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    SubjectRe: [PATCH 12/36] fs: add new vfs_poll and file_can_poll helpers
    On Mon, Mar 05, 2018 at 01:27:19PM -0800, Christoph Hellwig wrote:
    > 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 +-

    For the fs/include/mm changes,
    Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

    The other conversions look fine to me too but I've never looked at them
    before. :)

    --D

    > 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 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 1b3e8d2d5c8b..4d27e288bb1d 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 0f3494ed3ed0..2bebae5a38cf 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);
    > @@ -2020,7 +2019,7 @@ 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 c6c504a814f9..ba91103707ea 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;
    > @@ -819,13 +815,10 @@ 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 670e99b68aa6..8774ece5c3c3 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);
    > --
    > 2.14.2
    >

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