eventpoll: relocate KCMP helpers near compat syscalls

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>
Link: https://patch.msgid.link/20260424-work-epoll-rework-v1-9-249ed00a20f3@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 1fe9f1772a28c24eafe310c72c662da642de5402..fde2396342b64d06cac3e844b0ce41e59262619a 100644 (file)
--- 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,