[PATCH] Introduce sys_splice() system call
This adds support for the sys_splice system call. Using a pipe as a
transport, it can connect to files or sockets (latter as output only).
From the splice.c comments:
"splice": joining two ropes together by interweaving their strands.
This is the "extended pipe" functionality, where a pipe is used as
an arbitrary in-memory buffer. Think of a pipe as a small kernel
buffer that you can use to transfer data from one end to the other.
The traditional unix read/write is extended with a "splice()" operation
that transfers data buffers to or from a pipe buffer.
Named by Larry McVoy, original implementation from Linus, extended by
Jens to support splicing to files and fixing the initial implementation
bugs.
Signed-off-by: Jens Axboe <axboe@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/fs/pipe.c b/fs/pipe.c
index e2f4f1d..2414bf2 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -15,6 +15,7 @@
#include <linux/pipe_fs_i.h>
#include <linux/uio.h>
#include <linux/highmem.h>
+#include <linux/pagemap.h>
#include <asm/uaccess.h>
#include <asm/ioctls.h>
@@ -94,11 +95,20 @@
{
struct page *page = buf->page;
- if (info->tmp_page) {
- __free_page(page);
+ /*
+ * If nobody else uses this page, and we don't already have a
+ * temporary page, let's keep track of it as a one-deep
+ * allocation cache
+ */
+ if (page_count(page) == 1 && !info->tmp_page) {
+ info->tmp_page = page;
return;
}
- info->tmp_page = page;
+
+ /*
+ * Otherwise just release our reference to it
+ */
+ page_cache_release(page);
}
static void *anon_pipe_buf_map(struct file *file, struct pipe_inode_info *info, struct pipe_buffer *buf)
@@ -152,6 +162,11 @@
chars = total_len;
addr = ops->map(filp, info, buf);
+ if (IS_ERR(addr)) {
+ if (!ret)
+ ret = PTR_ERR(addr);
+ break;
+ }
error = pipe_iov_copy_to_user(iov, addr + buf->offset, chars);
ops->unmap(info, buf);
if (unlikely(error)) {
@@ -254,8 +269,16 @@
struct pipe_buf_operations *ops = buf->ops;
int offset = buf->offset + buf->len;
if (ops->can_merge && offset + chars <= PAGE_SIZE) {
- void *addr = ops->map(filp, info, buf);
- int error = pipe_iov_copy_from_user(offset + addr, iov, chars);
+ void *addr;
+ int error;
+
+ addr = ops->map(filp, info, buf);
+ if (IS_ERR(addr)) {
+ error = PTR_ERR(addr);
+ goto out;
+ }
+ error = pipe_iov_copy_from_user(offset + addr, iov,
+ chars);
ops->unmap(info, buf);
ret = error;
do_wakeup = 1;