linux-kernel - Re: [PATCH 1/4] powerpc/mm: Clean up error handling for htab_remove

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Message-ID: <87a8n9x7sh.fsf@linux.vnet.ibm.com>
Date:	Wed, 10 Feb 2016 14:26:46 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	David Gibson <david@...son.dropbear.id.au>, mpe@...erman.id.au,
	paulus@...ba.org, benh@...nel.crashing.org
Cc:	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	David Gibson <david@...son.dropbear.id.au>
Subject: Re: [PATCH 1/4] powerpc/mm: Clean up error handling for htab_remove_mapping

David Gibson <david@...son.dropbear.id.au> writes:

> Currently, the only error that htab_remove_mapping() can report is -EINVAL,
> if removal of bolted HPTEs isn't implemeted for this platform.  We make
> a few clean ups to the handling of this:
>
>  * EINVAL isn't really the right code - there's nothing wrong with the
>    function's arguments - use ENODEV instead
>  * We were also printing a warning message, but that's a decision better
>    left up to the callers, so remove it
>  * One caller is vmemmap_remove_mapping(), which will just BUG_ON() on
>    error, making the warning message redundant, so no change is needed
>    there.
>  * The other caller is remove_section_mapping().  This is called in the
>    memory hot remove path at a point after vmemmap_remove_mapping() so
>    if hpte_removebolted isn't implemented, we'd expect to have already
>    BUG()ed anyway.  Put a WARN_ON() here, in lieu of a printk() since this
>    really shouldn't be happening.
>

Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>

> Signed-off-by: David Gibson <david@...son.dropbear.id.au>
> ---
>  arch/powerpc/mm/hash_utils_64.c | 13 ++++++-------
>  1 file changed, 6 insertions(+), 7 deletions(-)
>
> diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
> index ba59d59..9f7d727 100644
> --- a/arch/powerpc/mm/hash_utils_64.c
> +++ b/arch/powerpc/mm/hash_utils_64.c
> @@ -273,11 +273,8 @@ int htab_remove_mapping(unsigned long vstart, unsigned long vend,
>  	shift = mmu_psize_defs[psize].shift;
>  	step = 1 << shift;
>  
> -	if (!ppc_md.hpte_removebolted) {
> -		printk(KERN_WARNING "Platform doesn't implement "
> -				"hpte_removebolted\n");
> -		return -EINVAL;
> -	}
> +	if (!ppc_md.hpte_removebolted)
> +		return -ENODEV;
>  
>  	for (vaddr = vstart; vaddr < vend; vaddr += step)
>  		ppc_md.hpte_removebolted(vaddr, psize, ssize);
> @@ -641,8 +638,10 @@ int create_section_mapping(unsigned long start, unsigned long end)
>  
>  int remove_section_mapping(unsigned long start, unsigned long end)
>  {
> -	return htab_remove_mapping(start, end, mmu_linear_psize,
> -			mmu_kernel_ssize);
> +	int rc = htab_remove_mapping(start, end, mmu_linear_psize,
> +				     mmu_kernel_ssize);
> +	WARN_ON(rc < 0);
> +	return rc;
>  }
>  #endif /* CONFIG_MEMORY_HOTPLUG */
>  
> -- 
> 2.5.0