There are only two kinds of pipe_buffer in the area used by ITER_PIPE.
1) anonymous - copy_to_iter() et.al. end up creating those and copying
data there. They have zero ->offset, and their ->ops points to
default_pipe_page_ops.
2) zero-copy ones - those come from copy_page_to_iter(), and page
comes from caller. ->offset is also caller-supplied - it might be
non-zero. ->ops points to page_cache_pipe_buf_ops.
Move creation and insertion of those into helpers - push_anon(pipe, size)
and push_page(pipe, page, offset, size) resp., separating them from
the "could we avoid creating a new buffer by merging with the current
head?" logics.
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
lib/iov_iter.c | 88 ++++++++++++++++++++++++++------------------------
1 file changed, 46 insertions(+), 42 deletions(-)
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 08bb393da677..924854c2a7ce 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -231,15 +231,39 @@ static bool sanity(const struct iov_iter *i)
#define sanity(i) true
#endif
+static struct page *push_anon(struct pipe_inode_info *pipe, unsigned size)
+{
+ struct page *page = alloc_page(GFP_USER);
+ if (page) {
+ struct pipe_buffer *buf = pipe_buf(pipe, pipe->head++);
+ *buf = (struct pipe_buffer) {
+ .ops = &default_pipe_buf_ops,
+ .page = page,
+ .offset = 0,
+ .len = size
+ };
+ }
+ return page;
+}
+
+static void push_page(struct pipe_inode_info *pipe, struct page *page,
+ unsigned int offset, unsigned int size)
+{
+ struct pipe_buffer *buf = pipe_buf(pipe, pipe->head++);
+ *buf = (struct pipe_buffer) {
+ .ops = &page_cache_pipe_buf_ops,
+ .page = page,
+ .offset = offset,
+ .len = size
+ };
+ get_page(page);
+}
+
static size_t copy_page_to_iter_pipe(struct page *page, size_t offset, size_t bytes,
struct iov_iter *i)
{
struct pipe_inode_info *pipe = i->pipe;
- struct pipe_buffer *buf;
- unsigned int p_tail = pipe->tail;
- unsigned int p_mask = pipe->ring_size - 1;
- unsigned int i_head = i->head;
- size_t off;
+ unsigned int head = pipe->head;
if (unlikely(bytes > i->count))
bytes = i->count;
@@ -250,32 +274,21 @@ static size_t copy_page_to_iter_pipe(struct page *page, size_t offset, size_t by
if (!sanity(i))
return 0;
- off = i->iov_offset;
- buf = &pipe->bufs[i_head & p_mask];
- if (off) {
- if (offset == off && buf->page == page) {
- /* merge with the last one */
+ if (offset && i->iov_offset == offset) { // could we merge it?
+ struct pipe_buffer *buf = pipe_buf(pipe, head - 1);
+ if (buf->page == page) {
buf->len += bytes;
i->iov_offset += bytes;
- goto out;
+ i->count -= bytes;
+ return bytes;
}
- i_head++;
- buf = &pipe->bufs[i_head & p_mask];
}
- if (pipe_full(i_head, p_tail, pipe->max_usage))
+ if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
return 0;
- buf->ops = &page_cache_pipe_buf_ops;
- buf->flags = 0;
- get_page(page);
- buf->page = page;
- buf->offset = offset;
- buf->len = bytes;
-
- pipe->head = i_head + 1;
+ push_page(pipe, page, offset, bytes);
i->iov_offset = offset + bytes;
- i->head = i_head;
-out:
+ i->head = head;
i->count -= bytes;
return bytes;
}
@@ -407,8 +420,6 @@ static size_t push_pipe(struct iov_iter *i, size_t size,
int *iter_headp, size_t *offp)
{
struct pipe_inode_info *pipe = i->pipe;
- unsigned int p_tail = pipe->tail;
- unsigned int p_mask = pipe->ring_size - 1;
unsigned int iter_head;
size_t off;
ssize_t left;
@@ -423,30 +434,23 @@ static size_t push_pipe(struct iov_iter *i, size_t size,
*iter_headp = iter_head;
*offp = off;
if (off) {
+ struct pipe_buffer *buf = pipe_buf(pipe, iter_head);
+
left -= PAGE_SIZE - off;
if (left <= 0) {
- pipe->bufs[iter_head & p_mask].len += size;
+ buf->len += size;
return size;
}
- pipe->bufs[iter_head & p_mask].len = PAGE_SIZE;
- iter_head++;
+ buf->len = PAGE_SIZE;
}
- while (!pipe_full(iter_head, p_tail, pipe->max_usage)) {
- struct pipe_buffer *buf = &pipe->bufs[iter_head & p_mask];
- struct page *page = alloc_page(GFP_USER);
+ while (!pipe_full(pipe->head, pipe->tail, pipe->max_usage)) {
+ struct page *page = push_anon(pipe,
+ min_t(ssize_t, left, PAGE_SIZE));
if (!page)
break;
- buf->ops = &default_pipe_buf_ops;
- buf->flags = 0;
- buf->page = page;
- buf->offset = 0;
- buf->len = min_t(ssize_t, left, PAGE_SIZE);
- left -= buf->len;
- iter_head++;
- pipe->head = iter_head;
-
- if (left == 0)
+ left -= PAGE_SIZE;
+ if (left <= 0)
return size;
}
return size - left;
--
2.30.2
