On 11/28/20 5:45 PM, Nadav Amit wrote: > From: Nadav Amit <[email protected]> > > iouring with userfaultfd cannot currently be used fixed buffers since > userfaultfd does not provide read_iter(). This is required to allow > asynchronous (queued) reads from userfaultfd. > > To support async-reads of userfaultfd provide read_iter() instead of > read(). > > Cc: Jens Axboe <[email protected]> > Cc: Andrea Arcangeli <[email protected]> > Cc: Peter Xu <[email protected]> > Cc: Alexander Viro <[email protected]> > Cc: [email protected] > Cc: [email protected] > Cc: [email protected] > Cc: [email protected] > Signed-off-by: Nadav Amit <[email protected]> > --- > fs/userfaultfd.c | 18 ++++++++++-------- > 1 file changed, 10 insertions(+), 8 deletions(-) > > diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c > index b6a04e526025..6333b4632742 100644 > --- a/fs/userfaultfd.c > +++ b/fs/userfaultfd.c > @@ -1195,9 +1195,9 @@ static ssize_t userfaultfd_ctx_read(struct > userfaultfd_ctx *ctx, int no_wait, > return ret; > } > > -static ssize_t userfaultfd_read(struct file *file, char __user *buf, > - size_t count, loff_t *ppos) > +static ssize_t userfaultfd_read_iter(struct kiocb *iocb, struct iov_iter *to) > { > + struct file *file = iocb->ki_filp; > struct userfaultfd_ctx *ctx = file->private_data; > ssize_t _ret, ret = 0; > struct uffd_msg msg; > @@ -1207,16 +1207,18 @@ static ssize_t userfaultfd_read(struct file *file, > char __user *buf, > return -EINVAL; > > for (;;) { > - if (count < sizeof(msg)) > + if (iov_iter_count(to) < sizeof(msg)) > return ret ? ret : -EINVAL; > _ret = userfaultfd_ctx_read(ctx, no_wait, &msg);
'no_wait' should be changed to factor in iocb->ki_flags & IOCB_NOWAIT as well, not just f_flags & O_NONBLOCK. I didn't check your write_iter, but if appropriate, that should do that too. -- Jens Axboe
