| Message ID | 20201129004548.1619714-8-namit@vmware.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | fs/userfaultfd: support iouring and polling | expand |
On 11/28/20 5:45 PM, Nadav Amit wrote: > From: Nadav Amit <namit@vmware.com> > > 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 <axboe@kernel.dk> > Cc: Andrea Arcangeli <aarcange@redhat.com> > Cc: Peter Xu <peterx@redhat.com> > Cc: Alexander Viro <viro@zeniv.linux.org.uk> > Cc: io-uring@vger.kernel.org > Cc: linux-fsdevel@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > Cc: linux-mm@kvack.org > Signed-off-by: Nadav Amit <namit@vmware.com> > --- > 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.
> On Nov 30, 2020, at 10:20 AM, Jens Axboe <axboe@kernel.dk> wrote: > > On 11/28/20 5:45 PM, Nadav Amit wrote: >> From: Nadav Amit <namit@vmware.com> >> >> 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 <axboe@kernel.dk> >> Cc: Andrea Arcangeli <aarcange@redhat.com> >> Cc: Peter Xu <peterx@redhat.com> >> Cc: Alexander Viro <viro@zeniv.linux.org.uk> >> Cc: io-uring@vger.kernel.org >> Cc: linux-fsdevel@vger.kernel.org >> Cc: linux-kernel@vger.kernel.org >> Cc: linux-mm@kvack.org >> Signed-off-by: Nadav Amit <namit@vmware.com> >> --- >> 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).
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); if (_ret < 0) return ret ? ret : _ret; - if (copy_to_user((__u64 __user *) buf, &msg, sizeof(msg))) - return ret ? ret : -EFAULT; + + _ret = copy_to_iter(&msg, sizeof(msg), to); + if (_ret != sizeof(msg)) + return ret ? ret : -EINVAL; + ret += sizeof(msg); - buf += sizeof(msg); - count -= sizeof(msg); + /* * Allow to read more than one fault at time but only * block if waiting for the very first one. @@ -1980,7 +1982,7 @@ static const struct file_operations userfaultfd_fops = { #endif .release = userfaultfd_release, .poll = userfaultfd_poll, - .read = userfaultfd_read, + .read_iter = userfaultfd_read_iter, .unlocked_ioctl = userfaultfd_ioctl, .compat_ioctl = compat_ptr_ioctl, .llseek = noop_llseek,