Helpers for lengths-from-number and number-from-lengths calculations.
Among them:
ep_polled_by_user()
- returns true if epoll was created with EPOLL_USERPOLL
ep_user_ring_events_available()
- returns true if there is something in user ring buffer
Signed-off-by: Roman Penyaev <rpenyaev@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Davidlohr Bueso <dbueso@xxxxxxx>
Cc: Jason Baron <jbaron@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Andrea Parri <andrea.parri@xxxxxxxxxxxxxxxxxxxx>
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
fs/eventpoll.c | 59 ++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 59 insertions(+)
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 9ec682b6488f..ae288f62aa4c 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -438,6 +438,65 @@ static void ep_nested_calls_init(struct nested_calls *ncalls)
spin_lock_init(&ncalls->lock);
}
+static inline unsigned int to_items_length(unsigned int nr)
+{
+ struct eventpoll *ep;
+
+ return (sizeof(*ep->user_header) +
+ (nr << ilog2(sizeof(ep->user_header->items[0]))));
+}
+
+static inline unsigned int to_index_length(unsigned int nr)
+{
+ struct eventpoll *ep;
+
+ return nr << ilog2(sizeof(*ep->user_index));
+}
+
+static inline unsigned int to_items_bm_length(unsigned int nr)
+{
+ return ALIGN(nr, 8) >> 3;
+}
+
+static inline unsigned int to_items_nr(unsigned int len)
+{
+ struct eventpoll *ep;
+
+ return (len - sizeof(*ep->user_header)) >>
+ ilog2(sizeof(ep->user_header->items[0]));
+}
+
+static inline unsigned int to_items_bm_nr(unsigned int len)
+{
+ return len << 3;
+}
+
+static inline unsigned int ep_max_items_nr(struct eventpoll *ep)
+{
+ return to_items_nr(ep->header_length);
+}
+
+static inline unsigned int ep_max_index_nr(struct eventpoll *ep)
+{
+ return ep->index_length >> ilog2(sizeof(*ep->user_index));
+}
+
+static inline unsigned int ep_max_items_bm_nr(struct eventpoll *ep)
+{
+ return to_items_bm_nr(ep->items_bm_length);
+}
+
+static inline bool ep_polled_by_user(struct eventpoll *ep)
+{
+ return !!ep->user_header;
+}
+
+static inline bool ep_user_ring_events_available(struct eventpoll *ep)
+{
+ return ep_polled_by_user(ep) &&
+ ep->user_header->head != ep->user_header->tail;
+}
+
/**
* ep_events_available - Checks if ready events might be available.
*
--
2.19.1
