Merge with Linux 2.3.99-pre4.

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

/*
 * 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.
 *
 * You cannot currently read the export information from the
 * kernel. It would be nice to have a /proc file though.
 *
 * Copyright (C) 1995, 1996 Olaf Kirch, <okir@monad.swb.de>
 */

#include <linux/unistd.h>
#include <linux/malloc.h>
#include <linux/stat.h>
#include <linux/in.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>

#define NFSDDBG_FACILITY        NFSDDBG_EXPORT
#define NFSD_PARANOIA 1

typedef struct svc_client       svc_client;
typedef struct svc_export       svc_export;

static svc_export *     exp_find(svc_client *clp, kdev_t dev);
static svc_export *     exp_parent(svc_client *clp, kdev_t dev,
                                        struct dentry *dentry);
static svc_export *     exp_child(svc_client *clp, kdev_t dev,
                                        struct dentry *dentry);
static void             exp_unexport_all(svc_client *clp);
static void             exp_do_unexport(svc_export *unexp);
static svc_client *     exp_getclientbyname(char *name);
static void             exp_freeclient(svc_client *clp);
static void             exp_unhashclient(svc_client *clp);
static int              exp_verify_string(char *cp, int max);

#define CLIENT_HASHBITS         6
#define CLIENT_HASHMAX          (1 << CLIENT_HASHBITS)
#define CLIENT_HASHMASK         (CLIENT_HASHMAX - 1)
#define CLIENT_HASH(a) \
                ((((a)>>24) ^ ((a)>>16) ^ ((a)>>8) ^(a)) & CLIENT_HASHMASK)
/* XXX: is this adequate for 32bit kdev_t ? */
#define EXPORT_HASH(dev)        ((dev) & (NFSCLNT_EXPMAX - 1))

struct svc_clnthash {
        struct svc_clnthash *   h_next;
        struct in_addr          h_addr;
        struct svc_client *     h_client;
};
static struct svc_clnthash *    clnt_hash[CLIENT_HASHMAX];
static svc_client *             clients = NULL;
static int                      initialized = 0;

static int                      hash_lock = 0;
static int                      want_lock = 0;
static int                      hash_count = 0;
static DECLARE_WAIT_QUEUE_HEAD( hash_wait );


/*
 * Find a client's export for a device.
 */
static inline svc_export *
exp_find(svc_client *clp, kdev_t dev)
{
        svc_export *    exp;

        exp = clp->cl_export[EXPORT_HASH(dev)];
        while (exp && exp->ex_dev != dev)
                exp = exp->ex_next;
        return exp;
}

/*
 * Find the client's export entry matching xdev/xino.
 */
svc_export *
exp_get(svc_client *clp, kdev_t dev, ino_t ino)
{
        svc_export *    exp;

        if (!clp)
                return NULL;

        exp = clp->cl_export[EXPORT_HASH(dev)];
        if (exp)
                do {
                        if (exp->ex_ino == ino && exp->ex_dev == dev)
                                goto out;
                } while (NULL != (exp = exp->ex_next));
        exp = NULL;
out:
        return exp;
}


/*
 * Look up the device of the parent fs.
 */
static inline int
nfsd_parentdev(kdev_t *devp)
{
        struct super_block      *sb;

        if (!(sb = get_super(*devp)) || !sb->s_root->d_covers)
                return 0;
        if (*devp == sb->s_root->d_covers->d_inode->i_dev)
                return 0;
        *devp = sb->s_root->d_covers->d_inode->i_dev;
        return 1;
}

/*
 * Find the export entry for a given dentry.  <gam3@acm.org>
 */
static svc_export *
exp_parent(svc_client *clp, kdev_t dev, struct dentry *dentry)
{
        svc_export      *exp;
        kdev_t          xdev = dev;
        struct dentry   *xdentry = dentry;
        struct dentry   *ndentry = NULL;

        if (clp == NULL || dentry == NULL)
                return NULL;

        do {
                xdev = dev;
                do {
                        exp = clp->cl_export[EXPORT_HASH(xdev)];
                        if (exp)
                                do {
                                        ndentry = exp->ex_dentry;
                                        if (ndentry == xdentry) {
#ifdef NFSD_PARANOIA
if (dev == xdev)
        dprintk("nfsd: exp_parent submount over mount.\n");
else
        dprintk("nfsd: exp_parent found.\n");
#endif
                                                goto out;
                                        }
                                } while (NULL != (exp = exp->ex_next));
                } while (nfsd_parentdev(&xdev));
                if (IS_ROOT(xdentry))
                        break;
        } while ((xdentry = xdentry->d_parent));
        exp = NULL;
out:
        return exp;
}

/*
 * Find the child export entry for a given fs. This function is used
 * only by the export syscall to keep the export tree consistent.
 * <gam3@acm.org>
 */
static svc_export *
exp_child(svc_client *clp, kdev_t dev, struct dentry *dentry)
{
        svc_export      *exp;
        struct dentry   *xdentry = dentry;
        struct dentry   *ndentry = NULL;

        if (clp == NULL || dentry == NULL)
                return NULL;

        exp = clp->cl_export[EXPORT_HASH(dev)];
        if (exp)
                do {
                        ndentry = exp->ex_dentry;
                        if (ndentry)
                                while ((ndentry = ndentry->d_parent)) {
                                        if (ndentry == xdentry) {
#ifdef NFSD_PARANOIA
dprintk("nfsd: exp_child mount under submount.\n");
#endif
                                                goto out;
                                        }
                                        if (IS_ROOT(ndentry))
                                                break;
                                }
                } while (NULL != (exp = exp->ex_next));
        exp = NULL;
out:
        return exp;
}

/*
 * Export a file system.
 */
int
exp_export(struct nfsctl_export *nxp)
{
        svc_client      *clp;
        svc_export      *exp, *parent;
        svc_export      **head;
        struct dentry   *dentry = NULL;
        struct inode    *inode = NULL;
        int             i, err;
        kdev_t          dev;
        ino_t           ino;

        /* 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,
                        nxp->ex_dev, (long) nxp->ex_ino, nxp->ex_flags);
        dev = to_kdev_t(nxp->ex_dev);
        ino = nxp->ex_ino;

        /* Try to lock the export table for update */
        if ((err = exp_writelock()) < 0)
                goto out;

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

        /*
         * If there's already an export for this file, assume this
         * is just a flag update.
         */
        if ((exp = exp_get(clp, dev, ino)) != NULL) {
                exp->ex_flags    = nxp->ex_flags;
                exp->ex_anon_uid = nxp->ex_anon_uid;
                exp->ex_anon_gid = nxp->ex_anon_gid;
                err = 0;
                goto out_unlock;
        }

        /* Look up the dentry */
        err = -EINVAL;
        dentry = lookup_dentry(nxp->ex_path, LOOKUP_POSITIVE);
        if (IS_ERR(dentry))
                goto out_unlock;

        inode = dentry->d_inode;
        err = -EINVAL;
        if (inode->i_dev != dev || inode->i_ino != nxp->ex_ino) {
                printk(KERN_DEBUG "exp_export: i_dev = %x, dev = %x\n",
                        inode->i_dev, dev); 
                /* I'm just being paranoid... */
                goto finish;
        }

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

        err = -EINVAL;
        if (!(inode->i_sb->s_type->fs_flags & FS_REQUIRES_DEV) ||
            inode->i_sb->s_op->read_inode == NULL) {
                dprintk("exp_export: export of invalid fs type.\n");
                goto finish;
        }

        if ((parent = exp_child(clp, dev, dentry)) != NULL) {
                dprintk("exp_export: export not valid (Rule 3).\n");
                goto finish;
        }
        /* Is this is a sub-export, must be a proper subset of FS */
        if ((parent = exp_parent(clp, dev, dentry)) != NULL) {
                if (dev == parent->ex_dev) {
                        dprintk("exp_export: sub-export not valid (Rule 2).\n");
                        goto finish;
                }
        }

        err = -ENOMEM;
        if (!(exp = kmalloc(sizeof(*exp), GFP_USER)))
                goto finish;
        dprintk("nfsd: created export entry %p for client %p\n", exp, clp);

        strcpy(exp->ex_path, nxp->ex_path);
        exp->ex_client = clp;
        exp->ex_parent = parent;
        exp->ex_dentry = dentry;
        exp->ex_flags = nxp->ex_flags;
        exp->ex_dev = dev;
        exp->ex_ino = ino;
        exp->ex_anon_uid = nxp->ex_anon_uid;
        exp->ex_anon_gid = nxp->ex_anon_gid;

        /* Update parent pointers of all exports */
        if (parent) {
                for (i = 0; i < NFSCLNT_EXPMAX; i++) {
                        svc_export *temp = clp->cl_export[i];

                        while (temp) {
                                if (temp->ex_parent == parent)
                                        temp->ex_parent = exp;
                                temp = temp->ex_next;
                        }
                }
        }

        head = clp->cl_export + EXPORT_HASH(dev);
        exp->ex_next = *head;
        *head = exp;

        err = 0;

        /* Unlock hashtable */
out_unlock:
        exp_unlock();
out:
        return err;

        /* Release the dentry */
finish:
        dput(dentry);
        goto out_unlock;
}

/*
 * 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)
{
        svc_export      *exp;
        svc_client      *clp;
        struct dentry   *dentry;
        struct inode    *inode;
        int             i;

        /* Update parent pointers. */
        clp = unexp->ex_client;
        for (i = 0; i < NFSCLNT_EXPMAX; i++) {
                for (exp = clp->cl_export[i]; exp; exp = exp->ex_next)
                        if (exp->ex_parent == unexp)
                                exp->ex_parent = unexp->ex_parent;
        }

        dentry = unexp->ex_dentry;
        inode = dentry->d_inode;
        if (unexp->ex_dev != inode->i_dev || unexp->ex_ino != inode->i_ino)
                printk(KERN_WARNING "nfsd: bad dentry in unexport!\n");
        dput(dentry);

        kfree(unexp);
}

/*
 * Revoke all exports for a given client.
 * This may look very awkward, but we have to do it this way in order
 * to avoid race conditions (aka mind the parent pointer).
 */
static void
exp_unexport_all(svc_client *clp)
{
        svc_export      *exp;
        int             i;

        dprintk("unexporting all fs's for clnt %p\n", clp);
        for (i = 0; i < NFSCLNT_EXPMAX; i++) {
                exp = clp->cl_export[i];
                clp->cl_export[i] = NULL;
                while (exp) {
                        svc_export *next = exp->ex_next;
                        exp_do_unexport(exp);
                        exp = next;
                }
        }
}

/*
 * unexport syscall.
 */
int
exp_unexport(struct nfsctl_export *nxp)
{
        svc_client      *clp;
        svc_export      **expp, *exp = NULL;
        int             err;

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

        if ((err = exp_writelock()) < 0)
                goto out;

        err = -EINVAL;
        clp = exp_getclientbyname(nxp->ex_client);
        if (clp) {
                expp = clp->cl_export + EXPORT_HASH(nxp->ex_dev);
                while ((exp = *expp) != NULL) {
                        if (exp->ex_dev == nxp->ex_dev) {
                                if (exp->ex_ino == nxp->ex_ino) {
                                        *expp = exp->ex_next;
                                        exp_do_unexport(exp);
                                        err = 0;
                                        break;
                                }
                        }
                        expp = &(exp->ex_next);
                }
        }

        exp_unlock();
out:
        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(struct svc_client *clp, kdev_t dev, ino_t ino,
           char *path, struct knfsd_fh *f, int maxsize)
{
        struct svc_export       *exp;
        struct dentry           *dentry = NULL;
        struct inode            *inode;
        struct svc_fh           fh;
        int                     err;

        err = -EPERM;
        if (path) {
                if (!(dentry = lookup_dentry(path, 0))) {
                        printk("nfsd: exp_rootfh path not found %s", path);
                        return -EPERM;
                }
                dev = dentry->d_inode->i_dev;
                ino = dentry->d_inode->i_ino;
        
                dprintk("nfsd: exp_rootfh(%s [%p] %s:%x/%ld)\n",
                         path, dentry, clp->cl_ident, dev, (long) ino);
                exp = exp_parent(clp, dev, dentry);
        } else {
                dprintk("nfsd: exp_rootfh(%s:%x/%ld)\n",
                         clp->cl_ident, dev, (long) ino);
                if ((exp = exp_get(clp, dev, ino)))
                        if (!(dentry = dget(exp->ex_dentry))) {
                                printk("exp_rootfh: Aieee, NULL dentry\n");
                                return -EPERM;
                        }
        }
        if (!exp) {
                dprintk("nfsd: exp_rootfh export not found.\n");
                goto out;
        }

        inode = dentry->d_inode;
        if (!inode) {
                printk("exp_rootfh: Aieee, NULL d_inode\n");
                goto out;
        }
        if (inode->i_dev != dev || inode->i_ino != ino) {
                printk("exp_rootfh: Aieee, ino/dev mismatch\n");
                printk("exp_rootfh: arg[dev(%x):ino(%ld)]"
                       " inode[dev(%x):ino(%ld)]\n",
                       dev, (long) ino, inode->i_dev, (long) inode->i_ino);
        }

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

out:
        dput(dentry);
        return err;
}

/*
 * Hashtable locking. Write locks are placed only by user processes
 * wanting to modify export information.
 */
void
exp_readlock(void)
{
        while (hash_lock || want_lock)
                sleep_on(&hash_wait);
        hash_count++;
}

int
exp_writelock(void)
{
        /* fast track */
        if (!hash_count && !hash_lock) {
        lock_it:
                hash_lock = 1;
                return 0;
        }

        current->sigpending = 0;
        want_lock++;
        while (hash_count || hash_lock) {
                interruptible_sleep_on(&hash_wait);
                if (signal_pending(current))
                        break;
        }
        want_lock--;

        /* restore the task's signals */
        spin_lock_irq(&current->sigmask_lock);
        recalc_sigpending(current);
        spin_unlock_irq(&current->sigmask_lock);

        if (!hash_count && !hash_lock)
                goto lock_it;
        return -EINTR;
}

void
exp_unlock(void)
{
        if (!hash_count && !hash_lock)
                printk(KERN_WARNING "exp_unlock: not locked!\n");
        if (hash_count)
                hash_count--;
        else
                hash_lock = 0;
        wake_up(&hash_wait);
}

/*
 * Find a valid client given an inet address. We always move the most
 * recently used client to the front of the hash chain to speed up
 * future lookups.
 * Locking against other processes is the responsibility of the caller.
 */
struct svc_client *
exp_getclient(struct sockaddr_in *sin)
{
        struct svc_clnthash     **hp, **head, *tmp;
        unsigned long           addr = sin->sin_addr.s_addr;

        if (!initialized)
                return NULL;

        head = &clnt_hash[CLIENT_HASH(addr)];

        for (hp = head; (tmp = *hp) != NULL; hp = &(tmp->h_next)) {
                if (tmp->h_addr.s_addr == addr) {
                        /* Move client to the front */
                        if (head != hp) {
                                *hp = tmp->h_next;
                                tmp->h_next = *head;
                                *head = tmp;
                        }

                        return tmp->h_client;
                }
        }

        return NULL;
}

/*
 * Find a client given its identifier.
 */
static svc_client *
exp_getclientbyname(char *ident)
{
        svc_client *    clp;

        for (clp = clients; clp; clp = clp->cl_next) {
                if (!strcmp(clp->cl_ident, ident))
                        return clp;
        }
        return NULL;
}

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", ""}},
        { NFSEXP_GATHERED_WRITES, {"wdelay", ""}},
        { NFSEXP_UIDMAP, {"uidmap", ""}},
        { NFSEXP_KERBEROS, { "kerberos", ""}},
        { NFSEXP_SUNSECURE, { "sunsecure", ""}},
        { NFSEXP_CROSSMNT, {"nohide", ""}},
        { NFSEXP_NOSUBTREECHECK, {"no_subtree_check", ""}},
        { NFSEXP_NOAUTHNLM, {"insecure_locks", ""}},
        { 0, {"", ""}}
};

static int
exp_flags(char *buffer, int flag)
{
    int len = 0, first = 0;
    struct flags *flg = expflags;

    for (;flg->flag;flg++) {
        int state = (flg->flag & flag)?0:1;
        if (!flg->flag)
                break;
        if (*flg->name[state]) {
                len += sprintf(buffer + len, "%s%s",
                               first++?",":"", flg->name[state]);
        }
    }
    return len;
}

int
exp_procfs_exports(char *buffer, char **start, off_t offset,
                             int length, int *eof, void *data)
{
        struct svc_clnthash     **hp, **head, *tmp;
        struct svc_client       *clp;
        svc_export *exp;
        off_t   pos = 0;
        off_t   begin = 0;
        int     len = 0;
        int     i,j;

        len += sprintf(buffer, "# Version 1.0\n");
        len += sprintf(buffer+len, "# Path Client(Flags) # IPs\n");

        for (clp = clients; clp; clp = clp->cl_next) {
                for (i = 0; i < NFSCLNT_EXPMAX; i++) {
                        exp = clp->cl_export[i];
                        while (exp) {
                                int first = 0;
                                len += sprintf(buffer+len, "%s\t", exp->ex_path);
                                len += sprintf(buffer+len, "%s", clp->cl_ident);
                                len += sprintf(buffer+len, "(");

                                len += exp_flags(buffer+len, exp->ex_flags);
                                len += sprintf(buffer+len, ") # ");
                                for (j = 0; j < clp->cl_naddr; j++) {
                                        struct in_addr  addr = clp->cl_addr[j]; 

                                        head = &clnt_hash[CLIENT_HASH(addr.s_addr)];
                                        for (hp = head; (tmp = *hp) != NULL; hp = &(tmp->h_next)) {
                                                if (tmp->h_addr.s_addr == addr.s_addr) {
                                                        if (first++) len += sprintf(buffer+len, "%s", " ");
                                                        if (tmp->h_client != clp)
                                                                len += sprintf(buffer+len, "(");
                                                        len += sprintf(buffer+len, "%d.%d.%d.%d",
                                                                        htonl(addr.s_addr) >> 24 & 0xff,
                                                                        htonl(addr.s_addr) >> 16 & 0xff,
                                                                        htonl(addr.s_addr) >>  8 & 0xff,
                                                                        htonl(addr.s_addr) >>  0 & 0xff);
                                                        if (tmp->h_client != clp)
                                                          len += sprintf(buffer+len, ")");
                                                        break;
                                                }
                                        }
                                }
                                exp = exp->ex_next;

                                buffer[len++]='\n';

                                pos=begin+len;
                                if(pos<offset) {
                                        len=0;
                                        begin=pos;
                                }
                                if (pos > offset + length)
                                        goto done;
                        }
                }
        }

        *eof = 1;

done:
        *start = buffer + (offset - begin);
        len -= (offset - begin);
        if ( len > length )
                len = length;
        return len;
}

/*
 * 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 svc_clnthash *   ch[NFSCLNT_ADDRMAX];
        svc_client *            clp;
        int                     i, err, change = 0, ilen;

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

        /* Lock the hashtable */
        if ((err = exp_writelock()) < 0)
                goto out;

        /* First check if this is a change request for a client. */
        for (clp = clients; clp; clp = clp->cl_next)
                if (!strcmp(clp->cl_ident, ncp->cl_ident))
                        break;

        err = -ENOMEM;
        if (clp) {
                change = 1;
        } else {
                if (!(clp = kmalloc(sizeof(*clp), GFP_KERNEL)))
                        goto out_unlock;
                memset(clp, 0, sizeof(*clp));

                dprintk("created client %s (%p)\n", ncp->cl_ident, clp);

                strcpy(clp->cl_ident, ncp->cl_ident);
                clp->cl_idlen = ilen;
        }

        /* Allocate hash buckets */
        for (i = 0; i < ncp->cl_naddr; i++) {
                ch[i] = kmalloc(sizeof(struct svc_clnthash), GFP_KERNEL);
                if (!ch[i]) {
                        while (i--)
                                kfree(ch[i]);
                        if (!change)
                                kfree(clp);
                        goto out_unlock;
                }
        }

        /* Copy addresses. */
        for (i = 0; i < ncp->cl_naddr; i++) {
                clp->cl_addr[i] = ncp->cl_addrlist[i];
        }
        clp->cl_naddr = ncp->cl_naddr;

        /* Remove old client hash entries. */
        if (change)
                exp_unhashclient(clp);

        /* Insert client into hashtable. */
        for (i = 0; i < ncp->cl_naddr; i++) {
                struct in_addr  addr = clp->cl_addr[i];
                int             hash;

                hash = CLIENT_HASH(addr.s_addr);
                ch[i]->h_client = clp;
                ch[i]->h_addr = addr;
                ch[i]->h_next = clnt_hash[hash];
                clnt_hash[hash] = ch[i];
        }

        if (!change) {
                clp->cl_next = clients;
                clients = clp;
        }
        err = 0;

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

/*
 * Delete a client given an identifier.
 */
int
exp_delclient(struct nfsctl_client *ncp)
{
        svc_client      **clpp, *clp;
        int             err;

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

        /* Lock the hashtable */
        if ((err = exp_writelock()) < 0)
                goto out;

        err = -EINVAL;
        for (clpp = &clients; (clp = *clpp); clpp = &(clp->cl_next))
                if (!strcmp(ncp->cl_ident, clp->cl_ident))
                        break;

        if (clp) {
                *clpp = clp->cl_next;
                exp_freeclient(clp);
                err = 0;
        }

        exp_unlock();
out:
        return err;
}

/*
 * Free a client. The caller has already removed it from the client list.
 */
static void
exp_freeclient(svc_client *clp)
{
        exp_unhashclient(clp);

        /* umap_free(&(clp->cl_umap)); */
        exp_unexport_all(clp);
        nfsd_lockd_unexport(clp);
        kfree (clp);
}

/*
 * Remove client from hashtable. We first collect all hashtable
 * entries and free them in one go.
 * The hash table must be writelocked by the caller.
 */
static void
exp_unhashclient(svc_client *clp)
{
        struct svc_clnthash     **hpp, *hp, *ch[NFSCLNT_ADDRMAX];
        int                     i, count, err;

again:
        err = 0;
        for (i = 0, count = 0; i < CLIENT_HASHMAX && !err; i++) {
                hpp = clnt_hash + i;
                while ((hp = *hpp) && !err) {
                        if (hp->h_client == clp) {
                                *hpp = hp->h_next;
                                ch[count++] = hp;
                                err = (count >= NFSCLNT_ADDRMAX);
                        } else {
                                hpp = &(hp->h_next);
                        }
                }
        }
        if (count != clp->cl_naddr)
                printk(KERN_WARNING "nfsd: bad address count in freeclient!\n");
        if (err)
                goto again;
        for (i = 0; i < count; i++)
                kfree (ch[i]);
}

/*
 * Lockd is shutting down and tells us to unregister all clients
 */
void
exp_nlmdetach(void)
{
        struct svc_client       *clp;

        for (clp = clients; clp; clp = clp->cl_next)
                nfsd_lockd_unexport(clp);
}

/*
 * 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.
 */
void
nfsd_export_init(void)
{
        int             i;

        dprintk("nfsd: initializing export module.\n");
        if (initialized)
                return;
        for (i = 0; i < CLIENT_HASHMAX; i++)
                clnt_hash[i] = NULL;
        clients = NULL;

        initialized = 1;
}

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

        dprintk("nfsd: shutting down export module.\n");
        if (!initialized)
                return;
        if (exp_writelock() < 0) {
                printk(KERN_WARNING "Weird: hashtable locked in exp_shutdown");
                return;
        }
        for (i = 0; i < CLIENT_HASHMAX; i++) {
                while (clnt_hash[i])
                        exp_freeclient(clnt_hash[i]->h_client);
        }
        clients = NULL; /* we may be restarted before the module unloads */
        
        exp_unlock();
        dprintk("nfsd: export shutdown complete.\n");
}