new helper: add_to_pipe()

single-buffer analogue of splice_to_pipe(); vmsplice_to_pipe() switched
to that, leaving splice_to_pipe() only for ->splice_read() instances
(and that only until they are converted as well).

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/splice.c b/fs/splice.c
index 2ca7e69..e13d935 100644 (file)
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -203,8 +203,6 @@ ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
                buf->len = spd->partial[page_nr].len;
                buf->private = spd->partial[page_nr].private;
                buf->ops = spd->ops;
-               if (spd->flags & SPLICE_F_GIFT)
-                       buf->flags |= PIPE_BUF_FLAG_GIFT;
 
                pipe->nrbufs++;
                page_nr++;
@@ -225,6 +223,27 @@ out:
 }
 EXPORT_SYMBOL_GPL(splice_to_pipe);
 
+ssize_t add_to_pipe(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
+{
+       int ret;
+
+       if (unlikely(!pipe->readers)) {
+               send_sig(SIGPIPE, current, 0);
+               ret = -EPIPE;
+       } else if (pipe->nrbufs == pipe->buffers) {
+               ret = -EAGAIN;
+       } else {
+               int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
+               pipe->bufs[newbuf] = *buf;
+               pipe->nrbufs++;
+               return buf->len;
+       }
+       buf->ops->release(pipe, buf);
+       buf->ops = NULL;
+       return ret;
+}
+EXPORT_SYMBOL(add_to_pipe);
+
 void spd_release_page(struct splice_pipe_desc *spd, unsigned int i)
 {
        put_page(spd->pages[i]);
@@ -1415,32 +1434,50 @@ static long do_splice(struct file *in, loff_t __user *off_in,
        return -EINVAL;
 }
 
-static int get_iovec_page_array(struct iov_iter *from,
-                               struct page **pages,
-                               struct partial_page *partial,
-                               unsigned int pipe_buffers)
+static int iter_to_pipe(struct iov_iter *from,
+                       struct pipe_inode_info *pipe,
+                       unsigned flags)
 {
-       int buffers = 0;
-       while (iov_iter_count(from)) {
+       struct pipe_buffer buf = {
+               .ops = &user_page_pipe_buf_ops,
+               .flags = flags
+       };
+       size_t total = 0;
+       int ret = 0;
+       bool failed = false;
+
+       while (iov_iter_count(from) && !failed) {
+               struct page *pages[16];
                ssize_t copied;
                size_t start;
+               int n;
 
-               copied = iov_iter_get_pages(from, pages + buffers, ~0UL,
-                                       pipe_buffers - buffers, &start);
-               if (copied <= 0)
-                       return buffers ? buffers : copied;
+               copied = iov_iter_get_pages(from, pages, ~0UL, 16, &start);
+               if (copied <= 0) {
+                       ret = copied;
+                       break;
+               }
 
-               iov_iter_advance(from, copied);
-               while (copied) {
+               for (n = 0; copied; n++, start = 0) {
                        int size = min_t(int, copied, PAGE_SIZE - start);
-                       partial[buffers].offset = start;
-                       partial[buffers].len = size;
+                       if (!failed) {
+                               buf.page = pages[n];
+                               buf.offset = start;
+                               buf.len = size;
+                               ret = add_to_pipe(pipe, &buf);
+                               if (unlikely(ret < 0)) {
+                                       failed = true;
+                               } else {
+                                       iov_iter_advance(from, ret);
+                                       total += ret;
+                               }
+                       } else {
+                               put_page(pages[n]);
+                       }
                        copied -= size;
-                       start = 0;
-                       buffers++;
                }
        }
-       return buffers;
+       return total ? total : ret;
 }
 
 static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
@@ -1501,17 +1538,11 @@ static long vmsplice_to_pipe(struct file *file, const struct iovec __user *uiov,
        struct iovec iovstack[UIO_FASTIOV];
        struct iovec *iov = iovstack;
        struct iov_iter from;
-       struct page *pages[PIPE_DEF_BUFFERS];
-       struct partial_page partial[PIPE_DEF_BUFFERS];
-       struct splice_pipe_desc spd = {
-               .pages = pages,
-               .partial = partial,
-               .nr_pages_max = PIPE_DEF_BUFFERS,
-               .flags = flags,
-               .ops = &user_page_pipe_buf_ops,
-               .spd_release = spd_release_page,
-       };
        long ret;
+       unsigned buf_flag = 0;
+
+       if (flags & SPLICE_F_GIFT)
+               buf_flag = PIPE_BUF_FLAG_GIFT;
 
        pipe = get_pipe_info(file);
        if (!pipe)
@@ -1522,26 +1553,13 @@ static long vmsplice_to_pipe(struct file *file, const struct iovec __user *uiov,
        if (ret < 0)
                return ret;
 
-       if (splice_grow_spd(pipe, &spd)) {
-               kfree(iov);
-               return -ENOMEM;
-       }
-
        pipe_lock(pipe);
        ret = wait_for_space(pipe, flags);
-       if (!ret) {
-               spd.nr_pages = get_iovec_page_array(&from, spd.pages,
-                                                   spd.partial,
-                                                   spd.nr_pages_max);
-               if (spd.nr_pages <= 0)
-                       ret = spd.nr_pages;
-               else
-                       ret = splice_to_pipe(pipe, &spd);
-       }
+       if (!ret)
+               ret = iter_to_pipe(&from, pipe, buf_flag);
        pipe_unlock(pipe);
        if (ret > 0)
                wakeup_pipe_readers(pipe);
-       splice_shrink_spd(&spd);
        kfree(iov);
        return ret;
 }

diff --git a/include/linux/splice.h b/include/linux/splice.h
index da2751d..58b300f 100644 (file)
--- a/include/linux/splice.h
+++ b/include/linux/splice.h
@@ -72,6 +72,8 @@ extern ssize_t __splice_from_pipe(struct pipe_inode_info *,
                                  struct splice_desc *, splice_actor *);
 extern ssize_t splice_to_pipe(struct pipe_inode_info *,
                              struct splice_pipe_desc *);
+extern ssize_t add_to_pipe(struct pipe_inode_info *,
+                             struct pipe_buffer *);
 extern ssize_t splice_direct_to_actor(struct file *, struct splice_desc *,
                                      splice_direct_actor *);