[PATCH 12/36] fs: add new vfs_poll and file_can_poll helpers

Christoph Hellwig
2018-01-17T19:28:30Z

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

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
drivers/staging/comedi/drivers/serial2002.c | 4 ++--
drivers/vfio/virqfd.c | 2 +-
drivers/vhost/vhost.c | 2 +-
fs/eventpoll.c | 5 ++---
fs/select.c | 23 ++++++++---------------
include/linux/poll.h | 12 ++++++++++++
mm/memcontrol.c | 2 +-
net/9p/trans_fd.c | 18 ++++--------------
virt/kvm/eventfd.c | 2 +-
9 files changed, 32 insertions(+), 38 deletions(-)

diff --git a/drivers/staging/comedi/drivers/serial2002.c b/drivers/staging/comedi/drivers/serial2002.c
index a557be8a5076..5e2a2dc372e0 100644
--- a/drivers/staging/comedi/drivers/serial2002.c
+++ b/drivers/staging/comedi/drivers/serial2002.c
@@ -121,7 +121,7 @@ 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 & (POLLRDNORM | POLLRDBAND | POLLIN |
POLLHUP | POLLERR)) {
break;
@@ -144,7 +144,7 @@ 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 8cc4b48ff127..ef539a07a08c 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 3bbeabff505a..b6311dc74d71 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -209,7 +209,7 @@ 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 & POLLERR) {
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 42e35a6977c9..7d65f628810e 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -882,8 +882,7 @@ static unsigned int 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);
@@ -2015,7 +2014,7 @@ 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 2ad66647f340..e96f1342c2f6 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;
@@ -818,13 +814,10 @@ static inline __poll_t do_pollfd(struct pollfd *pollfd, poll_table *pwait,

/* userland u16 ->events contains POLL... bitmap */
filter = demangle_poll(pollfd->events) | POLLERR | POLLHUP;
- 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 out unneeded events. */
mask &= filter;
diff --git a/include/linux/poll.h b/include/linux/poll.h
index a4b465fa2ca0..7afd259c570f 100644
--- a/include/linux/poll.h
+++ b/include/linux/poll.h
@@ -73,6 +73,18 @@ 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 9011997d8a5c..284e69f345f8 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3928,7 +3928,7 @@ 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 d6f7f7cb79c4..74df034726f8 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 POLLERR;
}

- 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 & ~POLLOUT) | (n & ~POLLIN);
- }
-
+ ret = vfs_poll(ts->rd, pt);
+ if (ts->rd != ts->wr)
+ ret = (vfs_poll(ts->wr, pt) & ~POLLIN) | (ret & ~POLLOUT);
return ret;
}

diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index a334399fafec..df8a23cbf457 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 & POLLIN)
schedule_work(&irqfd->inject);
--
2.14.2