[TCP]: Splice receive support.
Support for network splice receive.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index b628377..98420f9 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -52,6 +52,7 @@
#endif
#include <linux/string.h>
#include <linux/skbuff.h>
+#include <linux/splice.h>
#include <linux/cache.h>
#include <linux/rtnetlink.h>
#include <linux/init.h>
@@ -71,6 +72,40 @@
static struct kmem_cache *skbuff_head_cache __read_mostly;
static struct kmem_cache *skbuff_fclone_cache __read_mostly;
+static void sock_pipe_buf_release(struct pipe_inode_info *pipe,
+ struct pipe_buffer *buf)
+{
+ struct sk_buff *skb = (struct sk_buff *) buf->private;
+
+ kfree_skb(skb);
+}
+
+static void sock_pipe_buf_get(struct pipe_inode_info *pipe,
+ struct pipe_buffer *buf)
+{
+ struct sk_buff *skb = (struct sk_buff *) buf->private;
+
+ skb_get(skb);
+}
+
+static int sock_pipe_buf_steal(struct pipe_inode_info *pipe,
+ struct pipe_buffer *buf)
+{
+ return 1;
+}
+
+
+/* Pipe buffer operations for a socket. */
+static struct pipe_buf_operations sock_pipe_buf_ops = {
+ .can_merge = 0,
+ .map = generic_pipe_buf_map,
+ .unmap = generic_pipe_buf_unmap,
+ .confirm = generic_pipe_buf_confirm,
+ .release = sock_pipe_buf_release,
+ .steal = sock_pipe_buf_steal,
+ .get = sock_pipe_buf_get,
+};
+
/*
* Keep out-of-line to prevent kernel bloat.
* __builtin_return_address is not used because it is not always
@@ -1122,6 +1157,217 @@
return -EFAULT;
}
+/*
+ * Callback from splice_to_pipe(), if we need to release some pages
+ * at the end of the spd in case we error'ed out in filling the pipe.
+ */
+static void sock_spd_release(struct splice_pipe_desc *spd, unsigned int i)
+{
+ struct sk_buff *skb = (struct sk_buff *) spd->partial[i].private;
+
+ kfree_skb(skb);
+}
+
+/*
+ * Fill page/offset/length into spd, if it can hold more pages.
+ */
+static inline int spd_fill_page(struct splice_pipe_desc *spd, struct page *page,
+ unsigned int len, unsigned int offset,
+ struct sk_buff *skb)
+{
+ if (unlikely(spd->nr_pages == PIPE_BUFFERS))
+ return 1;
+
+ spd->pages[spd->nr_pages] = page;
+ spd->partial[spd->nr_pages].len = len;
+ spd->partial[spd->nr_pages].offset = offset;
+ spd->partial[spd->nr_pages].private = (unsigned long) skb_get(skb);
+ spd->nr_pages++;
+ return 0;
+}
+
+/*
+ * Map linear and fragment data from the skb to spd. Returns number of
+ * pages mapped.
+ */
+static int __skb_splice_bits(struct sk_buff *skb, unsigned int *offset,
+ unsigned int *total_len,
+ struct splice_pipe_desc *spd)
+{
+ unsigned int nr_pages = spd->nr_pages;
+ unsigned int poff, plen, len, toff, tlen;
+ int headlen, seg;
+
+ toff = *offset;
+ tlen = *total_len;
+ if (!tlen)
+ goto err;
+
+ /*
+ * if the offset is greater than the linear part, go directly to
+ * the fragments.
+ */
+ headlen = skb_headlen(skb);
+ if (toff >= headlen) {
+ toff -= headlen;
+ goto map_frag;
+ }
+
+ /*
+ * first map the linear region into the pages/partial map, skipping
+ * any potential initial offset.
+ */
+ len = 0;
+ while (len < headlen) {
+ void *p = skb->data + len;
+
+ poff = (unsigned long) p & (PAGE_SIZE - 1);
+ plen = min_t(unsigned int, headlen - len, PAGE_SIZE - poff);
+ len += plen;
+
+ if (toff) {
+ if (plen <= toff) {
+ toff -= plen;
+ continue;
+ }
+ plen -= toff;
+ poff += toff;
+ toff = 0;
+ }
+
+ plen = min(plen, tlen);
+ if (!plen)
+ break;
+
+ /*
+ * just jump directly to update and return, no point
+ * in going over fragments when the output is full.
+ */
+ if (spd_fill_page(spd, virt_to_page(p), plen, poff, skb))
+ goto done;
+
+ tlen -= plen;
+ }
+
+ /*
+ * then map the fragments
+ */
+map_frag:
+ for (seg = 0; seg < skb_shinfo(skb)->nr_frags; seg++) {
+ const skb_frag_t *f = &skb_shinfo(skb)->frags[seg];
+
+ plen = f->size;
+ poff = f->page_offset;
+
+ if (toff) {
+ if (plen <= toff) {
+ toff -= plen;
+ continue;
+ }
+ plen -= toff;
+ poff += toff;
+ toff = 0;
+ }
+
+ plen = min(plen, tlen);
+ if (!plen)
+ break;
+
+ if (spd_fill_page(spd, f->page, plen, poff, skb))
+ break;
+
+ tlen -= plen;
+ }
+
+done:
+ if (spd->nr_pages - nr_pages) {
+ *offset = 0;
+ *total_len = tlen;
+ return 0;
+ }
+err:
+ return 1;
+}
+
+/*
+ * Map data from the skb to a pipe. Should handle both the linear part,
+ * the fragments, and the frag list. It does NOT handle frag lists within
+ * the frag list, if such a thing exists. We'd probably need to recurse to
+ * handle that cleanly.
+ */
+int skb_splice_bits(struct sk_buff *__skb, unsigned int offset,
+ struct pipe_inode_info *pipe, unsigned int tlen,
+ unsigned int flags)
+{
+ struct partial_page partial[PIPE_BUFFERS];
+ struct page *pages[PIPE_BUFFERS];
+ struct splice_pipe_desc spd = {
+ .pages = pages,
+ .partial = partial,
+ .flags = flags,
+ .ops = &sock_pipe_buf_ops,
+ .spd_release = sock_spd_release,
+ };
+ struct sk_buff *skb;
+
+ /*
+ * I'd love to avoid the clone here, but tcp_read_sock()
+ * ignores reference counts and unconditonally kills the sk_buff
+ * on return from the actor.
+ */
+ skb = skb_clone(__skb, GFP_KERNEL);
+ if (unlikely(!skb))
+ return -ENOMEM;
+
+ /*
+ * __skb_splice_bits() only fails if the output has no room left,
+ * so no point in going over the frag_list for the error case.
+ */
+ if (__skb_splice_bits(skb, &offset, &tlen, &spd))
+ goto done;
+ else if (!tlen)
+ goto done;
+
+ /*
+ * now see if we have a frag_list to map
+ */
+ if (skb_shinfo(skb)->frag_list) {
+ struct sk_buff *list = skb_shinfo(skb)->frag_list;
+
+ for (; list && tlen; list = list->next) {
+ if (__skb_splice_bits(list, &offset, &tlen, &spd))
+ break;
+ }
+ }
+
+done:
+ /*
+ * drop our reference to the clone, the pipe consumption will
+ * drop the rest.
+ */
+ kfree_skb(skb);
+
+ if (spd.nr_pages) {
+ int ret;
+
+ /*
+ * Drop the socket lock, otherwise we have reverse
+ * locking dependencies between sk_lock and i_mutex
+ * here as compared to sendfile(). We enter here
+ * with the socket lock held, and splice_to_pipe() will
+ * grab the pipe inode lock. For sendfile() emulation,
+ * we call into ->sendpage() with the i_mutex lock held
+ * and networking will grab the socket lock.
+ */
+ release_sock(__skb->sk);
+ ret = splice_to_pipe(pipe, &spd);
+ lock_sock(__skb->sk);
+ return ret;
+ }
+
+ return 0;
+}
+
/**
* skb_store_bits - store bits from kernel buffer to skb
* @skb: destination buffer