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Date:      Tue, 4 Feb 2020 17:12:10 +0000 (UTC)
From:      Konstantin Belousov <kib@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-12@freebsd.org
Subject:   svn commit: r357506 - stable/12/sys/fs/nullfs
Message-ID:  <202002041712.014HCApj067488@repo.freebsd.org>
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Author: kib
Date: Tue Feb  4 17:12:09 2020
New Revision: 357506
URL: https://svnweb.freebsd.org/changeset/base/357506

Log:
  MFC r357199, r357306:
  Save lower root vnode in nullfs mnt data instead of upper.

Modified:
  stable/12/sys/fs/nullfs/null.h
  stable/12/sys/fs/nullfs/null_subr.c
  stable/12/sys/fs/nullfs/null_vfsops.c
Directory Properties:
  stable/12/   (props changed)

Modified: stable/12/sys/fs/nullfs/null.h
==============================================================================
--- stable/12/sys/fs/nullfs/null.h	Tue Feb  4 17:08:00 2020	(r357505)
+++ stable/12/sys/fs/nullfs/null.h	Tue Feb  4 17:12:09 2020	(r357506)
@@ -43,7 +43,7 @@
 
 struct null_mount {
 	struct mount	*nullm_vfs;
-	struct vnode	*nullm_rootvp;	/* Reference to root null_node */
+	struct vnode	*nullm_lowerrootvp;	/* Ref to lower root vnode */
 	uint64_t	nullm_flags;
 };
 

Modified: stable/12/sys/fs/nullfs/null_subr.c
==============================================================================
--- stable/12/sys/fs/nullfs/null_subr.c	Tue Feb  4 17:08:00 2020	(r357505)
+++ stable/12/sys/fs/nullfs/null_subr.c	Tue Feb  4 17:12:09 2020	(r357506)
@@ -256,6 +256,9 @@ null_nodeget(mp, lowervp, vpp)
 	error = insmntque1(vp, mp, null_insmntque_dtr, xp);
 	if (error != 0)
 		return (error);
+	if (lowervp == MOUNTTONULLMOUNT(mp)->nullm_lowerrootvp)
+		vp->v_vflag |= VV_ROOT;
+
 	/*
 	 * Atomically insert our new node into the hash or vget existing 
 	 * if someone else has beaten us to it.

Modified: stable/12/sys/fs/nullfs/null_vfsops.c
==============================================================================
--- stable/12/sys/fs/nullfs/null_vfsops.c	Tue Feb  4 17:08:00 2020	(r357505)
+++ stable/12/sys/fs/nullfs/null_vfsops.c	Tue Feb  4 17:12:09 2020	(r357506)
@@ -74,7 +74,7 @@ static vfs_extattrctl_t	nullfs_extattrctl;
 static int
 nullfs_mount(struct mount *mp)
 {
-	struct vnode *lowerrootvp, *vp;
+	struct vnode *lowerrootvp;
 	struct vnode *nullm_rootvp;
 	struct null_mount *xmp;
 	struct null_node *nn;
@@ -158,36 +158,24 @@ nullfs_mount(struct mount *mp)
 	    M_NULLFSMNT, M_WAITOK | M_ZERO);
 
 	/*
-	 * Save reference to underlying FS
+	 * Save pointer to underlying FS and the reference to the
+	 * lower root vnode.
 	 */
 	xmp->nullm_vfs = lowerrootvp->v_mount;
+	vref(lowerrootvp);
+	xmp->nullm_lowerrootvp = lowerrootvp;
+	mp->mnt_data = xmp;
 
 	/*
-	 * Save reference.  Each mount also holds
-	 * a reference on the root vnode.
+	 * Make sure the node alias worked.
 	 */
-	error = null_nodeget(mp, lowerrootvp, &vp);
-	/*
-	 * Make sure the node alias worked
-	 */
-	if (error) {
+	error = null_nodeget(mp, lowerrootvp, &nullm_rootvp);
+	if (error != 0) {
+		vrele(lowerrootvp);
 		free(xmp, M_NULLFSMNT);
 		return (error);
 	}
 
-	/*
-	 * Keep a held reference to the root vnode.
-	 * It is vrele'd in nullfs_unmount.
-	 */
-	nullm_rootvp = vp;
-	nullm_rootvp->v_vflag |= VV_ROOT;
-	xmp->nullm_rootvp = nullm_rootvp;
-
-	/*
-	 * Unlock the node (either the lower or the alias)
-	 */
-	VOP_UNLOCK(vp, 0);
-
 	if (NULLVPTOLOWERVP(nullm_rootvp)->v_mount->mnt_flag & MNT_LOCAL) {
 		MNT_ILOCK(mp);
 		mp->mnt_flag |= MNT_LOCAL;
@@ -209,7 +197,6 @@ nullfs_mount(struct mount *mp)
 	mp->mnt_kern_flag |= lowerrootvp->v_mount->mnt_kern_flag &
 	    (MNTK_USES_BCACHE | MNTK_NO_IOPF | MNTK_UNMAPPED_BUFS);
 	MNT_IUNLOCK(mp);
-	mp->mnt_data = xmp;
 	vfs_getnewfsid(mp);
 	if ((xmp->nullm_flags & NULLM_CACHE) != 0) {
 		MNT_ILOCK(xmp->nullm_vfs);
@@ -219,6 +206,7 @@ nullfs_mount(struct mount *mp)
 	}
 
 	vfs_mountedfrom(mp, target);
+	vput(nullm_rootvp);
 
 	NULLFSDEBUG("nullfs_mount: lower %s, alias at %s\n",
 		mp->mnt_stat.f_mntfromname, mp->mnt_stat.f_mntonname);
@@ -235,7 +223,7 @@ nullfs_unmount(mp, mntflags)
 {
 	struct null_mount *mntdata;
 	struct mount *ump;
-	int error, flags, rootrefs;
+	int error, flags;
 
 	NULLFSDEBUG("nullfs_unmount: mp = %p\n", (void *)mp);
 
@@ -244,9 +232,9 @@ nullfs_unmount(mp, mntflags)
 	else
 		flags = 0;
 
-	for (rootrefs = 1;; rootrefs = 0) {
+	for (;;) {
 		/* There is 1 extra root vnode reference (nullm_rootvp). */
-		error = vflush(mp, rootrefs, flags, curthread);
+		error = vflush(mp, 0, flags, curthread);
 		if (error)
 			return (error);
 		MNT_ILOCK(mp);
@@ -273,6 +261,7 @@ nullfs_unmount(mp, mntflags)
 		TAILQ_REMOVE(&ump->mnt_uppers, mp, mnt_upper_link);
 		MNT_IUNLOCK(ump);
 	}
+	vrele(mntdata->nullm_lowerrootvp);
 	mp->mnt_data = NULL;
 	free(mntdata, M_NULLFSMNT);
 	return (0);
@@ -285,21 +274,24 @@ nullfs_root(mp, flags, vpp)
 	struct vnode **vpp;
 {
 	struct vnode *vp;
+	struct null_mount *mntdata;
+	int error;
 
-	NULLFSDEBUG("nullfs_root(mp = %p, vp = %p->%p)\n", (void *)mp,
-	    (void *)MOUNTTONULLMOUNT(mp)->nullm_rootvp,
-	    (void *)NULLVPTOLOWERVP(MOUNTTONULLMOUNT(mp)->nullm_rootvp));
+	mntdata = MOUNTTONULLMOUNT(mp);
+	NULLFSDEBUG("nullfs_root(mp = %p, vp = %p)\n", mp,
+	    mntdata->nullm_lowerrootvp);
 
-	/*
-	 * Return locked reference to root.
-	 */
-	vp = MOUNTTONULLMOUNT(mp)->nullm_rootvp;
-	VREF(vp);
-
-	ASSERT_VOP_UNLOCKED(vp, "root vnode is locked");
-	vn_lock(vp, flags | LK_RETRY);
-	*vpp = vp;
-	return 0;
+	error = vget(mntdata->nullm_lowerrootvp, (flags & ~LK_TYPE_MASK) |
+	    LK_EXCLUSIVE, curthread);
+	if (error == 0) {
+		error = null_nodeget(mp, mntdata->nullm_lowerrootvp, &vp);
+		if (error == 0) {
+			if ((flags & LK_TYPE_MASK) == LK_SHARED)
+				vn_lock(vp, LK_DOWNGRADE | LK_RETRY);
+			*vpp = vp;
+		}
+	}
+	return (error);
 }
 
 static int

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