Re: [PATCH 1/3] core/coio_file: Use eio_sendfile_sync instead of a chunk mode

[Vladimir Davydov <vdavydov.dev@gmail.com>]

On Tue, Apr 16, 2019 at 11:08:56PM +0300, Cyrill Gorcunov wrote:
> eio library provides a portable version of sendfile syscall
> which works a way more efficient than explicit copying file
> by 4K chunks.
> 
> Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
> ---
>  src/lib/core/coio_file.c | 26 +++++++++++---------------
>  1 file changed, 11 insertions(+), 15 deletions(-)

The patch looks fine, but we typically don't split tests from the code
when submitting a patch, i.e. I'd squash all the three patches in one.

Also, after having added a new error injection, you have to update
box/errinj.result. Please do.

Also, please check that app/fio.test.lua works fine when Tarantool is
built in Release mode. The thing is we typically disable tests using
error injections for Release builds, because they don't work there
(see suite.ini:release_disabled). I assume the test case you submitted
should pass even without the error injection, nevertheless better check
that.

> 
> diff --git a/src/lib/core/coio_file.c b/src/lib/core/coio_file.c
> index c5b2db781..20053558e 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;
> -
> +	off_t pos, ret, left;

Nit: We don't have a requirement to define all variables in the
beginning of a code block. I'd define these variables right before
the 'for' loop where they are used.

>  	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);