do_pollfd(): convert to CLASS(fd)

lift setting ->revents into the caller, so that failure exits (including
the early one) would be plain returns.

We need the scope of our struct fd to end before the store to ->revents,
since that's shared with the failure exits prior to the point where we
can do fdget().

Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/select.c b/fs/select.c
index b41e2d651cc1b519c263077a84fec0dc7a736479..e223d1fe9d5541bc51655604166a627cd24e4610 100644 (file)
--- a/fs/select.c
+++ b/fs/select.c
@@ -855,15 +855,14 @@ static inline __poll_t do_pollfd(struct pollfd *pollfd, poll_table *pwait,
                                     __poll_t busy_flag)
 {
        int fd = pollfd->fd;
-       __poll_t mask = 0, filter;
-       struct fd f;
+       __poll_t mask, filter;
 
        if (fd < 0)
-               goto out;
-       mask = EPOLLNVAL;
-       f = fdget(fd);
-       if (!fd_file(f))
-               goto out;
+               return 0;
+
+       CLASS(fd, f)(fd);
+       if (fd_empty(f))
+               return EPOLLNVAL;
 
        /* userland u16 ->events contains POLL... bitmap */
        filter = demangle_poll(pollfd->events) | EPOLLERR | EPOLLHUP;
@@ -871,13 +870,7 @@ static inline __poll_t do_pollfd(struct pollfd *pollfd, poll_table *pwait,
        mask = vfs_poll(fd_file(f), pwait);
        if (mask & busy_flag)
                *can_busy_poll = true;
-       mask &= filter;         /* Mask out unneeded events. */
-       fdput(f);
-
-out:
-       /* ... and so does ->revents */
-       pollfd->revents = mangle_poll(mask);
-       return mask;
+       return mask & filter;           /* Mask out unneeded events. */
 }
 
 static int do_poll(struct poll_list *list, struct poll_wqueues *wait,
@@ -909,6 +902,7 @@ static int do_poll(struct poll_list *list, struct poll_wqueues *wait,
                        pfd = walk->entries;
                        pfd_end = pfd + walk->len;
                        for (; pfd != pfd_end; pfd++) {
+                               __poll_t mask;
                                /*
                                 * Fish for events. If we found one, record it
                                 * and kill poll_table->_qproc, so we don't
@@ -916,8 +910,9 @@ static int do_poll(struct poll_list *list, struct poll_wqueues *wait,
                                 * this. They'll get immediately deregistered
                                 * when we break out and return.
                                 */
-                               if (do_pollfd(pfd, pt, &can_busy_loop,
-                                             busy_flag)) {
+                               mask = do_pollfd(pfd, pt, &can_busy_loop, busy_flag);
+                               pfd->revents = mangle_poll(mask);
+                               if (mask) {
                                        count++;
                                        pt->_qproc = NULL;
                                        /* found something, stop busy polling */