Subject: Re: [PATCH v3] arm64: use generic free_initrd_mem()

From: Mike Rapoport <[email-masked]>
Date: Sat, 28 Sep 2019 10:19:02 +0300

On Fri, Sep 27, 2019 at 11:50:42AM +0530, Anshuman Khandual wrote:
> 
> On 09/25/2019 10:39 AM, Mike Rapoport wrote:
> > From: Mike Rapoport <[email-masked]>
> > 
> > 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 <[email-masked]>
> > ---
> > 
> > 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").

Well, the present behaviour as of v5.3[.1] is call memblock_free() for the
unaligned initrd area. The commit 13776f9d40a0 ("arm64: mm: free the initrd
reserved memblock in a aligned manner") indeed would fix the reporting in
/sys/fs/memblock/reserved, but it won't change anything beyond that despite
its commit log implies otherwise.

> Or does initrd always gets allocated with page alignment on other architectures.

powerpc reserves aligned area and s390 does not. Other architectures do not
keep memblock  after init.

I'll re-send with the aligned addresses.

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

-- 
Sincerely yours,
Mike.

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