pipe: add support for shrinking and growing pipes

This patch adds F_GETPIPE_SZ and F_SETPIPE_SZ fcntl() actions for
growing and shrinking the size of a pipe and adjusts pipe.c and splice.c
(and relay and network splice) usage to work with these larger (or smaller)
pipes.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 21 insertions, 17 deletions

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 93c4e06..9319817 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1417,12 +1417,13 @@ new_page:
 /*
  * 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,
+static inline int spd_fill_page(struct splice_pipe_desc *spd,
+				struct pipe_inode_info *pipe, struct page *page,
 				unsigned int *len, unsigned int offset,
 				struct sk_buff *skb, int linear,
 				struct sock *sk)
 {
-	if (unlikely(spd->nr_pages == PIPE_BUFFERS))
+	if (unlikely(spd->nr_pages == pipe->buffers))
 		return 1;
 
 	if (linear) {
@@ -1458,7 +1459,8 @@ static inline int __splice_segment(struct page *page, unsigned int poff,
 				   unsigned int plen, unsigned int *off,
 				   unsigned int *len, struct sk_buff *skb,
 				   struct splice_pipe_desc *spd, int linear,
-				   struct sock *sk)
+				   struct sock *sk,
+				   struct pipe_inode_info *pipe)
 {
 	if (!*len)
 		return 1;
@@ -1481,7 +1483,7 @@ static inline int __splice_segment(struct page *page, unsigned int poff,
 		/* the linear region may spread across several pages  */
 		flen = min_t(unsigned int, flen, PAGE_SIZE - poff);
 
-		if (spd_fill_page(spd, page, &flen, poff, skb, linear, sk))
+		if (spd_fill_page(spd, pipe, page, &flen, poff, skb, linear, sk))
 			return 1;
 
 		__segment_seek(&page, &poff, &plen, flen);
@@ -1496,9 +1498,9 @@ static inline int __splice_segment(struct page *page, unsigned int poff,
  * Map linear and fragment data from the skb to spd. It reports failure if the
  * pipe is full or if we already spliced the requested length.
  */
-static int __skb_splice_bits(struct sk_buff *skb, unsigned int *offset,
-			     unsigned int *len, struct splice_pipe_desc *spd,
-			     struct sock *sk)
+static int __skb_splice_bits(struct sk_buff *skb, struct pipe_inode_info *pipe,
+			     unsigned int *offset, unsigned int *len,
+			     struct splice_pipe_desc *spd, struct sock *sk)
 {
 	int seg;
 
@@ -1508,7 +1510,7 @@ static int __skb_splice_bits(struct sk_buff *skb, unsigned int *offset,
 	if (__splice_segment(virt_to_page(skb->data),
 			     (unsigned long) skb->data & (PAGE_SIZE - 1),
 			     skb_headlen(skb),
-			     offset, len, skb, spd, 1, sk))
+			     offset, len, skb, spd, 1, sk, pipe))
 		return 1;
 
 	/*
@@ -1518,7 +1520,7 @@ static int __skb_splice_bits(struct sk_buff *skb, unsigned int *offset,
 		const skb_frag_t *f = &skb_shinfo(skb)->frags[seg];
 
 		if (__splice_segment(f->page, f->page_offset, f->size,
-				     offset, len, skb, spd, 0, sk))
+				     offset, len, skb, spd, 0, sk, pipe))
 			return 1;
 	}
 
@@ -1535,8 +1537,8 @@ 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 partial_page partial[PIPE_DEF_BUFFERS];
+	struct page *pages[PIPE_DEF_BUFFERS];
 	struct splice_pipe_desc spd = {
 		.pages = pages,
 		.partial = partial,
@@ -1546,12 +1548,16 @@ int skb_splice_bits(struct sk_buff *skb, unsigned int offset,
 	};
 	struct sk_buff *frag_iter;
 	struct sock *sk = skb->sk;
+	int ret = 0;
+
+	if (splice_grow_spd(pipe, &spd))
+		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, sk))
+	if (__skb_splice_bits(skb, pipe, &offset, &tlen, &spd, sk))
 		goto done;
 	else if (!tlen)
 		goto done;
@@ -1562,14 +1568,12 @@ int skb_splice_bits(struct sk_buff *skb, unsigned int offset,
 	skb_walk_frags(skb, frag_iter) {
 		if (!tlen)
 			break;
-		if (__skb_splice_bits(frag_iter, &offset, &tlen, &spd, sk))
+		if (__skb_splice_bits(frag_iter, pipe, &offset, &tlen, &spd, sk))
 			break;
 	}
 
 done:
 	if (spd.nr_pages) {
-		int ret;
-
 		/*
 		 * Drop the socket lock, otherwise we have reverse
 		 * locking dependencies between sk_lock and i_mutex
@@ -1582,10 +1586,10 @@ done:
 		release_sock(sk);
 		ret = splice_to_pipe(pipe, &spd);
 		lock_sock(sk);
-		return ret;
 	}
 
-	return 0;
+	splice_shrink_spd(pipe, &spd);
+	return ret;
 }
 
 /**