[PATCH 09/17] eventpoll: relocate KCMP helpers near compat syscalls

[Christian Brauner <brauner@kernel.org>]

ep_find_tfd() and get_epoll_tfile_raw_ptr() are only used when
CONFIG_KCMP=y. They implement the lookup side of the kcmp(2)
KCMP_EPOLL_TFD query. The helpers currently live between ep_find()
and ep_poll_callback(), interrupting the run of hot-path code
(callback, wait-queue setup, path check, insert, modify, send_events,
poll) with a feature-gated block.

Move the #ifdef CONFIG_KCMP block next to #ifdef CONFIG_COMPAT, which
is also a peripheral ABI extension. Hot-path code becomes a
contiguous span, and the userspace-adjacent extensions cluster at the
end of the file just before eventpoll_init().

Pure code movement; diff is 44 removed and 44 added, all within one
block. No functional change.

Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---
 fs/eventpoll.c | 88 +++++++++++++++++++++++++++++-----------------------------
 1 file changed, 44 insertions(+), 44 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 1fe9f1772a28..fde2396342b6 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1399,50 +1399,6 @@ static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd)
 	return epir;
 }
 
-#ifdef CONFIG_KCMP
-static struct epitem *ep_find_tfd(struct eventpoll *ep, int tfd, unsigned long toff)
-{
-	struct rb_node *rbp;
-	struct epitem *epi;
-
-	for (rbp = rb_first_cached(&ep->rbr); rbp; rbp = rb_next(rbp)) {
-		epi = rb_entry(rbp, struct epitem, rbn);
-		if (epi->ffd.fd == tfd) {
-			if (toff == 0)
-				return epi;
-			else
-				toff--;
-		}
-		cond_resched();
-	}
-
-	return NULL;
-}
-
-struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd,
-				     unsigned long toff)
-{
-	struct file *file_raw;
-	struct eventpoll *ep;
-	struct epitem *epi;
-
-	if (!is_file_epoll(file))
-		return ERR_PTR(-EINVAL);
-
-	ep = file->private_data;
-
-	mutex_lock(&ep->mtx);
-	epi = ep_find_tfd(ep, tfd, toff);
-	if (epi)
-		file_raw = epi->ffd.file;
-	else
-		file_raw = ERR_PTR(-ENOENT);
-	mutex_unlock(&ep->mtx);
-
-	return file_raw;
-}
-#endif /* CONFIG_KCMP */
-
 /*
  * This is the callback that is passed to the wait queue wakeup
  * mechanism. It is called by the stored file descriptors when they
@@ -2733,6 +2689,50 @@ SYSCALL_DEFINE6(epoll_pwait2, int, epfd, struct epoll_event __user *, events,
 			      sigmask, sigsetsize);
 }
 
+#ifdef CONFIG_KCMP
+static struct epitem *ep_find_tfd(struct eventpoll *ep, int tfd, unsigned long toff)
+{
+	struct rb_node *rbp;
+	struct epitem *epi;
+
+	for (rbp = rb_first_cached(&ep->rbr); rbp; rbp = rb_next(rbp)) {
+		epi = rb_entry(rbp, struct epitem, rbn);
+		if (epi->ffd.fd == tfd) {
+			if (toff == 0)
+				return epi;
+			else
+				toff--;
+		}
+		cond_resched();
+	}
+
+	return NULL;
+}
+
+struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd,
+				     unsigned long toff)
+{
+	struct file *file_raw;
+	struct eventpoll *ep;
+	struct epitem *epi;
+
+	if (!is_file_epoll(file))
+		return ERR_PTR(-EINVAL);
+
+	ep = file->private_data;
+
+	mutex_lock(&ep->mtx);
+	epi = ep_find_tfd(ep, tfd, toff);
+	if (epi)
+		file_raw = epi->ffd.file;
+	else
+		file_raw = ERR_PTR(-ENOENT);
+	mutex_unlock(&ep->mtx);
+
+	return file_raw;
+}
+#endif /* CONFIG_KCMP */
+
 #ifdef CONFIG_COMPAT
 static int do_compat_epoll_pwait(int epfd, struct epoll_event __user *events,
 				 int maxevents, struct timespec64 *timeout,

-- 
2.47.3