eventpoll: support non-blocking do_epoll_ctl() calls

Also make it available outside of epoll, along with the helper that
decides if we need to copy the passed in epoll_event.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index cd848e8..b041b66 100644 (file)
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -354,12 +354,6 @@ static inline struct epitem *ep_item_from_epqueue(poll_table *p)
        return container_of(p, struct ep_pqueue, pt)->epi;
 }
 
-/* Tells if the epoll_ctl(2) operation needs an event copy from userspace */
-static inline int ep_op_has_event(int op)
-{
-       return op != EPOLL_CTL_DEL;
-}
-
 /* Initialize the poll safe wake up structure */
 static void ep_nested_calls_init(struct nested_calls *ncalls)
 {
@@ -2074,7 +2068,20 @@ SYSCALL_DEFINE1(epoll_create, int, size)
        return do_epoll_create(0);
 }
 
-static int do_epoll_ctl(int epfd, int op, int fd, struct epoll_event *epds)
+static inline int epoll_mutex_lock(struct mutex *mutex, int depth,
+                                  bool nonblock)
+{
+       if (!nonblock) {
+               mutex_lock_nested(mutex, depth);
+               return 0;
+       }
+       if (mutex_trylock(mutex))
+               return 0;
+       return -EAGAIN;
+}
+
+int do_epoll_ctl(int epfd, int op, int fd, struct epoll_event *epds,
+                bool nonblock)
 {
        int error;
        int full_check = 0;
@@ -2145,13 +2152,17 @@ static int do_epoll_ctl(int epfd, int op, int fd, struct epoll_event *epds)
         * deep wakeup paths from forming in parallel through multiple
         * EPOLL_CTL_ADD operations.
         */
-       mutex_lock_nested(&ep->mtx, 0);
+       error = epoll_mutex_lock(&ep->mtx, 0, nonblock);
+       if (error)
+               goto error_tgt_fput;
        if (op == EPOLL_CTL_ADD) {
                if (!list_empty(&f.file->f_ep_links) ||
                                                is_file_epoll(tf.file)) {
-                       full_check = 1;
                        mutex_unlock(&ep->mtx);
-                       mutex_lock(&epmutex);
+                       error = epoll_mutex_lock(&epmutex, 0, nonblock);
+                       if (error)
+                               goto error_tgt_fput;
+                       full_check = 1;
                        if (is_file_epoll(tf.file)) {
                                error = -ELOOP;
                                if (ep_loop_check(ep, tf.file) != 0) {
@@ -2161,10 +2172,19 @@ static int do_epoll_ctl(int epfd, int op, int fd, struct epoll_event *epds)
                        } else
                                list_add(&tf.file->f_tfile_llink,
                                                        &tfile_check_list);
-                       mutex_lock_nested(&ep->mtx, 0);
+                       error = epoll_mutex_lock(&ep->mtx, 0, nonblock);
+                       if (error) {
+out_del:
+                               list_del(&tf.file->f_tfile_llink);
+                               goto error_tgt_fput;
+                       }
                        if (is_file_epoll(tf.file)) {
                                tep = tf.file->private_data;
-                               mutex_lock_nested(&tep->mtx, 1);
+                               error = epoll_mutex_lock(&tep->mtx, 1, nonblock);
+                               if (error) {
+                                       mutex_unlock(&ep->mtx);
+                                       goto out_del;
+                               }
                        }
                }
        }
@@ -2233,7 +2253,7 @@ SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd,
            copy_from_user(&epds, event, sizeof(struct epoll_event)))
                return -EFAULT;
 
-       return do_epoll_ctl(epfd, op, fd, &epds);
+       return do_epoll_ctl(epfd, op, fd, &epds, false);
 }
 
 /*

diff --git a/include/linux/eventpoll.h b/include/linux/eventpoll.h
index bc6d79b..8f000fa 100644 (file)
--- a/include/linux/eventpoll.h
+++ b/include/linux/eventpoll.h
@@ -61,6 +61,15 @@ static inline void eventpoll_release(struct file *file)
        eventpoll_release_file(file);
 }
 
+int do_epoll_ctl(int epfd, int op, int fd, struct epoll_event *epds,
+                bool nonblock);
+
+/* Tells if the epoll_ctl(2) operation needs an event copy from userspace */
+static inline int ep_op_has_event(int op)
+{
+       return op != EPOLL_CTL_DEL;
+}
+
 #else
 
 static inline void eventpoll_init_file(struct file *file) {}