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Date:      Thu, 1 Aug 2019 14:40:37 +0000 (UTC)
From:      Konstantin Belousov <kib@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r350504 - head/sys/fs/unionfs
Message-ID:  <201908011440.x71Eeb8b041781@repo.freebsd.org>
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Author: kib
Date: Thu Aug  1 14:40:37 2019
New Revision: 350504
URL: https://svnweb.freebsd.org/changeset/base/350504

Log:
  Try to decrease the number of bugs in unionfs after the VV_TEXT flag removal.
  
  - Provide unionfs_add_writecount() which passes the writecount to the
    lower or upper vnode as appropriate.
  - In unionfs VOP_RECLAIM() implementation, annulate unionfs
    writecounts from upper or lower vnode.  It is not clear that it is
    always correct to remove the all references from either lower or
    upper vnode, but we currently do not track which vnode get how many
    refs anyway.
  
  Reported and tested by:	t_uemura@macome.co.jp
  MFC after:	1 week
  Sponsored by:	The FreeBSD Foundation

Modified:
  head/sys/fs/unionfs/union_subr.c
  head/sys/fs/unionfs/union_vnops.c

Modified: head/sys/fs/unionfs/union_subr.c
==============================================================================
--- head/sys/fs/unionfs/union_subr.c	Thu Aug  1 14:39:26 2019	(r350503)
+++ head/sys/fs/unionfs/union_subr.c	Thu Aug  1 14:40:37 2019	(r350504)
@@ -349,6 +349,13 @@ unionfs_noderem(struct vnode *vp, struct thread *td)
 	vp->v_vnlock = &(vp->v_lock);
 	vp->v_data = NULL;
 	vp->v_object = NULL;
+	if (vp->v_writecount > 0) {
+		if (uvp != NULL)
+			VOP_ADD_WRITECOUNT(uvp, -vp->v_writecount);
+		else if (lvp != NULL)
+			VOP_ADD_WRITECOUNT(lvp, -vp->v_writecount);
+	} else if (vp->v_writecount < 0)
+		vp->v_writecount = 0;
 	VI_UNLOCK(vp);
 
 	if (lvp != NULLVP)

Modified: head/sys/fs/unionfs/union_vnops.c
==============================================================================
--- head/sys/fs/unionfs/union_vnops.c	Thu Aug  1 14:39:26 2019	(r350503)
+++ head/sys/fs/unionfs/union_vnops.c	Thu Aug  1 14:40:37 2019	(r350504)
@@ -2511,6 +2511,33 @@ unionfs_vptofh(struct vop_vptofh_args *ap)
 	return (EOPNOTSUPP);
 }
 
+static int
+unionfs_add_writecount(struct vop_add_writecount_args *ap)
+{
+	struct vnode *tvp, *vp;
+	struct unionfs_node *unp;
+	int error;
+
+	vp = ap->a_vp;
+	unp = VTOUNIONFS(vp);
+	tvp = unp->un_uppervp != NULL ? unp->un_uppervp : unp->un_lowervp;
+	VI_LOCK(vp);
+	/* text refs are bypassed to lowervp */
+	VNASSERT(vp->v_writecount >= 0, vp, ("wrong null writecount"));
+	VNASSERT(vp->v_writecount + ap->a_inc >= 0, vp,
+	    ("wrong writecount inc %d", ap->a_inc));
+	if (tvp != NULL)
+		error = VOP_ADD_WRITECOUNT(tvp, ap->a_inc);
+	else if (vp->v_writecount < 0)
+		error = ETXTBSY;
+	else
+		error = 0;
+	if (error == 0)
+		vp->v_writecount += ap->a_inc;
+	VI_UNLOCK(vp);
+	return (error);
+}
+
 struct vop_vector unionfs_vnodeops = {
 	.vop_default =		&default_vnodeops,
 
@@ -2559,4 +2586,5 @@ struct vop_vector unionfs_vnodeops = {
 	.vop_whiteout =		unionfs_whiteout,
 	.vop_write =		unionfs_write,
 	.vop_vptofh =		unionfs_vptofh,
+	.vop_add_writecount =	unionfs_add_writecount,
 };

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