linux-ext4 - Re: [RFCv3 10/10] iomap: Add trace points for DIO path

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Message-ID: <ZDjs+/T/mf1nHUHI@infradead.org>
Date:   Thu, 13 Apr 2023 23:04:43 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     "Ritesh Harjani (IBM)" <ritesh.list@...il.com>
Cc:     linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
        Jan Kara <jack@...e.cz>, Christoph Hellwig <hch@...radead.org>,
        "Darrick J . Wong" <djwong@...nel.org>,
        Ojaswin Mujoo <ojaswin@...ux.ibm.com>,
        Disha Goel <disgoel@...ux.ibm.com>
Subject: Re: [RFCv3 10/10] iomap: Add trace points for DIO path

> +	trace_iomap_dio_rw_begin(iocb, iter, dio_flags, done_before, ret);
>  	dio = __iomap_dio_rw(iocb, iter, ops, dops, dio_flags, private,
>  			     done_before);
>  	if (IS_ERR_OR_NULL(dio)) {
> @@ -689,6 +691,7 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
>  	}
>  	ret = iomap_dio_complete(dio);
>  out:
> +	trace_iomap_dio_rw_end(iocb, iter, dio_flags, done_before, ret);

The trace_iomap_dio_rw_end tracepoint heere seems a bit weird,
and we'll miss it for file systems using  __iomap_dio_rw directly.

I'd instead add a trace_iomap_dio_rw_queued for the case where
__iomap_dio_rw returns ERR_PTR(-EIOCBQUEUED), as otherwise we're
nicely covered by the complete trace points.

> +		  __print_flags(__entry->dio_flags, "|", TRACE_IOMAP_DIO_STRINGS),

Please avoid the overly lone line here.