iov_iter: Add I/O discard iterator
Add a new iterator, ITER_DISCARD, that can only be used in READ mode and
just discards any data copied to it.
This is useful in a network filesystem for discarding any unwanted data
sent by a server.
Signed-off-by: David Howells <dhowells@redhat.com>
diff --git a/include/linux/uio.h b/include/linux/uio.h
index 3d8f1ac..55ce99d 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -26,6 +26,7 @@ enum iter_type {
ITER_KVEC = 2,
ITER_BVEC = 4,
ITER_PIPE = 8,
+ ITER_DISCARD = 16,
};
struct iov_iter {
@@ -72,6 +73,11 @@ static inline bool iov_iter_is_pipe(const struct iov_iter *i)
return iov_iter_type(i) == ITER_PIPE;
}
+static inline bool iov_iter_is_discard(const struct iov_iter *i)
+{
+ return iov_iter_type(i) == ITER_DISCARD;
+}
+
static inline unsigned char iov_iter_rw(const struct iov_iter *i)
{
return i->type & (READ | WRITE);
@@ -220,6 +226,7 @@ void iov_iter_bvec(struct iov_iter *i, unsigned int direction, const struct bio_
unsigned long nr_segs, size_t count);
void iov_iter_pipe(struct iov_iter *i, unsigned int direction, struct pipe_inode_info *pipe,
size_t count);
+void iov_iter_discard(struct iov_iter *i, unsigned int direction, size_t count);
ssize_t iov_iter_get_pages(struct iov_iter *i, struct page **pages,
size_t maxsize, unsigned maxpages, size_t *start);
ssize_t iov_iter_get_pages_alloc(struct iov_iter *i, struct page ***pages,