Messages in this thread Patch in this message | | | From | David Howells <> | Subject | [RFC PATCH 12/28] af_unix: Support MSG_SPLICE_PAGES | Date | Thu, 16 Mar 2023 15:26:02 +0000 |
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Make AF_UNIX sendmsg() support MSG_SPLICE_PAGES, splicing in pages from the source iterator if given and if ITER_BVEC and copying the data in otherwise.
This allows ->sendpage() to be replaced by something that can handle multiple multipage folios in a single transaction.
Signed-off-by: David Howells <dhowells@redhat.com> cc: "David S. Miller" <davem@davemloft.net> cc: Eric Dumazet <edumazet@google.com> cc: Jakub Kicinski <kuba@kernel.org> cc: Paolo Abeni <pabeni@redhat.com> cc: Jens Axboe <axboe@kernel.dk> cc: Matthew Wilcox <willy@infradead.org> cc: netdev@vger.kernel.org --- net/unix/af_unix.c | 84 +++++++++++++++++++++++++++++++++++++--------- 1 file changed, 68 insertions(+), 16 deletions(-)
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index 347122c3575e..6f3454db9c53 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -2151,6 +2151,44 @@ static int queue_oob(struct socket *sock, struct msghdr *msg, struct sock *other } #endif +/* + * Extract pages from a BVEC-type iterator and add them to the socket buffer. + */ +static ssize_t unix_extract_bvec_to_skb(struct sk_buff *skb, + struct iov_iter *iter, ssize_t maxsize) +{ + const struct bio_vec *bv = iter->bvec; + unsigned long start = iter->iov_offset; + unsigned int i; + ssize_t ret = 0; + + for (i = 0; i < iter->nr_segs; i++) { + size_t off, len; + + len = bv[i].bv_len; + if (start >= len) { + start -= len; + continue; + } + + len = min_t(size_t, maxsize, len - start); + off = bv[i].bv_offset + start; + + if (skb_append_pagefrags(skb, bv->bv_page, off, len) < 0) + break; + + ret += len; + maxsize -= len; + if (maxsize <= 0) + break; + start = 0; + } + + if (ret > 0) + iov_iter_advance(iter, ret); + return ret; +} + static int unix_stream_sendmsg(struct socket *sock, struct msghdr *msg, size_t len) { @@ -2194,19 +2232,25 @@ static int unix_stream_sendmsg(struct socket *sock, struct msghdr *msg, while (sent < len) { size = len - sent; - /* Keep two messages in the pipe so it schedules better */ - size = min_t(int, size, (sk->sk_sndbuf >> 1) - 64); + if (unlikely(msg->msg_flags & MSG_SPLICE_PAGES)) { + skb = sock_alloc_send_pskb(sk, 0, 0, + msg->msg_flags & MSG_DONTWAIT, + &err, 0); + } else { + /* Keep two messages in the pipe so it schedules better */ + size = min_t(int, size, (sk->sk_sndbuf >> 1) - 64); - /* allow fallback to order-0 allocations */ - size = min_t(int, size, SKB_MAX_HEAD(0) + UNIX_SKB_FRAGS_SZ); + /* allow fallback to order-0 allocations */ + size = min_t(int, size, SKB_MAX_HEAD(0) + UNIX_SKB_FRAGS_SZ); - data_len = max_t(int, 0, size - SKB_MAX_HEAD(0)); + data_len = max_t(int, 0, size - SKB_MAX_HEAD(0)); - data_len = min_t(size_t, size, PAGE_ALIGN(data_len)); + data_len = min_t(size_t, size, PAGE_ALIGN(data_len)); - skb = sock_alloc_send_pskb(sk, size - data_len, data_len, - msg->msg_flags & MSG_DONTWAIT, &err, - get_order(UNIX_SKB_FRAGS_SZ)); + skb = sock_alloc_send_pskb(sk, size - data_len, data_len, + msg->msg_flags & MSG_DONTWAIT, &err, + get_order(UNIX_SKB_FRAGS_SZ)); + } if (!skb) goto out_err; @@ -2218,13 +2262,21 @@ static int unix_stream_sendmsg(struct socket *sock, struct msghdr *msg, } fds_sent = true; - skb_put(skb, size - data_len); - skb->data_len = data_len; - skb->len = size; - err = skb_copy_datagram_from_iter(skb, 0, &msg->msg_iter, size); - if (err) { - kfree_skb(skb); - goto out_err; + if (unlikely(msg->msg_flags & MSG_SPLICE_PAGES)) { + size = unix_extract_bvec_to_skb(skb, &msg->msg_iter, size); + skb->data_len += size; + skb->len += size; + skb->truesize += size; + refcount_add(size, &sk->sk_wmem_alloc); + } else { + skb_put(skb, size - data_len); + skb->data_len = data_len; + skb->len = size; + err = skb_copy_datagram_from_iter(skb, 0, &msg->msg_iter, size); + if (err) { + kfree_skb(skb); + goto out_err; + } } unix_state_lock(other);
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