*(i->ex_stats));
        if (!i->ex_stats) {
                kfree(i);
                return NULL;
        }

        if (export_stats_init(i->ex_stats)) {
                kfree(i->ex_stats);
                kfree(i);
                return NULL;
        }

        return &i->h;
}

static const struct cache_detail svc_export_cache_template = {
        .owner          = THIS_MODULE,
        .hash_size      = EXPORT_HASHMAX,
        .name           = "nfsd.export",
        .cache_put      = svc_export_put,
        .cache_upcall   = svc_export_upcall,
        .cache_request  = svc_export_request,
        .cache_parse    = svc_export_parse,
        .cache_show     = svc_export_show,
        .match          = svc_export_match,
        .init           = svc_export_init,
        .update         = export_update,
        .alloc          = svc_export_alloc,
};

static int
svc_export_hash(struct svc_export *exp)
{
        int hash;

        hash = hash_ptr(exp->ex_client, EXPORT_HASHBITS);
        hash ^= hash_ptr(exp->ex_path.dentry, EXPORT_HASHBITS);
        hash ^= hash_ptr(exp->ex_path.mnt, EXPORT_HASHBITS);
        return hash;
}

static struct svc_export *
svc_export_lookup(struct svc_export *exp)
{
        struct cache_head *ch;
        int hash = svc_export_hash(exp);

        ch = sunrpc_cache_lookup_rcu(exp->cd, &exp->h, hash);
        if (ch)
                return container_of(ch, struct svc_export, h);
        else
                return NULL;
}

static struct svc_export *
svc_export_update(struct svc_export *new, struct svc_export *old)
{
        struct cache_head *ch;
        int hash = svc_export_hash(old);

        ch = sunrpc_cache_update(old->cd, &new->h, &old->h, hash);
        if (ch)
                return container_of(ch, struct svc_export, h);
        else
                return NULL;
}


static struct svc_expkey *
exp_find_key(struct cache_detail *cd, struct auth_domain *clp, int fsid_type,
             u32 *fsidv, struct cache_req *reqp)
{
        struct svc_expkey key, *ek;
        int err;
        
        if (!clp)
                return ERR_PTR(-ENOENT);

        key.ek_client = clp;
        key.ek_fsidtype = fsid_type;
        memcpy(key.ek_fsid, fsidv, key_len(fsid_type));

        ek = svc_expkey_lookup(cd, &key);
        if (ek == NULL)
                return ERR_PTR(-ENOMEM);
        err = cache_check(cd, &ek->h, reqp);
        if (err) {
                trace_nfsd_exp_find_key(&key, err);
                return ERR_PTR(err);
        }
        return ek;
}

static struct svc_export *
exp_get_by_name(struct cache_detail *cd, struct auth_domain *clp,
                const struct path *path, struct cache_req *reqp)
{
        struct svc_export *exp, key;
        int err;

        if (!clp)
                return ERR_PTR(-ENOENT);

        key.ex_client = clp;
        key.ex_path = *path;
        key.cd = cd;

        exp = svc_export_lookup(&key);
        if (exp == NULL)
                return ERR_PTR(-ENOMEM);
        err = cache_check(cd, &exp->h, reqp);
        if (err) {
                trace_nfsd_exp_get_by_name(&key, err);
                return ERR_PTR(err);
        }
        return exp;
}

/*
 * Find the export entry for a given dentry.
 */
static struct svc_export *
exp_parent(struct cache_detail *cd, struct auth_domain *clp, struct path *path)
{
        struct dentry *saved = dget(path->dentry);
        struct svc_export *exp = exp_get_by_name(cd, clp, path, NULL);

        while (PTR_ERR(exp) == -ENOENT && !IS_ROOT(path->dentry)) {
                struct dentry *parent = dget_parent(path->dentry);
                dput(path->dentry);
                path->dentry = parent;
                exp = exp_get_by_name(cd, clp, path, NULL);
        }
        dput(path->dentry);
        path->dentry = saved;
        return exp;
}



/*
 * Obtain the root fh on behalf of a client.
 * This could be done in user space, but I feel that it adds some safety
 * since its harder to fool a kernel module than a user space program.
 */
int
exp_rootfh(struct net *net, struct auth_domain *clp, char *name,
           struct knfsd_fh *f, int maxsize)
{
        struct svc_export       *exp;
        struct path             path;
        struct inode            *inode __maybe_unused;
        struct svc_fh           fh;
        int                     err;
        struct nfsd_net         *nn = net_generic(net, nfsd_net_id);
        struct cache_detail     *cd = nn->svc_export_cache;

        err = -EPERM;
        /* NB: we probably ought to check that it's NUL-terminated */
        if (kern_path(name, 0, &path)) {
                printk("nfsd: exp_rootfh path not found %s", name);
                return err;
        }
        inode = d_inode(path.dentry);

        dprintk("nfsd: exp_rootfh(%s [%p] %s:%s/%ld)\n",
                 name, path.dentry, clp->name,
                 inode->i_sb->s_id, inode->i_ino);
        exp = exp_parent(cd, clp, &path);
        if (IS_ERR(exp)) {
                err = PTR_ERR(exp);
                goto out;
        }

        /*
         * fh must be initialized before calling fh_compose
         */
        fh_init(&fh, maxsize);
        if (fh_compose(&fh, exp, path.dentry, NULL))
                err = -EINVAL;
        else
                err = 0;
        memcpy(f, &fh.fh_handle, sizeof(struct knfsd_fh));
        fh_put(&fh);
        exp_put(exp);
out:
        path_put(&path);
        return err;
}

static struct svc_export *exp_find(struct cache_detail *cd,
                                   struct auth_domain *clp, int fsid_type,
                                   u32 *fsidv, struct cache_req *reqp)
{
        struct svc_export *exp;
        struct nfsd_net *nn = net_generic(cd->net, nfsd_net_id);
        struct svc_expkey *ek = exp_find_key(nn->svc_expkey_cache, clp, fsid_type, fsidv, reqp);
        if (IS_ERR(ek))
                return ERR_CAST(ek);

        exp = exp_get_by_name(cd, clp, &ek->ek_path, reqp);
        cache_put(&ek->h, nn->svc_expkey_cache);

        if (IS_ERR(exp))
                return ERR_CAST(exp);
        return exp;
}

/**
 * check_xprtsec_policy - check if access to export is allowed by the
 *                        xprtsec policy
 * @exp: svc_export that is being accessed.
 * @rqstp: svc_rqst attempting to access @exp.
 *
 * Helper function for check_nfsd_access().  Note that callers should be
 * using check_nfsd_access() instead of calling this function directly.  The
 * one exception is __fh_verify() since it has logic that may result in one
 * or both of the helpers being skipped.
 *
 * Return values:
 *   %nfs_ok if access is granted, or
 *   %nfserr_wrongsec if access is denied
 */
__be32 check_xprtsec_policy(struct svc_export *exp, struct svc_rqst *rqstp)
{
        struct svc_xprt *xprt = rqstp->rq_xprt;

        if (exp->ex_xprtsec_modes & NFSEXP_XPRTSEC_NONE) {
                if (!test_bit(XPT_TLS_SESSION, &xprt->xpt_flags))
                        return nfs_ok;
        }
        if (exp->ex_xprtsec_modes & NFSEXP_XPRTSEC_TLS) {
                if (test_bit(XPT_TLS_SESSION, &xprt->xpt_flags) &&
                    !test_bit(XPT_PEER_AUTH, &xprt->xpt_flags))
                        return nfs_ok;
        }
        if (exp->ex_xprtsec_modes & NFSEXP_XPRTSEC_MTLS) {
                if (test_bit(XPT_TLS_SESSION, &xprt->xpt_flags) &&
                    test_bit(XPT_PEER_AUTH, &xprt->xpt_flags))
                        return nfs_ok;
        }
        return nfserr_wrongsec;
}

/**
 * check_security_flavor - check if access to export is allowed by the
 *                         security flavor
 * @exp: svc_export that is being accessed.
 * @rqstp: svc_rqst attempting to access @exp.
 * @may_bypass_gss: reduce strictness of authorization check
 *
 * Helper function for check_nfsd_access().  Note that callers should be
 * using check_nfsd_access() instead of calling this function directly.  The
 * one exception is __fh_verify() since it has logic that may result in one
 * or both of the helpers being skipped.
 *
 * Return values:
 *   %nfs_ok if access is granted, or
 *   %nfserr_wrongsec if access is denied
 */
__be32 check_security_flavor(struct svc_export *exp, struct svc_rqst *rqstp,
                             bool may_bypass_gss)
{
        struct exp_flavor_info *f, *end = exp->ex_flavors + exp->ex_nflavors;

        /* legacy gss-only clients are always OK: */
        if (exp->ex_client == rqstp->rq_gssclient)
                return nfs_ok;
        /* ip-address based client; check sec= export option: */
        for (f = exp->ex_flavors; f < end; f++) {
                if (f->pseudoflavor == rqstp->rq_cred.cr_flavor)
                        return nfs_ok;
        }
        /* defaults in absence of sec= options: */
        if (exp->ex_nflavors == 0) {
                if (rqstp->rq_cred.cr_flavor == RPC_AUTH_NULL ||
                    rqstp->rq_cred.cr_flavor == RPC_AUTH_UNIX)
                        return nfs_ok;
        }

        /* If the compound op contains a spo_must_allowed op,
         * it will be sent with integrity/protection which
         * will have to be expressly allowed on mounts that
         * don't support it
         */

        if (nfsd4_spo_must_allow(rqstp))
                return nfs_ok;

        /* Some calls may be processed without authentication
         * on GSS exports. For example NFS2/3 calls on root
         * directory, see section 2.3.2 of rfc 2623.
         * For "may_bypass_gss" check that export has really
         * enabled some flavor with authentication (GSS or any
         * other) and also check that the used auth flavor is
         * without authentication (none or sys).
         */
        if (may_bypass_gss && (
             rqstp->rq_cred.cr_flavor == RPC_AUTH_NULL ||
             rqstp->rq_cred.cr_flavor == RPC_AUTH_UNIX)) {
                for (f = exp->ex_flavors; f < end; f++) {
                        if (f->pseudoflavor >= RPC_AUTH_DES)
                                return 0;
                }
        }

        return nfserr_wrongsec;
}

/**
 * check_nfsd_access - check if access to export is allowed.
 * @exp: svc_export that is being accessed.
 * @rqstp: svc_rqst attempting to access @exp.
 * @may_bypass_gss: reduce strictness of authorization check
 *
 * Return values:
 *   %nfs_ok if access is granted, or
 *   %nfserr_wrongsec if access is denied
 */
__be32 check_nfsd_access(struct svc_export *exp, struct svc_rqst *rqstp,
                         bool may_bypass_gss)
{
        __be32 status;

        status = check_xprtsec_policy(exp, rqstp);
        if (status != nfs_ok)
                return status;
        return check_security_flavor(exp, rqstp, may_bypass_gss);
}

/*
 * Uses rq_client and rq_gssclient to find an export; uses rq_client (an
 * auth_unix client) if it's available and has secinfo information;
 * otherwise, will try to use rq_gssclient.
 *
 * Called from functions that handle requests; functions that do work on
 * behalf of mountd are passed a single client name to use, and should
 * use exp_get_by_name() or exp_find().
 */
struct svc_export *
rqst_exp_get_by_name(struct svc_rqst *rqstp, const struct path *path)
{
        struct svc_export *gssexp, *exp = ERR_PTR(-ENOENT);
        struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id);
        struct cache_detail *cd = nn->svc_export_cache;

        if (rqstp->rq_client == NULL)
                goto gss;

        /* First try the auth_unix client: */
        exp = exp_get_by_name(cd, rqstp->rq_client, path, &rqstp->rq_chandle);
        if (PTR_ERR(exp) == -ENOENT)
                goto gss;
        if (IS_ERR(exp))
                return exp;
        /* If it has secinfo, assume there are no gss/... clients */
        if (exp->ex_nflavors > 0)
                return exp;
gss:
        /* Otherwise, try falling back on gss client */
        if (rqstp->rq_gssclient == NULL)
                return exp;
        gssexp = exp_get_by_name(cd, rqstp->rq_gssclient, path, &rqstp->rq_chandle);
        if (PTR_ERR(gssexp) == -ENOENT)
                return exp;
        if (!IS_ERR(exp))
                exp_put(exp);
        return gssexp;
}

/**
 * rqst_exp_find - Find an svc_export in the context of a rqst or similar
 * @reqp:       The handle to be used to suspend the request if a cache-upcall is needed
 *              If NULL, missing in-cache information will result in failure.
 * @net:        The network namespace in which the request exists
 * @cl:         default auth_domain to use for looking up the export
 * @gsscl:      an alternate auth_domain defined using deprecated gss/krb5 format.
 * @fsid_type:  The type of fsid to look for
 * @fsidv:      The actual fsid to look up in the context of either client.
 *
 * Perform a lookup for @cl/@fsidv in the given @net for an export.  If
 * none found and @gsscl specified, repeat the lookup.
 *
 * Returns an export, or an error pointer.
 */
struct svc_export *
rqst_exp_find(struct cache_req *reqp, struct net *net,
              struct auth_domain *cl, struct auth_domain *gsscl,
              int fsid_type, u32 *fsidv)
{
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);
        struct svc_export *gssexp, *exp = ERR_PTR(-ENOENT);
        struct cache_detail *cd = nn->svc_export_cache;

        if (!cl)
                goto gss;

        /* First try the auth_unix client: */
        exp = exp_find(cd, cl, fsid_type, fsidv, reqp);
        if (PTR_ERR(exp) == -ENOENT)
                goto gss;
        if (IS_ERR(exp))
                return exp;
        /* If it has secinfo, assume there are no gss/... clients */
        if (exp->ex_nflavors > 0)
                return exp;
gss:
        /* Otherwise, try falling back on gss client */
        if (!gsscl)
                return exp;
        gssexp = exp_find(cd, gsscl, fsid_type, fsidv, reqp);
        if (PTR_ERR(gssexp) == -ENOENT)
                return exp;
        if (!IS_ERR(exp))
                exp_put(exp);
        return gssexp;
}

struct svc_export *
rqst_exp_parent(struct svc_rqst *rqstp, struct path *path)
{
        struct dentry *saved = dget(path->dentry);
        struct svc_export *exp = rqst_exp_get_by_name(rqstp, path);

        while (PTR_ERR(exp) == -ENOENT && !IS_ROOT(path->dentry)) {
                struct dentry *parent = dget_parent(path->dentry);
                dput(path->dentry);
                path->dentry = parent;
                exp = rqst_exp_get_by_name(rqstp, path);
        }
        dput(path->dentry);
        path->dentry = saved;
        return exp;
}

struct svc_export *rqst_find_fsidzero_export(struct svc_rqst *rqstp)
{
        u32 fsidv[2];

        mk_fsid(FSID_NUM, fsidv, 0, 0, 0, NULL);

        return rqst_exp_find(&rqstp->rq_chandle, SVC_NET(rqstp),
                             rqstp->rq_client, rqstp->rq_gssclient,
                             FSID_NUM, fsidv);
}

/*
 * Called when we need the filehandle for the root of the pseudofs,
 * for a given NFSv4 client.   The root is defined to be the
 * export point with fsid==0
 */
__be32
exp_pseudoroot(struct svc_rqst *rqstp, struct svc_fh *fhp)
{
        struct svc_export *exp;
        __be32 rv;

        exp = rqst_find_fsidzero_export(rqstp);
        if (IS_ERR(exp))
                return nfserrno(PTR_ERR(exp));
        rv = fh_compose(fhp, exp, exp->ex_path.dentry, NULL);
        exp_put(exp);
        return rv;
}

static struct flags {
        int flag;
        char *name[2];
} expflags[] = {
        { NFSEXP_READONLY, {"ro", "rw"}},
        { NFSEXP_INSECURE_PORT, {"insecure", ""}},
        { NFSEXP_ROOTSQUASH, {"root_squash", "no_root_squash"}},
        { NFSEXP_ALLSQUASH, {"all_squash", ""}},
        { NFSEXP_ASYNC, {"async", "sync"}},
        { NFSEXP_GATHERED_WRITES, {"wdelay", "no_wdelay"}},
        { NFSEXP_NOREADDIRPLUS, {"nordirplus", ""}},
        { NFSEXP_NOHIDE, {"nohide", ""}},
        { NFSEXP_CROSSMOUNT, {"crossmnt", ""}},
        { NFSEXP_NOSUBTREECHECK, {"no_subtree_check", ""}},
        { NFSEXP_NOAUTHNLM, {"insecure_locks", ""}},
        { NFSEXP_V4ROOT, {"v4root", ""}},
        { NFSEXP_PNFS, {"pnfs", ""}},
        { NFSEXP_SECURITY_LABEL, {"security_label", ""}},
        { 0, {"", ""}}
};

static void show_expflags(struct seq_file *m, int flags, int mask)
{
        struct flags *flg;
        int state, first = 0;

        for (flg = expflags; flg->flag; flg++) {
                if (flg->flag & ~mask)
                        continue;
                state = (flg->flag & flags) ? 0 : 1;
                if (*flg->name[state])
                        seq_printf(m, "%s%s", first++?",":"", flg->name[state]);
        }
}

static void show_secinfo_flags(struct seq_file *m, int flags)
{
        seq_printf(m, ",");
        show_expflags(m, flags, NFSEXP_SECINFO_FLAGS);
}

static bool secinfo_flags_equal(int f, int g)
{
        f &= NFSEXP_SECINFO_FLAGS;
        g &= NFSEXP_SECINFO_FLAGS;
        return f == g;
}

static int show_secinfo_run(struct seq_file *m, struct exp_flavor_info **fp, struct exp_flavor_info *end)
{
        int flags;

        flags = (*fp)->flags;
        seq_printf(m, ",sec=%d", (*fp)->pseudoflavor);
        (*fp)++;
        while (*fp != end && secinfo_flags_equal(flags, (*fp)->flags)) {
                seq_printf(m, ":%d", (*fp)->pseudoflavor);
                (*fp)++;
        }
        return flags;
}

static void show_secinfo(struct seq_file *m, struct svc_export *exp)
{
        struct exp_flavor_info *f;
        struct exp_flavor_info *end = exp->ex_flavors + exp->ex_nflavors;
        int flags;

        if (exp->ex_nflavors == 0)
                return;
        f = exp->ex_flavors;
        flags = show_secinfo_run(m, &f, end);
        if (!secinfo_flags_equal(flags, exp->ex_flags))
                show_secinfo_flags(m, flags);
        while (f != end) {
                flags = show_secinfo_run(m, &f, end);
                show_secinfo_flags(m, flags);
        }
}

static void exp_flags(struct seq_file *m, int flag, int fsid,
                kuid_t anonu, kgid_t anong, struct nfsd4_fs_locations *fsloc)
{
        struct user_namespace *userns = m->file->f_cred->user_ns;

        show_expflags(m, flag, NFSEXP_ALLFLAGS);
        if (flag & NFSEXP_FSID)
                seq_printf(m, ",fsid=%d", fsid);
        if (!uid_eq(anonu, make_kuid(userns, (uid_t)-2)) &&
            !uid_eq(anonu, make_kuid(userns, 0x10000-2)))
                seq_printf(m, ",anonuid=%u", from_kuid_munged(userns, anonu));
        if (!gid_eq(anong, make_kgid(userns, (gid_t)-2)) &&
            !gid_eq(anong, make_kgid(userns, 0x10000-2)))
                seq_printf(m, ",anongid=%u", from_kgid_munged(userns, anong));
        if (fsloc && fsloc->locations_count > 0) {
                char *loctype = (fsloc->migrated) ? "refer" : "replicas";
                int i;

                seq_printf(m, ",%s=", loctype);
                seq_escape(m, fsloc->locations[0].path, ",;@ \t\n\\");
                seq_putc(m, '@');
                seq_escape(m, fsloc->locations[0].hosts, ",;@ \t\n\\");
                for (i = 1; i < fsloc->locations_count; i++) {
                        seq_putc(m, ';');
                        seq_escape(m, fsloc->locations[i].path, ",;@ \t\n\\");
                        seq_putc(m, '@');
                        seq_escape(m, fsloc->locations[i].hosts, ",;@ \t\n\\");
                }
        }
}

static int e_show(struct seq_file *m, void *p)
{
        struct cache_head *cp = p;
        struct svc_export *exp = container_of(cp, struct svc_export, h);
        struct cache_detail *cd = m->private;
        bool export_stats = is_export_stats_file(m);

        if (p == SEQ_START_TOKEN) {
                seq_puts(m, "# Version 1.1\n");
                if (export_stats)
                        seq_puts(m, "# Path Client Start-time\n#\tStats\n");
                else
                        seq_puts(m, "# Path Client(Flags) # IPs\n");
                return 0;
        }

        if (cache_check_rcu(cd, &exp->h, NULL))
                return 0;

        return svc_export_show(m, cd, cp);
}

const struct seq_operations nfs_exports_op = {
        .start  = cache_seq_start_rcu,
        .next   = cache_seq_next_rcu,
        .stop   = cache_seq_stop_rcu,
        .show   = e_show,
};

/**
 * nfsd_export_wq_init - allocate the export release workqueue
 *
 * Called once at module load. The workqueue runs deferred svc_export and
 * svc_expkey release work scheduled by queue_rcu_work() in the cache put
 * callbacks.
 *
 * Return values:
 *   %0: workqueue allocated
 *   %-ENOMEM: allocation failed
 */
int nfsd_export_wq_init(void)
{
        nfsd_export_wq = alloc_workqueue("nfsd_export", WQ_UNBOUND, 0);
        if (!nfsd_export_wq)
                return -ENOMEM;
        return 0;
}

/**
 * nfsd_export_wq_shutdown - drain and free the export release workqueue
 *
 * Called once at module unload. Per-namespace teardown in
 * nfsd_export_shutdown() has already drained all deferred work.
 */
void nfsd_export_wq_shutdown(void)
{
        destroy_workqueue(nfsd_export_wq);
}

/*
 * Initialize the exports module.
 */
int
nfsd_export_init(struct net *net)
{
        int rv;
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);

        dprintk("nfsd: initializing export module (net: %x).\n", net->ns.inum);

        nn->svc_export_cache = cache_create_net(&svc_export_cache_template, net);
        if (IS_ERR(nn->svc_export_cache))
                return PTR_ERR(nn->svc_export_cache);
        rv = cache_register_net(nn->svc_export_cache, net);
        if (rv)
                goto destroy_export_cache;

        nn->svc_expkey_cache = cache_create_net(&svc_expkey_cache_template, net);
        if (IS_ERR(nn->svc_expkey_cache)) {
                rv = PTR_ERR(nn->svc_expkey_cache);
                goto unregister_export_cache;
        }
        rv = cache_register_net(nn->svc_expkey_cache, net);
        if (rv)
                goto destroy_expkey_cache;
        return 0;

destroy_expkey_cache:
        cache_destroy_net(nn->svc_expkey_cache, net);
unregister_export_cache:
        cache_unregister_net(nn->svc_export_cache, net);
destroy_export_cache:
        cache_destroy_net(nn->svc_export_cache, net);
        return rv;
}

/*
 * Flush exports table - called when last nfsd thread is killed
 */
void
nfsd_export_flush(struct net *net)
{
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);

        cache_purge(nn->svc_expkey_cache);
        cache_purge(nn->svc_export_cache);
}

/*
 * Shutdown the exports module.
 */
void
nfsd_export_shutdown(struct net *net)
{
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);

        dprintk("nfsd: shutting down export module (net: %x).\n", net->ns.inum);

        cache_unregister_net(nn->svc_expkey_cache, net);
        cache_unregister_net(nn->svc_export_cache, net);
        /* Drain deferred export and expkey release work. */
        rcu_barrier();
        flush_workqueue(nfsd_export_wq);
        cache_destroy_net(nn->svc_expkey_cache, net);
        cache_destroy_net(nn->svc_export_cache, net);
        svcauth_unix_purge(net);

        dprintk("nfsd: export shutdown complete (net: %x).\n", net->ns.inum);
}