Re: [RFC PATCH v3 5/8] ata_dev_printk: Use dev_printk

From: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
To: Tony Asleson <tasleson@redhat.com>
Cc: linux-scsi@vger.kernel.org, linux-block@vger.kernel.org,
	linux-ide@vger.kernel.org
Subject: Re: [RFC PATCH v3 5/8] ata_dev_printk: Use dev_printk
Date: Wed, 24 Jun 2020 12:35:31 +0200	[thread overview]
Message-ID: <d817c9dd-6852-9233-5f61-1c0bc0f65ca4@samsung.com> (raw)
In-Reply-To: <20200623191749.115200-6-tasleson@redhat.com>

[ added linux-ide ML to Cc: ]

Hi,

On 6/23/20 9:17 PM, Tony Asleson wrote:
> Utilize the dev_printk function which will add structured data
> to the log message.
> 
> Signed-off-by: Tony Asleson <tasleson@redhat.com>
> ---
>  drivers/ata/libata-core.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
> index beca5f91bb4c..44c874367fe3 100644
> --- a/drivers/ata/libata-core.c
> +++ b/drivers/ata/libata-core.c
> @@ -6475,6 +6475,7 @@ EXPORT_SYMBOL(ata_link_printk);
>  void ata_dev_printk(const struct ata_device *dev, const char *level,
>  		    const char *fmt, ...)
>  {
> +	const struct device *gendev;
>  	struct va_format vaf;
>  	va_list args;
>  
> @@ -6483,9 +6484,12 @@ void ata_dev_printk(const struct ata_device *dev, const char *level,
>  	vaf.fmt = fmt;
>  	vaf.va = &args;
>  
> -	printk("%sata%u.%02u: %pV",
> -	       level, dev->link->ap->print_id, dev->link->pmp + dev->devno,
> -	       &vaf);
> +	gendev = (dev->sdev) ? &dev->sdev->sdev_gendev : &dev->tdev;
> +
> +	dev_printk(level, gendev, "ata%u.%02u: %pV",
> +			dev->link->ap->print_id,

This duplicates the device information and breaks integrity of
libata logging functionality (ata_{dev,link,port}_printk() should
be all converted to use dev_printk() at the same time).

The root source of problem is that libata transport uses different
naming scheme for ->tdev devices (please see dev_set_name() in
ata_t{dev,link,port}_add()) than libata core for its logging
functionality (ata_{dev,link,port}_printk()).

Since libata transport is part of sysfs ABI we should be careful
to not break it so one idea for solving the issue is to convert
ata_t{dev,link,port}_add() to use libata logging naming scheme and
at the same time add sysfs symlinks for the old libata transport
naming scheme.

dev->sdev usage is not required for dev_printk() conversion and
should be considered as a separate change (since it also breaks
integrity of libata logging and can be considered as a mild
"layering violation" I don't think that it should be applied).

> +			dev->link->pmp + dev->devno,
> +			&vaf);
>  
>  	va_end(args);
>  }
> 

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics