union_subr.c

来自「早期freebsd实现」· C语言 代码 · 共 745 行 · 第 1/2 页

	 * otherwise lock the vp list while we call getnewvnode
	 * since that can block.
	 */ 
	hash = UNION_HASH(uppervp, lowervp);

	if (union_list_lock(hash))
		goto loop;

	error = getnewvnode(VT_UNION, mp, union_vnodeop_p, vpp);
	if (error) {
		if (uppervp) {
			if (dvp == uppervp)
				vrele(uppervp);
			else
				vput(uppervp);
		}
		if (lowervp)
			vrele(lowervp);

		goto out;
	}

	MALLOC((*vpp)->v_data, void *, sizeof(struct union_node),
		M_TEMP, M_WAITOK);

	if (uppervp)
		(*vpp)->v_type = uppervp->v_type;
	else
		(*vpp)->v_type = lowervp->v_type;
	un = VTOUNION(*vpp);
	un->un_vnode = *vpp;
	un->un_uppervp = uppervp;
	un->un_lowervp = lowervp;
	un->un_openl = 0;
	un->un_flags = UN_LOCKED;
	if (un->un_uppervp)
		un->un_flags |= UN_ULOCK;
#ifdef DIAGNOSTIC
	if (curproc)
		un->un_pid = curproc->p_pid;
	else
		un->un_pid = -1;
#endif
	if (cnp && (lowervp != NULLVP) && (lowervp->v_type == VREG)) {
		un->un_hash = cnp->cn_hash;
		un->un_path = malloc(cnp->cn_namelen+1, M_TEMP, M_WAITOK);
		bcopy(cnp->cn_nameptr, un->un_path, cnp->cn_namelen);
		un->un_path[cnp->cn_namelen] = '\0';
		VREF(dvp);
		un->un_dirvp = dvp;
	} else {
		un->un_hash = 0;
		un->un_path = 0;
		un->un_dirvp = 0;
	}

	LIST_INSERT_HEAD(&unhead[hash], un, un_cache);

	if (xlowervp)
		vrele(xlowervp);

out:
	union_list_unlock(hash);

	return (error);
}

int
union_freevp(vp)
	struct vnode *vp;
{
	struct union_node *un = VTOUNION(vp);

	LIST_REMOVE(un, un_cache);

	if (un->un_uppervp)
		vrele(un->un_uppervp);
	if (un->un_lowervp)
		vrele(un->un_lowervp);
	if (un->un_dirvp)
		vrele(un->un_dirvp);
	if (un->un_path)
		free(un->un_path, M_TEMP);

	FREE(vp->v_data, M_TEMP);
	vp->v_data = 0;

	return (0);
}

/*
 * copyfile.  copy the vnode (fvp) to the vnode (tvp)
 * using a sequence of reads and writes.  both (fvp)
 * and (tvp) are locked on entry and exit.
 */
int
union_copyfile(p, cred, fvp, tvp)
	struct proc *p;
	struct ucred *cred;
	struct vnode *fvp;
	struct vnode *tvp;
{
	char *buf;
	struct uio uio;
	struct iovec iov;
	int error = 0;

	/*
	 * strategy:
	 * allocate a buffer of size MAXBSIZE.
	 * loop doing reads and writes, keeping track
	 * of the current uio offset.
	 * give up at the first sign of trouble.
	 */

	uio.uio_procp = p;
	uio.uio_segflg = UIO_SYSSPACE;
	uio.uio_offset = 0;

	VOP_UNLOCK(fvp);				/* XXX */
	LEASE_CHECK(fvp, p, cred, LEASE_READ);
	VOP_LOCK(fvp);					/* XXX */
	VOP_UNLOCK(tvp);				/* XXX */
	LEASE_CHECK(tvp, p, cred, LEASE_WRITE);
	VOP_LOCK(tvp);					/* XXX */

	buf = malloc(MAXBSIZE, M_TEMP, M_WAITOK);

	/* ugly loop follows... */
	do {
		off_t offset = uio.uio_offset;

		uio.uio_iov = &iov;
		uio.uio_iovcnt = 1;
		iov.iov_base = buf;
		iov.iov_len = MAXBSIZE;
		uio.uio_resid = iov.iov_len;
		uio.uio_rw = UIO_READ;
		error = VOP_READ(fvp, &uio, 0, cred);

		if (error == 0) {
			uio.uio_iov = &iov;
			uio.uio_iovcnt = 1;
			iov.iov_base = buf;
			iov.iov_len = MAXBSIZE - uio.uio_resid;
			uio.uio_offset = offset;
			uio.uio_rw = UIO_WRITE;
			uio.uio_resid = iov.iov_len;

			if (uio.uio_resid == 0)
				break;

			do {
				error = VOP_WRITE(tvp, &uio, 0, cred);
			} while ((uio.uio_resid > 0) && (error == 0));
		}

	} while (error == 0);

	free(buf, M_TEMP);
	return (error);
}

/*
 * Create a shadow directory in the upper layer.
 * The new vnode is returned locked.
 *
 * (um) points to the union mount structure for access to the
 * the mounting process's credentials.
 * (dvp) is the directory in which to create the shadow directory.
 * it is unlocked on entry and exit.
 * (cnp) is the componentname to be created.
 * (vpp) is the returned newly created shadow directory, which
 * is returned locked.
 */
int
union_mkshadow(um, dvp, cnp, vpp)
	struct union_mount *um;
	struct vnode *dvp;
	struct componentname *cnp;
	struct vnode **vpp;
{
	int error;
	struct vattr va;
	struct proc *p = cnp->cn_proc;
	struct componentname cn;

	/*
	 * policy: when creating the shadow directory in the
	 * upper layer, create it owned by the user who did
	 * the mount, group from parent directory, and mode
	 * 777 modified by umask (ie mostly identical to the
	 * mkdir syscall).  (jsp, kb)
	 */

	/*
	 * A new componentname structure must be faked up because
	 * there is no way to know where the upper level cnp came
	 * from or what it is being used for.  This must duplicate
	 * some of the work done by NDINIT, some of the work done
	 * by namei, some of the work done by lookup and some of
	 * the work done by VOP_LOOKUP when given a CREATE flag.
	 * Conclusion: Horrible.
	 *
	 * The pathname buffer will be FREEed by VOP_MKDIR.
	 */
	cn.cn_pnbuf = malloc(cnp->cn_namelen+1, M_NAMEI, M_WAITOK);
	bcopy(cnp->cn_nameptr, cn.cn_pnbuf, cnp->cn_namelen);
	cn.cn_pnbuf[cnp->cn_namelen] = '\0';

	cn.cn_nameiop = CREATE;
	cn.cn_flags = (LOCKPARENT|HASBUF|SAVENAME|SAVESTART|ISLASTCN);
	cn.cn_proc = cnp->cn_proc;
	if (um->um_op == UNMNT_ABOVE)
		cn.cn_cred = cnp->cn_cred;
	else
		cn.cn_cred = um->um_cred;
	cn.cn_nameptr = cn.cn_pnbuf;
	cn.cn_namelen = cnp->cn_namelen;
	cn.cn_hash = cnp->cn_hash;
	cn.cn_consume = cnp->cn_consume;

	VREF(dvp);
	if (error = relookup(dvp, vpp, &cn))
		return (error);
	vrele(dvp);

	if (*vpp) {
		VOP_ABORTOP(dvp, &cn);
		VOP_UNLOCK(dvp);
		vrele(*vpp);
		*vpp = NULLVP;
		return (EEXIST);
	}

	VATTR_NULL(&va);
	va.va_type = VDIR;
	va.va_mode = um->um_cmode;

	/* LEASE_CHECK: dvp is locked */
	LEASE_CHECK(dvp, p, p->p_ucred, LEASE_WRITE);

	error = VOP_MKDIR(dvp, vpp, &cn, &va);
	return (error);
}

/*
 * union_vn_create: creates and opens a new shadow file
 * on the upper union layer.  this function is similar
 * in spirit to calling vn_open but it avoids calling namei().
 * the problem with calling namei is that a) it locks too many
 * things, and b) it doesn't start at the "right" directory,
 * whereas relookup is told where to start.
 */
int
union_vn_create(vpp, un, p)
	struct vnode **vpp;
	struct union_node *un;
	struct proc *p;
{
	struct vnode *vp;
	struct ucred *cred = p->p_ucred;
	struct vattr vat;
	struct vattr *vap = &vat;
	int fmode = FFLAGS(O_WRONLY|O_CREAT|O_TRUNC|O_EXCL);
	int error;
	int cmode = UN_FILEMODE & ~p->p_fd->fd_cmask;
	char *cp;
	struct componentname cn;

	*vpp = NULLVP;

	/*
	 * Build a new componentname structure (for the same
	 * reasons outlines in union_mkshadow).
	 * The difference here is that the file is owned by
	 * the current user, rather than by the person who
	 * did the mount, since the current user needs to be
	 * able to write the file (that's why it is being
	 * copied in the first place).
	 */
	cn.cn_namelen = strlen(un->un_path);
	cn.cn_pnbuf = (caddr_t) malloc(cn.cn_namelen, M_NAMEI, M_WAITOK);
	bcopy(un->un_path, cn.cn_pnbuf, cn.cn_namelen+1);
	cn.cn_nameiop = CREATE;
	cn.cn_flags = (LOCKPARENT|HASBUF|SAVENAME|SAVESTART|ISLASTCN);
	cn.cn_proc = p;
	cn.cn_cred = p->p_ucred;
	cn.cn_nameptr = cn.cn_pnbuf;
	cn.cn_hash = un->un_hash;
	cn.cn_consume = 0;

	VREF(un->un_dirvp);
	if (error = relookup(un->un_dirvp, &vp, &cn))
		return (error);
	vrele(un->un_dirvp);

	if (vp) {
		VOP_ABORTOP(un->un_dirvp, &cn);
		if (un->un_dirvp == vp)
			vrele(un->un_dirvp);
		else
			vput(un->un_dirvp);
		vrele(vp);
		return (EEXIST);
	}

	/*
	 * Good - there was no race to create the file
	 * so go ahead and create it.  The permissions
	 * on the file will be 0666 modified by the
	 * current user's umask.  Access to the file, while
	 * it is unioned, will require access to the top *and*
	 * bottom files.  Access when not unioned will simply
	 * require access to the top-level file.
	 * TODO: confirm choice of access permissions.
	 */
	VATTR_NULL(vap);
	vap->va_type = VREG;
	vap->va_mode = cmode;
	LEASE_CHECK(un->un_dirvp, p, cred, LEASE_WRITE);
	if (error = VOP_CREATE(un->un_dirvp, &vp, &cn, vap))
		return (error);

	if (error = VOP_OPEN(vp, fmode, cred, p)) {
		vput(vp);
		return (error);
	}

	vp->v_writecount++;
	*vpp = vp;
	return (0);
}

int
union_vn_close(vp, fmode, cred, p)
	struct vnode *vp;
	int fmode;
	struct ucred *cred;
	struct proc *p;
{
	if (fmode & FWRITE)
		--vp->v_writecount;
	return (VOP_CLOSE(vp, fmode));
}

void
union_removed_upper(un)
	struct union_node *un;
{
	if (un->un_flags & UN_ULOCK) {
		un->un_flags &= ~UN_ULOCK;
		VOP_UNLOCK(un->un_uppervp);
	}

	union_newupper(un, NULLVP);
}

struct vnode *
union_lowervp(vp)
	struct vnode *vp;
{
	struct union_node *un = VTOUNION(vp);

	if (un->un_lowervp && (vp->v_type == un->un_lowervp->v_type)) {
		if (vget(un->un_lowervp, 0))
			return (NULLVP);
	}

	return (un->un_lowervp);
}