md: Fix unfortunate interaction with evms

[linux-2.6/mini2440.git] / fs / nfsd / export.c

#define MSNFS   /* HACK HACK */
/*
 * linux/fs/nfsd/export.c
 *
 * 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/unistd.h>
#include <linux/slab.h>
#include <linux/stat.h>
#include <linux/in.h>
#include <linux/seq_file.h>
#include <linux/syscalls.h>
#include <linux/rwsem.h>
#include <linux/dcache.h>
#include <linux/namei.h>
#include <linux/mount.h>
#include <linux/hash.h>
#include <linux/module.h>
#include <linux/exportfs.h>

#include <linux/sunrpc/svc.h>
#include <linux/nfsd/nfsd.h>
#include <linux/nfsd/nfsfh.h>
#include <linux/nfsd/syscall.h>
#include <linux/lockd/bind.h>
#include <linux/sunrpc/msg_prot.h>
#include <linux/sunrpc/gss_api.h>
#include <net/ipv6.h>

#define NFSDDBG_FACILITY        NFSDDBG_EXPORT

typedef struct auth_domain      svc_client;
typedef struct svc_export       svc_export;

static void             exp_do_unexport(svc_export *unexp);
static int              exp_verify_string(char *cp, int max);

/*
 * 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.
 */

#define EXPKEY_HASHBITS         8
#define EXPKEY_HASHMAX          (1 << EXPKEY_HASHBITS)
#define EXPKEY_HASHMASK         (EXPKEY_HASHMAX -1)
static struct cache_head *expkey_table[EXPKEY_HASHMAX];

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

        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_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 svc_expkey *new, struct svc_expkey *old);
static struct svc_expkey *svc_expkey_lookup(struct svc_expkey *);
static struct cache_detail svc_expkey_cache;

static int expkey_parse(struct cache_detail *cd, char *mesg, int mlen)
{
        /* client fsidtype fsid [path] */
        char *buf;
        int len;
        struct auth_domain *dom = NULL;
        int err;
        int fsidtype;
        char *ep;
        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 ((len=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 ((len=qword_get(&mesg, buf, PAGE_SIZE)) <= 0)
                goto out;
        fsidtype = simple_strtoul(buf, &ep, 10);
        if (*ep)
                goto out;
        dprintk("found fsidtype %d\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;
        key.h.expiry_time = get_expiry(&mesg);
        if (key.h.expiry_time == 0)
                goto out;

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

        ek = svc_expkey_lookup(&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(&key, ek);
                if (!ek)
                        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(&key, ek);
                if (!ek)
                        err = -ENOMEM;
                path_put(&key.ek_path);
        }
        cache_flush();
 out:
        if (ek)
                cache_put(&ek->h, &svc_expkey_cache);
        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(sizeof(*i), GFP_KERNEL);
        if (i)
                return &i->h;
        else
                return NULL;
}

static struct cache_detail svc_expkey_cache = {
        .owner          = THIS_MODULE,
        .hash_size      = EXPKEY_HASHMAX,
        .hash_table     = expkey_table,
        .name           = "nfsd.fh",
        .cache_put      = expkey_put,
        .cache_request  = expkey_request,
        .cache_parse    = expkey_parse,
        .cache_show     = expkey_show,
        .match          = expkey_match,
        .init           = expkey_init,
        .update         = expkey_update,
        .alloc          = expkey_alloc,
};

static struct svc_expkey *
svc_expkey_lookup(struct svc_expkey *item)
{
        struct cache_head *ch;
        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;

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

static struct svc_expkey *
svc_expkey_update(struct svc_expkey *new, struct svc_expkey *old)
{
        struct cache_head *ch;
        int hash = new->ek_fsidtype;
        char * cp = (char*)new->ek_fsid;
        int len = key_len(new->ek_fsidtype);

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

        ch = sunrpc_cache_update(&svc_expkey_cache, &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)
#define EXPORT_HASHMASK         (EXPORT_HASHMAX -1)

static struct cache_head *export_table[EXPORT_HASHMAX];

static void nfsd4_fslocs_free(struct nfsd4_fs_locations *fsloc)
{
        int i;

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

static void svc_export_put(struct kref *ref)
{
        struct svc_export *exp = container_of(ref, struct svc_export, h.ref);
        path_put(&exp->ex_path);
        auth_domain_put(exp->ex_client);
        kfree(exp->ex_pathname);
        nfsd4_fslocs_free(&exp->ex_fslocs);
        kfree(exp);
}

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(struct inode *inode, int flags, unsigned char *uuid)
{

        /* We currently export only dirs and regular files.
         * This is what umountd does.
         */
        if (!S_ISDIR(inode->i_mode) &&
            !S_ISREG(inode->i_mode))
                return -ENOTDIR;

        /* 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.
         */
        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 (!inode->i_sb->s_export_op ||
            !inode->i_sb->s_export_op->fh_to_dentry) {
                dprintk("exp_export: export of invalid fs type.\n");
                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;

        /* listsize */
        err = get_int(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(fsloc->locations_count
                        * sizeof(struct nfsd4_fs_location), GFP_KERNEL);
        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)
{
        int listsize, err;
        struct exp_flavor_info *f;

        err = get_int(mesg, &listsize);
        if (err)
                return err;
        if (listsize < 0 || listsize > MAX_SECINFO_LIST)
                return -EINVAL;

        for (f = exp->ex_flavors; f < exp->ex_flavors + listsize; f++) {
                err = get_int(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_int(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 svc_export_parse(struct cache_detail *cd, char *mesg, int mlen)
{
        /* client path expiry [flags anonuid anongid fsid] */
        char *buf;
        int len;
        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;
        len = qword_get(&mesg, buf, PAGE_SIZE);
        if (len <= 0)
                goto out;

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

        /* path */
        err = -EINVAL;
        if ((len = 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;

        err = -ENOMEM;
        exp.ex_pathname = kstrdup(buf, GFP_KERNEL);
        if (!exp.ex_pathname)
                goto out2;

        /* expiry */
        err = -EINVAL;
        exp.h.expiry_time = get_expiry(&mesg);
        if (exp.h.expiry_time == 0)
                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= an_int;

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

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

                while ((len = 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) {
                                /* expect a 16 byte uuid encoded as \xXXXX... */
                                len = qword_get(&mesg, buf, PAGE_SIZE);
                                if (len != 16)
                                        err  = -EINVAL;
                                else {
                                        exp.ex_uuid =
                                                kmemdup(buf, 16, GFP_KERNEL);
                                        if (exp.ex_uuid == NULL)
                                                err = -ENOMEM;
                                }
                        } else if (strcmp(buf, "secinfo") == 0)
                                err = secinfo_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.dentry->d_inode, exp.ex_flags,
                                   exp.ex_uuid);
                if (err)
                        goto out4;
        }

        expp = svc_export_lookup(&exp);
        if (expp)
                expp = svc_export_update(&exp, expp);
        else
                err = -ENOMEM;
        cache_flush();
        if (expp == NULL)
                err = -ENOMEM;
        else
                exp_put(expp);
out4:
        nfsd4_fslocs_free(&exp.ex_fslocs);
        kfree(exp.ex_uuid);
out3:
        kfree(exp.ex_pathname);
out2:
        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,
                uid_t anonu, uid_t anong, struct nfsd4_fs_locations *fslocs);
static void show_secinfo(struct seq_file *m, struct svc_export *exp);

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

        if (h ==NULL) {
                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\\");
        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<16; 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 &&
                orig->ex_path.dentry == new->ex_path.dentry &&
                orig->ex_path.mnt == new->ex_path.mnt;
}

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.dentry = dget(item->ex_path.dentry);
        new->ex_path.mnt = mntget(item->ex_path.mnt);
        new->ex_pathname = NULL;
        new->ex_fslocs.locations = NULL;
        new->ex_fslocs.locations_count = 0;
        new->ex_fslocs.migrated = 0;
}

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_uuid = item->ex_uuid;
        item->ex_uuid = NULL;
        new->ex_pathname = item->ex_pathname;
        item->ex_pathname = 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_nflavors = item->ex_nflavors;
        for (i = 0; i < MAX_SECINFO_LIST; i++) {
                new->ex_flavors[i] = item->ex_flavors[i];
        }
}

static struct cache_head *svc_export_alloc(void)
{
        struct svc_export *i = kmalloc(sizeof(*i), GFP_KERNEL);
        if (i)
                return &i->h;
        else
                return NULL;
}

struct cache_detail svc_export_cache = {
        .owner          = THIS_MODULE,
        .hash_size      = EXPORT_HASHMAX,
        .hash_table     = export_table,
        .name           = "nfsd.export",
        .cache_put      = svc_export_put,
        .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 struct svc_export *
svc_export_lookup(struct svc_export *exp)
{
        struct cache_head *ch;
        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);

        ch = sunrpc_cache_lookup(&svc_export_cache, &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;
        hash = hash_ptr(old->ex_client, EXPORT_HASHBITS);
        hash ^= hash_ptr(old->ex_path.dentry, EXPORT_HASHBITS);
        hash ^= hash_ptr(old->ex_path.mnt, EXPORT_HASHBITS);

        ch = sunrpc_cache_update(&svc_export_cache, &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(svc_client *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(&key);
        if (ek == NULL)
                return ERR_PTR(-ENOMEM);
        err = cache_check(&svc_expkey_cache, &ek->h, reqp);
        if (err)
                return ERR_PTR(err);
        return ek;
}

static int exp_set_key(svc_client *clp, int fsid_type, u32 *fsidv,
                       struct svc_export *exp)
{
        struct svc_expkey key, *ek;

        key.ek_client = clp;
        key.ek_fsidtype = fsid_type;
        memcpy(key.ek_fsid, fsidv, key_len(fsid_type));
        key.ek_path = exp->ex_path;
        key.h.expiry_time = NEVER;
        key.h.flags = 0;

        ek = svc_expkey_lookup(&key);
        if (ek)
                ek = svc_expkey_update(&key,ek);
        if (ek) {
                cache_put(&ek->h, &svc_expkey_cache);
                return 0;
        }
        return -ENOMEM;
}

/*
 * Find the client's export entry matching xdev/xino.
 */
static inline struct svc_expkey *
exp_get_key(svc_client *clp, dev_t dev, ino_t ino)
{
        u32 fsidv[3];
        
        if (old_valid_dev(dev)) {
                mk_fsid(FSID_DEV, fsidv, dev, ino, 0, NULL);
                return exp_find_key(clp, FSID_DEV, fsidv, NULL);
        }
        mk_fsid(FSID_ENCODE_DEV, fsidv, dev, ino, 0, NULL);
        return exp_find_key(clp, FSID_ENCODE_DEV, fsidv, NULL);
}

/*
 * Find the client's export entry matching fsid
 */
static inline struct svc_expkey *
exp_get_fsid_key(svc_client *clp, int fsid)
{
        u32 fsidv[2];

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

        return exp_find_key(clp, FSID_NUM, fsidv, NULL);
}

static svc_export *exp_get_by_name(svc_client *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;

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

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

/*
 * Hashtable locking. Write locks are placed only by user processes
 * wanting to modify export information.
 * Write locking only done in this file.  Read locking
 * needed externally.
 */

static DECLARE_RWSEM(hash_sem);

void
exp_readlock(void)
{
        down_read(&hash_sem);
}

static inline void
exp_writelock(void)
{
        down_write(&hash_sem);
}

void
exp_readunlock(void)
{
        up_read(&hash_sem);
}

static inline void
exp_writeunlock(void)
{
        up_write(&hash_sem);
}

static void exp_fsid_unhash(struct svc_export *exp)
{
        struct svc_expkey *ek;

        if ((exp->ex_flags & NFSEXP_FSID) == 0)
                return;

        ek = exp_get_fsid_key(exp->ex_client, exp->ex_fsid);
        if (!IS_ERR(ek)) {
                ek->h.expiry_time = get_seconds()-1;
                cache_put(&ek->h, &svc_expkey_cache);
        }
        svc_expkey_cache.nextcheck = get_seconds();
}

static int exp_fsid_hash(svc_client *clp, struct svc_export *exp)
{
        u32 fsid[2];
 
        if ((exp->ex_flags & NFSEXP_FSID) == 0)
                return 0;

        mk_fsid(FSID_NUM, fsid, 0, 0, exp->ex_fsid, NULL);
        return exp_set_key(clp, FSID_NUM, fsid, exp);
}

static int exp_hash(struct auth_domain *clp, struct svc_export *exp)
{
        u32 fsid[2];
        struct inode *inode = exp->ex_path.dentry->d_inode;
        dev_t dev = inode->i_sb->s_dev;

        if (old_valid_dev(dev)) {
                mk_fsid(FSID_DEV, fsid, dev, inode->i_ino, 0, NULL);
                return exp_set_key(clp, FSID_DEV, fsid, exp);
        }
        mk_fsid(FSID_ENCODE_DEV, fsid, dev, inode->i_ino, 0, NULL);
        return exp_set_key(clp, FSID_ENCODE_DEV, fsid, exp);
}

static void exp_unhash(struct svc_export *exp)
{
        struct svc_expkey *ek;
        struct inode *inode = exp->ex_path.dentry->d_inode;

        ek = exp_get_key(exp->ex_client, inode->i_sb->s_dev, inode->i_ino);
        if (!IS_ERR(ek)) {
                ek->h.expiry_time = get_seconds()-1;
                cache_put(&ek->h, &svc_expkey_cache);
        }
        svc_expkey_cache.nextcheck = get_seconds();
}
        
/*
 * Export a file system.
 */
int
exp_export(struct nfsctl_export *nxp)
{
        svc_client      *clp;
        struct svc_export       *exp = NULL;
        struct svc_export       new;
        struct svc_expkey       *fsid_key = NULL;
        struct path path;
        int             err;

        /* Consistency check */
        err = -EINVAL;
        if (!exp_verify_string(nxp->ex_path, NFS_MAXPATHLEN) ||
            !exp_verify_string(nxp->ex_client, NFSCLNT_IDMAX))
                goto out;

        dprintk("exp_export called for %s:%s (%x/%ld fl %x).\n",
                        nxp->ex_client, nxp->ex_path,
                        (unsigned)nxp->ex_dev, (long)nxp->ex_ino,
                        nxp->ex_flags);

        /* Try to lock the export table for update */
        exp_writelock();

        /* Look up client info */
        if (!(clp = auth_domain_find(nxp->ex_client)))
                goto out_unlock;


        /* Look up the dentry */
        err = kern_path(nxp->ex_path, 0, &path);
        if (err)
                goto out_put_clp;
        err = -EINVAL;

        exp = exp_get_by_name(clp, &path, NULL);

        memset(&new, 0, sizeof(new));

        /* must make sure there won't be an ex_fsid clash */
        if ((nxp->ex_flags & NFSEXP_FSID) &&
            (!IS_ERR(fsid_key = exp_get_fsid_key(clp, nxp->ex_dev))) &&
            fsid_key->ek_path.mnt &&
            (fsid_key->ek_path.mnt != path.mnt ||
             fsid_key->ek_path.dentry != path.dentry))
                goto finish;

        if (!IS_ERR(exp)) {
                /* just a flags/id/fsid update */

                exp_fsid_unhash(exp);
                exp->ex_flags    = nxp->ex_flags;
                exp->ex_anon_uid = nxp->ex_anon_uid;
                exp->ex_anon_gid = nxp->ex_anon_gid;
                exp->ex_fsid     = nxp->ex_dev;

                err = exp_fsid_hash(clp, exp);
                goto finish;
        }

        err = check_export(path.dentry->d_inode, nxp->ex_flags, NULL);
        if (err) goto finish;

        err = -ENOMEM;

        dprintk("nfsd: creating export entry %p for client %p\n", exp, clp);

        new.h.expiry_time = NEVER;
        new.h.flags = 0;
        new.ex_pathname = kstrdup(nxp->ex_path, GFP_KERNEL);
        if (!new.ex_pathname)
                goto finish;
        new.ex_client = clp;
        new.ex_path = path;
        new.ex_flags = nxp->ex_flags;
        new.ex_anon_uid = nxp->ex_anon_uid;
        new.ex_anon_gid = nxp->ex_anon_gid;
        new.ex_fsid = nxp->ex_dev;

        exp = svc_export_lookup(&new);
        if (exp)
                exp = svc_export_update(&new, exp);

        if (!exp)
                goto finish;

        if (exp_hash(clp, exp) ||
            exp_fsid_hash(clp, exp)) {
                /* failed to create at least one index */
                exp_do_unexport(exp);
                cache_flush();
        } else
                err = 0;
finish:
        kfree(new.ex_pathname);
        if (exp)
                exp_put(exp);
        if (fsid_key && !IS_ERR(fsid_key))
                cache_put(&fsid_key->h, &svc_expkey_cache);
        path_put(&path);
out_put_clp:
        auth_domain_put(clp);
out_unlock:
        exp_writeunlock();
out:
        return err;
}

/*
 * Unexport a file system. The export entry has already
 * been removed from the client's list of exported fs's.
 */
static void
exp_do_unexport(svc_export *unexp)
{
        unexp->h.expiry_time = get_seconds()-1;
        svc_export_cache.nextcheck = get_seconds();
        exp_unhash(unexp);
        exp_fsid_unhash(unexp);
}


/*
 * unexport syscall.
 */
int
exp_unexport(struct nfsctl_export *nxp)
{
        struct auth_domain *dom;
        svc_export *exp;
        struct path path;
        int             err;

        /* Consistency check */
        if (!exp_verify_string(nxp->ex_path, NFS_MAXPATHLEN) ||
            !exp_verify_string(nxp->ex_client, NFSCLNT_IDMAX))
                return -EINVAL;

        exp_writelock();

        err = -EINVAL;
        dom = auth_domain_find(nxp->ex_client);
        if (!dom) {
                dprintk("nfsd: unexport couldn't find %s\n", nxp->ex_client);
                goto out_unlock;
        }

        err = kern_path(nxp->ex_path, 0, &path);
        if (err)
                goto out_domain;

        err = -EINVAL;
        exp = exp_get_by_name(dom, &path, NULL);
        path_put(&path);
        if (IS_ERR(exp))
                goto out_domain;

        exp_do_unexport(exp);
        exp_put(exp);
        err = 0;

out_domain:
        auth_domain_put(dom);
        cache_flush();
out_unlock:
        exp_writeunlock();
        return err;
}

/*
 * 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(svc_client *clp, char *name, struct knfsd_fh *f, int maxsize)
{
        struct svc_export       *exp;
        struct path             path;
        struct inode            *inode;
        struct svc_fh           fh;
        int                     err;

        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 = path.dentry->d_inode;

        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(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 auth_domain *clp, int fsid_type,
                                   u32 *fsidv, struct cache_req *reqp)
{
        struct svc_export *exp;
        struct svc_expkey *ek = exp_find_key(clp, fsid_type, fsidv, reqp);
        if (IS_ERR(ek))
                return ERR_CAST(ek);

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

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

__be32 check_nfsd_access(struct svc_export *exp, struct svc_rqst *rqstp)
{
        struct exp_flavor_info *f;
        struct exp_flavor_info *end = exp->ex_flavors + exp->ex_nflavors;

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

/*
 * 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, struct path *path)
{
        struct svc_export *gssexp, *exp = ERR_PTR(-ENOENT);

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

        /* First try the auth_unix client: */
        exp = exp_get_by_name(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(rqstp->rq_gssclient, path, &rqstp->rq_chandle);
        if (PTR_ERR(gssexp) == -ENOENT)
                return exp;
        if (!IS_ERR(exp))
                exp_put(exp);
        return gssexp;
}

struct svc_export *
rqst_exp_find(struct svc_rqst *rqstp, int fsid_type, u32 *fsidv)
{
        struct svc_export *gssexp, *exp = ERR_PTR(-ENOENT);

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

        /* First try the auth_unix client: */
        exp = exp_find(rqstp->rq_client, fsid_type, fsidv, &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_find(rqstp->rq_gssclient, fsid_type, fsidv,
                                                &rqstp->rq_chandle);
        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;
}

/*
 * 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;
        u32 fsidv[2];

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

        exp = rqst_exp_find(rqstp, FSID_NUM, fsidv);
        if (IS_ERR(exp))
                return nfserrno(PTR_ERR(exp));
        rv = fh_compose(fhp, exp, exp->ex_path.dentry, NULL);
        if (rv)
                goto out;
        rv = check_nfsd_access(exp, rqstp);
out:
        exp_put(exp);
        return rv;
}

/* Iterator */

static void *e_start(struct seq_file *m, loff_t *pos)
        __acquires(svc_export_cache.hash_lock)
{
        loff_t n = *pos;
        unsigned hash, export;
        struct cache_head *ch;
        
        exp_readlock();
        read_lock(&svc_export_cache.hash_lock);
        if (!n--)
                return SEQ_START_TOKEN;
        hash = n >> 32;
        export = n & ((1LL<<32) - 1);

        
        for (ch=export_table[hash]; ch; ch=ch->next)
                if (!export--)
                        return ch;
        n &= ~((1LL<<32) - 1);
        do {
                hash++;
                n += 1LL<<32;
        } while(hash < EXPORT_HASHMAX && export_table[hash]==NULL);
        if (hash >= EXPORT_HASHMAX)
                return NULL;
        *pos = n+1;
        return export_table[hash];
}

static void *e_next(struct seq_file *m, void *p, loff_t *pos)
{
        struct cache_head *ch = p;
        int hash = (*pos >> 32);

        if (p == SEQ_START_TOKEN)
                hash = 0;
        else if (ch->next == NULL) {
                hash++;
                *pos += 1LL<<32;
        } else {
                ++*pos;
                return ch->next;
        }
        *pos &= ~((1LL<<32) - 1);
        while (hash < EXPORT_HASHMAX && export_table[hash] == NULL) {
                hash++;
                *pos += 1LL<<32;
        }
        if (hash >= EXPORT_HASHMAX)
                return NULL;
        ++*pos;
        return export_table[hash];
}

static void e_stop(struct seq_file *m, void *p)
        __releases(svc_export_cache.hash_lock)
{
        read_unlock(&svc_export_cache.hash_lock);
        exp_readunlock();
}

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_NOHIDE, {"nohide", ""}},
        { NFSEXP_CROSSMOUNT, {"crossmnt", ""}},
        { NFSEXP_NOSUBTREECHECK, {"no_subtree_check", ""}},
        { NFSEXP_NOAUTHNLM, {"insecure_locks", ""}},
#ifdef MSNFS
        { NFSEXP_MSNFS, {"msnfs", ""}},
#endif
        { 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 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 lastflags = 0, first = 0;

        if (exp->ex_nflavors == 0)
                return;
        for (f = exp->ex_flavors; f < end; f++) {
                if (first || f->flags != lastflags) {
                        if (!first)
                                show_secinfo_flags(m, lastflags);
                        seq_printf(m, ",sec=%d", f->pseudoflavor);
                        lastflags = f->flags;
                } else {
                        seq_printf(m, ":%d", f->pseudoflavor);
                }
        }
        show_secinfo_flags(m, lastflags);
}

static void exp_flags(struct seq_file *m, int flag, int fsid,
                uid_t anonu, uid_t anong, struct nfsd4_fs_locations *fsloc)
{
        show_expflags(m, flag, NFSEXP_ALLFLAGS);
        if (flag & NFSEXP_FSID)
                seq_printf(m, ",fsid=%d", fsid);
        if (anonu != (uid_t)-2 && anonu != (0x10000-2))
                seq_printf(m, ",anonuid=%u", anonu);
        if (anong != (gid_t)-2 && anong != (0x10000-2))
                seq_printf(m, ",anongid=%u", 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);

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

        cache_get(&exp->h);
        if (cache_check(&svc_export_cache, &exp->h, NULL))
                return 0;
        cache_put(&exp->h, &svc_export_cache);
        return svc_export_show(m, &svc_export_cache, cp);
}

struct seq_operations nfs_exports_op = {
        .start  = e_start,
        .next   = e_next,
        .stop   = e_stop,
        .show   = e_show,
};

/*
 * Add or modify a client.
 * Change requests may involve the list of host addresses. The list of
 * exports and possibly existing uid maps are left untouched.
 */
int
exp_addclient(struct nfsctl_client *ncp)
{
        struct auth_domain      *dom;
        int                     i, err;
        struct in6_addr addr6;

        /* First, consistency check. */
        err = -EINVAL;
        if (! exp_verify_string(ncp->cl_ident, NFSCLNT_IDMAX))
                goto out;
        if (ncp->cl_naddr > NFSCLNT_ADDRMAX)
                goto out;

        /* Lock the hashtable */
        exp_writelock();

        dom = unix_domain_find(ncp->cl_ident);

        err = -ENOMEM;
        if (!dom)
                goto out_unlock;

        /* Insert client into hashtable. */
        for (i = 0; i < ncp->cl_naddr; i++) {
                ipv6_addr_set_v4mapped(ncp->cl_addrlist[i].s_addr, &addr6);
                auth_unix_add_addr(&addr6, dom);
        }
        auth_unix_forget_old(dom);
        auth_domain_put(dom);

        err = 0;

out_unlock:
        exp_writeunlock();
out:
        return err;
}

/*
 * Delete a client given an identifier.
 */
int
exp_delclient(struct nfsctl_client *ncp)
{
        int             err;
        struct auth_domain *dom;

        err = -EINVAL;
        if (!exp_verify_string(ncp->cl_ident, NFSCLNT_IDMAX))
                goto out;

        /* Lock the hashtable */
        exp_writelock();

        dom = auth_domain_find(ncp->cl_ident);
        /* just make sure that no addresses work 
         * and that it will expire soon 
         */
        if (dom) {
                err = auth_unix_forget_old(dom);
                auth_domain_put(dom);
        }

        exp_writeunlock();
out:
        return err;
}

/*
 * Verify that string is non-empty and does not exceed max length.
 */
static int
exp_verify_string(char *cp, int max)
{
        int     i;

        for (i = 0; i < max; i++)
                if (!cp[i])
                        return i;
        cp[i] = 0;
        printk(KERN_NOTICE "nfsd: couldn't validate string %s\n", cp);
        return 0;
}

/*
 * Initialize the exports module.
 */
int
nfsd_export_init(void)
{
        int rv;
        dprintk("nfsd: initializing export module.\n");

        rv = cache_register(&svc_export_cache);
        if (rv)
                return rv;
        rv = cache_register(&svc_expkey_cache);
        if (rv)
                cache_unregister(&svc_export_cache);
        return rv;

}

/*
 * Flush exports table - called when last nfsd thread is killed
 */
void
nfsd_export_flush(void)
{
        exp_writelock();
        cache_purge(&svc_expkey_cache);
        cache_purge(&svc_export_cache);
        exp_writeunlock();
}

/*
 * Shutdown the exports module.
 */
void
nfsd_export_shutdown(void)
{

        dprintk("nfsd: shutting down export module.\n");

        exp_writelock();

        cache_unregister(&svc_expkey_cache);
        cache_unregister(&svc_export_cache);
        svcauth_unix_purge();

        exp_writeunlock();
        dprintk("nfsd: export shutdown complete.\n");
}