Re: [PATCH v20 23/32] splice: Convert trace/seq to use direct_splice_read()

[Steven Rostedt]

On Fri, 19 May 2023 08:40:38 +0100
David Howells <dhowells@xxxxxxxxxx> wrote:

> For the splice from the trace seq buffer, just use direct_splice_read().
> 
> In the future, something better can probably be done by gifting pages from
> seq->buf into the pipe, but that would require changing seq->buf into a
> vmap over an array of pages.

If you can give me a POC of what needs to be done, I could possibly
implement it.

> 
> Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
> cc: Christoph Hellwig <hch@xxxxxx>
> cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> cc: Jens Axboe <axboe@xxxxxxxxx>
> cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
> cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> cc: linux-kernel@xxxxxxxxxxxxxxx
> cc: linux-trace-kernel@xxxxxxxxxxxxxxx
> cc: linux-fsdevel@xxxxxxxxxxxxxxx
> cc: linux-block@xxxxxxxxxxxxxxx
> cc: linux-mm@xxxxxxxxx
> ---
>  kernel/trace/trace.c | 2 +-

Acked-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>

-- Steve

>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index ebc59781456a..b664020efcb7 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -5171,7 +5171,7 @@ static const struct file_operations tracing_fops = {
>  	.open		= tracing_open,
>  	.read		= seq_read,
>  	.read_iter	= seq_read_iter,
> -	.splice_read	= generic_file_splice_read,
> +	.splice_read	= direct_splice_read,
>  	.write		= tracing_write_stub,
>  	.llseek		= tracing_lseek,
>  	.release	= tracing_release,