export.c

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#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, <[e-mail]>
 */

#include <linux/unistd.h>
#include <linux/slab.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;
static int			initialized;

static int			hash_lock;
static int			want_lock;
static int			hash_count;
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;
}

/*
 * Find the export entry for a given dentry.  <[e-mail]>
 */
static svc_export *
exp_parent(svc_client *clp, kdev_t dev, struct dentry *dentry)
{
	svc_export      *exp;

	if (clp == NULL)
		return NULL;

	for (exp = clp->cl_export[EXPORT_HASH(dev)]; exp; exp = exp->ex_next)
		if (is_subdir(dentry, exp->ex_dentry))
			break;
	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.
 * <[e-mail]>
 */
static svc_export *
exp_child(svc_client *clp, kdev_t dev, struct dentry *dentry)
{
	svc_export      *exp;

	if (clp == NULL)
		return NULL;

	for (exp = clp->cl_export[EXPORT_HASH(dev)]; exp; exp = exp->ex_next) {
		struct dentry	*ndentry = exp->ex_dentry;
		if (ndentry && is_subdir(ndentry->d_parent, dentry))
			break;
	}
	return exp;
}

/*
 * Export a file system.
 */
int
exp_export(struct nfsctl_export *nxp)
{
	svc_client	*clp;
	svc_export	*exp, *parent;
	svc_export	**head;
	struct nameidata nd;
	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 = 0;
	if (path_init(nxp->ex_path, LOOKUP_POSITIVE, &nd))
		err = path_walk(nxp->ex_path, &nd);
	if (err)
		goto out_unlock;

	inode = nd.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
	     && inode->i_sb->s_op->fh_to_dentry == NULL)) {
		dprintk("exp_export: export of invalid fs type.\n");
		goto finish;
	}

	if ((parent = exp_child(clp, dev, nd.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, nd.dentry)) != NULL) {
		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 = nd.dentry;
	exp->ex_mnt = nd.mnt;
	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:
	path_release(&nd);
	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 vfsmount *mnt;
	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;
	mnt = unexp->ex_mnt;
	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);
	mntput(mnt);

	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 nameidata	nd;
	struct inode		*inode;
	struct svc_fh		fh;
	int			err;

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

	inode = nd.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, dget(nd.dentry), NULL))
		err = -EINVAL;
	else
		err = 0;
	memcpy(f, &fh.fh_handle, sizeof(struct knfsd_fh));
	fh_put(&fh);

out:
	if (path)
		path_release(&nd);
	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;
	}