namei.c

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	DQUOT_INIT(dir);
	lock_kernel();
	error = dir->i_op->symlink(dir, dentry, oldname);
	unlock_kernel();

exit_lock:
	up(&dir->i_zombie);
	if (!error)
		inode_dir_notify(dir, DN_CREATE);
	return error;
}

asmlinkage long sys_symlink(const char * oldname, const char * newname)
{
	int error = 0;
	char * from;
	char * to;

	from = getname(oldname);
	if(IS_ERR(from))
		return PTR_ERR(from);
	to = getname(newname);
	error = PTR_ERR(to);
	if (!IS_ERR(to)) {
		struct dentry *dentry;
		struct nameidata nd;

		if (path_init(to, LOOKUP_PARENT, &nd))
			error = path_walk(to, &nd);
		if (error)
			goto out;
		dentry = lookup_create(&nd, 0);
		error = PTR_ERR(dentry);
		if (!IS_ERR(dentry)) {
			error = vfs_symlink(nd.dentry->d_inode, dentry, from);
			dput(dentry);
		}
		up(&nd.dentry->d_inode->i_sem);
		path_release(&nd);
out:
		putname(to);
	}
	putname(from);
	return error;
}

int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry)
{
	struct inode *inode;
	int error;

	down(&dir->i_zombie);
	error = -ENOENT;
	inode = old_dentry->d_inode;
	if (!inode)
		goto exit_lock;

	error = may_create(dir, new_dentry);
	if (error)
		goto exit_lock;

	error = -EXDEV;
	if (dir->i_dev != inode->i_dev)
		goto exit_lock;

	/*
	 * A link to an append-only or immutable file cannot be created.
	 */
	error = -EPERM;
	if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
		goto exit_lock;
	if (!dir->i_op || !dir->i_op->link)
		goto exit_lock;

	DQUOT_INIT(dir);
	lock_kernel();
	error = dir->i_op->link(old_dentry, dir, new_dentry);
	unlock_kernel();

exit_lock:
	up(&dir->i_zombie);
	if (!error)
		inode_dir_notify(dir, DN_CREATE);
	return error;
}

/*
 * Hardlinks are often used in delicate situations.  We avoid
 * security-related surprises by not following symlinks on the
 * newname.  --KAB
 *
 * We don't follow them on the oldname either to be compatible
 * with linux 2.0, and to avoid hard-linking to directories
 * and other special files.  --ADM
 */
asmlinkage long sys_link(const char * oldname, const char * newname)
{
	int error;
	char * from;
	char * to;

	from = getname(oldname);
	if(IS_ERR(from))
		return PTR_ERR(from);
	to = getname(newname);
	error = PTR_ERR(to);
	if (!IS_ERR(to)) {
		struct dentry *new_dentry;
		struct nameidata nd, old_nd;

		error = 0;
		if (path_init(from, LOOKUP_POSITIVE, &old_nd))
			error = path_walk(from, &old_nd);
		if (error)
			goto exit;
		if (path_init(to, LOOKUP_PARENT, &nd))
			error = path_walk(to, &nd);
		if (error)
			goto out;
		error = -EXDEV;
		if (old_nd.mnt != nd.mnt)
			goto out_release;
		new_dentry = lookup_create(&nd, 0);
		error = PTR_ERR(new_dentry);
		if (!IS_ERR(new_dentry)) {
			error = vfs_link(old_nd.dentry, nd.dentry->d_inode, new_dentry);
			dput(new_dentry);
		}
		up(&nd.dentry->d_inode->i_sem);
out_release:
		path_release(&nd);
out:
		path_release(&old_nd);
exit:
		putname(to);
	}
	putname(from);

	return error;
}

/*
 * The worst of all namespace operations - renaming directory. "Perverted"
 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
 * Problems:
 *	a) we can get into loop creation. Check is done in is_subdir().
 *	b) race potential - two innocent renames can create a loop together.
 *	   That's where 4.4 screws up. Current fix: serialization on
 *	   sb->s_vfs_rename_sem. We might be more accurate, but that's another
 *	   story.
 *	c) we have to lock _three_ objects - parents and victim (if it exists).
 *	   And that - after we got ->i_sem on parents (until then we don't know
 *	   whether the target exists at all, let alone whether it is a directory
 *	   or not). Solution: ->i_zombie. Taken only after ->i_sem. Always taken
 *	   on link creation/removal of any kind. And taken (without ->i_sem) on
 *	   directory that will be removed (both in rmdir() and here).
 *	d) some filesystems don't support opened-but-unlinked directories,
 *	   either because of layout or because they are not ready to deal with
 *	   all cases correctly. The latter will be fixed (taking this sort of
 *	   stuff into VFS), but the former is not going away. Solution: the same
 *	   trick as in rmdir().
 *	e) conversion from fhandle to dentry may come in the wrong moment - when
 *	   we are removing the target. Solution: we will have to grab ->i_zombie
 *	   in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
 *	   ->i_sem on parents, which works but leads to some truely excessive
 *	   locking].
 */
int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
	       struct inode *new_dir, struct dentry *new_dentry)
{
	int error;
	struct inode *target;

	if (old_dentry->d_inode == new_dentry->d_inode)
		return 0;

	error = may_delete(old_dir, old_dentry, 1);
	if (error)
		return error;

	if (new_dir->i_dev != old_dir->i_dev)
		return -EXDEV;

	if (!new_dentry->d_inode)
		error = may_create(new_dir, new_dentry);
	else
		error = may_delete(new_dir, new_dentry, 1);
	if (error)
		return error;

	if (!old_dir->i_op || !old_dir->i_op->rename)
		return -EPERM;

	/*
	 * If we are going to change the parent - check write permissions,
	 * we'll need to flip '..'.
	 */
	if (new_dir != old_dir) {
		error = permission(old_dentry->d_inode, MAY_WRITE);
	}
	if (error)
		return error;

	DQUOT_INIT(old_dir);
	DQUOT_INIT(new_dir);
	down(&old_dir->i_sb->s_vfs_rename_sem);
	error = -EINVAL;
	if (is_subdir(new_dentry, old_dentry))
		goto out_unlock;
	/* Don't eat your daddy, dear... */
	/* This also avoids locking issues */
	if (old_dentry->d_parent == new_dentry)
		goto out_unlock;
	target = new_dentry->d_inode;
	if (target) { /* Hastur! Hastur! Hastur! */
		triple_down(&old_dir->i_zombie,
			    &new_dir->i_zombie,
			    &target->i_zombie);
		d_unhash(new_dentry);
	} else
		double_down(&old_dir->i_zombie,
			    &new_dir->i_zombie);
	if (IS_DEADDIR(old_dir)||IS_DEADDIR(new_dir))
		error = -ENOENT;
	else if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
		error = -EBUSY;
	else 
		error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
	if (target) {
		if (!error)
			target->i_flags |= S_DEAD;
		triple_up(&old_dir->i_zombie,
			  &new_dir->i_zombie,
			  &target->i_zombie);
		if (d_unhashed(new_dentry))
			d_rehash(new_dentry);
		dput(new_dentry);
	} else
		double_up(&old_dir->i_zombie,
			  &new_dir->i_zombie);
		
	if (!error)
		d_move(old_dentry,new_dentry);
out_unlock:
	up(&old_dir->i_sb->s_vfs_rename_sem);
	return error;
}

int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
	       struct inode *new_dir, struct dentry *new_dentry)
{
	int error;

	if (old_dentry->d_inode == new_dentry->d_inode)
		return 0;

	error = may_delete(old_dir, old_dentry, 0);
	if (error)
		return error;

	if (new_dir->i_dev != old_dir->i_dev)
		return -EXDEV;

	if (!new_dentry->d_inode)
		error = may_create(new_dir, new_dentry);
	else
		error = may_delete(new_dir, new_dentry, 0);
	if (error)
		return error;

	if (!old_dir->i_op || !old_dir->i_op->rename)
		return -EPERM;

	DQUOT_INIT(old_dir);
	DQUOT_INIT(new_dir);
	double_down(&old_dir->i_zombie, &new_dir->i_zombie);
	if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
		error = -EBUSY;
	else
		error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
	double_up(&old_dir->i_zombie, &new_dir->i_zombie);
	if (error)
		return error;
	/* The following d_move() should become unconditional */
	if (!(old_dir->i_sb->s_type->fs_flags & FS_ODD_RENAME)) {
		d_move(old_dentry, new_dentry);
	}
	return 0;
}

int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
	       struct inode *new_dir, struct dentry *new_dentry)
{
	int error;
	if (S_ISDIR(old_dentry->d_inode->i_mode))
		error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry);
	else
		error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry);
	if (!error) {
		if (old_dir == new_dir)
			inode_dir_notify(old_dir, DN_RENAME);
		else {
			inode_dir_notify(old_dir, DN_DELETE);
			inode_dir_notify(new_dir, DN_CREATE);
		}
	}
	return error;
}

static inline int do_rename(const char * oldname, const char * newname)
{
	int error = 0;
	struct dentry * old_dir, * new_dir;
	struct dentry * old_dentry, *new_dentry;
	struct nameidata oldnd, newnd;

	if (path_init(oldname, LOOKUP_PARENT, &oldnd))
		error = path_walk(oldname, &oldnd);

	if (error)
		goto exit;

	if (path_init(newname, LOOKUP_PARENT, &newnd))
		error = path_walk(newname, &newnd);
	if (error)
		goto exit1;

	error = -EXDEV;
	if (oldnd.mnt != newnd.mnt)
		goto exit2;

	old_dir = oldnd.dentry;
	error = -EBUSY;
	if (oldnd.last_type != LAST_NORM)
		goto exit2;

	new_dir = newnd.dentry;
	if (newnd.last_type != LAST_NORM)
		goto exit2;

	double_lock(new_dir, old_dir);

	old_dentry = lookup_hash(&oldnd.last, old_dir);
	error = PTR_ERR(old_dentry);
	if (IS_ERR(old_dentry))
		goto exit3;
	/* source must exist */
	error = -ENOENT;
	if (!old_dentry->d_inode)
		goto exit4;
	/* unless the source is a directory trailing slashes give -ENOTDIR */
	if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
		error = -ENOTDIR;
		if (oldnd.last.name[oldnd.last.len])
			goto exit4;
		if (newnd.last.name[newnd.last.len])
			goto exit4;
	}
	new_dentry = lookup_hash(&newnd.last, new_dir);
	error = PTR_ERR(new_dentry);
	if (IS_ERR(new_dentry))
		goto exit4;

	lock_kernel();
	error = vfs_rename(old_dir->d_inode, old_dentry,
				   new_dir->d_inode, new_dentry);
	unlock_kernel();

	dput(new_dentry);
exit4:
	dput(old_dentry);
exit3:
	double_up(&new_dir->d_inode->i_sem, &old_dir->d_inode->i_sem);
exit2:
	path_release(&newnd);
exit1:
	path_release(&oldnd);
exit:
	return error;
}

asmlinkage long sys_rename(const char * oldname, const char * newname)
{
	int error;
	char * from;
	char * to;

	from = getname(oldname);
	if(IS_ERR(from))
		return PTR_ERR(from);
	to = getname(newname);
	error = PTR_ERR(to);
	if (!IS_ERR(to)) {
		error = do_rename(from,to);
		putname(to);
	}
	putname(from);
	return error;
}

int vfs_readlink(struct dentry *dentry, char *buffer, int buflen, const char *link)
{
	int len;

	len = PTR_ERR(link);
	if (IS_ERR(link))
		goto out;

	len = strlen(link);
	if (len > (unsigned) buflen)
		len = buflen;
	if (copy_to_user(buffer, link, len))
		len = -EFAULT;
out:
	return len;
}

static inline int
__vfs_follow_link(struct nameidata *nd, const char *link)
{
	int res = 0;
	char *name;
	if (IS_ERR(link))
		goto fail;

	if (*link == '/') {
		path_release(nd);
		if (!walk_init_root(link, nd))
			/* weird __emul_prefix() stuff did it */
			goto out;
	}
	res = link_path_walk(link, nd);
out:
	if (current->link_count || res || nd->last_type!=LAST_NORM)
		return res;
	/*
	 * If it is an iterative symlinks resolution in open_namei() we
	 * have to copy the last component. And all that crap because of
	 * bloody create() on broken symlinks. Furrfu...
	 */
	name = __getname();
	if (!name)
		return -ENOMEM;
	strcpy(name, nd->last.name);
	nd->last.name = name;
	return 0;
fail:
	path_release(nd);
	return PTR_ERR(link);
}

int vfs_follow_link(struct nameidata *nd, const char *link)
{
	return __vfs_follow_link(nd, link);
}

/* get the link contents into pagecache */
static char *page_getlink(struct dentry * dentry, struct page **ppage)
{
	struct page * page;
	struct address_space *mapping = dentry->d_inode->i_mapping;
	page = read_cache_page(mapping, 0, (filler_t *)mapping->a_ops->readpage,
				NULL);
	if (IS_ERR(page))
		goto sync_fail;
	wait_on_page(page);
	if (!Page_Uptodate(page))
		goto async_fail;
	*ppage = page;
	return kmap(page);

async_fail:
	page_cache_release(page);
	return ERR_PTR(-EIO);

sync_fail:
	return (char*)page;
}

int page_readlink(struct dentry *dentry, char *buffer, int buflen)
{
	struct page *page = NULL;
	char *s = page_getlink(dentry, &page);
	int res = vfs_readlink(dentry,buffer,buflen,s);
	if (page) {
		kunmap(page);
		page_cache_release(page);
	}
	return res;
}

int page_follow_link(struct dentry *dentry, struct nameidata *nd)
{
	struct page *page = NULL;
	char *s = page_getlink(dentry, &page);
	int res = __vfs_follow_link(nd, s);
	if (page) {
		kunmap(page);
		page_cache_release(page);
	}
	return res;
}

struct inode_operations page_symlink_inode_operations = {
	readlink:	page_readlink,
	follow_link:	page_follow_link,
};