fs: add new vfs_poll and file_can_poll helpers

These abstract out calls to the poll method in preparation for changes
in how we poll.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

9 files changed, 32 insertions, 38 deletions

diff --git a/drivers/staging/comedi/drivers/serial2002.c b/drivers/staging/comedi/drivers/serial2002.c
index b3f3b4a201af..5471b2212a62 100644
--- a/drivers/staging/comedi/drivers/serial2002.c
+++ b/drivers/staging/comedi/drivers/serial2002.c
@@ -113,7 +113,7 @@ static void serial2002_tty_read_poll_wait(struct file *f, int timeout)
                 long elapsed;
                 __poll_t mask;
 
-                mask = f->f_op->poll(f, &table.pt);
+                mask = vfs_poll(f, &table.pt);
                 if (mask & (EPOLLRDNORM | EPOLLRDBAND | EPOLLIN |
                             EPOLLHUP | EPOLLERR)) {
                         break;
@@ -136,7 +136,7 @@ static int serial2002_tty_read(struct file *f, int timeout)
 
         result = -1;
         if (!IS_ERR(f)) {
-                if (f->f_op->poll) {
+                if (file_can_poll(f)) {
                         serial2002_tty_read_poll_wait(f, timeout);
 
                         if (kernel_read(f, &ch, 1, &pos) == 1)
diff --git a/drivers/vfio/virqfd.c b/drivers/vfio/virqfd.c
index 085700f1be10..2a1be859ee71 100644
--- a/drivers/vfio/virqfd.c
+++ b/drivers/vfio/virqfd.c
@@ -166,7 +166,7 @@ int vfio_virqfd_enable(void *opaque,
         init_waitqueue_func_entry(&virqfd->wait, virqfd_wakeup);
         init_poll_funcptr(&virqfd->pt, virqfd_ptable_queue_proc);
 
-        events = irqfd.file->f_op->poll(irqfd.file, &virqfd->pt);
+        events = vfs_poll(irqfd.file, &virqfd->pt);
 
         /*
          * Check if there was an event already pending on the eventfd
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index f3bd8e941224..f6022881f147 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -208,7 +208,7 @@ int vhost_poll_start(struct vhost_poll *poll, struct file *file)
         if (poll->wqh)
                 return 0;
 
-        mask = file->f_op->poll(file, &poll->table);
+        mask = vfs_poll(file, &poll->table);
         if (mask)
                 vhost_poll_wakeup(&poll->wait, 0, 0, poll_to_key(mask));
         if (mask & EPOLLERR) {
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 602ca4285b2e..67db22fe99c5 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -884,8 +884,7 @@ static __poll_t ep_item_poll(const struct epitem *epi, poll_table *pt,
 
         pt->_key = epi->event.events;
         if (!is_file_epoll(epi->ffd.file))
-                return epi->ffd.file->f_op->poll(epi->ffd.file, pt) &
-                       epi->event.events;
+                return vfs_poll(epi->ffd.file, pt) & epi->event.events;
 
         ep = epi->ffd.file->private_data;
         poll_wait(epi->ffd.file, &ep->poll_wait, pt);
@@ -2025,7 +2024,7 @@ SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd,
 
         /* The target file descriptor must support poll */
         error = -EPERM;
-        if (!tf.file->f_op->poll)
+        if (!file_can_poll(tf.file))
                 goto error_tgt_fput;
 
         /* Check if EPOLLWAKEUP is allowed */
diff --git a/fs/select.c b/fs/select.c
index 25da26253485..e30def680b2e 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -502,14 +502,10 @@ static int do_select(int n, fd_set_bits *fds, struct timespec64 *end_time)
                                         continue;
                                 f = fdget(i);
                                 if (f.file) {
-                                        const struct file_operations *f_op;
-                                        f_op = f.file->f_op;
-                                        mask = DEFAULT_POLLMASK;
-                                        if (f_op->poll) {
-                                                wait_key_set(wait, in, out,
-                                                             bit, busy_flag);
-                                                mask = (*f_op->poll)(f.file, wait);
-                                        }
+                                        wait_key_set(wait, in, out, bit,
+                                                     busy_flag);
+                                        mask = vfs_poll(f.file, wait);
+
                                         fdput(f);
                                         if ((mask & POLLIN_SET) && (in & bit)) {
                                                 res_in |= bit;
@@ -825,13 +821,10 @@ static inline __poll_t do_pollfd(struct pollfd *pollfd, poll_table *pwait,
 
         /* userland u16 ->events contains POLL... bitmap */
         filter = demangle_poll(pollfd->events) | EPOLLERR | EPOLLHUP;
-        mask = DEFAULT_POLLMASK;
-        if (f.file->f_op->poll) {
-                pwait->_key = filter | busy_flag;
-                mask = f.file->f_op->poll(f.file, pwait);
-                if (mask & busy_flag)
-                        *can_busy_poll = true;
-        }
+        pwait->_key = filter | busy_flag;
+        mask = vfs_poll(f.file, pwait);
+        if (mask & busy_flag)
+                *can_busy_poll = true;
         mask &= filter;         /* Mask out unneeded events. */
         fdput(f);
 
diff --git a/include/linux/poll.h b/include/linux/poll.h
index a3576da63377..7e0fdcf905d2 100644
--- a/include/linux/poll.h
+++ b/include/linux/poll.h
@@ -74,6 +74,18 @@ static inline void init_poll_funcptr(poll_table *pt, poll_queue_proc qproc)
         pt->_key   = ~(__poll_t)0; /* all events enabled */
 }
 
+static inline bool file_can_poll(struct file *file)
+{
+        return file->f_op->poll;
+}
+
+static inline __poll_t vfs_poll(struct file *file, struct poll_table_struct *pt)
+{
+        if (unlikely(!file->f_op->poll))
+                return DEFAULT_POLLMASK;
+        return file->f_op->poll(file, pt);
+}
+
 struct poll_table_entry {
         struct file *filp;
         __poll_t key;
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2bd3df3d101a..1695f38630f1 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3849,7 +3849,7 @@ static ssize_t memcg_write_event_control(struct kernfs_open_file *of,
         if (ret)
                 goto out_put_css;
 
-        efile.file->f_op->poll(efile.file, &event->pt);
+        vfs_poll(efile.file, &event->pt);
 
         spin_lock(&memcg->event_list_lock);
         list_add(&event->list, &memcg->event_list);
diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c
index 0cfba919d167..3811775692d0 100644
--- a/net/9p/trans_fd.c
+++ b/net/9p/trans_fd.c
@@ -231,7 +231,7 @@ static void p9_conn_cancel(struct p9_conn *m, int err)
 static __poll_t
 p9_fd_poll(struct p9_client *client, struct poll_table_struct *pt, int *err)
 {
-        __poll_t ret, n;
+        __poll_t ret;
         struct p9_trans_fd *ts = NULL;
 
         if (client && client->status == Connected)
@@ -243,19 +243,9 @@ p9_fd_poll(struct p9_client *client, struct poll_table_struct *pt, int *err)
                 return EPOLLERR;
         }
 
-        if (!ts->rd->f_op->poll)
-                ret = DEFAULT_POLLMASK;
-        else
-                ret = ts->rd->f_op->poll(ts->rd, pt);
-
-        if (ts->rd != ts->wr) {
-                if (!ts->wr->f_op->poll)
-                        n = DEFAULT_POLLMASK;
-                else
-                        n = ts->wr->f_op->poll(ts->wr, pt);
-                ret = (ret & ~EPOLLOUT) | (n & ~EPOLLIN);
-        }
-
+        ret = vfs_poll(ts->rd, pt);
+        if (ts->rd != ts->wr)
+                ret = (ret & ~EPOLLOUT) | (vfs_poll(ts->wr, pt) & ~EPOLLIN);
         return ret;
 }
 
diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index 6e865e8b5b10..90d30fbe95ae 100644
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -397,7 +397,7 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args)
          * Check if there was an event already pending on the eventfd
          * before we registered, and trigger it as if we didn't miss it.
          */
-        events = f.file->f_op->poll(f.file, &irqfd->pt);
+        events = vfs_poll(f.file, &irqfd->pt);
 
         if (events & EPOLLIN)
                 schedule_work(&irqfd->inject);