Subject: Re: [PATCH] powerpc: fix pgtable pmd cache init

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Wed, 04 Jan 2017 07:34:41 +0530

Nicholas Piggin <[email-masked]> writes:

> Commit 9b081e10805cd ("powerpc: port 64 bits pgtable_cache to 32 bits")
> mixed up PMD_INDEX_SIZE and PMD_CACHE_INDEX a couple of times. This
> resulted in 64s/hash/4k configs to panic at boot with a false positive
> error check.
>
> Fix that and simplify error handling by moving the check to the caller.
>
> Fixes: 9b081e10805cd ("powerpc: port 64 bits pgtable_cache to 32 bits")
> Cc: Christophe Leroy <[email-masked]>
> Cc: Aneesh Kumar K.V <[email-masked]>
> Cc: Scott Wood <[email-masked]>
> Cc: [email-masked]
> Signed-off-by: Nicholas Piggin <[email-masked]>

I did another fix here.

https://lkml.kernel.org/r/[email-masked]

But this patch makes it much simpler. Hence.

Reviewed-by: Aneesh Kumar K.V <[email-masked]>

There is this hunk in the patch I did.

--- a/arch/powerpc/include/asm/book3s/64/hash.h
+++ b/arch/powerpc/include/asm/book3s/64/hash.h
@@ -33,9 +33,9 @@
				 H_PUD_INDEX_SIZE + H_PGD_INDEX_SIZE + PAGE_SHIFT)
 #define H_PGTABLE_RANGE		(ASM_CONST(1) << H_PGTABLE_EADDR_SIZE)

-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+#if defined(CONFIG_TRANSPARENT_HUGEPAGE) &&  defined(CONFIG_PPC_64K_PAGES)
 /*
- * only with hash we need to use the second half of pmd page table
+ * only with hash 64k we need to use the second half of pmd page table
  * to store pointer to deposited pgtable_t
  */
 #define H_PMD_CACHE_INDEX	(H_PMD_INDEX_SIZE + 1)

> ---
>  arch/powerpc/mm/hugetlbpage.c |  6 +-----
>  arch/powerpc/mm/init-common.c | 11 +++--------
>  2 files changed, 4 insertions(+), 13 deletions(-)
>
> diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
> index 289df38fb7e0..f21f6b907d99 100644
> --- a/arch/powerpc/mm/hugetlbpage.c
> +++ b/arch/powerpc/mm/hugetlbpage.c
> @@ -810,12 +810,8 @@ static int __init hugetlbpage_init(void)
>  		 * if we have pdshift and shift value same, we don't
>  		 * use pgt cache for hugepd.
>  		 */
> -		if (pdshift > shift) {
> +		if (pdshift > shift)
>  			pgtable_cache_add(pdshift - shift, NULL);
> -			if (!PGT_CACHE(pdshift - shift))
> -				panic("hugetlbpage_init(): could not create "
> -				      "pgtable cache for %d bit pagesize\n", shift);
> -		}
>  #if defined(CONFIG_PPC_FSL_BOOK3E) || defined(CONFIG_PPC_8xx)
>  		else if (!hugepte_cache) {
>  			/*
> diff --git a/arch/powerpc/mm/init-common.c b/arch/powerpc/mm/init-common.c
> index a175cd82ae8c..1a3be5ae1d07 100644
> --- a/arch/powerpc/mm/init-common.c
> +++ b/arch/powerpc/mm/init-common.c
> @@ -80,6 +80,8 @@ void pgtable_cache_add(unsigned shift, void (*ctor)(void *))
>  	new = kmem_cache_create(name, table_size, align, 0, ctor);
>  	kfree(name);
>  	pgtable_cache[shift - 1] = new;
> +	if (!new)
> +		panic("Could not allocate pgtable cache for order %d", shift);
>  	pr_debug("Allocated pgtable cache for order %d\n", shift);
>  }
>
> @@ -88,7 +90,7 @@ void pgtable_cache_init(void)
>  {
>  	pgtable_cache_add(PGD_INDEX_SIZE, pgd_ctor);
>
> -	if (PMD_INDEX_SIZE && !PGT_CACHE(PMD_INDEX_SIZE))
> +	if (PMD_CACHE_INDEX && !PGT_CACHE(PMD_CACHE_INDEX))
>  		pgtable_cache_add(PMD_CACHE_INDEX, pmd_ctor);
>  	/*
>  	 * In all current configs, when the PUD index exists it's the
> @@ -97,11 +99,4 @@ void pgtable_cache_init(void)
>  	 */
>  	if (PUD_INDEX_SIZE && !PGT_CACHE(PUD_INDEX_SIZE))
>  		pgtable_cache_add(PUD_INDEX_SIZE, pud_ctor);
> -
> -	if (!PGT_CACHE(PGD_INDEX_SIZE))
> -		panic("Couldn't allocate pgd cache");
> -	if (PMD_INDEX_SIZE && !PGT_CACHE(PMD_INDEX_SIZE))
> -		panic("Couldn't allocate pmd pgtable caches");
> -	if (PUD_INDEX_SIZE && !PGT_CACHE(PUD_INDEX_SIZE))
> -		panic("Couldn't allocate pud pgtable caches");
>  }
> -- 
> 2.11.0