linux-kernel - Re: [PATCH v20 23/32] splice: Convert trace/seq to use direct_splice

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Date:   Mon, 22 May 2023 10:29:20 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     David Howells <dhowells@...hat.com>
Cc:     Jens Axboe <axboe@...nel.dk>, Al Viro <viro@...iv.linux.org.uk>,
        Christoph Hellwig <hch@...radead.org>,
        Matthew Wilcox <willy@...radead.org>, Jan Kara <jack@...e.cz>,
        Jeff Layton <jlayton@...nel.org>,
        David Hildenbrand <david@...hat.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Logan Gunthorpe <logang@...tatee.com>,
        Hillf Danton <hdanton@...a.com>,
        Christian Brauner <brauner@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-fsdevel@...r.kernel.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Christoph Hellwig <hch@....de>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH v20 23/32] splice: Convert trace/seq to use
 direct_splice_read()

On Fri, 19 May 2023 08:40:38 +0100
David Howells <dhowells@...hat.com> 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@...hat.com>
> cc: Christoph Hellwig <hch@....de>
> cc: Al Viro <viro@...iv.linux.org.uk>
> cc: Jens Axboe <axboe@...nel.dk>
> cc: Steven Rostedt <rostedt@...dmis.org>
> cc: Masami Hiramatsu <mhiramat@...nel.org>
> cc: linux-kernel@...r.kernel.org
> cc: linux-trace-kernel@...r.kernel.org
> cc: linux-fsdevel@...r.kernel.org
> cc: linux-block@...r.kernel.org
> cc: linux-mm@...ck.org
> ---
>  kernel/trace/trace.c | 2 +-

Acked-by: Steven Rostedt (Google) <rostedt@...dmis.org>

-- 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,