new iov_iter flavour: pipe-backed
iov_iter variant for passing data into pipe. copy_to_iter()
copies data into page(s) it has allocated and stuffs them into
the pipe; copy_page_to_iter() stuffs there a reference to the
page given to it. Both will try to coalesce if possible.
iov_iter_zero() is similar to copy_to_iter(); iov_iter_get_pages()
and friends will do as copy_to_iter() would have and return the
pages where the data would've been copied. iov_iter_advance()
will truncate everything past the spot it has advanced to.
New primitive: iov_iter_pipe(), used for initializing those.
pipe should be locked all along.
Running out of space acts as fault would for iovec-backed ones;
in other words, giving it to ->read_iter() may result in short
read if the pipe overflows, or -EFAULT if it happens with nothing
copied there.
In other words, ->read_iter() on those acts pretty much like
->splice_read(). Moreover, all generic_file_splice_read() users,
as well as many other ->splice_read() instances can be switched
to that scheme - that'll happen in the next commit.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/include/linux/uio.h b/include/linux/uio.h
index 75b4aaf..b5ebe6d 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -13,6 +13,7 @@
#include <uapi/linux/uio.h>
struct page;
+struct pipe_inode_info;
struct kvec {
void *iov_base; /* and that should *never* hold a userland pointer */
@@ -23,6 +24,7 @@
ITER_IOVEC = 0,
ITER_KVEC = 2,
ITER_BVEC = 4,
+ ITER_PIPE = 8,
};
struct iov_iter {
@@ -33,8 +35,12 @@
const struct iovec *iov;
const struct kvec *kvec;
const struct bio_vec *bvec;
+ struct pipe_inode_info *pipe;
};
- unsigned long nr_segs;
+ union {
+ unsigned long nr_segs;
+ int idx;
+ };
};
/*
@@ -64,7 +70,7 @@
}
#define iov_for_each(iov, iter, start) \
- if (!((start).type & ITER_BVEC)) \
+ if (!((start).type & (ITER_BVEC | ITER_PIPE))) \
for (iter = (start); \
(iter).count && \
((iov = iov_iter_iovec(&(iter))), 1); \
@@ -94,6 +100,8 @@
unsigned long nr_segs, size_t count);
void iov_iter_bvec(struct iov_iter *i, int direction, const struct bio_vec *bvec,
unsigned long nr_segs, size_t count);
+void iov_iter_pipe(struct iov_iter *i, int direction, struct pipe_inode_info *pipe,
+ 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,
@@ -109,7 +117,7 @@
static inline bool iter_is_iovec(struct iov_iter *i)
{
- return !(i->type & (ITER_BVEC | ITER_KVEC));
+ return !(i->type & (ITER_BVEC | ITER_KVEC | ITER_PIPE));
}
/*