Nandfs use of MNT_VNODE_FOREACH

[Konstantin Belousov]

I took a look at removing MNT_VNODE_FOREACH interface in the HEAD,
and apparently we still have one user of the said interface, probably,
due to cross-commits.

Namely, nandfs utilizes the interface. First, it is obsoleted and
is going to be removed. Second, I believe that MNT_VNODE_FOREACH_ACTIVE
would be better choice there, because intent of the loop is to do
something with each dirty vnode, and dirty vnode must be active, because
there are dirty buffers attached to it.

That said, use of vget(LK_RETRY) and immediate check for VI_DOOMED
is not useful, I removed the LK_RETRY from the lockflags. Another issue is
that intent was to avoid sleep for locked vnode, but the check is racy.
I used LK_NOWAIT instead.

Check for mnt_syncer is also usually done as vp->v_type == VNON, but
lets postpone this.

Could someone who uses the filesystem test the patch below, please ?

diff --git a/sys/fs/nandfs/nandfs_segment.c b/sys/fs/nandfs/nandfs_segment.c
index 836bead..a73b7f2 100644
--- a/sys/fs/nandfs/nandfs_segment.c
+++ b/sys/fs/nandfs/nandfs_segment.c
@@ -481,36 +481,20 @@ nandfs_iterate_dirty_vnodes(struct mount *mp, struct nandfs_seginfo *seginfo)
 	int error, lockreq, update;
 
 	td = curthread;
-	lockreq = LK_EXCLUSIVE | LK_INTERLOCK | LK_RETRY;
+	lockreq = LK_EXCLUSIVE | LK_INTERLOCK;
 
-	MNT_ILOCK(mp);
-
-	MNT_VNODE_FOREACH(vp, mp, mvp) {
+	MNT_VNODE_FOREACH_ACTIVE(vp, mp, mvp) {
 		update = 0;
 
 		if (mp->mnt_syncer == vp)
 			continue;
-		if (VOP_ISLOCKED(vp))
-			continue;
-
-		VI_LOCK(vp);
-		MNT_IUNLOCK(mp);
-		if (vp->v_iflag & VI_DOOMED) {
+		if (VOP_ISLOCKED(vp)) {
 			VI_UNLOCK(vp);
-			MNT_ILOCK(mp);
-			continue;
-		}
-
-		if ((error = vget(vp, lockreq, td)) != 0) {
-			MNT_ILOCK(mp);
 			continue;
 		}
 
-		if (vp->v_iflag & VI_DOOMED) {
-			vput(vp);
-			MNT_ILOCK(mp);
+		if (vget(vp, lockreq, td) != 0)
 			continue;
-		}
 
 		nandfs_node = VTON(vp);
 		if (nandfs_node->nn_flags & IN_MODIFIED) {
@@ -532,12 +516,8 @@ nandfs_iterate_dirty_vnodes(struct mount *mp, struct nandfs_seginfo *seginfo)
 
 		if (update)
 			nandfs_node_update(nandfs_node);
-
-		MNT_ILOCK(mp);
 	}
 
-	MNT_IUNLOCK(mp);
-
 	return (0);
 }
 
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