vfs_lookup.c

基于组件方式开发操作系统的OSKIT源代码

			goto bad;
		}
		if (wantparent) {
			ndp->ni_dvp = dp;
			VREF(dp);
		}
		ndp->ni_vp = dp;
		if (!(cnp->cn_flags & (LOCKPARENT | LOCKLEAF)))
			VOP_UNLOCK(dp);
		if (cnp->cn_flags & SAVESTART)
			panic("lookup: SAVESTART");
		return (0);
	}

	/*
	 * Handle "..": two special cases.
	 * 1. If at root directory (e.g. after chroot)
	 *    or at absolute root directory
	 *    then ignore it so can't get out.
	 * 2. If this vnode is the root of a mounted
	 *    filesystem, then replace it with the
	 *    vnode which was mounted on so we take the
	 *    .. in the other file system.
	 */
	if (cnp->cn_flags & ISDOTDOT) {
		for (;;) {
			if (dp == ndp->ni_rootdir || dp == rootvnode) {
				ndp->ni_dvp = dp;
				ndp->ni_vp = dp;
				VREF(dp);
				goto nextname;
			}
			if ((dp->v_flag & VROOT) == 0 ||
			    (cnp->cn_flags & NOCROSSMOUNT))
				break;
			tdp = dp;
			dp = dp->v_mount->mnt_vnodecovered;
			vput(tdp);
			VREF(dp);
			VOP_LOCK(dp);
		}
	}

	/*
	 * We now have a segment name to search for, and a directory to search.
	 */
unionlookup:
	ndp->ni_dvp = dp;
	if ((error = VOP_LOOKUP(dp, &ndp->ni_vp, cnp)) != 0) {
#ifdef DIAGNOSTIC
		if (ndp->ni_vp != NULL)
			panic("leaf should be empty");
#endif
#ifdef NAMEI_DIAGNOSTIC
		printf("not found\n");
#endif
		if ((error == ENOENT) &&
		    (dp->v_flag & VROOT) &&
		    (dp->v_mount->mnt_flag & MNT_UNION)) {
			tdp = dp;
			dp = dp->v_mount->mnt_vnodecovered;
			vput(tdp);
			VREF(dp);
			VOP_LOCK(dp);
			goto unionlookup;
		}

		if (error != EJUSTRETURN)
			goto bad;
		/*
		 * If creating and at end of pathname, then can consider
		 * allowing file to be created.
		 */
		if (rdonly || (ndp->ni_dvp->v_mount->mnt_flag & MNT_RDONLY)) {
			error = EROFS;
			goto bad;
		}
		/*
		 * We return with ni_vp NULL to indicate that the entry
		 * doesn't currently exist, leaving a pointer to the
		 * (possibly locked) directory inode in ndp->ni_dvp.
		 */
		if (cnp->cn_flags & SAVESTART) {
			ndp->ni_startdir = ndp->ni_dvp;
			VREF(ndp->ni_startdir);
		}
		return (0);
	}
#ifdef NAMEI_DIAGNOSTIC
	printf("found\n");
#endif

	/*
	 * Take into account any additional components consumed by
	 * the underlying filesystem.
	 */
	if (cnp->cn_consume > 0) {
		cnp->cn_nameptr += cnp->cn_consume;
		ndp->ni_next += cnp->cn_consume;
		ndp->ni_pathlen -= cnp->cn_consume;
		cnp->cn_consume = 0;
	}

	dp = ndp->ni_vp;
	/*
	 * Check to see if the vnode has been mounted on;
	 * if so find the root of the mounted file system.
	 */
	while (dp->v_type == VDIR && (mp = dp->v_mountedhere) &&
	       (cnp->cn_flags & NOCROSSMOUNT) == 0) {
		if (mp->mnt_flag & MNT_MLOCK) {
			mp->mnt_flag |= MNT_MWAIT;
			sleep((caddr_t)mp, PVFS);
			continue;
		}
		if ((error = VFS_ROOT(dp->v_mountedhere, &tdp)) != 0)
			goto bad2;
		vput(dp);
		ndp->ni_vp = dp = tdp;
	}

	/*
	 * Check for symbolic link
	 */
	if ((dp->v_type == VLNK) &&
	    ((cnp->cn_flags & FOLLOW) || *ndp->ni_next == '/')) {
		cnp->cn_flags |= ISSYMLINK;
		return (0);
	}

nextname:
	/*
	 * Not a symbolic link.  If more pathname,
	 * continue at next component, else return.
	 */
	if (*ndp->ni_next == '/') {
		cnp->cn_nameptr = ndp->ni_next;
		while (*cnp->cn_nameptr == '/') {
			cnp->cn_nameptr++;
			ndp->ni_pathlen--;
		}
		vrele(ndp->ni_dvp);
		goto dirloop;
	}
	/*
	 * Check for read-only file systems.
	 */
	if (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME) {
		/*
		 * Disallow directory write attempts on read-only
		 * file systems.
		 */
		if (rdonly || (dp->v_mount->mnt_flag & MNT_RDONLY) ||
		    (wantparent &&
		     (ndp->ni_dvp->v_mount->mnt_flag & MNT_RDONLY))) {
			error = EROFS;
			goto bad2;
		}
	}
	if (cnp->cn_flags & SAVESTART) {
		ndp->ni_startdir = ndp->ni_dvp;
		VREF(ndp->ni_startdir);
	}
	if (!wantparent)
		vrele(ndp->ni_dvp);
	if ((cnp->cn_flags & LOCKLEAF) == 0)
		VOP_UNLOCK(dp);
	return (0);

bad2:
	if ((cnp->cn_flags & LOCKPARENT) && *ndp->ni_next == '\0')
		VOP_UNLOCK(ndp->ni_dvp);
	vrele(ndp->ni_dvp);
bad:
	vput(dp);
	ndp->ni_vp = NULL;
	return (error);
}

/*
 * Reacquire a path name component.
 */
int
relookup(dvp, vpp, cnp)
	struct vnode *dvp, **vpp;
	struct componentname *cnp;
{
	register struct vnode *dp = 0;	/* the directory we are searching */
	int docache;			/* == 0 do not cache last component */
	int wantparent;			/* 1 => wantparent or lockparent flag */
	int rdonly;			/* lookup read-only flag bit */
	int error = 0;
#ifdef NAMEI_DIAGNOSTIC
	int newhash;			/* DEBUG: check name hash */
	char *cp;			/* DEBUG: check name ptr/len */
#endif

	/*
	 * Setup: break out flag bits into variables.
	 */
	wantparent = cnp->cn_flags & (LOCKPARENT|WANTPARENT);
	docache = (cnp->cn_flags & NOCACHE) ^ NOCACHE;
	if (cnp->cn_nameiop == DELETE ||
	    (wantparent && cnp->cn_nameiop != CREATE))
		docache = 0;
	rdonly = cnp->cn_flags & RDONLY;
	cnp->cn_flags &= ~ISSYMLINK;
	dp = dvp;
	VOP_LOCK(dp);

/* dirloop: */
	/*
	 * Search a new directory.
	 *
	 * The cn_hash value is for use by vfs_cache.
	 * The last component of the filename is left accessible via
	 * cnp->cn_nameptr for callers that need the name. Callers needing
	 * the name set the SAVENAME flag. When done, they assume
	 * responsibility for freeing the pathname buffer.
	 */
#ifdef NAMEI_DIAGNOSTIC
	for (newhash = 0, cp = cnp->cn_nameptr; *cp != 0 && *cp != '/'; cp++)
		newhash += (unsigned char)*cp;
	if (newhash != cnp->cn_hash)
		panic("relookup: bad hash");
	if (cnp->cn_namelen != cp - cnp->cn_nameptr)
		panic ("relookup: bad len");
	if (*cp != 0)
		panic("relookup: not last component");
	printf("{%s}: ", cnp->cn_nameptr);
#endif

	/*
	 * Check for degenerate name (e.g. / or "")
	 * which is a way of talking about a directory,
	 * e.g. like "/." or ".".
	 */
	if (cnp->cn_nameptr[0] == '\0') {
		if (dp->v_type != VDIR) {
			error = ENOTDIR;
			goto bad;
		}
		if (cnp->cn_nameiop != LOOKUP || wantparent) {
			error = EISDIR;
			goto bad;
		}
		if (!(cnp->cn_flags & LOCKLEAF))
			VOP_UNLOCK(dp);
		*vpp = dp;
		if (cnp->cn_flags & SAVESTART)
			panic("lookup: SAVESTART");
		return (0);
	}

	if (cnp->cn_flags & ISDOTDOT)
		panic ("relookup: lookup on dot-dot");

	/*
	 * We now have a segment name to search for, and a directory to search.
	 */
	if ((error = VOP_LOOKUP(dp, vpp, cnp)) != 0) {
#ifdef DIAGNOSTIC
		if (*vpp != NULL)
			panic("leaf should be empty");
#endif
		if (error != EJUSTRETURN)
			goto bad;
		/*
		 * If creating and at end of pathname, then can consider
		 * allowing file to be created.
		 */
		if (rdonly || (dvp->v_mount->mnt_flag & MNT_RDONLY)) {
			error = EROFS;
			goto bad;
		}
		/* ASSERT(dvp == ndp->ni_startdir) */
		if (cnp->cn_flags & SAVESTART)
			VREF(dvp);
		/*
		 * We return with ni_vp NULL to indicate that the entry
		 * doesn't currently exist, leaving a pointer to the
		 * (possibly locked) directory inode in ndp->ni_dvp.
		 */
		return (0);
	}
	dp = *vpp;

#ifdef DIAGNOSTIC
	/*
	 * Check for symbolic link
	 */
	if (dp->v_type == VLNK && (cnp->cn_flags & FOLLOW))
		panic ("relookup: symlink found.\n");
#endif

	/*
	 * Check for read-only file systems.
	 */
	if (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME) {
		/*
		 * Disallow directory write attempts on read-only
		 * file systems.
		 */
		if (rdonly || (dp->v_mount->mnt_flag & MNT_RDONLY) ||
		    (wantparent &&
		     (dvp->v_mount->mnt_flag & MNT_RDONLY))) {
			error = EROFS;
			goto bad2;
		}
	}
	/* ASSERT(dvp == ndp->ni_startdir) */
	if (cnp->cn_flags & SAVESTART)
		VREF(dvp);
	
	if (!wantparent)
		vrele(dvp);
	if ((cnp->cn_flags & LOCKLEAF) == 0)
		VOP_UNLOCK(dp);
	return (0);

bad2:
	if ((cnp->cn_flags & LOCKPARENT) && (cnp->cn_flags & ISLASTCN))
		VOP_UNLOCK(dvp);
	vrele(dvp);
bad:
	vput(dp);
	*vpp = NULL;
	return (error);
}