[deliverable/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;
	struct inode *inode;

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

	inode = result->d_inode;
	spin_lock(&inode->i_lock);
	list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
		dget(dentry);
		spin_unlock(&inode->i_lock);
		if (toput)
			dput(toput);
		if (dentry != result && acceptable(context, dentry)) {
			dput(result);
			return dentry;
		}
		spin_lock(&inode->i_lock);
		toput = dentry;
	}
	spin_unlock(&inode->i_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 (connectable && (len < 4)) {
		*max_len = 4;
		return 255;
	} else if (len < 2) {
		*max_len = 2;
		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.
	 */
	if (!nop || !nop->fh_to_dentry)
		return ERR_PTR(-ESTALE);
	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;
873feea0	46	struct inode *inode;
e2f99018	47
fb66a198 CH	48	if (acceptable(context, result))
	49	return result;
	50
873feea0 NP	51	inode = result->d_inode;
	52	spin_lock(&inode->i_lock);
	53	list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
dc0474be	54	dget(dentry);
873feea0	55	spin_unlock(&inode->i_lock);
e2f99018 CH	56	if (toput)
	57	dput(toput);
	58	if (dentry != result && acceptable(context, dentry)) {
	59	dput(result);
	60	return dentry;
	61	}
873feea0	62	spin_lock(&inode->i_lock);
e2f99018 CH	63	toput = dentry;
e2f99018 CH	64	}
873feea0	65	spin_unlock(&inode->i_lock);
e2f99018 CH	66
	67	if (toput)
	68	dput(toput);
	69	return NULL;
	70	}
	71
dd90b509 CH	72	/*
	73	* Find root of a disconnected subtree and return a reference to it.
	74	*/
	75	static struct dentry *
	76	find_disconnected_root(struct dentry *dentry)
	77	{
	78	dget(dentry);
0461ee26 CH	79	while (!IS_ROOT(dentry)) {
	80	struct dentry *parent = dget_parent(dentry);
	81
	82	if (!(parent->d_flags & DCACHE_DISCONNECTED)) {
	83	dput(parent);
	84	break;
	85	}
	86
dd90b509 CH	87	dput(dentry);
dd90b509 CH	88	dentry = parent;
dd90b509	89	}
dd90b509 CH	90	return dentry;
	91	}
	92
019ab801 CH	93	/*
019ab801 CH	94	* Make sure target_dir is fully connected to the dentry tree.
1da177e4	95	*
019ab801	96	* It may already be, as the flag isn't always updated when connection happens.
1da177e4	97	*/
019ab801	98	static int
f3f8e175	99	reconnect_path(struct vfsmount mnt, struct dentry target_dir, char *nbuf)
1da177e4	100	{
019ab801 CH	101	int noprogress = 0;
019ab801 CH	102	int err = -ESTALE;
1da177e4 LT	103
1da177e4 LT	104	/*
019ab801	105	* It is possible that a confused file system might not let us complete
1da177e4 LT	106	* the path to the root. For example, if get_parent returns a directory
	107	* in which we cannot find a name for the child. While this implies a
	108	* very sick filesystem we don't want it to cause knfsd to spin. Hence
	109	* the noprogress counter. If we go through the loop 10 times (2 is
	110	* probably enough) without getting anywhere, we just give up
	111	*/
1da177e4	112	while (target_dir->d_flags & DCACHE_DISCONNECTED && noprogress++ < 10) {
dd90b509	113	struct dentry *pd = find_disconnected_root(target_dir);
1da177e4 LT	114
	115	if (!IS_ROOT(pd)) {
	116	/* must have found a connected parent - great */
	117	spin_lock(&pd->d_lock);
	118	pd->d_flags &= ~DCACHE_DISCONNECTED;
	119	spin_unlock(&pd->d_lock);
	120	noprogress = 0;
e38f9817	121	} else if (pd == mnt->mnt_sb->s_root) {
1da177e4 LT	122	printk(KERN_ERR "export: Eeek filesystem root is not connected, impossible\n");
	123	spin_lock(&pd->d_lock);
	124	pd->d_flags &= ~DCACHE_DISCONNECTED;
	125	spin_unlock(&pd->d_lock);
	126	noprogress = 0;
	127	} else {
10f11c34 CH	128	/*
	129	* We have hit the top of a disconnected path, try to
	130	* find parent and connect.
	131	*
	132	* Racing with some other process renaming a directory
	133	* isn't much of a problem here. If someone renames
	134	* the directory, it will end up properly connected,
	135	* which is what we want
	136	*
	137	* Getting the parent can't be supported generically,
	138	* the locking is too icky.
	139	*
	140	* Instead we just return EACCES. If server reboots
	141	* or inodes get flushed, you lose
1da177e4	142	*/
10f11c34	143	struct dentry *ppd = ERR_PTR(-EACCES);
1da177e4 LT	144	struct dentry *npd;
1da177e4 LT	145
1b1dcc1b	146	mutex_lock(&pd->d_inode->i_mutex);
e38f9817 CH	147	if (mnt->mnt_sb->s_export_op->get_parent)
e38f9817 CH	148	ppd = mnt->mnt_sb->s_export_op->get_parent(pd);
1b1dcc1b	149	mutex_unlock(&pd->d_inode->i_mutex);
1da177e4 LT	150
	151	if (IS_ERR(ppd)) {
	152	err = PTR_ERR(ppd);
019ab801	153	dprintk("%s: get_parent of %ld failed, err %d\n",
8e24eea7	154	__func__, pd->d_inode->i_ino, err);
1da177e4 LT	155	dput(pd);
	156	break;
	157	}
019ab801	158
8e24eea7	159	dprintk("%s: find name of %lu in %lu\n", __func__,
019ab801	160	pd->d_inode->i_ino, ppd->d_inode->i_ino);
e38f9817	161	err = exportfs_get_name(mnt, ppd, nbuf, pd);
1da177e4 LT	162	if (err) {
	163	dput(ppd);
	164	dput(pd);
	165	if (err == -ENOENT)
	166	/* some race between get_parent and
	167	* get_name? just try again
	168	*/
	169	continue;
	170	break;
	171	}
8e24eea7	172	dprintk("%s: found name: %s\n", __func__, nbuf);
1b1dcc1b	173	mutex_lock(&ppd->d_inode->i_mutex);
1da177e4	174	npd = lookup_one_len(nbuf, ppd, strlen(nbuf));
1b1dcc1b	175	mutex_unlock(&ppd->d_inode->i_mutex);
1da177e4 LT	176	if (IS_ERR(npd)) {
1da177e4 LT	177	err = PTR_ERR(npd);
019ab801	178	dprintk("%s: lookup failed: %d\n",
8e24eea7	179	__func__, err);
1da177e4 LT	180	dput(ppd);
	181	dput(pd);
	182	break;
	183	}
	184	/* we didn't really want npd, we really wanted
	185	* a side-effect of the lookup.
	186	* hopefully, npd == pd, though it isn't really
	187	* a problem if it isn't
	188	*/
	189	if (npd == pd)
	190	noprogress = 0;
	191	else
8e24eea7	192	printk("%s: npd != pd\n", __func__);
1da177e4 LT	193	dput(npd);
	194	dput(ppd);
	195	if (IS_ROOT(pd)) {
	196	/* something went wrong, we have to give up */
	197	dput(pd);
	198	break;
	199	}
	200	}
	201	dput(pd);
	202	}
	203
	204	if (target_dir->d_flags & DCACHE_DISCONNECTED) {
	205	/* something went wrong - oh-well */
	206	if (!err)
	207	err = -ESTALE;
019ab801	208	return err;
1da177e4	209	}
019ab801 CH	210
	211	return 0;
	212	}
	213
1da177e4 LT	214	struct getdents_callback {
	215	char name; / name that was found. It already points to a
	216	buffer NAME_MAX+1 is size */
	217	unsigned long ino; /* the inum we are looking for */
	218	int found; /* inode matched? */
	219	int sequence; /* sequence counter */
	220	};
	221
	222	/*
	223	* A rather strange filldir function to capture
	224	* the name matching the specified inode number.
	225	*/
	226	static int filldir_one(void * __buf, const char * name, int len,
afefdbb2	227	loff_t pos, u64 ino, unsigned int d_type)
1da177e4 LT	228	{
	229	struct getdents_callback *buf = __buf;
	230	int result = 0;
	231
	232	buf->sequence++;
	233	if (buf->ino == ino) {
	234	memcpy(buf->name, name, len);
	235	buf->name[len] = '\0';
	236	buf->found = 1;
	237	result = -1;
	238	}
	239	return result;
	240	}
	241
	242	/**
	243	* get_name - default export_operations->get_name function
	244	* @dentry: the directory in which to find a name
	245	* @name: a pointer to a %NAME_MAX+1 char buffer to store the name
	246	* @child: the dentry for the child directory.
	247	*
	248	* calls readdir on the parent until it finds an entry with
	249	* the same inode number as the child, and returns that.
	250	*/
e38f9817 CH	251	static int get_name(struct vfsmount mnt, struct dentry dentry,
e38f9817 CH	252	char name, struct dentry child)
1da177e4	253	{
745ca247	254	const struct cred *cred = current_cred();
1da177e4 LT	255	struct inode *dir = dentry->d_inode;
	256	int error;
	257	struct file *file;
	258	struct getdents_callback buffer;
	259
	260	error = -ENOTDIR;
	261	if (!dir \|\| !S_ISDIR(dir->i_mode))
	262	goto out;
	263	error = -EINVAL;
	264	if (!dir->i_fop)
	265	goto out;
	266	/*
	267	* Open the directory ...
	268	*/
745ca247	269	file = dentry_open(dget(dentry), mntget(mnt), O_RDONLY, cred);
1da177e4 LT	270	error = PTR_ERR(file);
	271	if (IS_ERR(file))
	272	goto out;
	273
	274	error = -EINVAL;
	275	if (!file->f_op->readdir)
	276	goto out_close;
	277
	278	buffer.name = name;
	279	buffer.ino = child->d_inode->i_ino;
	280	buffer.found = 0;
	281	buffer.sequence = 0;
	282	while (1) {
	283	int old_seq = buffer.sequence;
	284
	285	error = vfs_readdir(file, filldir_one, &buffer);
53c9c5c0 AV	286	if (buffer.found) {
	287	error = 0;
	288	break;
	289	}
1da177e4 LT	290
	291	if (error < 0)
	292	break;
	293
1da177e4 LT	294	error = -ENOENT;
	295	if (old_seq == buffer.sequence)
	296	break;
	297	}
	298
	299	out_close:
	300	fput(file);
	301	out:
	302	return error;
	303	}
	304
1da177e4 LT	305	/**
	306	* export_encode_fh - default export_operations->encode_fh function
	307	* @dentry: the dentry to encode
	308	* @fh: where to store the file handle fragment
	309	* @max_len: maximum length to store there
	310	* @connectable: whether to store parent information
	311	*
	312	* This default encode_fh function assumes that the 32 inode number
	313	* is suitable for locating an inode, and that the generation number
	314	* can be used to check that it is still valid. It places them in the
	315	* filehandle fragment where export_decode_fh expects to find them.
	316	*/
6e91ea2b CH	317	static int export_encode_fh(struct dentry dentry, struct fid fid,
6e91ea2b CH	318	int *max_len, int connectable)
1da177e4 LT	319	{
	320	struct inode * inode = dentry->d_inode;
	321	int len = *max_len;
6e91ea2b	322	int type = FILEID_INO32_GEN;
5fe0c237 AK	323
	324	if (connectable && (len < 4)) {
	325	*max_len = 4;
	326	return 255;
	327	} else if (len < 2) {
	328	*max_len = 2;
1da177e4	329	return 255;
5fe0c237	330	}
1da177e4 LT	331
1da177e4 LT	332	len = 2;
6e91ea2b CH	333	fid->i32.ino = inode->i_ino;
6e91ea2b CH	334	fid->i32.gen = inode->i_generation;
1da177e4 LT	335	if (connectable && !S_ISDIR(inode->i_mode)) {
	336	struct inode *parent;
	337
	338	spin_lock(&dentry->d_lock);
	339	parent = dentry->d_parent->d_inode;
6e91ea2b CH	340	fid->i32.parent_ino = parent->i_ino;
6e91ea2b CH	341	fid->i32.parent_gen = parent->i_generation;
1da177e4 LT	342	spin_unlock(&dentry->d_lock);
1da177e4 LT	343	len = 4;
6e91ea2b	344	type = FILEID_INO32_GEN_PARENT;
1da177e4 LT	345	}
	346	*max_len = len;
	347	return type;
	348	}
	349
6e91ea2b	350	int exportfs_encode_fh(struct dentry dentry, struct fid fid, int *max_len,
d37065cd CH	351	int connectable)
d37065cd CH	352	{
39655164	353	const struct export_operations *nop = dentry->d_sb->s_export_op;
10f11c34	354	int error;
d37065cd	355
10f11c34	356	if (nop->encode_fh)
6e91ea2b	357	error = nop->encode_fh(dentry, fid->raw, max_len, connectable);
10f11c34	358	else
6e91ea2b	359	error = export_encode_fh(dentry, fid, max_len, connectable);
10f11c34 CH	360
10f11c34 CH	361	return error;
d37065cd CH	362	}
	363	EXPORT_SYMBOL_GPL(exportfs_encode_fh);
	364
6e91ea2b CH	365	struct dentry exportfs_decode_fh(struct vfsmount mnt, struct fid *fid,
	366	int fh_len, int fileid_type,
	367	int (acceptable)(void , struct dentry ), void context)
d37065cd	368	{
39655164	369	const struct export_operations *nop = mnt->mnt_sb->s_export_op;
2596110a	370	struct dentry result, alias;
f3f8e175	371	char nbuf[NAME_MAX+1];
2596110a	372	int err;
d37065cd	373
2596110a CH	374	/*
	375	* Try to get any dentry for the given file handle from the filesystem.
	376	*/
becfd1f3 AK	377	if (!nop \|\| !nop->fh_to_dentry)
becfd1f3 AK	378	return ERR_PTR(-ESTALE);
2596110a	379	result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type);
a4f4d6df BF	380	if (!result)
a4f4d6df BF	381	result = ERR_PTR(-ESTALE);
2596110a CH	382	if (IS_ERR(result))
	383	return result;
	384
	385	if (S_ISDIR(result->d_inode->i_mode)) {
	386	/*
	387	* This request is for a directory.
	388	*
	389	* On the positive side there is only one dentry for each
	390	* directory inode. On the negative side this implies that we
	391	* to ensure our dentry is connected all the way up to the
	392	* filesystem root.
	393	*/
	394	if (result->d_flags & DCACHE_DISCONNECTED) {
f3f8e175	395	err = reconnect_path(mnt, result, nbuf);
2596110a CH	396	if (err)
	397	goto err_result;
	398	}
	399
	400	if (!acceptable(context, result)) {
	401	err = -EACCES;
	402	goto err_result;
	403	}
	404
	405	return result;
10f11c34	406	} else {
2596110a CH	407	/*
	408	* It's not a directory. Life is a little more complicated.
	409	*/
	410	struct dentry target_dir, nresult;
2596110a CH	411
	412	/*
	413	* See if either the dentry we just got from the filesystem
	414	* or any alias for it is acceptable. This is always true
	415	* if this filesystem is exported without the subtreecheck
	416	* option. If the filesystem is exported with the subtree
	417	* check option there's a fair chance we need to look at
	418	* the parent directory in the file handle and make sure
	419	* it's connected to the filesystem root.
	420	*/
	421	alias = find_acceptable_alias(result, acceptable, context);
	422	if (alias)
	423	return alias;
	424
	425	/*
	426	* Try to extract a dentry for the parent directory from the
	427	* file handle. If this fails we'll have to give up.
	428	*/
	429	err = -ESTALE;
	430	if (!nop->fh_to_parent)
	431	goto err_result;
	432
	433	target_dir = nop->fh_to_parent(mnt->mnt_sb, fid,
	434	fh_len, fileid_type);
a4f4d6df BF	435	if (!target_dir)
a4f4d6df BF	436	goto err_result;
2596110a CH	437	err = PTR_ERR(target_dir);
	438	if (IS_ERR(target_dir))
	439	goto err_result;
	440
	441	/*
	442	* And as usual we need to make sure the parent directory is
	443	* connected to the filesystem root. The VFS really doesn't
	444	* like disconnected directories..
	445	*/
f3f8e175	446	err = reconnect_path(mnt, target_dir, nbuf);
2596110a CH	447	if (err) {
	448	dput(target_dir);
	449	goto err_result;
	450	}
	451
	452	/*
	453	* Now that we've got both a well-connected parent and a
	454	* dentry for the inode we're after, make sure that our
	455	* inode is actually connected to the parent.
	456	*/
e38f9817	457	err = exportfs_get_name(mnt, target_dir, nbuf, result);
2596110a CH	458	if (!err) {
	459	mutex_lock(&target_dir->d_inode->i_mutex);
	460	nresult = lookup_one_len(nbuf, target_dir,
	461	strlen(nbuf));
	462	mutex_unlock(&target_dir->d_inode->i_mutex);
	463	if (!IS_ERR(nresult)) {
	464	if (nresult->d_inode) {
	465	dput(result);
	466	result = nresult;
	467	} else
	468	dput(nresult);
	469	}
	470	}
	471
	472	/*
	473	* At this point we are done with the parent, but it's pinned
	474	* by the child dentry anyway.
	475	*/
	476	dput(target_dir);
	477
	478	/*
	479	* And finally make sure the dentry is actually acceptable
	480	* to NFSD.
	481	*/
	482	alias = find_acceptable_alias(result, acceptable, context);
	483	if (!alias) {
	484	err = -EACCES;
	485	goto err_result;
	486	}
	487
	488	return alias;
10f11c34 CH	489	}
10f11c34 CH	490
2596110a CH	491	err_result:
	492	dput(result);
	493	return ERR_PTR(err);
d37065cd CH	494	}
	495	EXPORT_SYMBOL_GPL(exportfs_decode_fh);
	496
1da177e4	497	MODULE_LICENSE("GPL");