linux-kernel - Re: [PATCH v3] arm64: use generic free_initrd

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Date:   Fri, 27 Sep 2019 11:50:42 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Mike Rapoport <rppt@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Cc:     Laura Abbott <labbott@...hat.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Mike Rapoport <rppt@...ux.ibm.com>
Subject: Re: [PATCH v3] arm64: use generic free_initrd_mem()


On 09/25/2019 10:39 AM, Mike Rapoport wrote:
> From: Mike Rapoport <rppt@...ux.ibm.com>
> 
> arm64 calls memblock_free() for the initrd area in its implementation of
> free_initrd_mem(), but this call has no actual effect that late in the boot
> process. By the time initrd is freed, all the reserved memory is managed by
> the page allocator and the memblock.reserved is unused, so the only purpose
> of the memblock_free() call is to keep track of initrd memory for debugging
> and accounting.
> 
> Without the memblock_free() call the only difference between arm64 and the
> generic versions of free_initrd_mem() is the memory poisoning.
> 
> Move memblock_free() call to the generic code, enable it there
> for the architectures that define ARCH_KEEP_MEMBLOCK and use the generic
> implementaion of free_initrd_mem() on arm64.

Small nit. s/implementaion/implementation.

> 
> Signed-off-by: Mike Rapoport <rppt@...ux.ibm.com>
> ---
> 
> v3:
> * fix powerpc build
> 
> v2: 
> * add memblock_free() to the generic free_initrd_mem()
> * rebase on the current upstream
> 
> 
>  arch/arm64/mm/init.c | 12 ------------
>  init/initramfs.c     |  5 +++++
>  2 files changed, 5 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 45c00a5..87a0e3b 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -580,18 +580,6 @@ void free_initmem(void)
>  	unmap_kernel_range((u64)__init_begin, (u64)(__init_end - __init_begin));
>  }
>  
> -#ifdef CONFIG_BLK_DEV_INITRD
> -void __init free_initrd_mem(unsigned long start, unsigned long end)
> -{
> -	unsigned long aligned_start, aligned_end;
> -
> -	aligned_start = __virt_to_phys(start) & PAGE_MASK;
> -	aligned_end = PAGE_ALIGN(__virt_to_phys(end));
> -	memblock_free(aligned_start, aligned_end - aligned_start);
> -	free_reserved_area((void *)start, (void *)end, 0, "initrd");
> -}
> -#endif
> -
>  /*
>   * Dump out memory limit information on panic.
>   */
> diff --git a/init/initramfs.c b/init/initramfs.c
> index c47dad0..3d61e13 100644
> --- a/init/initramfs.c
> +++ b/init/initramfs.c
> @@ -10,6 +10,7 @@
>  #include <linux/syscalls.h>
>  #include <linux/utime.h>
>  #include <linux/file.h>
> +#include <linux/memblock.h>
>  
>  static ssize_t __init xwrite(int fd, const char *p, size_t count)
>  {
> @@ -531,6 +532,10 @@ void __weak free_initrd_mem(unsigned long start, unsigned long end)
>  {
>  	free_reserved_area((void *)start, (void *)end, POISON_FREE_INITMEM,
>  			"initrd");
> +
> +#ifdef CONFIG_ARCH_KEEP_MEMBLOCK

Should not the addresses here be aligned first before calling memblock_free() ?
Without alignment, it breaks present behavior on arm64 which was explicitly added
with 13776f9d40a0 ("arm64: mm: free the initrd reserved memblock in a aligned manner").
Or does initrd always gets allocated with page alignment on other architectures.

> +	memblock_free(__pa(start), end - start);
> +#endif
>  }
>  
>  #ifdef CONFIG_KEXEC_CORE
>