linux-kernel - Re: [RFC PATCH] ata: pata_macio: Use WARN instead of BUG

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Message-ID: <737ad178-1198-4103-b1ee-46a67ecf12e4@kernel.org>
Date: Mon, 19 Aug 2024 20:01:53 +0900
From: Damien Le Moal <dlemoal@...nel.org>
To: Michael Ellerman <mpe@...erman.id.au>, cassel@...nel.org
Cc: linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org,
 linuxppc-dev@...ts.ozlabs.org, hch@....de, linux-ppc@...la.no,
 vidra@...l.mff.cuni.cz
Subject: Re: [RFC PATCH] ata: pata_macio: Use WARN instead of BUG

On 8/19/24 19:19, Michael Ellerman wrote:
> The overflow/underflow conditions in pata_macio_qc_prep() should never
> happen. But if they do there's no need to kill the system entirely, a
> WARN and failing the IO request should be sufficient and might allow the
> system to keep running.
> 
> Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
> ---
>  drivers/ata/pata_macio.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> Not sure if AC_ERR_OTHER is the right error code to use?

Given that this would trigger if the command split has is buggy, I think that
AC_ERR_SYSTEM would be better. Can you resend with the change and no "RFC" ?

> 
> diff --git a/drivers/ata/pata_macio.c b/drivers/ata/pata_macio.c
> index eaffa510de49..552e3ac0d391 100644
> --- a/drivers/ata/pata_macio.c
> +++ b/drivers/ata/pata_macio.c
> @@ -554,7 +554,8 @@ static enum ata_completion_errors pata_macio_qc_prep(struct ata_queued_cmd *qc)
>  
>  		while (sg_len) {
>  			/* table overflow should never happen */
> -			BUG_ON (pi++ >= MAX_DCMDS);
> +			if (WARN_ON_ONCE(pi >= MAX_DCMDS))
> +				return AC_ERR_OTHER;
>  
>  			len = (sg_len < MAX_DBDMA_SEG) ? sg_len : MAX_DBDMA_SEG;
>  			table->command = cpu_to_le16(write ? OUTPUT_MORE: INPUT_MORE);
> @@ -566,11 +567,13 @@ static enum ata_completion_errors pata_macio_qc_prep(struct ata_queued_cmd *qc)
>  			addr += len;
>  			sg_len -= len;
>  			++table;
> +			++pi;
>  		}
>  	}
>  
>  	/* Should never happen according to Tejun */
> -	BUG_ON(!pi);
> +	if (WARN_ON_ONCE(!pi))
> +		return AC_ERR_OTHER;
>  
>  	/* Convert the last command to an input/output */
>  	table--;

-- 
Damien Le Moal
Western Digital Research