linux-kernel - Re: [PATCH v4 6/6] RISC-V: Free-up initrd in free_initrd

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Date:   Wed, 13 Feb 2019 09:38:36 +0200
From:   Mike Rapoport <rppt@...ux.ibm.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Anup Patel <Anup.Patel@....com>,
        Palmer Dabbelt <palmer@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Atish Patra <Atish.Patra@....com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 6/6] RISC-V: Free-up initrd in free_initrd_mem()

Hi,

On Tue, Feb 12, 2019 at 10:44:19PM -0800, Christoph Hellwig wrote:
> On Wed, Feb 13, 2019 at 06:32:24AM +0000, Anup Patel wrote:
> > index 9cd583b6d1cd..c22b873de856 100644
> > --- a/arch/riscv/kernel/setup.c
> > +++ b/arch/riscv/kernel/setup.c
> > @@ -97,8 +97,9 @@ static void __init setup_initrd(void)
> >  	initrd_end = 0;
> >  }
> >  
> > -void free_initrd_mem(unsigned long start, unsigned long end)
> > +void __init free_initrd_mem(unsigned long start, unsigned long end)
> >  {
> > +	memblock_free(__pa(start), end - start);
> 
> I'm pretty sure this should be a call to free_reserved_area instead.
> 
> All regions reserved using memblock_reserved and not freed before
> initializing the MM are marked reserved and don't have valid page
> counts, etc.
> 
> So we need the actions in free_reserved_area to actually make the
> memory useful.  Now every other architecture except for arm64
> seems to do fine without a memblock_free.  I'm not an expert on
> memblock (but I've CCed one), but I guess the reason is that once
> the kernel has booted we don't really care about freeing memblock
> area.

This late in the boot process there should be a call to
free_reserved_area() to give pages to the buddy allocator.

memblock_free() is has no real effect at this point, no idea why arm64
calls it.

-- 
Sincerely yours,
Mike.