[net-next-2.6.git] / fs / exportfs / expfs.c

/*
 * Copyright (C) Neil Brown 2002
 * Copyright (C) Christoph Hellwig 2007
 *
 * This file contains the code mapping from inodes to NFS file handles,
 * and for mapping back from file handles to dentries.
 *
 * For details on why we do all the strange and hairy things in here
 * take a look at Documentation/filesystems/nfs/Exporting.
 */
#include <linux/exportfs.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/module.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/sched.h>

#define dprintk(fmt, args...) do{}while(0)


static int get_name(struct vfsmount *mnt, struct dentry *dentry, char *name,
		struct dentry *child);


static int exportfs_get_name(struct vfsmount *mnt, struct dentry *dir,
		char *name, struct dentry *child)
{
	const struct export_operations *nop = dir->d_sb->s_export_op;

	if (nop->get_name)
		return nop->get_name(dir, name, child);
	else
		return get_name(mnt, dir, name, child);
}

/*
 * Check if the dentry or any of it's aliases is acceptable.
 */
static struct dentry *
find_acceptable_alias(struct dentry *result,
		int (*acceptable)(void *context, struct dentry *dentry),
		void *context)
{
	struct dentry *dentry, *toput = NULL;

	if (acceptable(context, result))
		return result;

	spin_lock(&dcache_lock);
	list_for_each_entry(dentry, &result->d_inode->i_dentry, d_alias) {
		dget_locked(dentry);
		spin_unlock(&dcache_lock);
		if (toput)
			dput(toput);
		if (dentry != result && acceptable(context, dentry)) {
			dput(result);
			return dentry;
		}
		spin_lock(&dcache_lock);
		toput = dentry;
	}
	spin_unlock(&dcache_lock);

	if (toput)
		dput(toput);
	return NULL;
}

/*
 * Find root of a disconnected subtree and return a reference to it.
 */
static struct dentry *
find_disconnected_root(struct dentry *dentry)
{
	dget(dentry);
	while (!IS_ROOT(dentry)) {
		struct dentry *parent = dget_parent(dentry);

		if (!(parent->d_flags & DCACHE_DISCONNECTED)) {
			dput(parent);
			break;
		}

		dput(dentry);
		dentry = parent;
	}
	return dentry;
}

/*
 * Make sure target_dir is fully connected to the dentry tree.
 *
 * It may already be, as the flag isn't always updated when connection happens.
 */
static int
reconnect_path(struct vfsmount *mnt, struct dentry *target_dir, char *nbuf)
{
	int noprogress = 0;
	int err = -ESTALE;

	/*
	 * It is possible that a confused file system might not let us complete
	 * the path to the root.  For example, if get_parent returns a directory
	 * in which we cannot find a name for the child.  While this implies a
	 * very sick filesystem we don't want it to cause knfsd to spin.  Hence
	 * the noprogress counter.  If we go through the loop 10 times (2 is
	 * probably enough) without getting anywhere, we just give up
	 */
	while (target_dir->d_flags & DCACHE_DISCONNECTED && noprogress++ < 10) {
		struct dentry *pd = find_disconnected_root(target_dir);

		if (!IS_ROOT(pd)) {
			/* must have found a connected parent - great */
			spin_lock(&pd->d_lock);
			pd->d_flags &= ~DCACHE_DISCONNECTED;
			spin_unlock(&pd->d_lock);
			noprogress = 0;
		} else if (pd == mnt->mnt_sb->s_root) {
			printk(KERN_ERR "export: Eeek filesystem root is not connected, impossible\n");
			spin_lock(&pd->d_lock);
			pd->d_flags &= ~DCACHE_DISCONNECTED;
			spin_unlock(&pd->d_lock);
			noprogress = 0;
		} else {
			/*
			 * We have hit the top of a disconnected path, try to
			 * find parent and connect.
			 *
			 * Racing with some other process renaming a directory
			 * isn't much of a problem here.  If someone renames
			 * the directory, it will end up properly connected,
			 * which is what we want
			 *
			 * Getting the parent can't be supported generically,
			 * the locking is too icky.
			 *
			 * Instead we just return EACCES.  If server reboots
			 * or inodes get flushed, you lose
			 */
			struct dentry *ppd = ERR_PTR(-EACCES);
			struct dentry *npd;

			mutex_lock(&pd->d_inode->i_mutex);
			if (mnt->mnt_sb->s_export_op->get_parent)
				ppd = mnt->mnt_sb->s_export_op->get_parent(pd);
			mutex_unlock(&pd->d_inode->i_mutex);

			if (IS_ERR(ppd)) {
				err = PTR_ERR(ppd);
				dprintk("%s: get_parent of %ld failed, err %d\n",
					__func__, pd->d_inode->i_ino, err);
				dput(pd);
				break;
			}

			dprintk("%s: find name of %lu in %lu\n", __func__,
				pd->d_inode->i_ino, ppd->d_inode->i_ino);
			err = exportfs_get_name(mnt, ppd, nbuf, pd);
			if (err) {
				dput(ppd);
				dput(pd);
				if (err == -ENOENT)
					/* some race between get_parent and
					 * get_name?  just try again
					 */
					continue;
				break;
			}
			dprintk("%s: found name: %s\n", __func__, nbuf);
			mutex_lock(&ppd->d_inode->i_mutex);
			npd = lookup_one_len(nbuf, ppd, strlen(nbuf));
			mutex_unlock(&ppd->d_inode->i_mutex);
			if (IS_ERR(npd)) {
				err = PTR_ERR(npd);
				dprintk("%s: lookup failed: %d\n",
					__func__, err);
				dput(ppd);
				dput(pd);
				break;
			}
			/* we didn't really want npd, we really wanted
			 * a side-effect of the lookup.
			 * hopefully, npd == pd, though it isn't really
			 * a problem if it isn't
			 */
			if (npd == pd)
				noprogress = 0;
			else
				printk("%s: npd != pd\n", __func__);
			dput(npd);
			dput(ppd);
			if (IS_ROOT(pd)) {
				/* something went wrong, we have to give up */
				dput(pd);
				break;
			}
		}
		dput(pd);
	}

	if (target_dir->d_flags & DCACHE_DISCONNECTED) {
		/* something went wrong - oh-well */
		if (!err)
			err = -ESTALE;
		return err;
	}

	return 0;
}

struct getdents_callback {
	char *name;		/* name that was found. It already points to a
				   buffer NAME_MAX+1 is size */
	unsigned long ino;	/* the inum we are looking for */
	int found;		/* inode matched? */
	int sequence;		/* sequence counter */
};

/*
 * A rather strange filldir function to capture
 * the name matching the specified inode number.
 */
static int filldir_one(void * __buf, const char * name, int len,
			loff_t pos, u64 ino, unsigned int d_type)
{
	struct getdents_callback *buf = __buf;
	int result = 0;

	buf->sequence++;
	if (buf->ino == ino) {
		memcpy(buf->name, name, len);
		buf->name[len] = '\0';
		buf->found = 1;
		result = -1;
	}
	return result;
}

/**
 * get_name - default export_operations->get_name function
 * @dentry: the directory in which to find a name
 * @name:   a pointer to a %NAME_MAX+1 char buffer to store the name
 * @child:  the dentry for the child directory.
 *
 * calls readdir on the parent until it finds an entry with
 * the same inode number as the child, and returns that.
 */
static int get_name(struct vfsmount *mnt, struct dentry *dentry,
		char *name, struct dentry *child)
{
	const struct cred *cred = current_cred();
	struct inode *dir = dentry->d_inode;
	int error;
	struct file *file;
	struct getdents_callback buffer;

	error = -ENOTDIR;
	if (!dir || !S_ISDIR(dir->i_mode))
		goto out;
	error = -EINVAL;
	if (!dir->i_fop)
		goto out;
	/*
	 * Open the directory ...
	 */
	file = dentry_open(dget(dentry), mntget(mnt), O_RDONLY, cred);
	error = PTR_ERR(file);
	if (IS_ERR(file))
		goto out;

	error = -EINVAL;
	if (!file->f_op->readdir)
		goto out_close;

	buffer.name = name;
	buffer.ino = child->d_inode->i_ino;
	buffer.found = 0;
	buffer.sequence = 0;
	while (1) {
		int old_seq = buffer.sequence;

		error = vfs_readdir(file, filldir_one, &buffer);
		if (buffer.found) {
			error = 0;
			break;
		}

		if (error < 0)
			break;

		error = -ENOENT;
		if (old_seq == buffer.sequence)
			break;
	}

out_close:
	fput(file);
out:
	return error;
}

/**
 * export_encode_fh - default export_operations->encode_fh function
 * @dentry:  the dentry to encode
 * @fh:      where to store the file handle fragment
 * @max_len: maximum length to store there
 * @connectable: whether to store parent information
 *
 * This default encode_fh function assumes that the 32 inode number
 * is suitable for locating an inode, and that the generation number
 * can be used to check that it is still valid.  It places them in the
 * filehandle fragment where export_decode_fh expects to find them.
 */
static int export_encode_fh(struct dentry *dentry, struct fid *fid,
		int *max_len, int connectable)
{
	struct inode * inode = dentry->d_inode;
	int len = *max_len;
	int type = FILEID_INO32_GEN;
	
	if (len < 2 || (connectable && len < 4))
		return 255;

	len = 2;
	fid->i32.ino = inode->i_ino;
	fid->i32.gen = inode->i_generation;
	if (connectable && !S_ISDIR(inode->i_mode)) {
		struct inode *parent;

		spin_lock(&dentry->d_lock);
		parent = dentry->d_parent->d_inode;
		fid->i32.parent_ino = parent->i_ino;
		fid->i32.parent_gen = parent->i_generation;
		spin_unlock(&dentry->d_lock);
		len = 4;
		type = FILEID_INO32_GEN_PARENT;
	}
	*max_len = len;
	return type;
}

int exportfs_encode_fh(struct dentry *dentry, struct fid *fid, int *max_len,
		int connectable)
{
	const struct export_operations *nop = dentry->d_sb->s_export_op;
	int error;

	if (nop->encode_fh)
		error = nop->encode_fh(dentry, fid->raw, max_len, connectable);
	else
		error = export_encode_fh(dentry, fid, max_len, connectable);

	return error;
}
EXPORT_SYMBOL_GPL(exportfs_encode_fh);

struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
		int fh_len, int fileid_type,
		int (*acceptable)(void *, struct dentry *), void *context)
{
	const struct export_operations *nop = mnt->mnt_sb->s_export_op;
	struct dentry *result, *alias;
	char nbuf[NAME_MAX+1];
	int err;

	/*
	 * Try to get any dentry for the given file handle from the filesystem.
	 */
	result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type);
	if (!result)
		result = ERR_PTR(-ESTALE);
	if (IS_ERR(result))
		return result;

	if (S_ISDIR(result->d_inode->i_mode)) {
		/*
		 * This request is for a directory.
		 *
		 * On the positive side there is only one dentry for each
		 * directory inode.  On the negative side this implies that we
		 * to ensure our dentry is connected all the way up to the
		 * filesystem root.
		 */
		if (result->d_flags & DCACHE_DISCONNECTED) {
			err = reconnect_path(mnt, result, nbuf);
			if (err)
				goto err_result;
		}

		if (!acceptable(context, result)) {
			err = -EACCES;
			goto err_result;
		}

		return result;
	} else {
		/*
		 * It's not a directory.  Life is a little more complicated.
		 */
		struct dentry *target_dir, *nresult;

		/*
		 * See if either the dentry we just got from the filesystem
		 * or any alias for it is acceptable.  This is always true
		 * if this filesystem is exported without the subtreecheck
		 * option.  If the filesystem is exported with the subtree
		 * check option there's a fair chance we need to look at
		 * the parent directory in the file handle and make sure
		 * it's connected to the filesystem root.
		 */
		alias = find_acceptable_alias(result, acceptable, context);
		if (alias)
			return alias;

		/*
		 * Try to extract a dentry for the parent directory from the
		 * file handle.  If this fails we'll have to give up.
		 */
		err = -ESTALE;
		if (!nop->fh_to_parent)
			goto err_result;

		target_dir = nop->fh_to_parent(mnt->mnt_sb, fid,
				fh_len, fileid_type);
		if (!target_dir)
			goto err_result;
		err = PTR_ERR(target_dir);
		if (IS_ERR(target_dir))
			goto err_result;

		/*
		 * And as usual we need to make sure the parent directory is
		 * connected to the filesystem root.  The VFS really doesn't
		 * like disconnected directories..
		 */
		err = reconnect_path(mnt, target_dir, nbuf);
		if (err) {
			dput(target_dir);
			goto err_result;
		}

		/*
		 * Now that we've got both a well-connected parent and a
		 * dentry for the inode we're after, make sure that our
		 * inode is actually connected to the parent.
		 */
		err = exportfs_get_name(mnt, target_dir, nbuf, result);
		if (!err) {
			mutex_lock(&target_dir->d_inode->i_mutex);
			nresult = lookup_one_len(nbuf, target_dir,
						 strlen(nbuf));
			mutex_unlock(&target_dir->d_inode->i_mutex);
			if (!IS_ERR(nresult)) {
				if (nresult->d_inode) {
					dput(result);
					result = nresult;
				} else
					dput(nresult);
			}
		}

		/*
		 * At this point we are done with the parent, but it's pinned
		 * by the child dentry anyway.
		 */
		dput(target_dir);

		/*
		 * And finally make sure the dentry is actually acceptable
		 * to NFSD.
		 */
		alias = find_acceptable_alias(result, acceptable, context);
		if (!alias) {
			err = -EACCES;
			goto err_result;
		}

		return alias;
	}

 err_result:
	dput(result);
	return ERR_PTR(err);
}
EXPORT_SYMBOL_GPL(exportfs_decode_fh);

MODULE_LICENSE("GPL");
Commit	Line	Data
e38f9817 CH	1	/*
	2	* Copyright (C) Neil Brown 2002
	3	* Copyright (C) Christoph Hellwig 2007
	4	*
	5	* This file contains the code mapping from inodes to NFS file handles,
	6	* and for mapping back from file handles to dentries.
	7	*
	8	* For details on why we do all the strange and hairy things in here
dc7a0816	9	* take a look at Documentation/filesystems/nfs/Exporting.
e38f9817	10	*/
a5694255	11	#include <linux/exportfs.h>
1da177e4 LT	12	#include <linux/fs.h>
	13	#include <linux/file.h>
	14	#include <linux/module.h>
d37065cd	15	#include <linux/mount.h>
1da177e4	16	#include <linux/namei.h>
745ca247	17	#include <linux/sched.h>
1da177e4	18
10f11c34	19	#define dprintk(fmt, args...) do{}while(0)
1da177e4	20
1da177e4	21
e38f9817	22	static int get_name(struct vfsmount mnt, struct dentry dentry, char *name,
10f11c34 CH	23	struct dentry *child);
	24
	25
e38f9817 CH	26	static int exportfs_get_name(struct vfsmount mnt, struct dentry dir,
e38f9817 CH	27	char name, struct dentry child)
10f11c34	28	{
39655164	29	const struct export_operations *nop = dir->d_sb->s_export_op;
10f11c34 CH	30
	31	if (nop->get_name)
	32	return nop->get_name(dir, name, child);
	33	else
e38f9817	34	return get_name(mnt, dir, name, child);
10f11c34	35	}
1da177e4	36
fb66a198 CH	37	/*
	38	* Check if the dentry or any of it's aliases is acceptable.
	39	*/
e2f99018 CH	40	static struct dentry *
	41	find_acceptable_alias(struct dentry *result,
	42	int (acceptable)(void context, struct dentry *dentry),
	43	void *context)
	44	{
	45	struct dentry dentry, toput = NULL;
	46
fb66a198 CH	47	if (acceptable(context, result))
	48	return result;
	49
e2f99018 CH	50	spin_lock(&dcache_lock);
	51	list_for_each_entry(dentry, &result->d_inode->i_dentry, d_alias) {
	52	dget_locked(dentry);
	53	spin_unlock(&dcache_lock);
	54	if (toput)
	55	dput(toput);
	56	if (dentry != result && acceptable(context, dentry)) {
	57	dput(result);
	58	return dentry;
	59	}
	60	spin_lock(&dcache_lock);
	61	toput = dentry;
	62	}
	63	spin_unlock(&dcache_lock);
	64
	65	if (toput)
	66	dput(toput);
	67	return NULL;
	68	}
	69
dd90b509 CH	70	/*
	71	* Find root of a disconnected subtree and return a reference to it.
	72	*/
	73	static struct dentry *
	74	find_disconnected_root(struct dentry *dentry)
	75	{
	76	dget(dentry);
0461ee26 CH	77	while (!IS_ROOT(dentry)) {
	78	struct dentry *parent = dget_parent(dentry);
	79
	80	if (!(parent->d_flags & DCACHE_DISCONNECTED)) {
	81	dput(parent);
	82	break;
	83	}
	84
dd90b509 CH	85	dput(dentry);
dd90b509 CH	86	dentry = parent;
dd90b509	87	}
dd90b509 CH	88	return dentry;
	89	}
	90
019ab801 CH	91	/*
019ab801 CH	92	* Make sure target_dir is fully connected to the dentry tree.
1da177e4	93	*
019ab801	94	* It may already be, as the flag isn't always updated when connection happens.
1da177e4	95	*/
019ab801	96	static int
f3f8e175	97	reconnect_path(struct vfsmount mnt, struct dentry target_dir, char *nbuf)
1da177e4	98	{
019ab801 CH	99	int noprogress = 0;
019ab801 CH	100	int err = -ESTALE;
1da177e4 LT	101
1da177e4 LT	102	/*
019ab801	103	* It is possible that a confused file system might not let us complete
1da177e4 LT	104	* the path to the root. For example, if get_parent returns a directory
	105	* in which we cannot find a name for the child. While this implies a
	106	* very sick filesystem we don't want it to cause knfsd to spin. Hence
	107	* the noprogress counter. If we go through the loop 10 times (2 is
	108	* probably enough) without getting anywhere, we just give up
	109	*/
1da177e4	110	while (target_dir->d_flags & DCACHE_DISCONNECTED && noprogress++ < 10) {
dd90b509	111	struct dentry *pd = find_disconnected_root(target_dir);
1da177e4 LT	112
	113	if (!IS_ROOT(pd)) {
	114	/* must have found a connected parent - great */
	115	spin_lock(&pd->d_lock);
	116	pd->d_flags &= ~DCACHE_DISCONNECTED;
	117	spin_unlock(&pd->d_lock);
	118	noprogress = 0;
e38f9817	119	} else if (pd == mnt->mnt_sb->s_root) {
1da177e4 LT	120	printk(KERN_ERR "export: Eeek filesystem root is not connected, impossible\n");
	121	spin_lock(&pd->d_lock);
	122	pd->d_flags &= ~DCACHE_DISCONNECTED;
	123	spin_unlock(&pd->d_lock);
	124	noprogress = 0;
	125	} else {
10f11c34 CH	126	/*
	127	* We have hit the top of a disconnected path, try to
	128	* find parent and connect.
	129	*
	130	* Racing with some other process renaming a directory
	131	* isn't much of a problem here. If someone renames
	132	* the directory, it will end up properly connected,
	133	* which is what we want
	134	*
	135	* Getting the parent can't be supported generically,
	136	* the locking is too icky.
	137	*
	138	* Instead we just return EACCES. If server reboots
	139	* or inodes get flushed, you lose
1da177e4	140	*/
10f11c34	141	struct dentry *ppd = ERR_PTR(-EACCES);
1da177e4 LT	142	struct dentry *npd;
1da177e4 LT	143
1b1dcc1b	144	mutex_lock(&pd->d_inode->i_mutex);
e38f9817 CH	145	if (mnt->mnt_sb->s_export_op->get_parent)
e38f9817 CH	146	ppd = mnt->mnt_sb->s_export_op->get_parent(pd);
1b1dcc1b	147	mutex_unlock(&pd->d_inode->i_mutex);
1da177e4 LT	148
	149	if (IS_ERR(ppd)) {
	150	err = PTR_ERR(ppd);
019ab801	151	dprintk("%s: get_parent of %ld failed, err %d\n",
8e24eea7	152	__func__, pd->d_inode->i_ino, err);
1da177e4 LT	153	dput(pd);
	154	break;
	155	}
019ab801	156
8e24eea7	157	dprintk("%s: find name of %lu in %lu\n", __func__,
019ab801	158	pd->d_inode->i_ino, ppd->d_inode->i_ino);
e38f9817	159	err = exportfs_get_name(mnt, ppd, nbuf, pd);
1da177e4 LT	160	if (err) {
	161	dput(ppd);
	162	dput(pd);
	163	if (err == -ENOENT)
	164	/* some race between get_parent and
	165	* get_name? just try again
	166	*/
	167	continue;
	168	break;
	169	}
8e24eea7	170	dprintk("%s: found name: %s\n", __func__, nbuf);
1b1dcc1b	171	mutex_lock(&ppd->d_inode->i_mutex);
1da177e4	172	npd = lookup_one_len(nbuf, ppd, strlen(nbuf));
1b1dcc1b	173	mutex_unlock(&ppd->d_inode->i_mutex);
1da177e4 LT	174	if (IS_ERR(npd)) {
1da177e4 LT	175	err = PTR_ERR(npd);
019ab801	176	dprintk("%s: lookup failed: %d\n",
8e24eea7	177	__func__, err);
1da177e4 LT	178	dput(ppd);
	179	dput(pd);
	180	break;
	181	}
	182	/* we didn't really want npd, we really wanted
	183	* a side-effect of the lookup.
	184	* hopefully, npd == pd, though it isn't really
	185	* a problem if it isn't
	186	*/
	187	if (npd == pd)
	188	noprogress = 0;
	189	else
8e24eea7	190	printk("%s: npd != pd\n", __func__);
1da177e4 LT	191	dput(npd);
	192	dput(ppd);
	193	if (IS_ROOT(pd)) {
	194	/* something went wrong, we have to give up */
	195	dput(pd);
	196	break;
	197	}
	198	}
	199	dput(pd);
	200	}
	201
	202	if (target_dir->d_flags & DCACHE_DISCONNECTED) {
	203	/* something went wrong - oh-well */
	204	if (!err)
	205	err = -ESTALE;
019ab801	206	return err;
1da177e4	207	}
019ab801 CH	208
	209	return 0;
	210	}
	211
1da177e4 LT	212	struct getdents_callback {
	213	char name; / name that was found. It already points to a
	214	buffer NAME_MAX+1 is size */
	215	unsigned long ino; /* the inum we are looking for */
	216	int found; /* inode matched? */
	217	int sequence; /* sequence counter */
	218	};
	219
	220	/*
	221	* A rather strange filldir function to capture
	222	* the name matching the specified inode number.
	223	*/
	224	static int filldir_one(void * __buf, const char * name, int len,
afefdbb2	225	loff_t pos, u64 ino, unsigned int d_type)
1da177e4 LT	226	{
	227	struct getdents_callback *buf = __buf;
	228	int result = 0;
	229
	230	buf->sequence++;
	231	if (buf->ino == ino) {
	232	memcpy(buf->name, name, len);
	233	buf->name[len] = '\0';
	234	buf->found = 1;
	235	result = -1;
	236	}
	237	return result;
	238	}
	239
	240	/**
	241	* get_name - default export_operations->get_name function
	242	* @dentry: the directory in which to find a name
	243	* @name: a pointer to a %NAME_MAX+1 char buffer to store the name
	244	* @child: the dentry for the child directory.
	245	*
	246	* calls readdir on the parent until it finds an entry with
	247	* the same inode number as the child, and returns that.
	248	*/
e38f9817 CH	249	static int get_name(struct vfsmount mnt, struct dentry dentry,
e38f9817 CH	250	char name, struct dentry child)
1da177e4	251	{
745ca247	252	const struct cred *cred = current_cred();
1da177e4 LT	253	struct inode *dir = dentry->d_inode;
	254	int error;
	255	struct file *file;
	256	struct getdents_callback buffer;
	257
	258	error = -ENOTDIR;
	259	if (!dir \|\| !S_ISDIR(dir->i_mode))
	260	goto out;
	261	error = -EINVAL;
	262	if (!dir->i_fop)
	263	goto out;
	264	/*
	265	* Open the directory ...
	266	*/
745ca247	267	file = dentry_open(dget(dentry), mntget(mnt), O_RDONLY, cred);
1da177e4 LT	268	error = PTR_ERR(file);
	269	if (IS_ERR(file))
	270	goto out;
	271
	272	error = -EINVAL;
	273	if (!file->f_op->readdir)
	274	goto out_close;
	275
	276	buffer.name = name;
	277	buffer.ino = child->d_inode->i_ino;
	278	buffer.found = 0;
	279	buffer.sequence = 0;
	280	while (1) {
	281	int old_seq = buffer.sequence;
	282
	283	error = vfs_readdir(file, filldir_one, &buffer);
53c9c5c0 AV	284	if (buffer.found) {
	285	error = 0;
	286	break;
	287	}
1da177e4 LT	288
	289	if (error < 0)
	290	break;
	291
1da177e4 LT	292	error = -ENOENT;
	293	if (old_seq == buffer.sequence)
	294	break;
	295	}
	296
	297	out_close:
	298	fput(file);
	299	out:
	300	return error;
	301	}
	302
1da177e4 LT	303	/**
	304	* export_encode_fh - default export_operations->encode_fh function
	305	* @dentry: the dentry to encode
	306	* @fh: where to store the file handle fragment
	307	* @max_len: maximum length to store there
	308	* @connectable: whether to store parent information
	309	*
	310	* This default encode_fh function assumes that the 32 inode number
	311	* is suitable for locating an inode, and that the generation number
	312	* can be used to check that it is still valid. It places them in the
	313	* filehandle fragment where export_decode_fh expects to find them.
	314	*/
6e91ea2b CH	315	static int export_encode_fh(struct dentry dentry, struct fid fid,
6e91ea2b CH	316	int *max_len, int connectable)
1da177e4 LT	317	{
	318	struct inode * inode = dentry->d_inode;
	319	int len = *max_len;
6e91ea2b	320	int type = FILEID_INO32_GEN;
1da177e4 LT	321
	322	if (len < 2 \|\| (connectable && len < 4))
	323	return 255;
	324
	325	len = 2;
6e91ea2b CH	326	fid->i32.ino = inode->i_ino;
6e91ea2b CH	327	fid->i32.gen = inode->i_generation;
1da177e4 LT	328	if (connectable && !S_ISDIR(inode->i_mode)) {
	329	struct inode *parent;
	330
	331	spin_lock(&dentry->d_lock);
	332	parent = dentry->d_parent->d_inode;
6e91ea2b CH	333	fid->i32.parent_ino = parent->i_ino;
6e91ea2b CH	334	fid->i32.parent_gen = parent->i_generation;
1da177e4 LT	335	spin_unlock(&dentry->d_lock);
1da177e4 LT	336	len = 4;
6e91ea2b	337	type = FILEID_INO32_GEN_PARENT;
1da177e4 LT	338	}
	339	*max_len = len;
	340	return type;
	341	}
	342
6e91ea2b	343	int exportfs_encode_fh(struct dentry dentry, struct fid fid, int *max_len,
d37065cd CH	344	int connectable)
d37065cd CH	345	{
39655164	346	const struct export_operations *nop = dentry->d_sb->s_export_op;
10f11c34	347	int error;
d37065cd	348
10f11c34	349	if (nop->encode_fh)
6e91ea2b	350	error = nop->encode_fh(dentry, fid->raw, max_len, connectable);
10f11c34	351	else
6e91ea2b	352	error = export_encode_fh(dentry, fid, max_len, connectable);
10f11c34 CH	353
10f11c34 CH	354	return error;
d37065cd CH	355	}
	356	EXPORT_SYMBOL_GPL(exportfs_encode_fh);
	357
6e91ea2b CH	358	struct dentry exportfs_decode_fh(struct vfsmount mnt, struct fid *fid,
	359	int fh_len, int fileid_type,
	360	int (acceptable)(void , struct dentry ), void context)
d37065cd	361	{
39655164	362	const struct export_operations *nop = mnt->mnt_sb->s_export_op;
2596110a	363	struct dentry result, alias;
f3f8e175	364	char nbuf[NAME_MAX+1];
2596110a	365	int err;
d37065cd	366
2596110a CH	367	/*
	368	* Try to get any dentry for the given file handle from the filesystem.
	369	*/
	370	result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type);
a4f4d6df BF	371	if (!result)
a4f4d6df BF	372	result = ERR_PTR(-ESTALE);
2596110a CH	373	if (IS_ERR(result))
	374	return result;
	375
	376	if (S_ISDIR(result->d_inode->i_mode)) {
	377	/*
	378	* This request is for a directory.
	379	*
	380	* On the positive side there is only one dentry for each
	381	* directory inode. On the negative side this implies that we
	382	* to ensure our dentry is connected all the way up to the
	383	* filesystem root.
	384	*/
	385	if (result->d_flags & DCACHE_DISCONNECTED) {
f3f8e175	386	err = reconnect_path(mnt, result, nbuf);
2596110a CH	387	if (err)
	388	goto err_result;
	389	}
	390
	391	if (!acceptable(context, result)) {
	392	err = -EACCES;
	393	goto err_result;
	394	}
	395
	396	return result;
10f11c34	397	} else {
2596110a CH	398	/*
	399	* It's not a directory. Life is a little more complicated.
	400	*/
	401	struct dentry target_dir, nresult;
2596110a CH	402
	403	/*
	404	* See if either the dentry we just got from the filesystem
	405	* or any alias for it is acceptable. This is always true
	406	* if this filesystem is exported without the subtreecheck
	407	* option. If the filesystem is exported with the subtree
	408	* check option there's a fair chance we need to look at
	409	* the parent directory in the file handle and make sure
	410	* it's connected to the filesystem root.
	411	*/
	412	alias = find_acceptable_alias(result, acceptable, context);
	413	if (alias)
	414	return alias;
	415
	416	/*
	417	* Try to extract a dentry for the parent directory from the
	418	* file handle. If this fails we'll have to give up.
	419	*/
	420	err = -ESTALE;
	421	if (!nop->fh_to_parent)
	422	goto err_result;
	423
	424	target_dir = nop->fh_to_parent(mnt->mnt_sb, fid,
	425	fh_len, fileid_type);
a4f4d6df BF	426	if (!target_dir)
a4f4d6df BF	427	goto err_result;
2596110a CH	428	err = PTR_ERR(target_dir);
	429	if (IS_ERR(target_dir))
	430	goto err_result;
	431
	432	/*
	433	* And as usual we need to make sure the parent directory is
	434	* connected to the filesystem root. The VFS really doesn't
	435	* like disconnected directories..
	436	*/
f3f8e175	437	err = reconnect_path(mnt, target_dir, nbuf);
2596110a CH	438	if (err) {
	439	dput(target_dir);
	440	goto err_result;
	441	}
	442
	443	/*
	444	* Now that we've got both a well-connected parent and a
	445	* dentry for the inode we're after, make sure that our
	446	* inode is actually connected to the parent.
	447	*/
e38f9817	448	err = exportfs_get_name(mnt, target_dir, nbuf, result);
2596110a CH	449	if (!err) {
	450	mutex_lock(&target_dir->d_inode->i_mutex);
	451	nresult = lookup_one_len(nbuf, target_dir,
	452	strlen(nbuf));
	453	mutex_unlock(&target_dir->d_inode->i_mutex);
	454	if (!IS_ERR(nresult)) {
	455	if (nresult->d_inode) {
	456	dput(result);
	457	result = nresult;
	458	} else
	459	dput(nresult);
	460	}
	461	}
	462
	463	/*
	464	* At this point we are done with the parent, but it's pinned
	465	* by the child dentry anyway.
	466	*/
	467	dput(target_dir);
	468
	469	/*
	470	* And finally make sure the dentry is actually acceptable
	471	* to NFSD.
	472	*/
	473	alias = find_acceptable_alias(result, acceptable, context);
	474	if (!alias) {
	475	err = -EACCES;
	476	goto err_result;
	477	}
	478
	479	return alias;
10f11c34 CH	480	}
10f11c34 CH	481
2596110a CH	482	err_result:
	483	dput(result);
	484	return ERR_PTR(err);
d37065cd CH	485	}
	486	EXPORT_SYMBOL_GPL(exportfs_decode_fh);
	487
1da177e4	488	MODULE_LICENSE("GPL");