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); 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, -- 2.25.1
