From patchwork Fri Mar 21 16:14:04 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Howells X-Patchwork-Id: 14025742 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0B5B622D784 for ; Fri, 21 Mar 2025 16:14:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742573683; cv=none; b=QQY9QrGHlPuVy++xkMqtudtmJ7K4rQfxAVyjsaH/stcvKRoygWpke8XobGs8wRoqD6u8BDWe+gTJUhRVm2ql9vfNwdqLHXtXR5zakZvWEXqVRVBMbgKhb9n3gnSAXofGQUgTqk4w/IySIpQbISvEl4SHbxTOpXfFtxD+Qo7JW4k= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742573683; c=relaxed/simple; bh=QJbi407Gq8VLLgi9E0vdiZ8uX6C0oRfqhu+9aRZPznQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=daf9Kc8qBWAh2eyahM3RwOU6y2rDFcNCQviNS7yNvYmcMjX3pcq/4Fq1KcquJyD7mgSYN2R6UQ0SwGPYpVFui4pqOlHbRfERb4Y2xK44egekI8pHkhEbJn4I1jS5t0oF5DC5LTWuZe+xpyeNqque/RL176RliqUITTS3Bgfz7DM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=fUyR66yB; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="fUyR66yB" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1742573681; 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=ZSC5YwicpO03gYExoUotpiHs2EHAFn+TU50pqasUPmU=; b=fUyR66yBRHzm/ShjZ21CTTJI+8j7fFOJ0k+OCDh6tDA+EnLgilXsMuHmvNu6vScYXBY6rF mzZ0WpWL7eZrjC0D/efBRkM6TxoIr9JqttFZTDxyyY4AO6CuuGeQLVT5udaaw0A0BywPxR WCK529Xwxu0h5X1r1AaBV6FBDaUTe8U= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-208-Ev37cor8PDCv9N0Af2ivaQ-1; Fri, 21 Mar 2025 12:14:37 -0400 X-MC-Unique: Ev37cor8PDCv9N0Af2ivaQ-1 X-Mimecast-MFC-AGG-ID: Ev37cor8PDCv9N0Af2ivaQ_1742573674 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 3680C1801A07; Fri, 21 Mar 2025 16:14:34 +0000 (UTC) Received: from warthog.procyon.org.com (unknown [10.42.28.61]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id ED872180174E; Fri, 21 Mar 2025 16:14:30 +0000 (UTC) From: David Howells To: Leon Romanovsky Cc: David Howells , Christian Brauner , Matthew Wilcox , Chuck Lever , Steve French , Ilya Dryomov , netfs@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [RFC PATCH 4/4] iov_iter: Add a scatterlist iterator type [INCOMPLETE] Date: Fri, 21 Mar 2025 16:14:04 +0000 Message-ID: <20250321161407.3333724-5-dhowells@redhat.com> In-Reply-To: <20250321161407.3333724-1-dhowells@redhat.com> References: <20250321161407.3333724-1-dhowells@redhat.com> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Add an iterator type that can iterate over a socket buffer. [!] Note this is not yet completely implemented and won't compile. Signed-off-by: David Howells --- include/linux/uio.h | 10 ++++ lib/iov_iter.c | 121 ++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 131 insertions(+) diff --git a/include/linux/uio.h b/include/linux/uio.h index 0e50f4af6877..87d6ba660489 100644 --- a/include/linux/uio.h +++ b/include/linux/uio.h @@ -13,6 +13,7 @@ struct page; struct folio_queue; struct scatterlist; +struct sk_buff; typedef unsigned int __bitwise iov_iter_extraction_t; @@ -32,6 +33,7 @@ enum iter_type { ITER_DISCARD, ITER_ITERLIST, ITER_SCATTERLIST, + ITER_SKBUFF, }; #define ITER_SOURCE 1 // == WRITE @@ -77,6 +79,7 @@ struct iov_iter { void __user *ubuf; struct iov_iterlist *iterlist; struct scatterlist *sglist; + const struct sk_buff *skb; }; size_t count; }; @@ -171,6 +174,11 @@ static inline bool iov_iter_is_scatterlist(const struct iov_iter *i) return iov_iter_type(i) == ITER_SCATTERLIST; } +static inline bool iov_iter_is_skbuff(const struct iov_iter *i) +{ + return iov_iter_type(i) == ITER_SKBUFF; +} + static inline unsigned char iov_iter_rw(const struct iov_iter *i) { return i->data_source ? WRITE : READ; @@ -329,6 +337,8 @@ void iov_iter_iterlist(struct iov_iter *i, unsigned int direction, size_t count); void iov_iter_scatterlist(struct iov_iter *i, unsigned int direction, struct scatterlist *sglist, size_t count); +void iov_iter_skbuff(struct iov_iter *i, unsigned int direction, + const struct sk_buff *skb, size_t count); ssize_t iov_iter_get_pages2(struct iov_iter *i, struct page **pages, size_t maxsize, unsigned maxpages, size_t *start); ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i, struct page ***pages, diff --git a/lib/iov_iter.c b/lib/iov_iter.c index ed9859af3c5d..01215316d272 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -12,6 +12,7 @@ #include #include #include +#include static __always_inline size_t copy_to_user_iter(void __user *iter_to, size_t progress, @@ -918,6 +919,29 @@ void iov_iter_scatterlist(struct iov_iter *iter, unsigned int direction, } EXPORT_SYMBOL(iov_iter_scatterlist); +/** + * iov_iter_skbuff - Initialise an I/O iterator for a socket buffer + * @iter: The iterator to initialise. + * @direction: The direction of the transfer. + * @skb: The socket buffer + * @count: The size of the I/O buffer in bytes. + * + * Set up an I/O iterator that walks over a socket buffer. + */ +void iov_iter_skbuff(struct iov_iter *i, unsigned int direction, + const struct sk_buff *skb, size_t count) +{ + WARN_ON(direction & ~(READ | WRITE)); + *iter = (struct iov_iter){ + .iter_type = ITER_SKBUFF, + .data_source = direction, + .skb = skb, + .iov_offset = 0, + .count = count, + }; +} +EXPORT_SYMBOL(iov_iter_skbuff); + static bool iov_iter_aligned_iovec(const struct iov_iter *i, unsigned addr_mask, unsigned len_mask) { @@ -2314,6 +2338,10 @@ ssize_t iov_iter_extract_pages(struct iov_iter *i, return iov_iter_extract_scatterlist_pages(i, pages, maxsize, maxpages, extraction_flags, offset0); + if (iov_iter_is_skbuff(i)) + return iov_iter_extract_skbuff_pages(i, pages, maxsize, + maxpages, extraction_flags, + offset0); return -EFAULT; } EXPORT_SYMBOL_GPL(iov_iter_extract_pages); @@ -2449,6 +2477,97 @@ static size_t iterate_scatterlist(struct iov_iter *iter, size_t len, void *priv, return progress; } +struct skbuff_iter_ctx { + iov_step_f step; + size_t progress; + void *priv; + void *priv2; +}; + +static bool iterate_skbuff_frag(const struct sk_buff *skb, struct skbuff_iter_ctx *ctx, + int offset, int len, int recursion_level) +{ + struct sk_buff *frag_iter; + size_t skip = offset, part, remain, consumed; + + if (unlikely(recursion_level >= 24)) + return false; + + part = skb_headlen(skb); + if (skip < part) { + part = umin(part - skip, len); + remain = ctx->step(skb->data + skip, ctx->progress, part, + ctx->priv, ctx->priv2); + consumed = part - remain; + ctx->progress += consumed; + len -= consumed; + if (remain > 0 || len <= 0) + return false; + skip = 0; + } else { + skip -= part; + } + + for (int i = 0; i < skb_shinfo(skb)->nr_frags; i++) { + const skb_frag_t *frag = &skb_shinfo(skb)->frags[i]; + size_t fsize = skb_frag_size(frag); + + if (skip >= fsize) { + skip -= fsize; + continue; + } + + part = umin(fsize - skip, len); + remain = ctx->step(skb_frag_address(frag) + skip, + ctx->progress, part, ctx->priv, ctx->priv2); + consumed = part - remain; + ctx->progress += consumed; + len -= consumed; + if (remain > 0 || len <= 0) + return false; + skip = 0; + } + + skb_walk_frags(skb, frag_iter) { + size_t fsize = frag_iter->len; + + if (skip >= fsize) { + skip -= fsize; + continue; + } + + part = umin(fsize - skip, len); + if (!iterate_skbuff_frag(frag_iter, ctx, skb_headlen(skb) + skip, + part, recursion_level + 1)) + return false; + len -= part; + if (len <= 0) + return false; + skip = 0; + } + return true; +} + +/* + * Handle iteration over ITER_SKBUFF. Modelled on __skb_to_sgvec(). + */ +static size_t iterate_skbuff(struct iov_iter *iter, size_t len, void *priv, void *priv2, + iov_step_f step) +{ + struct skbuff_iter_ctx ctx = { + .step = step, + .progress = 0, + .priv = priv, + .priv2 = priv2, + }; + + iterate_skbuff_frag(iter->skb, &ctx, iter->iov_offset, len, 0); + + iter->iov_offset += ctx.progress; + iter->count -= ctx.progress; + return ctx.progress; +} + /* * Out of line iteration for iterator types that don't need such fast handling. */ @@ -2463,6 +2582,8 @@ size_t __iterate_and_advance2(struct iov_iter *iter, size_t len, void *priv, return iterate_iterlist(iter, len, priv, priv2, ustep, step); if (iov_iter_is_scatterlist(iter)) return iterate_scatterlist(iter, len, priv, priv2, step); + if (iov_iter_is_skbuff(iter)) + return iterate_skbuff(iter, len, priv, priv2, step); WARN_ON(1); return 0; }