linux-kernel - Re: [PATCH v2] x86/setup: Merge {early_,}reserve

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Date:	Tue, 9 Feb 2016 10:16:26 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Alexander Kuleshov <kuleshovmail@...il.com>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H . Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...e.de>,
	Joerg Roedel <jroedel@...e.de>, Dave Young <dyoung@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jiri Kosina <jkosina@...e.cz>, Baoquan He <bhe@...hat.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Mark Salter <msalter@...hat.com>, linux-kernel@...r.kernel.org,
	x86@...nel.org
Subject: Re: [PATCH v2] x86/setup: Merge {early_,}reserve_initrd() to one
 function


* Alexander Kuleshov <kuleshovmail@...il.com> wrote:

> The check and definitions related to ramdisk are similar in the
> early_reserve_initrd() and reserve_initrd(). So we can get rid of
> early_reserve_initrd() and and use late or early algorithm for
> initrd reservation depends on reserve_initrd() parameter value.
> 
> Save 396 bytes of code:
> 
>    text            data      bss      dec     hex filename
>    9281618      5010736 15474688 29767042 1c63582 vmlinux.orig
> 
>    text            data      bss      dec     hex filename
>    9281222      5010672 15474688 29766582 1c633b6 vmlinux.new
> 
> Signed-off-by: Alexander Kuleshov <kuleshovmail@...il.com>
> ---
> Changelog:
> 
> v2: parameter of reserve_initrd() - int -> bool.
>     commit message updated.
> 
>  arch/x86/kernel/setup.c | 29 +++++++++--------------------
>  1 file changed, 9 insertions(+), 20 deletions(-)
> 
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index d3d80e6..0a2fa55 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -349,20 +349,7 @@ static void __init relocate_initrd(void)
>  		relocated_ramdisk, relocated_ramdisk + ramdisk_size - 1);
>  }
>  
> -static void __init early_reserve_initrd(void)
> -{
> -	/* Assume only end is not page aligned */
> -	u64 ramdisk_image = get_ramdisk_image();
> -	u64 ramdisk_size  = get_ramdisk_size();
> -	u64 ramdisk_end   = PAGE_ALIGN(ramdisk_image + ramdisk_size);
> -
> -	if (!boot_params.hdr.type_of_loader ||
> -	    !ramdisk_image || !ramdisk_size)
> -		return;		/* No initrd provided by bootloader */
> -
> -	memblock_reserve(ramdisk_image, ramdisk_end - ramdisk_image);
> -}
> -static void __init reserve_initrd(void)
> +static void __init reserve_initrd(bool early)
>  {
>  	/* Assume only end is not page aligned */
>  	u64 ramdisk_image = get_ramdisk_image();
> @@ -374,6 +361,11 @@ static void __init reserve_initrd(void)
>  	    !ramdisk_image || !ramdisk_size)
>  		return;		/* No initrd provided by bootloader */
>  
> +	if (early) {
> +		memblock_reserve(ramdisk_image, ramdisk_end - ramdisk_image);
> +		return;
> +	}
> +
>  	initrd_start = 0;
>  
>  	mapped_size = memblock_mem_size(max_pfn_mapped);
> @@ -398,10 +390,7 @@ static void __init reserve_initrd(void)
>  	memblock_free(ramdisk_image, ramdisk_end - ramdisk_image);
>  }
>  #else
> -static void __init early_reserve_initrd(void)
> -{
> -}
> -static void __init reserve_initrd(void)
> +static void __init reserve_initrd(bool early)
>  {
>  }
>  #endif /* CONFIG_BLK_DEV_INITRD */
> @@ -850,7 +839,7 @@ void __init setup_arch(char **cmdline_p)
>  	memblock_reserve(__pa_symbol(_text),
>  			 (unsigned long)__bss_stop - (unsigned long)_text);
>  
> -	early_reserve_initrd();
> +	reserve_initrd(true);
>  
>  	/*
>  	 * At this point everything still needed from the boot loader
> @@ -1135,7 +1124,7 @@ void __init setup_arch(char **cmdline_p)
>  	/* Allocate bigger log buffer */
>  	setup_log_buf(1);
>  
> -	reserve_initrd();
> +	reserve_initrd(false);
>  
>  #if defined(CONFIG_ACPI) && defined(CONFIG_BLK_DEV_INITRD)
>  	acpi_initrd_override((void *)initrd_start, initrd_end - initrd_start);

So I don't think the code got easier to understand - in particular the 
memblock_reserve()/free() pattern, depending on a flag value, is confusing.

The duplication is there - but please factor it out into a helper structure 
('struct ramdisk') and a helper function that sets up the structure.

Thanks,

	Ingo