io_uring/rsrc: replace reg buffer bit field with flags

I'll need a flag in the registered buffer struct for dmabuf work, and
it'll be more convenient to have a flags field rather than bit fields,
especially for io_mapped_ubuf initialisation.

We might want to add more flags in the future as well. For example, it
might be useful for debugging and potentially optimisations to split out
a flag indicating the shape of the buffer to gate iov_iter_advance()
walks vs bit/mask arithmetics. It can also be combined with the
direction mask field.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: isilence

io_uring/rsrc.c

@@ -828,7 +828,7 @@ static struct io_rsrc_node *io_sqe_buffer_register(struct io_ring_ctx *ctx,
 	imu->folio_shift = PAGE_SHIFT;
 	imu->release = io_release_ubuf;
 	imu->priv = imu;
-	imu->is_kbuf = false;
+	imu->flags = 0;
 	imu->dir = IO_IMU_DEST | IO_IMU_SOURCE;
 	if (coalesced)
 		imu->folio_shift = data.folio_shift;
@@ -985,7 +985,7 @@ int io_buffer_register_bvec(struct io_uring_cmd *cmd, struct request *rq,
 	refcount_set(&imu->refs, 1);
 	imu->release = release;
 	imu->priv = rq;
-	imu->is_kbuf = true;
+	imu->flags = IO_REGBUF_F_KBUF;
 	imu->dir = 1 << rq_data_dir(rq);
 
 	rq_for_each_bvec(bv, rq, rq_iter)
@@ -1020,7 +1020,7 @@ int io_buffer_unregister_bvec(struct io_uring_cmd *cmd, unsigned int index,
 		ret = -EINVAL;
 		goto unlock;
 	}
-	if (!node->buf->is_kbuf) {
+	if (!(node->buf->flags & IO_REGBUF_F_KBUF)) {
 		ret = -EBUSY;
 		goto unlock;
 	}
@@ -1076,7 +1076,7 @@ static int io_import_fixed(int ddir, struct iov_iter *iter,
 
 	offset = buf_addr - imu->ubuf;
 
-	if (imu->is_kbuf)
+	if (imu->flags & IO_REGBUF_F_KBUF)
 		return io_import_kbuf(ddir, iter, imu, len, offset);
 
 	/*
@@ -1496,7 +1496,7 @@ int io_import_reg_vec(int ddir, struct iov_iter *iter,
 	iovec_off = vec->nr - nr_iovs;
 	iov = vec->iovec + iovec_off;
 
-	if (imu->is_kbuf) {
+	if (imu->flags & IO_REGBUF_F_KBUF) {
 		int ret = io_kern_bvec_size(iov, nr_iovs, imu, &nr_segs);
 
 		if (unlikely(ret))
@@ -1534,7 +1534,7 @@ int io_import_reg_vec(int ddir, struct iov_iter *iter,
 		req->flags |= REQ_F_NEED_CLEANUP;
 	}
 
-	if (imu->is_kbuf)
+	if (imu->flags & IO_REGBUF_F_KBUF)
 		return io_vec_fill_kern_bvec(ddir, iter, imu, iov, nr_iovs, vec);
 
 	return io_vec_fill_bvec(ddir, iter, imu, iov, nr_iovs, vec);

io_uring/rsrc.h

@@ -28,6 +28,10 @@ enum {
 	IO_IMU_SOURCE	= 1 << ITER_SOURCE,
 };
 
+enum {
+	IO_REGBUF_F_KBUF		= 1,
+};
+
 struct io_mapped_ubuf {
 	u64		ubuf;
 	unsigned int	len;
@@ -37,7 +41,7 @@ struct io_mapped_ubuf {
 	unsigned long	acct_pages;
 	void		(*release)(void *);
 	void		*priv;
-	bool		is_kbuf;
+	u8		flags;
 	u8		dir;
 	struct bio_vec	bvec[] __counted_by(nr_bvecs);
 };

io_uring/rw.c

@@ -702,7 +702,8 @@ static ssize_t loop_rw_iter(int ddir, struct io_rw *rw, struct iov_iter *iter)
 	if ((kiocb->ki_flags & IOCB_NOWAIT) &&
 	    !(kiocb->ki_filp->f_flags & O_NONBLOCK))
 		return -EAGAIN;
-	if ((req->flags & REQ_F_BUF_NODE) && req->buf_node->buf->is_kbuf)
+	if ((req->flags & REQ_F_BUF_NODE) &&
+	     (req->buf_node->buf->flags & IO_REGBUF_F_KBUF))
 		return -EFAULT;
 
 	ppos = io_kiocb_ppos(kiocb);