[PATCH V4 11/18] powerpc/mm: Hugetlbfs is book3s_64 and fsl_book3e (32 or 64)

[Paul Mackerras]

On Tue, Feb 23, 2016 at 10:18:13AM +0530, Aneesh Kumar K.V wrote:
> We move large part of fsl related code to hugetlbpage-book3e.c.
> Only code movement. This also avoid #ifdef in the code.
> 
> Eventhough we allow hugetlbfs only for book3s 64 and fsl book3e, I am
> still retaining the #ifdef in hugetlbpage-book3e.c. It looks like there
> was an attempt to support hugetlbfs on other non hash platforms. I
> didn't want to loose that work.

Well... that stuff is always in git.  It seems that the only 64-bit
non-Freescale Book E platform we had was A2, and that code got deleted
because the product was never released.

You get rid of some but not all of the ifdefs in hugetlbpage-book3e.c,
and the result is a bit confusing (see below).  In fact that file will
only get compiled for Freescale Book E processors, because the
Makefile has an ifdef on HUGETLB_PAGE, which ultimately depends on
SYS_SUPPORTS_HUGETLBFS, which is only set for Freescale Book E and
64-bit server.

However, a larger question is why this cleanup is necessary for
preparing for the radix tree.  Nothing in the following patches in
this series seems to depend on this patch.

> diff --git a/arch/powerpc/mm/hugetlbpage-book3e.c b/arch/powerpc/mm/hugetlbpage-book3e.c
> index 7e6d0880813f..4c43a104e35c 100644
> --- a/arch/powerpc/mm/hugetlbpage-book3e.c
> +++ b/arch/powerpc/mm/hugetlbpage-book3e.c
> @@ -7,6 +7,39 @@
>   */
>  #include <linux/mm.h>
>  #include <linux/hugetlb.h>
> +#include <linux/bootmem.h>
> +#include <linux/moduleparam.h>
> +#include <linux/memblock.h>
> +#include <asm/tlb.h>
> +#include <asm/setup.h>
> +
> +/*
> + * Tracks gpages after the device tree is scanned and before the
> + * huge_boot_pages list is ready.  On non-Freescale implementations, this is
> + * just used to track 16G pages and so is a single array.  FSL-based
> + * implementations may have more than one gpage size, so we need multiple
> + * arrays
> + */

This comment should be fixed to refer only to FSL implementations.

> +#ifdef CONFIG_PPC_FSL_BOOK3E
> +#define MAX_NUMBER_GPAGES	128
> +struct psize_gpages {
> +	u64 gpage_list[MAX_NUMBER_GPAGES];
> +	unsigned int nr_gpages;
> +};
> +static struct psize_gpages gpage_freearray[MMU_PAGE_COUNT];
> +#endif
> +
> +/*
> + * These macros define how to determine which level of the page table holds
> + * the hpdp.
> + */
> +#ifdef CONFIG_PPC_FSL_BOOK3E
> +#define HUGEPD_PGD_SHIFT PGDIR_SHIFT
> +#define HUGEPD_PUD_SHIFT PUD_SHIFT
> +#else
> +#define HUGEPD_PGD_SHIFT PUD_SHIFT
> +#define HUGEPD_PUD_SHIFT PMD_SHIFT
> +#endif

This ifdef is confusing, because the other code you are adding to this
file only handles the FSL hugepd scheme.

> diff --git a/arch/powerpc/mm/hugetlbpage-hash64.c b/arch/powerpc/mm/hugetlbpage-hash64.c
> index 08efcad7cae0..821f5213d925 100644
> --- a/arch/powerpc/mm/hugetlbpage-hash64.c
> +++ b/arch/powerpc/mm/hugetlbpage-hash64.c
> @@ -14,6 +14,17 @@
>  #include <asm/cacheflush.h>
>  #include <asm/machdep.h>
>  
> +/*
> + * Tracks gpages after the device tree is scanned and before the
> + * huge_boot_pages list is ready.  On non-Freescale implementations, this is
> + * just used to track 16G pages and so is a single array.  FSL-based
> + * implementations may have more than one gpage size, so we need multiple
> + * arrays
> + */

This comment should be fixed to not refer to FSL-based
implementations.

Paul.