ufs_lookup.c

来自「基于组件方式开发操作系统的OSKIT源代码」· C语言 代码 · 共 1,062 行 · 第 1/3 页

					 * Note that we wouldn't expect to
					 * shrink the directory while rewriting
					 * an existing entry anyway.
					 */
					enduseful = endsearch;
					ap->a_cnp->cn_flags |= ISWHITEOUT;
					numdirpasses--;
					goto notfound;
				}
				dp->i_ino = ep->d_ino;
				dp->i_reclen = ep->d_reclen;
				brelse(bp);
				goto found;
			}
		}
		prevoff = dp->i_offset;
		dp->i_offset += ep->d_reclen;
		entryoffsetinblock += ep->d_reclen;
		if (ep->d_ino)
			enduseful = dp->i_offset;
	}
notfound:
	/*
	 * If we started in the middle of the directory and failed
	 * to find our target, we must check the beginning as well.
	 */
	if (numdirpasses == 2) {
		numdirpasses--;
		dp->i_offset = 0;
		endsearch = dp->i_diroff;
		goto searchloop;
	}
	if (bp != NULL)
		brelse(bp);
	/*
	 * If creating, and at end of pathname and current
	 * directory has not been removed, then can consider
	 * allowing file to be created.
	 */
	if ((nameiop == CREATE || nameiop == RENAME ||
	     (nameiop == DELETE &&
	      (ap->a_cnp->cn_flags & DOWHITEOUT) &&
	      (ap->a_cnp->cn_flags & ISWHITEOUT))) &&
	    (flags & ISLASTCN) && dp->i_nlink != 0) {
		/*
		 * Access for write is interpreted as allowing
		 * creation of files in the directory.
		 */
		error = VOP_ACCESS(vdp, VWRITE, cred, cnp->cn_proc);
		if (error)
			return (error);
		/*
		 * Return an indication of where the new directory
		 * entry should be put.  If we didn't find a slot,
		 * then set dp->i_count to 0 indicating
		 * that the new slot belongs at the end of the
		 * directory. If we found a slot, then the new entry
		 * can be put in the range from dp->i_offset to
		 * dp->i_offset + dp->i_count.
		 */
		if (slotstatus == NONE) {
			dp->i_offset = roundup(dp->i_size, DIRBLKSIZ);
			dp->i_count = 0;
			enduseful = dp->i_offset;
		} else if (nameiop == DELETE) {
			dp->i_offset = slotoffset;
			if ((dp->i_offset & (DIRBLKSIZ - 1)) == 0)
				dp->i_count = 0;
			else
				dp->i_count = dp->i_offset - prevoff;
		} else {
			dp->i_offset = slotoffset;
			dp->i_count = slotsize;
			if (enduseful < slotoffset + slotsize)
				enduseful = slotoffset + slotsize;
		}
		dp->i_endoff = roundup(enduseful, DIRBLKSIZ);
		dp->i_flag |= IN_CHANGE | IN_UPDATE;
		/*
		 * We return with the directory locked, so that
		 * the parameters we set up above will still be
		 * valid if we actually decide to do a direnter().
		 * We return ni_vp == NULL to indicate that the entry
		 * does not currently exist; we leave a pointer to
		 * the (locked) directory inode in ndp->ni_dvp.
		 * The pathname buffer is saved so that the name
		 * can be obtained later.
		 *
		 * NB - if the directory is unlocked, then this
		 * information cannot be used.
		 */
		cnp->cn_flags |= SAVENAME;
		if (!lockparent)
			VOP_UNLOCK(vdp);
		return (EJUSTRETURN);
	}
	/*
	 * Insert name into cache (as non-existent) if appropriate.
	 */
	if ((cnp->cn_flags & MAKEENTRY) && nameiop != CREATE)
		cache_enter(vdp, *vpp, cnp);
	return (ENOENT);

found:
	if (numdirpasses == 2)
		nchstats.ncs_pass2++;
	/*
	 * Check that directory length properly reflects presence
	 * of this entry.
	 */
	if (entryoffsetinblock + DIRSIZ(FSFMT(vdp), ep) > dp->i_size) {
		ufs_dirbad(dp, dp->i_offset, "i_size too small");
		dp->i_size = entryoffsetinblock + DIRSIZ(FSFMT(vdp), ep);
		dp->i_flag |= IN_CHANGE | IN_UPDATE;
	}

	/*
	 * Found component in pathname.
	 * If the final component of path name, save information
	 * in the cache as to where the entry was found.
	 */
	if ((flags & ISLASTCN) && nameiop == LOOKUP)
		dp->i_diroff = dp->i_offset &~ (DIRBLKSIZ - 1);

	/*
	 * If deleting, and at end of pathname, return
	 * parameters which can be used to remove file.
	 * If the wantparent flag isn't set, we return only
	 * the directory (in ndp->ni_dvp), otherwise we go
	 * on and lock the inode, being careful with ".".
	 */
	if (nameiop == DELETE && (flags & ISLASTCN)) {
		/*
		 * Write access to directory required to delete files.
		 */
		error = VOP_ACCESS(vdp, VWRITE, cred, cnp->cn_proc);
		if (error)
			return (error);
		/*
		 * Return pointer to current entry in dp->i_offset,
		 * and distance past previous entry (if there
		 * is a previous entry in this block) in dp->i_count.
		 * Save directory inode pointer in ndp->ni_dvp for dirremove().
		 */
		if ((dp->i_offset & (DIRBLKSIZ - 1)) == 0)
			dp->i_count = 0;
		else
			dp->i_count = dp->i_offset - prevoff;
		if (dp->i_number == dp->i_ino) {
			VREF(vdp);
			*vpp = vdp;
			return (0);
		}
		error = VFS_VGET(vdp->v_mount, dp->i_ino, &tdp);
		if (error)
			return (error);
		/*
		 * If directory is "sticky", then user must own
		 * the directory, or the file in it, else she
		 * may not delete it (unless she's root). This
		 * implements append-only directories.
		 */
		if ((dp->i_mode & ISVTX) &&
		    cred->cr_uid != 0 &&
		    cred->cr_uid != dp->i_uid &&
		    VTOI(tdp)->i_uid != cred->cr_uid) {
			vput(tdp);
			return (EPERM);
		}
		*vpp = tdp;
		if (!lockparent)
			VOP_UNLOCK(vdp);
		return (0);
	}

	/*
	 * 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)) {
		error = VOP_ACCESS(vdp, VWRITE, cred, cnp->cn_proc);
		if (error)
			return (error);
		/*
		 * Careful about locking second inode.
		 * This can only occur if the target is ".".
		 */
		if (dp->i_number == dp->i_ino)
			return (EISDIR);
		error = VFS_VGET(vdp->v_mount, dp->i_ino, &tdp);
		if (error)
			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 */
		error = VFS_VGET(vdp->v_mount, dp->i_ino, &tdp);
		if (error) {
			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 {
		error = VFS_VGET(vdp->v_mount, dp->i_ino, &tdp);
		if (error)
			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;
	}
	if (ep->d_ino == 0)
		return (0);
	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 (0);
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 inode *dp;
	struct direct newdir;

#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
	}
	return (ufs_direnter2(dvp, &newdir, cnp->cn_cred, cnp->cn_proc));
}