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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 v8 03/16] net: Add a function to splice pages into an skbuff for MSG_SPLICE_PAGES Date: Thu, 18 May 2023 12:34:40 +0100 Message-Id: <20230518113453.1350757-4-dhowells@redhat.com> In-Reply-To: <20230518113453.1350757-1-dhowells@redhat.com> References: <20230518113453.1350757-1-dhowells@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.7 X-Stat-Signature: eho85ramhnwe5361gtu75mg88rdfs8dx X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 82FFA1C000F X-Rspam-User: X-HE-Tag: 1684409723-761374 X-HE-Meta: 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 aGMhcbJZ 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 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: 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 #8) - Order local variables in reverse xmas tree order. - Remove duplicate coalescence check. - Warn if sendpage_ok() fails. ver #7) - Export function. - Never copy data, return -EIO if sendpage_ok() returns false. include/linux/skbuff.h | 3 ++ net/core/skbuff.c | 88 ++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 91 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..f4a5b51aed22 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -6892,3 +6892,91 @@ 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) +{ + size_t frag_limit = READ_ONCE(sysctl_max_skb_frags); + struct page *pages[8], **ppages = pages; + ssize_t spliced = 0, ret = 0; + unsigned int i; + + 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; + } + + i = 0; + do { + struct page *page = pages[i++]; + size_t part = min_t(size_t, PAGE_SIZE - off, len); + + ret = -EIO; + if (WARN_ON_ONCE(!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);