linux-kernel - [RFC PATCH 14/27] ep_scan_ready

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Message-Id: <20201004023929.2740074-14-viro@ZenIV.linux.org.uk>
Date:   Sun,  4 Oct 2020 03:39:16 +0100
From:   Al Viro <viro@...IV.linux.org.uk>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Marc Zyngier <maz@...nel.org>
Subject: [RFC PATCH 14/27] ep_scan_ready_list(): prepare to splitup

From: Al Viro <viro@...iv.linux.org.uk>

take the stuff done before and after the callback into separate helpers

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 fs/eventpoll.c | 63 +++++++++++++++++++++++++++++++++-------------------------
 1 file changed, 36 insertions(+), 27 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index e971e3ace557..eb012fdc152e 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -561,28 +561,10 @@ static inline void ep_pm_stay_awake_rcu(struct epitem *epi)
 	rcu_read_unlock();
 }
 
-/**
- * ep_scan_ready_list - Scans the ready list in a way that makes possible for
- *                      the scan code, to call f_op->poll(). Also allows for
- *                      O(NumReady) performance.
- *
- * @ep: Pointer to the epoll private data structure.
- * @sproc: Pointer to the scan callback.
- * @priv: Private opaque data passed to the @sproc callback.
- * @depth: The current depth of recursive f_op->poll calls.
- * @ep_locked: caller already holds ep->mtx
- *
- * Returns: The same integer error code returned by the @sproc callback.
- */
-static __poll_t ep_scan_ready_list(struct eventpoll *ep,
-			      __poll_t (*sproc)(struct eventpoll *,
-					   struct list_head *, void *),
-			      void *priv, int depth, bool ep_locked)
+static void ep_start_scan(struct eventpoll *ep,
+			  int depth, bool ep_locked,
+			  struct list_head *txlist)
 {
-	__poll_t res;
-	struct epitem *epi, *nepi;
-	LIST_HEAD(txlist);
-
 	lockdep_assert_irqs_enabled();
 
 	/*
@@ -602,14 +584,16 @@ static __poll_t ep_scan_ready_list(struct eventpoll *ep,
 	 * in a lockless way.
 	 */
 	write_lock_irq(&ep->lock);
-	list_splice_init(&ep->rdllist, &txlist);
+	list_splice_init(&ep->rdllist, txlist);
 	WRITE_ONCE(ep->ovflist, NULL);
 	write_unlock_irq(&ep->lock);
+}
 
-	/*
-	 * Now call the callback function.
-	 */
-	res = (*sproc)(ep, &txlist, priv);
+static void ep_done_scan(struct eventpoll *ep,
+			 int depth, bool ep_locked,
+			 struct list_head *txlist)
+{
+	struct epitem *epi, *nepi;
 
 	write_lock_irq(&ep->lock);
 	/*
@@ -644,13 +628,38 @@ static __poll_t ep_scan_ready_list(struct eventpoll *ep,
 	/*
 	 * Quickly re-inject items left on "txlist".
 	 */
-	list_splice(&txlist, &ep->rdllist);
+	list_splice(txlist, &ep->rdllist);
 	__pm_relax(ep->ws);
 	write_unlock_irq(&ep->lock);
 
 	if (!ep_locked)
 		mutex_unlock(&ep->mtx);
+}
 
+/**
+ * ep_scan_ready_list - Scans the ready list in a way that makes possible for
+ *                      the scan code, to call f_op->poll(). Also allows for
+ *                      O(NumReady) performance.
+ *
+ * @ep: Pointer to the epoll private data structure.
+ * @sproc: Pointer to the scan callback.
+ * @priv: Private opaque data passed to the @sproc callback.
+ * @depth: The current depth of recursive f_op->poll calls.
+ * @ep_locked: caller already holds ep->mtx
+ *
+ * Returns: The same integer error code returned by the @sproc callback.
+ */
+static __poll_t ep_scan_ready_list(struct eventpoll *ep,
+			      __poll_t (*sproc)(struct eventpoll *,
+					   struct list_head *, void *),
+			      void *priv, int depth, bool ep_locked)
+{
+	__poll_t res;
+	LIST_HEAD(txlist);
+
+	ep_start_scan(ep, depth, ep_locked, &txlist);
+	res = (*sproc)(ep, &txlist, priv);
+	ep_done_scan(ep, depth, ep_locked, &txlist);
 	return res;
 }
 
-- 
2.11.0