[linux.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);
	spin_lock(&dentry->d_lock);
	while (!IS_ROOT(dentry) &&
	       (dentry->d_parent->d_flags & DCACHE_DISCONNECTED)) {
		struct dentry *parent = dentry->d_parent;
		dget(parent);
		spin_unlock(&dentry->d_lock);
		dput(dentry);
		dentry = parent;
		spin_lock(&dentry->d_lock);
	}
	spin_unlock(&dentry->d_lock);
	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);
	77	spin_lock(&dentry->d_lock);
	78	while (!IS_ROOT(dentry) &&
	79	(dentry->d_parent->d_flags & DCACHE_DISCONNECTED)) {
	80	struct dentry *parent = dentry->d_parent;
	81	dget(parent);
	82	spin_unlock(&dentry->d_lock);
	83	dput(dentry);
	84	dentry = parent;
	85	spin_lock(&dentry->d_lock);
	86	}
	87	spin_unlock(&dentry->d_lock);
	88	return dentry;
	89	}
	90
019ab801 CH	91
	92	/*
	93	* Make sure target_dir is fully connected to the dentry tree.
1da177e4	94	*
019ab801	95	* It may already be, as the flag isn't always updated when connection happens.
1da177e4	96	*/
019ab801	97	static int
f3f8e175	98	reconnect_path(struct vfsmount mnt, struct dentry target_dir, char *nbuf)
1da177e4	99	{
019ab801 CH	100	int noprogress = 0;
019ab801 CH	101	int err = -ESTALE;
1da177e4 LT	102
1da177e4 LT	103	/*
019ab801	104	* It is possible that a confused file system might not let us complete
1da177e4 LT	105	* the path to the root. For example, if get_parent returns a directory
	106	* in which we cannot find a name for the child. While this implies a
	107	* very sick filesystem we don't want it to cause knfsd to spin. Hence
	108	* the noprogress counter. If we go through the loop 10 times (2 is
	109	* probably enough) without getting anywhere, we just give up
	110	*/
1da177e4	111	while (target_dir->d_flags & DCACHE_DISCONNECTED && noprogress++ < 10) {
dd90b509	112	struct dentry *pd = find_disconnected_root(target_dir);
1da177e4 LT	113
	114	if (!IS_ROOT(pd)) {
	115	/* must have found a connected parent - great */
	116	spin_lock(&pd->d_lock);
	117	pd->d_flags &= ~DCACHE_DISCONNECTED;
	118	spin_unlock(&pd->d_lock);
	119	noprogress = 0;
e38f9817	120	} else if (pd == mnt->mnt_sb->s_root) {
1da177e4 LT	121	printk(KERN_ERR "export: Eeek filesystem root is not connected, impossible\n");
	122	spin_lock(&pd->d_lock);
	123	pd->d_flags &= ~DCACHE_DISCONNECTED;
	124	spin_unlock(&pd->d_lock);
	125	noprogress = 0;
	126	} else {
10f11c34 CH	127	/*
	128	* We have hit the top of a disconnected path, try to
	129	* find parent and connect.
	130	*
	131	* Racing with some other process renaming a directory
	132	* isn't much of a problem here. If someone renames
	133	* the directory, it will end up properly connected,
	134	* which is what we want
	135	*
	136	* Getting the parent can't be supported generically,
	137	* the locking is too icky.
	138	*
	139	* Instead we just return EACCES. If server reboots
	140	* or inodes get flushed, you lose
1da177e4	141	*/
10f11c34	142	struct dentry *ppd = ERR_PTR(-EACCES);
1da177e4 LT	143	struct dentry *npd;
1da177e4 LT	144
1b1dcc1b	145	mutex_lock(&pd->d_inode->i_mutex);
e38f9817 CH	146	if (mnt->mnt_sb->s_export_op->get_parent)
e38f9817 CH	147	ppd = mnt->mnt_sb->s_export_op->get_parent(pd);
1b1dcc1b	148	mutex_unlock(&pd->d_inode->i_mutex);
1da177e4 LT	149
	150	if (IS_ERR(ppd)) {
	151	err = PTR_ERR(ppd);
019ab801	152	dprintk("%s: get_parent of %ld failed, err %d\n",
8e24eea7	153	__func__, pd->d_inode->i_ino, err);
1da177e4 LT	154	dput(pd);
	155	break;
	156	}
019ab801	157
8e24eea7	158	dprintk("%s: find name of %lu in %lu\n", __func__,
019ab801	159	pd->d_inode->i_ino, ppd->d_inode->i_ino);
e38f9817	160	err = exportfs_get_name(mnt, ppd, nbuf, pd);
1da177e4 LT	161	if (err) {
	162	dput(ppd);
	163	dput(pd);
	164	if (err == -ENOENT)
	165	/* some race between get_parent and
	166	* get_name? just try again
	167	*/
	168	continue;
	169	break;
	170	}
8e24eea7	171	dprintk("%s: found name: %s\n", __func__, nbuf);
1b1dcc1b	172	mutex_lock(&ppd->d_inode->i_mutex);
1da177e4	173	npd = lookup_one_len(nbuf, ppd, strlen(nbuf));
1b1dcc1b	174	mutex_unlock(&ppd->d_inode->i_mutex);
1da177e4 LT	175	if (IS_ERR(npd)) {
1da177e4 LT	176	err = PTR_ERR(npd);
019ab801	177	dprintk("%s: lookup failed: %d\n",
8e24eea7	178	__func__, err);
1da177e4 LT	179	dput(ppd);
	180	dput(pd);
	181	break;
	182	}
	183	/* we didn't really want npd, we really wanted
	184	* a side-effect of the lookup.
	185	* hopefully, npd == pd, though it isn't really
	186	* a problem if it isn't
	187	*/
	188	if (npd == pd)
	189	noprogress = 0;
	190	else
8e24eea7	191	printk("%s: npd != pd\n", __func__);
1da177e4 LT	192	dput(npd);
	193	dput(ppd);
	194	if (IS_ROOT(pd)) {
	195	/* something went wrong, we have to give up */
	196	dput(pd);
	197	break;
	198	}
	199	}
	200	dput(pd);
	201	}
	202
	203	if (target_dir->d_flags & DCACHE_DISCONNECTED) {
	204	/* something went wrong - oh-well */
	205	if (!err)
	206	err = -ESTALE;
019ab801	207	return err;
1da177e4	208	}
019ab801 CH	209
	210	return 0;
	211	}
	212
1da177e4 LT	213	struct getdents_callback {
	214	char name; / name that was found. It already points to a
	215	buffer NAME_MAX+1 is size */
	216	unsigned long ino; /* the inum we are looking for */
	217	int found; /* inode matched? */
	218	int sequence; /* sequence counter */
	219	};
	220
	221	/*
	222	* A rather strange filldir function to capture
	223	* the name matching the specified inode number.
	224	*/
	225	static int filldir_one(void * __buf, const char * name, int len,
afefdbb2	226	loff_t pos, u64 ino, unsigned int d_type)
1da177e4 LT	227	{
	228	struct getdents_callback *buf = __buf;
	229	int result = 0;
	230
	231	buf->sequence++;
	232	if (buf->ino == ino) {
	233	memcpy(buf->name, name, len);
	234	buf->name[len] = '\0';
	235	buf->found = 1;
	236	result = -1;
	237	}
	238	return result;
	239	}
	240
	241	/**
	242	* get_name - default export_operations->get_name function
	243	* @dentry: the directory in which to find a name
	244	* @name: a pointer to a %NAME_MAX+1 char buffer to store the name
	245	* @child: the dentry for the child directory.
	246	*
	247	* calls readdir on the parent until it finds an entry with
	248	* the same inode number as the child, and returns that.
	249	*/
e38f9817 CH	250	static int get_name(struct vfsmount mnt, struct dentry dentry,
e38f9817 CH	251	char name, struct dentry child)
1da177e4	252	{
745ca247	253	const struct cred *cred = current_cred();
1da177e4 LT	254	struct inode *dir = dentry->d_inode;
	255	int error;
	256	struct file *file;
	257	struct getdents_callback buffer;
	258
	259	error = -ENOTDIR;
	260	if (!dir \|\| !S_ISDIR(dir->i_mode))
	261	goto out;
	262	error = -EINVAL;
	263	if (!dir->i_fop)
	264	goto out;
	265	/*
	266	* Open the directory ...
	267	*/
745ca247	268	file = dentry_open(dget(dentry), mntget(mnt), O_RDONLY, cred);
1da177e4 LT	269	error = PTR_ERR(file);
	270	if (IS_ERR(file))
	271	goto out;
	272
	273	error = -EINVAL;
	274	if (!file->f_op->readdir)
	275	goto out_close;
	276
	277	buffer.name = name;
	278	buffer.ino = child->d_inode->i_ino;
	279	buffer.found = 0;
	280	buffer.sequence = 0;
	281	while (1) {
	282	int old_seq = buffer.sequence;
	283
	284	error = vfs_readdir(file, filldir_one, &buffer);
53c9c5c0 AV	285	if (buffer.found) {
	286	error = 0;
	287	break;
	288	}
1da177e4 LT	289
	290	if (error < 0)
	291	break;
	292
1da177e4 LT	293	error = -ENOENT;
	294	if (old_seq == buffer.sequence)
	295	break;
	296	}
	297
	298	out_close:
	299	fput(file);
	300	out:
	301	return error;
	302	}
	303
1da177e4 LT	304	/**
	305	* export_encode_fh - default export_operations->encode_fh function
	306	* @dentry: the dentry to encode
	307	* @fh: where to store the file handle fragment
	308	* @max_len: maximum length to store there
	309	* @connectable: whether to store parent information
	310	*
	311	* This default encode_fh function assumes that the 32 inode number
	312	* is suitable for locating an inode, and that the generation number
	313	* can be used to check that it is still valid. It places them in the
	314	* filehandle fragment where export_decode_fh expects to find them.
	315	*/
6e91ea2b CH	316	static int export_encode_fh(struct dentry dentry, struct fid fid,
6e91ea2b CH	317	int *max_len, int connectable)
1da177e4 LT	318	{
	319	struct inode * inode = dentry->d_inode;
	320	int len = *max_len;
6e91ea2b	321	int type = FILEID_INO32_GEN;
1da177e4 LT	322
	323	if (len < 2 \|\| (connectable && len < 4))
	324	return 255;
	325
	326	len = 2;
6e91ea2b CH	327	fid->i32.ino = inode->i_ino;
6e91ea2b CH	328	fid->i32.gen = inode->i_generation;
1da177e4 LT	329	if (connectable && !S_ISDIR(inode->i_mode)) {
	330	struct inode *parent;
	331
	332	spin_lock(&dentry->d_lock);
	333	parent = dentry->d_parent->d_inode;
6e91ea2b CH	334	fid->i32.parent_ino = parent->i_ino;
6e91ea2b CH	335	fid->i32.parent_gen = parent->i_generation;
1da177e4 LT	336	spin_unlock(&dentry->d_lock);
1da177e4 LT	337	len = 4;
6e91ea2b	338	type = FILEID_INO32_GEN_PARENT;
1da177e4 LT	339	}
	340	*max_len = len;
	341	return type;
	342	}
	343
6e91ea2b	344	int exportfs_encode_fh(struct dentry dentry, struct fid fid, int *max_len,
d37065cd CH	345	int connectable)
d37065cd CH	346	{
39655164	347	const struct export_operations *nop = dentry->d_sb->s_export_op;
10f11c34	348	int error;
d37065cd	349
10f11c34	350	if (nop->encode_fh)
6e91ea2b	351	error = nop->encode_fh(dentry, fid->raw, max_len, connectable);
10f11c34	352	else
6e91ea2b	353	error = export_encode_fh(dentry, fid, max_len, connectable);
10f11c34 CH	354
10f11c34 CH	355	return error;
d37065cd CH	356	}
	357	EXPORT_SYMBOL_GPL(exportfs_encode_fh);
	358
6e91ea2b CH	359	struct dentry exportfs_decode_fh(struct vfsmount mnt, struct fid *fid,
	360	int fh_len, int fileid_type,
	361	int (acceptable)(void , struct dentry ), void context)
d37065cd	362	{
39655164	363	const struct export_operations *nop = mnt->mnt_sb->s_export_op;
2596110a	364	struct dentry result, alias;
f3f8e175	365	char nbuf[NAME_MAX+1];
2596110a	366	int err;
d37065cd	367
2596110a CH	368	/*
	369	* Try to get any dentry for the given file handle from the filesystem.
	370	*/
	371	result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type);
a4f4d6df BF	372	if (!result)
a4f4d6df BF	373	result = ERR_PTR(-ESTALE);
2596110a CH	374	if (IS_ERR(result))
	375	return result;
	376
	377	if (S_ISDIR(result->d_inode->i_mode)) {
	378	/*
	379	* This request is for a directory.
	380	*
	381	* On the positive side there is only one dentry for each
	382	* directory inode. On the negative side this implies that we
	383	* to ensure our dentry is connected all the way up to the
	384	* filesystem root.
	385	*/
	386	if (result->d_flags & DCACHE_DISCONNECTED) {
f3f8e175	387	err = reconnect_path(mnt, result, nbuf);
2596110a CH	388	if (err)
	389	goto err_result;
	390	}
	391
	392	if (!acceptable(context, result)) {
	393	err = -EACCES;
	394	goto err_result;
	395	}
	396
	397	return result;
10f11c34	398	} else {
2596110a CH	399	/*
	400	* It's not a directory. Life is a little more complicated.
	401	*/
	402	struct dentry target_dir, nresult;
2596110a CH	403
	404	/*
	405	* See if either the dentry we just got from the filesystem
	406	* or any alias for it is acceptable. This is always true
	407	* if this filesystem is exported without the subtreecheck
	408	* option. If the filesystem is exported with the subtree
	409	* check option there's a fair chance we need to look at
	410	* the parent directory in the file handle and make sure
	411	* it's connected to the filesystem root.
	412	*/
	413	alias = find_acceptable_alias(result, acceptable, context);
	414	if (alias)
	415	return alias;
	416
	417	/*
	418	* Try to extract a dentry for the parent directory from the
	419	* file handle. If this fails we'll have to give up.
	420	*/
	421	err = -ESTALE;
	422	if (!nop->fh_to_parent)
	423	goto err_result;
	424
	425	target_dir = nop->fh_to_parent(mnt->mnt_sb, fid,
	426	fh_len, fileid_type);
a4f4d6df BF	427	if (!target_dir)
a4f4d6df BF	428	goto err_result;
2596110a CH	429	err = PTR_ERR(target_dir);
	430	if (IS_ERR(target_dir))
	431	goto err_result;
	432
	433	/*
	434	* And as usual we need to make sure the parent directory is
	435	* connected to the filesystem root. The VFS really doesn't
	436	* like disconnected directories..
	437	*/
f3f8e175	438	err = reconnect_path(mnt, target_dir, nbuf);
2596110a CH	439	if (err) {
	440	dput(target_dir);
	441	goto err_result;
	442	}
	443
	444	/*
	445	* Now that we've got both a well-connected parent and a
	446	* dentry for the inode we're after, make sure that our
	447	* inode is actually connected to the parent.
	448	*/
e38f9817	449	err = exportfs_get_name(mnt, target_dir, nbuf, result);
2596110a CH	450	if (!err) {
	451	mutex_lock(&target_dir->d_inode->i_mutex);
	452	nresult = lookup_one_len(nbuf, target_dir,
	453	strlen(nbuf));
	454	mutex_unlock(&target_dir->d_inode->i_mutex);
	455	if (!IS_ERR(nresult)) {
	456	if (nresult->d_inode) {
	457	dput(result);
	458	result = nresult;
	459	} else
	460	dput(nresult);
	461	}
	462	}
	463
	464	/*
	465	* At this point we are done with the parent, but it's pinned
	466	* by the child dentry anyway.
	467	*/
	468	dput(target_dir);
	469
	470	/*
	471	* And finally make sure the dentry is actually acceptable
	472	* to NFSD.
	473	*/
	474	alias = find_acceptable_alias(result, acceptable, context);
	475	if (!alias) {
	476	err = -EACCES;
	477	goto err_result;
	478	}
	479
	480	return alias;
10f11c34 CH	481	}
10f11c34 CH	482
2596110a CH	483	err_result:
	484	dput(result);
	485	return ERR_PTR(err);
d37065cd CH	486	}
	487	EXPORT_SYMBOL_GPL(exportfs_decode_fh);
	488
1da177e4	489	MODULE_LICENSE("GPL");