Add an internal struct iovec that we can return as a pointer, with the
fields of the iovec overlapping with the ITER_UBUF ubuf and length
fields.
This allows doing:
struct iovec *vec = &iter->__ubuf_iovec;
interchangably with iter->iov for the first segment, enabling writing
code that deals with both without needing to check if we're dealing with
ITER_IOVEC or ITER_UBUF.
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
include/linux/uio.h | 29 ++++++++++++++++++++++-------
1 file changed, 22 insertions(+), 7 deletions(-)
diff --git a/include/linux/uio.h b/include/linux/uio.h
index 3b4403efcce1..192831775d2b 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -49,14 +49,29 @@ struct iov_iter {
size_t iov_offset;
int last_offset;
};
- size_t count;
+ /*
+ * Hack alert: overlay ubuf_iovec with iovec + count, so
+ * that the members resolve correctly regardless of the type
+ * of iterator used. This means that you can use:
+ *
+ * &iter->ubuf or iter->iov
+ *
+ * interchangably for the user_backed cases, hence simplifying
+ * some of the cases that need to deal with both.
+ */
union {
- const struct iovec *iov;
- const struct kvec *kvec;
- const struct bio_vec *bvec;
- struct xarray *xarray;
- struct pipe_inode_info *pipe;
- void __user *ubuf;
+ struct iovec __ubuf_iovec;
+ struct {
+ union {
+ const struct iovec *iov;
+ const struct kvec *kvec;
+ const struct bio_vec *bvec;
+ struct xarray *xarray;
+ struct pipe_inode_info *pipe;
+ void __user *ubuf;
+ };
+ size_t count;
+ };
};
union {
unsigned long nr_segs;
--
2.39.2
