ufs_lookup.c

早期freebsd实现

	 * If rewriting (RENAME), return the inode and the
	 * information required to rewrite the present directory
	 * Must get inode of directory entry to verify it's a
	 * regular file, or empty directory.
	 */
	if (nameiop == RENAME && wantparent &&
	    (flags & ISLASTCN)) {
		if (error = VOP_ACCESS(vdp, VWRITE, cred, cnp->cn_proc))
			return (error);
		/*
		 * Careful about locking second inode.
		 * This can only occur if the target is ".".
		 */
		if (dp->i_number == dp->i_ino)
			return (EISDIR);
		if (error = VFS_VGET(vdp->v_mount, dp->i_ino, &tdp))
			return (error);
		*vpp = tdp;
		cnp->cn_flags |= SAVENAME;
		if (!lockparent)
			VOP_UNLOCK(vdp);
		return (0);
	}

	/*
	 * Step through the translation in the name.  We do not `vput' the
	 * directory because we may need it again if a symbolic link
	 * is relative to the current directory.  Instead we save it
	 * unlocked as "pdp".  We must get the target inode before unlocking
	 * the directory to insure that the inode will not be removed
	 * before we get it.  We prevent deadlock by always fetching
	 * inodes from the root, moving down the directory tree. Thus
	 * when following backward pointers ".." we must unlock the
	 * parent directory before getting the requested directory.
	 * There is a potential race condition here if both the current
	 * and parent directories are removed before the VFS_VGET for the
	 * inode associated with ".." returns.  We hope that this occurs
	 * infrequently since we cannot avoid this race condition without
	 * implementing a sophisticated deadlock detection algorithm.
	 * Note also that this simple deadlock detection scheme will not
	 * work if the file system has any hard links other than ".."
	 * that point backwards in the directory structure.
	 */
	pdp = vdp;
	if (flags & ISDOTDOT) {
		VOP_UNLOCK(pdp);	/* race to get the inode */
		if (error = VFS_VGET(vdp->v_mount, dp->i_ino, &tdp)) {
			VOP_LOCK(pdp);
			return (error);
		}
		if (lockparent && (flags & ISLASTCN) &&
		    (error = VOP_LOCK(pdp))) {
			vput(tdp);
			return (error);
		}
		*vpp = tdp;
	} else if (dp->i_number == dp->i_ino) {
		VREF(vdp);	/* we want ourself, ie "." */
		*vpp = vdp;
	} else {
		if (error = VFS_VGET(vdp->v_mount, dp->i_ino, &tdp))
			return (error);
		if (!lockparent || !(flags & ISLASTCN))
			VOP_UNLOCK(pdp);
		*vpp = tdp;
	}

	/*
	 * Insert name into cache if appropriate.
	 */
	if (cnp->cn_flags & MAKEENTRY)
		cache_enter(vdp, *vpp, cnp);
	return (0);
}

void
ufs_dirbad(ip, offset, how)
	struct inode *ip;
	doff_t offset;
	char *how;
{
	struct mount *mp;

	mp = ITOV(ip)->v_mount;
	(void)printf("%s: bad dir ino %d at offset %d: %s\n",
	    mp->mnt_stat.f_mntonname, ip->i_number, offset, how);
	if ((mp->mnt_stat.f_flags & MNT_RDONLY) == 0)
		panic("bad dir");
}

/*
 * Do consistency checking on a directory entry:
 *	record length must be multiple of 4
 *	entry must fit in rest of its DIRBLKSIZ block
 *	record must be large enough to contain entry
 *	name is not longer than MAXNAMLEN
 *	name must be as long as advertised, and null terminated
 */
int
ufs_dirbadentry(dp, ep, entryoffsetinblock)
	struct vnode *dp;
	register struct direct *ep;
	int entryoffsetinblock;
{
	register int i;
	int namlen;

#	if (BYTE_ORDER == LITTLE_ENDIAN)
		if (dp->v_mount->mnt_maxsymlinklen > 0)
			namlen = ep->d_namlen;
		else
			namlen = ep->d_type;
#	else
		namlen = ep->d_namlen;
#	endif
	if ((ep->d_reclen & 0x3) != 0 ||
	    ep->d_reclen > DIRBLKSIZ - (entryoffsetinblock & (DIRBLKSIZ - 1)) ||
	    ep->d_reclen < DIRSIZ(FSFMT(dp), ep) || namlen > MAXNAMLEN) {
		/*return (1); */
		printf("First bad\n");
		goto bad;
	}
	for (i = 0; i < namlen; i++)
		if (ep->d_name[i] == '\0') {
			/*return (1); */
			printf("Second bad\n");
			goto bad;
	}
	if (ep->d_name[i])
		goto bad;
	return (ep->d_name[i]);
bad:
	return(1);
}

/*
 * Write a directory entry after a call to namei, using the parameters
 * that it left in nameidata.  The argument ip is the inode which the new
 * directory entry will refer to.  Dvp is a pointer to the directory to
 * be written, which was left locked by namei. Remaining parameters
 * (dp->i_offset, dp->i_count) indicate how the space for the new
 * entry is to be obtained.
 */
int
ufs_direnter(ip, dvp, cnp)
	struct inode *ip;
	struct vnode *dvp;
	register struct componentname *cnp;
{
	register struct direct *ep, *nep;
	register struct inode *dp;
	struct buf *bp;
	struct direct newdir;
	struct iovec aiov;
	struct uio auio;
	u_int dsize;
	int error, loc, newentrysize, spacefree;
	char *dirbuf;

#ifdef DIAGNOSTIC
	if ((cnp->cn_flags & SAVENAME) == 0)
		panic("direnter: missing name");
#endif
	dp = VTOI(dvp);
	newdir.d_ino = ip->i_number;
	newdir.d_namlen = cnp->cn_namelen;
	bcopy(cnp->cn_nameptr, newdir.d_name, (unsigned)cnp->cn_namelen + 1);
	if (dvp->v_mount->mnt_maxsymlinklen > 0)
		newdir.d_type = IFTODT(ip->i_mode);
	else {
		newdir.d_type = 0;
#		if (BYTE_ORDER == LITTLE_ENDIAN)
			{ u_char tmp = newdir.d_namlen;
			newdir.d_namlen = newdir.d_type;
			newdir.d_type = tmp; }
#		endif
	}
	newentrysize = DIRSIZ(FSFMT(dvp), &newdir);
	if (dp->i_count == 0) {
		/*
		 * If dp->i_count is 0, then namei could find no
		 * space in the directory. Here, dp->i_offset will
		 * be on a directory block boundary and we will write the
		 * new entry into a fresh block.
		 */
		if (dp->i_offset & (DIRBLKSIZ - 1))
			panic("ufs_direnter: newblk");
		auio.uio_offset = dp->i_offset;
		newdir.d_reclen = DIRBLKSIZ;
		auio.uio_resid = newentrysize;
		aiov.iov_len = newentrysize;
		aiov.iov_base = (caddr_t)&newdir;
		auio.uio_iov = &aiov;
		auio.uio_iovcnt = 1;
		auio.uio_rw = UIO_WRITE;
		auio.uio_segflg = UIO_SYSSPACE;
		auio.uio_procp = (struct proc *)0;
		error = VOP_WRITE(dvp, &auio, IO_SYNC, cnp->cn_cred);
		if (DIRBLKSIZ >
		    VFSTOUFS(dvp->v_mount)->um_mountp->mnt_stat.f_bsize)
			/* XXX should grow with balloc() */
			panic("ufs_direnter: frag size");
		else if (!error) {
			dp->i_size = roundup(dp->i_size, DIRBLKSIZ);
			dp->i_flag |= IN_CHANGE;
		}
		return (error);
	}

	/*
	 * If dp->i_count is non-zero, then namei found space
	 * for the new entry in the range dp->i_offset to
	 * dp->i_offset + dp->i_count in the directory.
	 * To use this space, we may have to compact the entries located
	 * there, by copying them together towards the beginning of the
	 * block, leaving the free space in one usable chunk at the end.
	 */

	/*
	 * Increase size of directory if entry eats into new space.
	 * This should never push the size past a new multiple of
	 * DIRBLKSIZE.
	 *
	 * N.B. - THIS IS AN ARTIFACT OF 4.2 AND SHOULD NEVER HAPPEN.
	 */
	if (dp->i_offset + dp->i_count > dp->i_size)
		dp->i_size = dp->i_offset + dp->i_count;
	/*
	 * Get the block containing the space for the new directory entry.
	 */
	if (error = VOP_BLKATOFF(dvp, (off_t)dp->i_offset, &dirbuf, &bp))
		return (error);
	/*
	 * Find space for the new entry. In the simple case, the entry at
	 * offset base will have the space. If it does not, then namei
	 * arranged that compacting the region dp->i_offset to
	 * dp->i_offset + dp->i_count would yield the
	 * space.
	 */
	ep = (struct direct *)dirbuf;
	dsize = DIRSIZ(FSFMT(dvp), ep);
	spacefree = ep->d_reclen - dsize;
	for (loc = ep->d_reclen; loc < dp->i_count; ) {
		nep = (struct direct *)(dirbuf + loc);
		if (ep->d_ino) {
			/* trim the existing slot */
			ep->d_reclen = dsize;
			ep = (struct direct *)((char *)ep + dsize);
		} else {
			/* overwrite; nothing there; header is ours */
			spacefree += dsize;
		}
		dsize = DIRSIZ(FSFMT(dvp), nep);
		spacefree += nep->d_reclen - dsize;
		loc += nep->d_reclen;
		bcopy((caddr_t)nep, (caddr_t)ep, dsize);
	}
	/*
	 * Update the pointer fields in the previous entry (if any),
	 * copy in the new entry, and write out the block.
	 */
	if (ep->d_ino == 0) {
		if (spacefree + dsize < newentrysize)
			panic("ufs_direnter: compact1");
		newdir.d_reclen = spacefree + dsize;
	} else {
		if (spacefree < newentrysize)
			panic("ufs_direnter: compact2");
		newdir.d_reclen = spacefree;
		ep->d_reclen = dsize;
		ep = (struct direct *)((char *)ep + dsize);
	}
	bcopy((caddr_t)&newdir, (caddr_t)ep, (u_int)newentrysize);
	error = VOP_BWRITE(bp);
	dp->i_flag |= IN_CHANGE | IN_UPDATE;
	if (!error && dp->i_endoff && dp->i_endoff < dp->i_size)
		error = VOP_TRUNCATE(dvp, (off_t)dp->i_endoff, IO_SYNC,
		    cnp->cn_cred, cnp->cn_proc);
	return (error);
}

/*
 * Remove a directory entry after a call to namei, using
 * the parameters which it left in nameidata. The entry
 * dp->i_offset contains the offset into the directory of the
 * entry to be eliminated.  The dp->i_count field contains the
 * size of the previous record in the directory.  If this
 * is 0, the first entry is being deleted, so we need only
 * zero the inode number to mark the entry as free.  If the
 * entry is not the first in the directory, we must reclaim
 * the space of the now empty record by adding the record size
 * to the size of the previous entry.
 */
int
ufs_dirremove(dvp, cnp)
	struct vnode *dvp;
	struct componentname *cnp;
{
	register struct inode *dp;
	struct direct *ep;
	struct buf *bp;
	int error;

	dp = VTOI(dvp);
	if (dp->i_count == 0) {
		/*
		 * First entry in block: set d_ino to zero.
		 */
		if (error =
		    VOP_BLKATOFF(dvp, (off_t)dp->i_offset, (char **)&ep, &bp))
			return (error);
		ep->d_ino = 0;
		error = VOP_BWRITE(bp);
		dp->i_flag |= IN_CHANGE | IN_UPDATE;
		return (error);
	}
	/*
	 * Collapse new free space into previous entry.
	 */
	if (error = VOP_BLKATOFF(dvp, (off_t)(dp->i_offset - dp->i_count),
	    (char **)&ep, &bp))
		return (error);
	ep->d_reclen += dp->i_reclen;
	error = VOP_BWRITE(bp);
	dp->i_flag |= IN_CHANGE | IN_UPDATE;
	return (error);
}

/*
 * Rewrite an existing directory entry to point at the inode
 * supplied.  The parameters describing the directory entry are
 * set up by a call to namei.
 */
int
ufs_dirrewrite(dp, ip, cnp)
	struct inode *dp, *ip;
	struct componentname *cnp;
{
	struct buf *bp;
	struct direct *ep;
	struct vnode *vdp = ITOV(dp);
	int error;

	if (error = VOP_BLKATOFF(vdp, (off_t)dp->i_offset, (char **)&ep, &bp))
		return (error);
	ep->d_ino = ip->i_number;
	if (vdp->v_mount->mnt_maxsymlinklen > 0)
		ep->d_type = IFTODT(ip->i_mode);
	error = VOP_BWRITE(bp);
	dp->i_flag |= IN_CHANGE | IN_UPDATE;
	return (error);
}

/*
 * Check if a directory is empty or not.
 * Inode supplied must be locked.
 *
 * Using a struct dirtemplate here is not precisely
 * what we want, but better than using a struct direct.
 *
 * NB: does not handle corrupted directories.
 */
int
ufs_dirempty(ip, parentino, cred)
	register struct inode *ip;
	ino_t parentino;
	struct ucred *cred;
{
	register off_t off;
	struct dirtemplate dbuf;
	register struct direct *dp = (struct direct *)&dbuf;
	int error, count, namlen;
#define	MINDIRSIZ (sizeof (struct dirtemplate) / 2)

	for (off = 0; off < ip->i_size; off += dp->d_reclen) {
		error = vn_rdwr(UIO_READ, ITOV(ip), (caddr_t)dp, MINDIRSIZ, off,
		   UIO_SYSSPACE, IO_NODELOCKED, cred, &count, (struct proc *)0);
		/*
		 * Since we read MINDIRSIZ, residual must
		 * be 0 unless we're at end of file.
		 */
		if (error || count != 0)
			return (0);
		/* avoid infinite loops */
		if (dp->d_reclen == 0)
			return (0);
		/* skip empty entries */
		if (dp->d_ino == 0)
			continue;
		/* accept only "." and ".." */
#		if (BYTE_ORDER == LITTLE_ENDIAN)
			if (ITOV(ip)->v_mount->mnt_maxsymlinklen > 0)
				namlen = dp->d_namlen;
			else
				namlen = dp->d_type;
#		else
			namlen = dp->d_namlen;
#		endif
		if (namlen > 2)
			return (0);
		if (dp->d_name[0] != '.')
			return (0);
		/*
		 * At this point namlen must be 1 or 2.
		 * 1 implies ".", 2 implies ".." if second
		 * char is also "."
		 */
		if (namlen == 1)
			continue;
		if (dp->d_name[1] == '.' && dp->d_ino == parentino)
			continue;
		return (0);
	}
	return (1);
}

/*
 * Check if source directory is in the path of the target directory.
 * Target is supplied locked, source is unlocked.
 * The target is always vput before returning.
 */
int
ufs_checkpath(source, target, cred)
	struct inode *source, *target;
	struct ucred *cred;
{
	struct vnode *vp;
	int error, rootino, namlen;
	struct dirtemplate dirbuf;

	vp = ITOV(target);
	if (target->i_number == source->i_number) {
		error = EEXIST;
		goto out;
	}
	rootino = ROOTINO;
	error = 0;
	if (target->i_number == rootino)
		goto out;

	for (;;) {
		if (vp->v_type != VDIR) {
			error = ENOTDIR;
			break;
		}
		error = vn_rdwr(UIO_READ, vp, (caddr_t)&dirbuf,
			sizeof (struct dirtemplate), (off_t)0, UIO_SYSSPACE,
			IO_NODELOCKED, cred, (int *)0, (struct proc *)0);
		if (error != 0)
			break;
#		if (BYTE_ORDER == LITTLE_ENDIAN)
			if (vp->v_mount->mnt_maxsymlinklen > 0)
				namlen = dirbuf.dotdot_namlen;
			else
				namlen = dirbuf.dotdot_type;
#		else
			namlen = dirbuf.dotdot_namlen;
#		endif
		if (namlen != 2 ||
		    dirbuf.dotdot_name[0] != '.' ||
		    dirbuf.dotdot_name[1] != '.') {
			error = ENOTDIR;
			break;
		}
		if (dirbuf.dotdot_ino == source->i_number) {
			error = EINVAL;
			break;
		}
		if (dirbuf.dotdot_ino == rootino)
			break;
		vput(vp);
		if (error = VFS_VGET(vp->v_mount, dirbuf.dotdot_ino, &vp)) {
			vp = NULL;
			break;
		}
	}

out:
	if (error == ENOTDIR)
		printf("checkpath: .. not a directory\n");
	if (vp != NULL)
		vput(vp);
	return (error);
}