nfsd: simplify the delayed disposal list code

When queueing a dispose list to the appropriate "freeme" lists, it
pointlessly queues the objects one at a time to an intermediate list.

Remove a few helpers and just open code a list_move to make it more
clear and efficient. Better document the resulting functions with
kerneldoc comments.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

Author: jtlayton

fs/nfsd/filecache.c

@@ -402,49 +402,26 @@ nfsd_file_dispose_list(struct list_head *dispose)
 	}
 }
 
-static void
-nfsd_file_list_remove_disposal(struct list_head *dst,
-		struct nfsd_fcache_disposal *l)
-{
-	spin_lock(&l->lock);
-	list_splice_init(&l->freeme, dst);
-	spin_unlock(&l->lock);
-}
-
-static void
-nfsd_file_list_add_disposal(struct list_head *files, struct net *net)
-{
-	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
-	struct nfsd_fcache_disposal *l = nn->fcache_disposal;
-
-	spin_lock(&l->lock);
-	list_splice_tail_init(files, &l->freeme);
-	spin_unlock(&l->lock);
-	queue_work(nfsd_filecache_wq, &l->work);
-}
-
-static void
-nfsd_file_list_add_pernet(struct list_head *dst, struct list_head *src,
-		struct net *net)
-{
-	struct nfsd_file *nf, *tmp;
-
-	list_for_each_entry_safe(nf, tmp, src, nf_lru) {
-		if (nf->nf_net == net)
-			list_move_tail(&nf->nf_lru, dst);
-	}
-}
-
+/**
+ * nfsd_file_dispose_list_delayed - move list of dead files to net's freeme list
+ * @dispose: list of nfsd_files to be disposed
+ *
+ * Transfers each file to the "freeme" list for its nfsd_net, to eventually
+ * be disposed of by the per-net garbage collector.
+ */
 static void
 nfsd_file_dispose_list_delayed(struct list_head *dispose)
 {
-	LIST_HEAD(list);
-	struct nfsd_file *nf;
-
 	while(!list_empty(dispose)) {
-		nf = list_first_entry(dispose, struct nfsd_file, nf_lru);
-		nfsd_file_list_add_pernet(&list, dispose, nf->nf_net);
-		nfsd_file_list_add_disposal(&list, nf->nf_net);
+		struct nfsd_file *nf = list_first_entry(dispose,
+						struct nfsd_file, nf_lru);
+		struct nfsd_net *nn = net_generic(nf->nf_net, nfsd_net_id);
+		struct nfsd_fcache_disposal *l = nn->fcache_disposal;
+
+		spin_lock(&l->lock);
+		list_move_tail(&nf->nf_lru, &l->freeme);
+		spin_unlock(&l->lock);
+		queue_work(nfsd_filecache_wq, &l->work);
 	}
 }
 
@@ -665,8 +642,8 @@ nfsd_file_close_inode_sync(struct inode *inode)
  * nfsd_file_delayed_close - close unused nfsd_files
  * @work: dummy
  *
- * Walk the LRU list and destroy any entries that have not been used since
- * the last scan.
+ * Scrape the freeme list for this nfsd_net, and then dispose of them
+ * all.
  */
 static void
 nfsd_file_delayed_close(struct work_struct *work)
@@ -675,7 +652,10 @@ nfsd_file_delayed_close(struct work_struct *work)
 	struct nfsd_fcache_disposal *l = container_of(work,
 			struct nfsd_fcache_disposal, work);
 
-	nfsd_file_list_remove_disposal(&head, l);
+	spin_lock(&l->lock);
+	list_splice_init(&l->freeme, &head);
+	spin_unlock(&l->lock);
+
 	nfsd_file_dispose_list(&head);
 }