vfs_subr.c

早期freebsd实现

		panic("brelvp: NULL");
	/*
	 * Delete from old vnode list, if on one.
	 */
	if (bp->b_vnbufs.le_next != NOLIST)
		bufremvn(bp);
	vp = bp->b_vp;
	bp->b_vp = (struct vnode *) 0;
	HOLDRELE(vp);
}

/*
 * Reassign a buffer from one vnode to another.
 * Used to assign file specific control information
 * (indirect blocks) to the vnode to which they belong.
 */
reassignbuf(bp, newvp)
	register struct buf *bp;
	register struct vnode *newvp;
{
	register struct buflists *listheadp;

	if (newvp == NULL) {
		printf("reassignbuf: NULL");
		return;
	}
	/*
	 * Delete from old vnode list, if on one.
	 */
	if (bp->b_vnbufs.le_next != NOLIST)
		bufremvn(bp);
	/*
	 * If dirty, put on list of dirty buffers;
	 * otherwise insert onto list of clean buffers.
	 */
	if (bp->b_flags & B_DELWRI)
		listheadp = &newvp->v_dirtyblkhd;
	else
		listheadp = &newvp->v_cleanblkhd;
	bufinsvn(bp, listheadp);
}

/*
 * Create a vnode for a block device.
 * Used for root filesystem, argdev, and swap areas.
 * Also used for memory file system special devices.
 */
bdevvp(dev, vpp)
	dev_t dev;
	struct vnode **vpp;
{
	register struct vnode *vp;
	struct vnode *nvp;
	int error;

	if (dev == NODEV)
		return (0);
	error = getnewvnode(VT_NON, (struct mount *)0, spec_vnodeop_p, &nvp);
	if (error) {
		*vpp = 0;
		return (error);
	}
	vp = nvp;
	vp->v_type = VBLK;
	if (nvp = checkalias(vp, dev, (struct mount *)0)) {
		vput(vp);
		vp = nvp;
	}
	*vpp = vp;
	return (0);
}

/*
 * Check to see if the new vnode represents a special device
 * for which we already have a vnode (either because of
 * bdevvp() or because of a different vnode representing
 * the same block device). If such an alias exists, deallocate
 * the existing contents and return the aliased vnode. The
 * caller is responsible for filling it with its new contents.
 */
struct vnode *
checkalias(nvp, nvp_rdev, mp)
	register struct vnode *nvp;
	dev_t nvp_rdev;
	struct mount *mp;
{
	register struct vnode *vp;
	struct vnode **vpp;

	if (nvp->v_type != VBLK && nvp->v_type != VCHR)
		return (NULLVP);

	vpp = &speclisth[SPECHASH(nvp_rdev)];
loop:
	for (vp = *vpp; vp; vp = vp->v_specnext) {
		if (nvp_rdev != vp->v_rdev || nvp->v_type != vp->v_type)
			continue;
		/*
		 * Alias, but not in use, so flush it out.
		 */
		if (vp->v_usecount == 0) {
			vgone(vp);
			goto loop;
		}
		if (vget(vp, 1))
			goto loop;
		break;
	}
	if (vp == NULL || vp->v_tag != VT_NON) {
		MALLOC(nvp->v_specinfo, struct specinfo *,
			sizeof(struct specinfo), M_VNODE, M_WAITOK);
		nvp->v_rdev = nvp_rdev;
		nvp->v_hashchain = vpp;
		nvp->v_specnext = *vpp;
		nvp->v_specflags = 0;
		*vpp = nvp;
		if (vp != NULL) {
			nvp->v_flag |= VALIASED;
			vp->v_flag |= VALIASED;
			vput(vp);
		}
		return (NULLVP);
	}
	VOP_UNLOCK(vp);
	vclean(vp, 0);
	vp->v_op = nvp->v_op;
	vp->v_tag = nvp->v_tag;
	nvp->v_type = VNON;
	insmntque(vp, mp);
	return (vp);
}

/*
 * Grab a particular vnode from the free list, increment its
 * reference count and lock it. The vnode lock bit is set the
 * vnode is being eliminated in vgone. The process is awakened
 * when the transition is completed, and an error returned to
 * indicate that the vnode is no longer usable (possibly having
 * been changed to a new file system type).
 */
vget(vp, lockflag)
	register struct vnode *vp;
	int lockflag;
{

	/*
	 * If the vnode is in the process of being cleaned out for
	 * another use, we wait for the cleaning to finish and then
	 * return failure. Cleaning is determined either by checking
	 * that the VXLOCK flag is set, or that the use count is
	 * zero with the back pointer set to show that it has been
	 * removed from the free list by getnewvnode. The VXLOCK
	 * flag may not have been set yet because vclean is blocked in
	 * the VOP_LOCK call waiting for the VOP_INACTIVE to complete.
	 */
	if ((vp->v_flag & VXLOCK) ||
	    (vp->v_usecount == 0 &&
	     vp->v_freelist.tqe_prev == (struct vnode **)0xdeadb)) {
		vp->v_flag |= VXWANT;
		sleep((caddr_t)vp, PINOD);
		return (1);
	}
	if (vp->v_usecount == 0)
		TAILQ_REMOVE(&vnode_free_list, vp, v_freelist);
	vp->v_usecount++;
	if (lockflag)
		VOP_LOCK(vp);
	return (0);
}

/*
 * Vnode reference, just increment the count
 */
void vref(vp)
	struct vnode *vp;
{

	if (vp->v_usecount <= 0)
		panic("vref used where vget required");
	vp->v_usecount++;
}

/*
 * vput(), just unlock and vrele()
 */
void vput(vp)
	register struct vnode *vp;
{

	VOP_UNLOCK(vp);
	vrele(vp);
}

/*
 * Vnode release.
 * If count drops to zero, call inactive routine and return to freelist.
 */
void vrele(vp)
	register struct vnode *vp;
{

#ifdef DIAGNOSTIC
	if (vp == NULL)
		panic("vrele: null vp");
#endif
	vp->v_usecount--;
	if (vp->v_usecount > 0)
		return;
#ifdef DIAGNOSTIC
	if (vp->v_usecount != 0 || vp->v_writecount != 0) {
		vprint("vrele: bad ref count", vp);
		panic("vrele: ref cnt");
	}
#endif
	/*
	 * insert at tail of LRU list
	 */
	TAILQ_INSERT_TAIL(&vnode_free_list, vp, v_freelist);
	VOP_INACTIVE(vp);
}

/*
 * Page or buffer structure gets a reference.
 */
void vhold(vp)
	register struct vnode *vp;
{

	vp->v_holdcnt++;
}

/*
 * Page or buffer structure frees a reference.
 */
void holdrele(vp)
	register struct vnode *vp;
{

	if (vp->v_holdcnt <= 0)
		panic("holdrele: holdcnt");
	vp->v_holdcnt--;
}

/*
 * Remove any vnodes in the vnode table belonging to mount point mp.
 *
 * If MNT_NOFORCE is specified, there should not be any active ones,
 * return error if any are found (nb: this is a user error, not a
 * system error). If MNT_FORCE is specified, detach any active vnodes
 * that are found.
 */
#ifdef DIAGNOSTIC
int busyprt = 0;	/* print out busy vnodes */
struct ctldebug debug1 = { "busyprt", &busyprt };
#endif

vflush(mp, skipvp, flags)
	struct mount *mp;
	struct vnode *skipvp;
	int flags;
{
	register struct vnode *vp, *nvp;
	int busy = 0;

	if ((mp->mnt_flag & MNT_MPBUSY) == 0)
		panic("vflush: not busy");
loop:
	for (vp = mp->mnt_vnodelist.lh_first; vp; vp = nvp) {
		if (vp->v_mount != mp)
			goto loop;
		nvp = vp->v_mntvnodes.le_next;
		/*
		 * Skip over a selected vnode.
		 */
		if (vp == skipvp)
			continue;
		/*
		 * Skip over a vnodes marked VSYSTEM.
		 */
		if ((flags & SKIPSYSTEM) && (vp->v_flag & VSYSTEM))
			continue;
		/*
		 * If WRITECLOSE is set, only flush out regular file
		 * vnodes open for writing.
		 */
		if ((flags & WRITECLOSE) &&
		    (vp->v_writecount == 0 || vp->v_type != VREG))
			continue;
		/*
		 * With v_usecount == 0, all we need to do is clear
		 * out the vnode data structures and we are done.
		 */
		if (vp->v_usecount == 0) {
			vgone(vp);
			continue;
		}
		/*
		 * If FORCECLOSE is set, forcibly close the vnode.
		 * For block or character devices, revert to an
		 * anonymous device. For all other files, just kill them.
		 */
		if (flags & FORCECLOSE) {
			if (vp->v_type != VBLK && vp->v_type != VCHR) {
				vgone(vp);
			} else {
				vclean(vp, 0);
				vp->v_op = spec_vnodeop_p;
				insmntque(vp, (struct mount *)0);
			}
			continue;
		}
#ifdef DIAGNOSTIC
		if (busyprt)
			vprint("vflush: busy vnode", vp);
#endif
		busy++;
	}
	if (busy)
		return (EBUSY);
	return (0);
}

/*
 * Disassociate the underlying file system from a vnode.
 */
void
vclean(vp, flags)
	register struct vnode *vp;
	int flags;
{
	int active;

	/*
	 * Check to see if the vnode is in use.
	 * If so we have to reference it before we clean it out
	 * so that its count cannot fall to zero and generate a
	 * race against ourselves to recycle it.
	 */
	if (active = vp->v_usecount)
		VREF(vp);
	/*
	 * Even if the count is zero, the VOP_INACTIVE routine may still
	 * have the object locked while it cleans it out. The VOP_LOCK
	 * ensures that the VOP_INACTIVE routine is done with its work.
	 * For active vnodes, it ensures that no other activity can
	 * occur while the underlying object is being cleaned out.
	 */
	VOP_LOCK(vp);
	/*
	 * Prevent the vnode from being recycled or
	 * brought into use while we clean it out.
	 */
	if (vp->v_flag & VXLOCK)
		panic("vclean: deadlock");
	vp->v_flag |= VXLOCK;
	/*
	 * Clean out any buffers associated with the vnode.
	 */
	if (flags & DOCLOSE)
		vinvalbuf(vp, V_SAVE, NOCRED, NULL, 0, 0);
	/*
	 * Any other processes trying to obtain this lock must first
	 * wait for VXLOCK to clear, then call the new lock operation.
	 */
	VOP_UNLOCK(vp);
	/*
	 * If purging an active vnode, it must be closed and
	 * deactivated before being reclaimed.
	 */
	if (active) {
		if (flags & DOCLOSE)
			VOP_CLOSE(vp, IO_NDELAY, NOCRED, NULL);
		VOP_INACTIVE(vp);
	}
	/*
	 * Reclaim the vnode.
	 */
	if (VOP_RECLAIM(vp))
		panic("vclean: cannot reclaim");
	if (active)
		vrele(vp);

	/*
	 * Done with purge, notify sleepers of the grim news.
	 */
	vp->v_op = dead_vnodeop_p;
	vp->v_tag = VT_NON;
	vp->v_flag &= ~VXLOCK;
	if (vp->v_flag & VXWANT) {
		vp->v_flag &= ~VXWANT;
		wakeup((caddr_t)vp);
	}
}

/*
 * Eliminate all activity associated with  the requested vnode
 * and with all vnodes aliased to the requested vnode.
 */
void vgoneall(vp)
	register struct vnode *vp;
{
	register struct vnode *vq;

	if (vp->v_flag & VALIASED) {
		/*
		 * If a vgone (or vclean) is already in progress,
		 * wait until it is done and return.
		 */
		if (vp->v_flag & VXLOCK) {
			vp->v_flag |= VXWANT;
			sleep((caddr_t)vp, PINOD);
			return;
		}
		/*
		 * Ensure that vp will not be vgone'd while we
		 * are eliminating its aliases.
		 */
		vp->v_flag |= VXLOCK;
		while (vp->v_flag & VALIASED) {
			for (vq = *vp->v_hashchain; vq; vq = vq->v_specnext) {
				if (vq->v_rdev != vp->v_rdev ||
				    vq->v_type != vp->v_type || vp == vq)
					continue;
				vgone(vq);
				break;
			}
		}
		/*
		 * Remove the lock so that vgone below will
		 * really eliminate the vnode after which time
		 * vgone will awaken any sleepers.
		 */
		vp->v_flag &= ~VXLOCK;
	}
	vgone(vp);
}

/*
 * Eliminate all activity associated with a vnode
 * in preparation for reuse.
 */