From febe4e6e91057701646038ee282ff0d56df65c5d Mon Sep 17 00:00:00 2001
From: kib <kib@FreeBSD.org>
Date: Wed, 1 Jul 2015 06:54:25 +0000
Subject: MFC r284495: Keep a vnode which is freed but still owing
 inactivation, on the active list. This closes a race where such vnode is not
 msync-ed until reboot.

---
 sys/kern/vfs_subr.c      | 46 +++++++++++++++++++++++++++-------------------
 sys/ufs/ffs/ffs_vfsops.c | 14 +++++++++++---
 2 files changed, 38 insertions(+), 22 deletions(-)

(limited to 'sys')

diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index a03d516..8de6dcf 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -173,6 +173,11 @@ static int reassignbufcalls;
 SYSCTL_INT(_vfs, OID_AUTO, reassignbufcalls, CTLFLAG_RW, &reassignbufcalls, 0,
     "Number of calls to reassignbuf");
 
+static u_long free_owe_inact;
+SYSCTL_ULONG(_vfs, OID_AUTO, free_owe_inact, CTLFLAG_RD, &free_owe_inact, 0,
+    "Number of times free vnodes kept on active list due to VFS "
+    "owing inactivation");
+
 /*
  * Cache for the mount type id assigned to NFS.  This is used for
  * special checks in nfs/nfs_nqlease.c and vm/vnode_pager.c.
@@ -2361,11 +2366,8 @@ vholdl(struct vnode *vp)
 	CTR2(KTR_VFS, "%s: vp %p", __func__, vp);
 #ifdef INVARIANTS
 	/* getnewvnode() calls v_incr_usecount() without holding interlock. */
-	if (vp->v_type != VNON || vp->v_data != NULL) {
+	if (vp->v_type != VNON || vp->v_data != NULL)
 		ASSERT_VI_LOCKED(vp, "vholdl");
-		VNASSERT(vp->v_holdcnt > 0 || (vp->v_iflag & VI_FREE) != 0,
-		    vp, ("vholdl: free vnode is held"));
-	}
 #endif
 	vp->v_holdcnt++;
 	if ((vp->v_iflag & VI_FREE) == 0)
@@ -2434,23 +2436,29 @@ vdropl(struct vnode *vp)
 		VNASSERT(vp->v_holdcnt == 0, vp,
 		    ("vdropl: freeing when we shouldn't"));
 		active = vp->v_iflag & VI_ACTIVE;
-		vp->v_iflag &= ~VI_ACTIVE;
-		mp = vp->v_mount;
-		mtx_lock(&vnode_free_list_mtx);
-		if (active) {
-			TAILQ_REMOVE(&mp->mnt_activevnodelist, vp,
-			    v_actfreelist);
-			mp->mnt_activevnodelistsize--;
-		}
-		if (vp->v_iflag & VI_AGE) {
-			TAILQ_INSERT_HEAD(&vnode_free_list, vp, v_actfreelist);
+		if ((vp->v_iflag & VI_OWEINACT) == 0) {
+			vp->v_iflag &= ~VI_ACTIVE;
+			mp = vp->v_mount;
+			mtx_lock(&vnode_free_list_mtx);
+			if (active) {
+				TAILQ_REMOVE(&mp->mnt_activevnodelist, vp,
+				    v_actfreelist);
+				mp->mnt_activevnodelistsize--;
+			}
+			if (vp->v_iflag & VI_AGE) {
+				TAILQ_INSERT_HEAD(&vnode_free_list, vp,
+				    v_actfreelist);
+			} else {
+				TAILQ_INSERT_TAIL(&vnode_free_list, vp,
+				    v_actfreelist);
+			}
+			freevnodes++;
+			vp->v_iflag &= ~VI_AGE;
+			vp->v_iflag |= VI_FREE;
+			mtx_unlock(&vnode_free_list_mtx);
 		} else {
-			TAILQ_INSERT_TAIL(&vnode_free_list, vp, v_actfreelist);
+			atomic_add_long(&free_owe_inact, 1);
 		}
-		freevnodes++;
-		vp->v_iflag &= ~VI_AGE;
-		vp->v_iflag |= VI_FREE;
-		mtx_unlock(&vnode_free_list_mtx);
 		VI_UNLOCK(vp);
 		return;
 	}
diff --git a/sys/ufs/ffs/ffs_vfsops.c b/sys/ufs/ffs/ffs_vfsops.c
index 0bcb084..53d85bd 100644
--- a/sys/ufs/ffs/ffs_vfsops.c
+++ b/sys/ufs/ffs/ffs_vfsops.c
@@ -1409,6 +1409,14 @@ ffs_statfs(mp, sbp)
 	return (0);
 }
 
+static bool
+sync_doupdate(struct inode *ip)
+{
+
+	return ((ip->i_flag & (IN_ACCESS | IN_CHANGE | IN_MODIFIED |
+	    IN_UPDATE)) != 0);
+}
+
 /*
  * For a lazy sync, we only care about access times, quotas and the
  * superblock.  Other filesystem changes are already converted to
@@ -1442,15 +1450,15 @@ ffs_sync_lazy(mp)
 		 * Test also all the other timestamp flags too, to pick up
 		 * any other cases that could be missed.
 		 */
-		if ((ip->i_flag & (IN_ACCESS | IN_CHANGE | IN_MODIFIED |
-		    IN_UPDATE)) == 0) {
+		if (!sync_doupdate(ip) && (vp->v_iflag & VI_OWEINACT) == 0) {
 			VI_UNLOCK(vp);
 			continue;
 		}
 		if ((error = vget(vp, LK_EXCLUSIVE | LK_NOWAIT | LK_INTERLOCK,
 		    td)) != 0)
 			continue;
-		error = ffs_update(vp, 0);
+		if (sync_doupdate(ip))
+			error = ffs_update(vp, 0);
 		if (error != 0)
 			allerror = error;
 		vput(vp);
-- 
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