linux-kernel - Re: [PATCH v3 1/3] iommu/iova: Tidy up iova_cache

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Date: Tue, 6 Feb 2024 11:01:16 +0000
From: John Garry <john.g.garry@...cle.com>
To: Robin Murphy <robin.murphy@....com>, joro@...tes.org
Cc: will@...nel.org, pasha.tatashin@...een.com, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org, rientjes@...gle.com,
        yosryahmed@...gle.com
Subject: Re: [PATCH v3 1/3] iommu/iova: Tidy up iova_cache_get() failure

On 05/02/2024 15:32, Robin Murphy wrote:
> Failure handling in iova_cache_get() is a little messy, and we'd like
> to add some more to it, so let's tidy up a bit first. By leaving the
> hotplug handler until last we can take advantage of kmem_cache_destroy()
> being NULL-safe to have a single cleanup label. We can also improve the
> error reporting, noting that kmem_cache_create() already screams if it
> fails, so that one is redundant.
> 
> Signed-off-by: Robin Murphy <robin.murphy@....com>

Regardless of a couple of minor comments, below, FWIW:
Reviewed-by: John Garry <john.g.garry@...cle.com>

> ---
>   drivers/iommu/iova.c | 33 ++++++++++++++++-----------------
>   1 file changed, 16 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
> index d30e453d0fb4..cf95001d85c0 100644
> --- a/drivers/iommu/iova.c
> +++ b/drivers/iommu/iova.c
> @@ -254,26 +254,20 @@ static void free_iova_mem(struct iova *iova)
>   
>   int iova_cache_get(void)
>   {
> +	int err = -ENOMEM;
> +
>   	mutex_lock(&iova_cache_mutex);
>   	if (!iova_cache_users) {
> -		int ret;
> +		iova_cache = kmem_cache_create("iommu_iova", sizeof(struct iova), 0,
> +					       SLAB_HWCACHE_ALIGN, NULL);

Maybe can use KMEM_CACHE(), but it would mean that the name would change.

> +		if (!iova_cache)
> +			goto out_err;
>   
> -		ret = cpuhp_setup_state_multi(CPUHP_IOMMU_IOVA_DEAD, "iommu/iova:dead", NULL,
> -					iova_cpuhp_dead);
> -		if (ret) {
> -			mutex_unlock(&iova_cache_mutex);
> -			pr_err("Couldn't register cpuhp handler\n");
> -			return ret;
> -		}
> -
> -		iova_cache = kmem_cache_create(
> -			"iommu_iova", sizeof(struct iova), 0,
> -			SLAB_HWCACHE_ALIGN, NULL);
> -		if (!iova_cache) {
> -			cpuhp_remove_multi_state(CPUHP_IOMMU_IOVA_DEAD);
> -			mutex_unlock(&iova_cache_mutex);
> -			pr_err("Couldn't create iova cache\n");
> -			return -ENOMEM;
> +		err = cpuhp_setup_state_multi(CPUHP_IOMMU_IOVA_DEAD, "iommu/iova:dead",
> +					      NULL, iova_cpuhp_dead);
> +		if (err) {
> +			pr_err("IOVA: Couldn't register cpuhp handler: %pe\n", ERR_PTR(err));

Maybe can use pr_fmt with "iova".

> +			goto out_err;
>   		}
>   	}
>   
> @@ -281,6 +275,11 @@ int iova_cache_get(void)
>   	mutex_unlock(&iova_cache_mutex);
>   
>   	return 0;
> +
> +out_err:
> +	kmem_cache_destroy(iova_cache);
> +	mutex_unlock(&iova_cache_mutex);
> +	return err;
>   }
>   EXPORT_SYMBOL_GPL(iova_cache_get);
>