[PATCH] x86: kvm: propagate register_shrinker return code

[PATCH] x86: kvm: propagate register_shrinker return code

[Arnd Bergmann]

Patch "mm,vmscan: mark register_shrinker() as __must_check" is
queued for 4.16 in linux-mm and adds a warning about the unchecked
call to register_shrinker:

arch/x86/kvm/mmu.c:5485:2: warning: ignoring return value of 'register_shrinker', declared with attribute warn_unused_result [-Wunused-result]

This changes the kvm_mmu_module_init() function to fail itself
when the call to register_shrinker fails.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 arch/x86/kvm/mmu.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 89da688784fa..765c8e9df5d9 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -5465,30 +5465,34 @@ static void mmu_destroy_caches(void)
 
 int kvm_mmu_module_init(void)
 {
+	int ret = -ENOMEM;
+
 	kvm_mmu_clear_all_pte_masks();
 
 	pte_list_desc_cache = kmem_cache_create("pte_list_desc",
 					    sizeof(struct pte_list_desc),
 					    0, SLAB_ACCOUNT, NULL);
 	if (!pte_list_desc_cache)
-		goto nomem;
+		goto out;
 
 	mmu_page_header_cache = kmem_cache_create("kvm_mmu_page_header",
 						  sizeof(struct kvm_mmu_page),
 						  0, SLAB_ACCOUNT, NULL);
 	if (!mmu_page_header_cache)
-		goto nomem;
+		goto out;
 
 	if (percpu_counter_init(&kvm_total_used_mmu_pages, 0, GFP_KERNEL))
-		goto nomem;
+		goto out;
 
-	register_shrinker(&mmu_shrinker);
+	ret = register_shrinker(&mmu_shrinker);
+	if (ret)
+		goto out;
 
 	return 0;
 
-nomem:
+out:
 	mmu_destroy_caches();
-	return -ENOMEM;
+	return ret;
 }
 
 /*
-- 
2.9.0

Re: [PATCH] x86: kvm: propagate register_shrinker return code

[Paolo Bonzini]

On 10/01/2018 17:26, Arnd Bergmann wrote:
> Patch "mm,vmscan: mark register_shrinker() as __must_check" is
> queued for 4.16 in linux-mm and adds a warning about the unchecked
> call to register_shrinker:
> 
> arch/x86/kvm/mmu.c:5485:2: warning: ignoring return value of 'register_shrinker', declared with attribute warn_unused_result [-Wunused-result]
> 
> This changes the kvm_mmu_module_init() function to fail itself
> when the call to register_shrinker fails.
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  arch/x86/kvm/mmu.c | 16 ++++++++++------
>  1 file changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 89da688784fa..765c8e9df5d9 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -5465,30 +5465,34 @@ static void mmu_destroy_caches(void)
>  
>  int kvm_mmu_module_init(void)
>  {
> +	int ret = -ENOMEM;
> +
>  	kvm_mmu_clear_all_pte_masks();
>  
>  	pte_list_desc_cache = kmem_cache_create("pte_list_desc",
>  					    sizeof(struct pte_list_desc),
>  					    0, SLAB_ACCOUNT, NULL);
>  	if (!pte_list_desc_cache)
> -		goto nomem;
> +		goto out;
>  
>  	mmu_page_header_cache = kmem_cache_create("kvm_mmu_page_header",
>  						  sizeof(struct kvm_mmu_page),
>  						  0, SLAB_ACCOUNT, NULL);
>  	if (!mmu_page_header_cache)
> -		goto nomem;
> +		goto out;
>  
>  	if (percpu_counter_init(&kvm_total_used_mmu_pages, 0, GFP_KERNEL))
> -		goto nomem;
> +		goto out;
>  
> -	register_shrinker(&mmu_shrinker);
> +	ret = register_shrinker(&mmu_shrinker);
> +	if (ret)
> +		goto out;
>  
>  	return 0;
>  
> -nomem:
> +out:
>  	mmu_destroy_caches();
> -	return -ENOMEM;
> +	return ret;
>  }
>  
>  /*
> 

Queued, thanks.

Paolo