linux-kernel - Re: [PATCH] mm/ioremap: Fix iomap_max_page

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Message-Id: <1619951627.yczq2mwbu6.astroid@bobo.none>
Date:   Sun, 02 May 2021 20:36:14 +1000
From:   Nicholas Piggin <npiggin@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] mm/ioremap: Fix iomap_max_page_shift

Excerpts from Christophe Leroy's message of May 1, 2021 5:58 pm:
> iomap_max_page_shift is expected to contain a page shift,
> so it can't be a 'bool', has to be an 'unsigned int'
> 
> And fix the default values: P4D_SHIFT is when huge iomap is allowed.

Ugh, thanks that's obviously right.

Reviewed-by: Nicholas Piggin <npiggin@...il.com>

> 
> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
> Fixes: bbc180a5adb0 ("mm: HUGE_VMAP arch support cleanup")
> ---
>  mm/ioremap.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/ioremap.c b/mm/ioremap.c
> index d1dcc7e744ac..2f7193c6a99e 100644
> --- a/mm/ioremap.c
> +++ b/mm/ioremap.c
> @@ -16,16 +16,16 @@
>  #include "pgalloc-track.h"
>  
>  #ifdef CONFIG_HAVE_ARCH_HUGE_VMAP
> -static bool __ro_after_init iomap_max_page_shift = PAGE_SHIFT;
> +static unsigned int __ro_after_init iomap_max_page_shift = P4D_SHIFT;
>  
>  static int __init set_nohugeiomap(char *str)
>  {
> -	iomap_max_page_shift = P4D_SHIFT;
> +	iomap_max_page_shift = PAGE_SHIFT;
>  	return 0;
>  }
>  early_param("nohugeiomap", set_nohugeiomap);
>  #else /* CONFIG_HAVE_ARCH_HUGE_VMAP */
> -static const bool iomap_max_page_shift = PAGE_SHIFT;
> +static const unsigned int iomap_max_page_shift = PAGE_SHIFT;
>  #endif	/* CONFIG_HAVE_ARCH_HUGE_VMAP */
>  
>  int ioremap_page_range(unsigned long addr,
> -- 
> 2.25.0
> 
>