Even if we're returning an iovec, we can trivially fill it in with the
details from an ITER_UBUF as well. This enables loops that assume
ITER_IOVEC to deal with ITER_UBUF transparently.
This is done in preparation for automatically importing single segment
iovecs as ITER_UBUF.
Suggested-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
include/linux/uio.h | 26 +++++++++++++++++++++-----
1 file changed, 21 insertions(+), 5 deletions(-)
diff --git a/include/linux/uio.h b/include/linux/uio.h
index 27e3fd942960..3b4403efcce1 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -143,13 +143,29 @@ static inline size_t iov_length(const struct iovec *iov, unsigned long nr_segs)
return ret;
}
+/*
+ * Don't assume we're called with ITER_IOVEC, enable usage of ITER_UBUF
+ * as well by simply filling in the iovec.
+ */
static inline struct iovec iov_iter_iovec(const struct iov_iter *iter)
{
- return (struct iovec) {
- .iov_base = iter->iov->iov_base + iter->iov_offset,
- .iov_len = min(iter->count,
- iter->iov->iov_len - iter->iov_offset),
- };
+ if (WARN_ON_ONCE(!iter->user_backed)) {
+ return (struct iovec) {
+ .iov_base = NULL,
+ .iov_len = 0
+ };
+ } else if (iter_is_ubuf(iter)) {
+ return (struct iovec) {
+ .iov_base = iter->ubuf + iter->iov_offset,
+ .iov_len = iter->count
+ };
+ } else {
+ return (struct iovec) {
+ .iov_base = iter->iov->iov_base + iter->iov_offset,
+ .iov_len = min(iter->count,
+ iter->iov->iov_len - iter->iov_offset),
+ };
+ }
}
size_t copy_page_from_iter_atomic(struct page *page, unsigned offset,
--
2.39.2
