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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> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 4E38C20017 X-Stat-Signature: 5gb48h7xb3zotesw73qtmk3fpep66bni X-HE-Tag: 1742573682-149159 X-HE-Meta: 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 a1CDB5gk VyPxxKqGWu5hOubb5s8dX/GNdWD0ZvD5w/+v/0x/GYnM6r/vxf4fMUCAwfXny6m9Lf+x8LEIqgTVMURixBpbzBA0dRUtOvUzLTf1DWQ819s/zdh5ZcsPBNS+U7cCrwdzNi8l25XeWD2SrGobSo7Iz+Uq+1ymj2WZUrOHtZJZ5TucR/mCog3McMI1sGwnW4FR6TTJQey3RXg4NEI0oAP861KwygNgSvRaImfSBNKKgi7ImNp+z0cxXUEmbxvAH5ycFPHbviEKCxjRCjw7YD36p9XLMaJWVSbGCkOGmQg+9iXBKhygLXh2Fvs33ePYLuxLAtDYmDgxVa6DOo3tCvPexf+LwlKbvzbBV0IGmXHF30kc2rMz3DijLOWjUqv9Tk0DUBPxN X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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; }