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Subject: Re: [PATCH 2/3] powerpc/pseries: break early in
 dlpar_memory_add_by_count() loops
To: Daniel Henrique Barboza <danielhb413@gmail.com>,
 linuxppc-dev@lists.ozlabs.org
References: <20210622133923.295373-1-danielhb413@gmail.com>
 <20210622133923.295373-3-danielhb413@gmail.com>
From: Laurent Dufour <ldufour@linux.ibm.com>
Message-ID: <c0a3bb20-e3ed-1522-8411-510e94633511@linux.ibm.com>
Date: Thu, 24 Jun 2021 10:45:40 +0200
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Le 22/06/2021 à 15:39, Daniel Henrique Barboza a écrit :
> After a successful dlpar_add_lmb() call the LMB is marked as reserved.
> Later on, depending whether we added enough LMBs or not, we rely on
> the marked LMBs to see which ones might need to be removed, and we
> remove the reservation of all of them.
> 
> These are done in for_each_drmem_lmb() loops without any break
> condition. This means that we're going to check all LMBs of the partition
> even after going through all the reserved ones.
> 
> This patch adds break conditions in both loops to avoid this. The
> 'lmbs_added' variable was renamed to 'lmbs_reserved', and it's now
> being decremented each time a lmb reservation is removed, indicating
> if there are still marked LMBs to be processed.

Reviewed-by: Laurent Dufour <ldufour@linux.ibm.com>

> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
> ---
>   arch/powerpc/platforms/pseries/hotplug-memory.c | 17 ++++++++++++-----
>   1 file changed, 12 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c
> index 28a7fd90232f..c0a03e1537cb 100644
> --- a/arch/powerpc/platforms/pseries/hotplug-memory.c
> +++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
> @@ -673,7 +673,7 @@ static int dlpar_memory_add_by_count(u32 lmbs_to_add)
>   {
>   	struct drmem_lmb *lmb;
>   	int lmbs_available = 0;
> -	int lmbs_added = 0;
> +	int lmbs_reserved = 0;
>   	int rc;
>   
>   	pr_info("Attempting to hot-add %d LMB(s)\n", lmbs_to_add);
> @@ -714,13 +714,12 @@ static int dlpar_memory_add_by_count(u32 lmbs_to_add)
>   		 * requested LMBs cannot be added.
>   		 */
>   		drmem_mark_lmb_reserved(lmb);
> -
> -		lmbs_added++;
> -		if (lmbs_added == lmbs_to_add)
> +		lmbs_reserved++;
> +		if (lmbs_reserved == lmbs_to_add)
>   			break;
>   	}
>   
> -	if (lmbs_added != lmbs_to_add) {
> +	if (lmbs_reserved != lmbs_to_add) {
>   		pr_err("Memory hot-add failed, removing any added LMBs\n");
>   
>   		for_each_drmem_lmb(lmb) {
> @@ -735,6 +734,10 @@ static int dlpar_memory_add_by_count(u32 lmbs_to_add)
>   				dlpar_release_drc(lmb->drc_index);
>   
>   			drmem_remove_lmb_reservation(lmb);
> +			lmbs_reserved--;
> +
> +			if (lmbs_reserved == 0)
> +				break;
>   		}
>   		rc = -EINVAL;
>   	} else {
> @@ -745,6 +748,10 @@ static int dlpar_memory_add_by_count(u32 lmbs_to_add)
>   			pr_debug("Memory at %llx (drc index %x) was hot-added\n",
>   				 lmb->base_addr, lmb->drc_index);
>   			drmem_remove_lmb_reservation(lmb);
> +			lmbs_reserved--;
> +
> +			if (lmbs_reserved == 0)
> +				break;
>   		}
>   		rc = 0;
>   	}
>