From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2A0E6C77B75 for ; Mon, 15 May 2023 09:35:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238648AbjEOJfE (ORCPT ); Mon, 15 May 2023 05:35:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39502 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238179AbjEOJfA (ORCPT ); Mon, 15 May 2023 05:35:00 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A8B4A1BD for ; Mon, 15 May 2023 02:34:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1684143248; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=rQETt65RGaUyqHGF2SRFOY3ON9kc871DZcLjRArLuXs=; b=ZMBEZAg/C2kWhScEThf2oQ6zFFwRX3jnodgaFzziTtJLjFSu2/Ryb7Ss5IcHiE5mOdBatJ JLmDWXeMDgXTIiQBuVQDc2YSWheJ27GMBB5kjZpiZoQzY7AC1uoCH95SStIFbe7qaEzT0A 5W8zPXedV3Wz6fhrhUUbF48kgKTGqKM= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-516-ea5lFs8TOwOYnV30iV30Iw-1; Mon, 15 May 2023 05:34:05 -0400 X-MC-Unique: ea5lFs8TOwOYnV30iV30Iw-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id B2060185A79C; Mon, 15 May 2023 09:34:04 +0000 (UTC) Received: from warthog.procyon.org.uk (unknown [10.42.28.221]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1B4DF63F84; Mon, 15 May 2023 09:34:00 +0000 (UTC) From: David Howells To: netdev@vger.kernel.org Cc: David Howells , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Willem de Bruijn , David Ahern , Matthew Wilcox , Al Viro , Christoph Hellwig , Jens Axboe , Jeff Layton , Christian Brauner , Chuck Lever III , Linus Torvalds , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH net-next v7 03/16] net: Add a function to splice pages into an skbuff for MSG_SPLICE_PAGES Date: Mon, 15 May 2023 10:33:32 +0100 Message-Id: <20230515093345.396978-4-dhowells@redhat.com> In-Reply-To: <20230515093345.396978-1-dhowells@redhat.com> References: <20230515093345.396978-1-dhowells@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Add a function to handle MSG_SPLICE_PAGES being passed internally to sendmsg(). Pages are spliced into the given socket buffer if possible and copied in if not (e.g. they're slab pages or have a zero refcount). Signed-off-by: David Howells cc: Eric Dumazet cc: "David S. Miller" cc: David Ahern cc: Jakub Kicinski cc: Paolo Abeni cc: Al Viro cc: Jens Axboe cc: Matthew Wilcox cc: netdev@vger.kernel.org --- Notes: ver #7) - Export function. - Never copy data, return -EIO if sendpage_ok() returns false. include/linux/skbuff.h | 3 ++ net/core/skbuff.c | 95 ++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 98 insertions(+) diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 4c0ad48e38ca..1c5f0ac6f8c3 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -5097,5 +5097,8 @@ static inline void skb_mark_for_recycle(struct sk_buff *skb) #endif } +ssize_t skb_splice_from_iter(struct sk_buff *skb, struct iov_iter *iter, + ssize_t maxsize, gfp_t gfp); + #endif /* __KERNEL__ */ #endif /* _LINUX_SKBUFF_H */ diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 7f53dcb26ad3..56d629ea2f3d 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -6892,3 +6892,98 @@ nodefer: __kfree_skb(skb); if (unlikely(kick) && !cmpxchg(&sd->defer_ipi_scheduled, 0, 1)) smp_call_function_single_async(cpu, &sd->defer_csd); } + +static void skb_splice_csum_page(struct sk_buff *skb, struct page *page, + size_t offset, size_t len) +{ + const char *kaddr; + __wsum csum; + + kaddr = kmap_local_page(page); + csum = csum_partial(kaddr + offset, len, 0); + kunmap_local(kaddr); + skb->csum = csum_block_add(skb->csum, csum, skb->len); +} + +/** + * skb_splice_from_iter - Splice (or copy) pages to skbuff + * @skb: The buffer to add pages to + * @iter: Iterator representing the pages to be added + * @maxsize: Maximum amount of pages to be added + * @gfp: Allocation flags + * + * This is a common helper function for supporting MSG_SPLICE_PAGES. It + * extracts pages from an iterator and adds them to the socket buffer if + * possible, copying them to fragments if not possible (such as if they're slab + * pages). + * + * Returns the amount of data spliced/copied or -EMSGSIZE if there's + * insufficient space in the buffer to transfer anything. + */ +ssize_t skb_splice_from_iter(struct sk_buff *skb, struct iov_iter *iter, + ssize_t maxsize, gfp_t gfp) +{ + struct page *pages[8], **ppages = pages; + unsigned int i; + ssize_t spliced = 0, ret = 0; + size_t frag_limit = READ_ONCE(sysctl_max_skb_frags); + + while (iter->count > 0) { + ssize_t space, nr; + size_t off, len; + + ret = -EMSGSIZE; + space = frag_limit - skb_shinfo(skb)->nr_frags; + if (space < 0) + break; + + /* We might be able to coalesce without increasing nr_frags */ + nr = clamp_t(size_t, space, 1, ARRAY_SIZE(pages)); + + len = iov_iter_extract_pages(iter, &ppages, maxsize, nr, 0, &off); + if (len <= 0) { + ret = len ?: -EIO; + break; + } + + if (space == 0 && + !skb_can_coalesce(skb, skb_shinfo(skb)->nr_frags, + pages[0], off)) { + iov_iter_revert(iter, len); + break; + } + + i = 0; + do { + struct page *page = pages[i++]; + size_t part = min_t(size_t, PAGE_SIZE - off, len); + + ret = -EIO; + if (!sendpage_ok(page)) + goto out; + + ret = skb_append_pagefrags(skb, page, off, part, + frag_limit); + if (ret < 0) { + iov_iter_revert(iter, len); + goto out; + } + + if (skb->ip_summed == CHECKSUM_NONE) + skb_splice_csum_page(skb, page, off, part); + + off = 0; + spliced += part; + maxsize -= part; + len -= part; + } while (len > 0); + + if (maxsize <= 0) + break; + } + +out: + skb_len_add(skb, spliced); + return spliced ?: ret; +} +EXPORT_SYMBOL(skb_splice_from_iter);