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io_uring/zcrx: prepare fallback for larger pages

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io_zcrx_copy_chunk() processes one page at a time, which won't be
sufficient when the net_iov size grows. Introduce a structure keeping
the target niov page and other parameters, it's more convenient and can
be reused later. And add a helper function that can efficient copy
buffers of an arbitrary length. For 64bit archs the loop inside should
be compiled out.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/e84bc705a4e1edeb9aefff470d96558d8232388f.1751466461.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2025-07-02 15:29:09 +01:00 committed by Jens Axboe
parent 1b4dc1ff0a
commit e67645bb7f
1 changed files with 56 additions and 27 deletions
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83
io_uring/zcrx.c
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@ -929,6 +929,51 @@ static struct net_iov *io_zcrx_alloc_fallback(struct io_zcrx_area *area)
return niov;
}
struct io_copy_cache {
struct page *page;
unsigned long offset;
size_t size;
};
static ssize_t io_copy_page(struct io_copy_cache *cc, struct page *src_page,
unsigned int src_offset, size_t len)
{
size_t copied = 0;
len = min(len, cc->size);
while (len) {
void *src_addr, *dst_addr;
struct page *dst_page = cc->page;
unsigned dst_offset = cc->offset;
size_t n = len;
if (folio_test_partial_kmap(page_folio(dst_page)) ||
folio_test_partial_kmap(page_folio(src_page))) {
dst_page = nth_page(dst_page, dst_offset / PAGE_SIZE);
dst_offset = offset_in_page(dst_offset);
src_page = nth_page(src_page, src_offset / PAGE_SIZE);
src_offset = offset_in_page(src_offset);
n = min(PAGE_SIZE - src_offset, PAGE_SIZE - dst_offset);
n = min(n, len);
}
dst_addr = kmap_local_page(dst_page) + dst_offset;
src_addr = kmap_local_page(src_page) + src_offset;
memcpy(dst_addr, src_addr, n);
kunmap_local(src_addr);
kunmap_local(dst_addr);
cc->size -= n;
cc->offset += n;
len -= n;
copied += n;
}
return copied;
}
static ssize_t io_zcrx_copy_chunk(struct io_kiocb *req, struct io_zcrx_ifq *ifq,
struct page *src_page, unsigned int src_offset,
size_t len)
@ -941,11 +986,9 @@ static ssize_t io_zcrx_copy_chunk(struct io_kiocb *req, struct io_zcrx_ifq *ifq,
return -EFAULT;
while (len) {
size_t copy_size = min_t(size_t, PAGE_SIZE, len);
const int dst_off = 0;
struct io_copy_cache cc;
struct net_iov *niov;
struct page *dst_page;
void *dst_addr, *src_addr;
size_t n;
niov = io_zcrx_alloc_fallback(area);
if (!niov) {
@ -953,25 +996,22 @@ static ssize_t io_zcrx_copy_chunk(struct io_kiocb *req, struct io_zcrx_ifq *ifq,
break;
}
dst_page = io_zcrx_iov_page(niov);
dst_addr = kmap_local_page(dst_page);
src_addr = kmap_local_page(src_page);
cc.page = io_zcrx_iov_page(niov);
cc.offset = 0;
cc.size = PAGE_SIZE;
memcpy(dst_addr, src_addr + src_offset, copy_size);
n = io_copy_page(&cc, src_page, src_offset, len);
kunmap_local(src_addr);
kunmap_local(dst_addr);
if (!io_zcrx_queue_cqe(req, niov, ifq, dst_off, copy_size)) {
if (!io_zcrx_queue_cqe(req, niov, ifq, 0, n)) {
io_zcrx_return_niov(niov);
ret = -ENOSPC;
break;
}
io_zcrx_get_niov_uref(niov);
src_offset += copy_size;
len -= copy_size;
copied += copy_size;
src_offset += n;
len -= n;
copied += n;
}
return copied ? copied : ret;
@ -981,19 +1021,8 @@ static int io_zcrx_copy_frag(struct io_kiocb *req, struct io_zcrx_ifq *ifq,
const skb_frag_t *frag, int off, int len)
{
struct page *page = skb_frag_page(frag);
u32 p_off, p_len, t, copied = 0;
int ret = 0;
off += skb_frag_off(frag);
skb_frag_foreach_page(frag, off, len,
page, p_off, p_len, t) {
ret = io_zcrx_copy_chunk(req, ifq, page, p_off, p_len);
if (ret < 0)
return copied ? copied : ret;
copied += ret;
}
return copied;
return io_zcrx_copy_chunk(req, ifq, page, off + skb_frag_off(frag), len);
}
static int io_zcrx_recv_frag(struct io_kiocb *req, struct io_zcrx_ifq *ifq,