linux-kernel - Re: [PATCH v2] powerpc/mm: move a KERN_WARNING message to pr

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Message-ID: <20190207030305.GA518@umbus.fritz.box>
Date:   Thu, 7 Feb 2019 14:03:05 +1100
From:   David Gibson <david@...son.dropbear.id.au>
To:     Laurent Vivier <lvivier@...hat.com>
Cc:     linux-kernel@...r.kernel.org,
        Michael Ellerman <mpe@...erman.id.au>,
        linuxppc-dev@...ts.ozlabs.org,
        Christophe Leroy <christophe.leroy@....fr>
Subject: Re: [PATCH v2] powerpc/mm: move a KERN_WARNING message to pr_debug()

On Tue, Feb 05, 2019 at 09:21:33PM +0100, Laurent Vivier wrote:
> resize_hpt_for_hotplug() reports a warning when it cannot
> increase the hash page table ("Unable to resize hash page
> table to target order") but this is not blocking and
> can make user thinks something has not worked properly.
> As we move the message to the debug area, report again the
> ENODEV error.
> 
> If the operation cannot be done the real error message
> will be reported by arch_add_memory() if create_section_mapping()
> fails.
> 
> Fixes: 7339390d772dd
>        powerpc/pseries: Don't give a warning when HPT resizing isn't available
> Signed-off-by: Laurent Vivier <lvivier@...hat.com>

Sorry, I'm pretty dubious about this.  It's true that in the case for
which this bug was filed this is a harmless situation which deserves a
pr_debug() at most.

But that's not necessarily true in all paths leading to this message.
It will also trip if we fail to reshrink the HPT after genuinely
hotunplugging a bunch of memory, in which case failing to release
expected resources does deserve a warning.

> ---
> 
> Notes:
>     v2:
>      - use pr_debug instead of printk(KERN_DEBUG
>      - remove check for ENODEV
> 
>  arch/powerpc/mm/hash_utils_64.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
> index 0cc7fbc3bd1c..6a0cc4eb2c83 100644
> --- a/arch/powerpc/mm/hash_utils_64.c
> +++ b/arch/powerpc/mm/hash_utils_64.c
> @@ -777,10 +777,9 @@ void resize_hpt_for_hotplug(unsigned long new_mem_size)
>  		int rc;
>  
>  		rc = mmu_hash_ops.resize_hpt(target_hpt_shift);
> -		if (rc && (rc != -ENODEV))
> -			printk(KERN_WARNING
> -			       "Unable to resize hash page table to target order %d: %d\n",
> -			       target_hpt_shift, rc);
> +		if (rc)
> +			pr_debug("Unable to resize hash page table to target order %d: %d\n",
> +				 target_hpt_shift, rc);
>  	}
>  }
>  

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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