From cfa563a4a4b04303d788302fa6827bfdc841582f Mon Sep 17 00:00:00 2001
From: Zach Brown <zab@versity.com>
Date: Fri, 19 Apr 2019 11:00:02 -0700
Subject: [PATCH] scoutfs: expand the per_task API

This adds some minor functionality to the per_task API for use by the
upcoming offline waiting work.

Add scoutfs_per_task_add_excl() so that a caller can tell if their task
was already put on a per-task list by their caller.

Make scoutfs_per_task_del() return a bool to indicate if the entry was
found on a list and was in fact deleted, or not.

Add scoutfs_per_task_init_entry() for initializing entries that aren't
declared on the stack.

Signed-off-by: Zach Brown <zab@versity.com>
---
 kmod/src/per_task.c | 32 +++++++++++++++++++++++++++++++-
 kmod/src/per_task.h |  5 ++++-
 2 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/kmod/src/per_task.c b/kmod/src/per_task.c
index 24b7f412..c0424e4d 100644
--- a/kmod/src/per_task.c
+++ b/kmod/src/per_task.c
@@ -62,7 +62,27 @@ void scoutfs_per_task_add(struct scoutfs_per_task *pt,
 	spin_unlock(&pt->lock);
 }
 
-void scoutfs_per_task_del(struct scoutfs_per_task *pt,
+/*
+ * Add the entry to the per-task list if the task didn't already have an
+ * entry on the list.  Returns true if the entry was added, false if it
+ * wasn't.
+ */
+bool scoutfs_per_task_add_excl(struct scoutfs_per_task *pt,
+			       struct scoutfs_per_task_entry *ent, void *ptr)
+{
+	if (!scoutfs_per_task_get(pt)) {
+		scoutfs_per_task_add(pt, ent, ptr);
+		return true;
+	}
+
+	return false;
+}
+
+/*
+ * Return true if the entry was found on the list and was deleted,
+ * returns false if the entry wasn't present on a list.
+ */
+bool scoutfs_per_task_del(struct scoutfs_per_task *pt,
 			  struct scoutfs_per_task_entry *ent)
 {
 	BUG_ON(!list_empty(&ent->head) && ent->task != current);
@@ -71,7 +91,10 @@ void scoutfs_per_task_del(struct scoutfs_per_task *pt,
 		spin_lock(&pt->lock);
 		list_del_init(&ent->head);
 		spin_unlock(&pt->lock);
+		return true;
 	}
+
+	return false;
 }
 
 void scoutfs_per_task_init(struct scoutfs_per_task *pt)
@@ -79,3 +102,10 @@ void scoutfs_per_task_init(struct scoutfs_per_task *pt)
 	spin_lock_init(&pt->lock);
 	INIT_LIST_HEAD(&pt->list);
 }
+
+void scoutfs_per_task_init_entry(struct scoutfs_per_task_entry *ent)
+{
+	INIT_LIST_HEAD(&ent->head);
+	ent->task = NULL;
+	ent->ptr = NULL;
+}
diff --git a/kmod/src/per_task.h b/kmod/src/per_task.h
index 6a055391..38616616 100644
--- a/kmod/src/per_task.h
+++ b/kmod/src/per_task.h
@@ -21,8 +21,11 @@ struct scoutfs_per_task_entry {
 void *scoutfs_per_task_get(struct scoutfs_per_task *pt);
 void scoutfs_per_task_add(struct scoutfs_per_task *pt,
 			  struct scoutfs_per_task_entry *ent, void *ptr);
-void scoutfs_per_task_del(struct scoutfs_per_task *pt,
+bool scoutfs_per_task_add_excl(struct scoutfs_per_task *pt,
+			       struct scoutfs_per_task_entry *ent, void *ptr);
+bool scoutfs_per_task_del(struct scoutfs_per_task *pt,
 			  struct scoutfs_per_task_entry *ent);
 void scoutfs_per_task_init(struct scoutfs_per_task *pt);
+void scoutfs_per_task_init_entry(struct scoutfs_per_task_entry *ent);
 
 #endif