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 93c4e060c91e..931981774b1a 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;
 }
 
 /**