> On Nov 30, 2020, at 10:20 AM, Jens Axboe <[email protected]> wrote: > > 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.
Thanks, I completely missed this point and will fix it in v1 (if I get a positive feedback on the rest from the userfaultfd people).
