[PATCH v2] core/coio_file: Use eio_sendfile_sync instead of a chunk mode

[Cyrill Gorcunov <gorcunov@gmail.com>]

eio library provides a portable version of sendfile syscall
which works more efficient than explicit copying fileby 4K
chunks.

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
---
v2:
 - Use sendfile in a cycle to address files more than 2G size
 - Proper testing of large files remains opened: current CI engine
   is hardly capable of managing it. I tested 200M files with manual
   splitting (to make sure the offsets do really work) but for longterm
   we still might need to invent something
 - Another question which remains -- what to do with partially copied
   files, neither code before the patch or after do not clean up parts
   of copied data. Should not we clean it up on error path? If yes then
   I'll prepare another patch on top.

 src/lib/core/coio_file.c | 26 +++++++++++---------------
 1 file changed, 11 insertions(+), 15 deletions(-)

diff --git a/src/lib/core/coio_file.c b/src/lib/core/coio_file.c
index c5b2db781..541e0f05a 100644
--- a/src/lib/core/coio_file.c
+++ b/src/lib/core/coio_file.c
@@ -571,7 +571,7 @@ static void
 coio_do_copyfile(eio_req *req)
 {
 	struct coio_file_task *eio = (struct coio_file_task *)req->data;
-
+	ssize_t pos, ret, left;
 	struct stat st;
 	if (stat(eio->copyfile.source, &st) < 0) {
 		goto error;
@@ -588,22 +588,18 @@ coio_do_copyfile(eio_req *req)
 		goto error_dest;
 	}
 
-	enum { COPY_FILE_BUF_SIZE = 4096 };
-
-	char buf[COPY_FILE_BUF_SIZE];
-
-	while (true) {
-		ssize_t nread = fio_read(source_fd, buf, sizeof(buf));
-		if (nread < 0)
-			goto error_copy;
-
-		if (nread == 0)
-			break; /* eof */
-
-		ssize_t nwritten = fio_writen(dest_fd, buf, nread);
-		if (nwritten < 0)
+	for (left = st.st_size, pos = 0; left > 0;) {
+		ret = eio_sendfile_sync(dest_fd, source_fd, pos, left);
+		if (ret < 0) {
+			say_syserror("sendfile, [%s -> %s]",
+				     fio_filename(source_fd),
+				     fio_filename(dest_fd));
 			goto error_copy;
+		}
+		pos += ret;
+		left -= ret;
 	}
+
 	req->result = 0;
 	close(source_fd);
 	close(dest_fd);
-- 
2.20.1