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

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Date:   Wed, 13 Feb 2019 07:49:39 +0000
From:   Anup Patel <Anup.Patel@....com>
To:     Mike Rapoport <rppt@...ux.ibm.com>,
        Christoph Hellwig <hch@...radead.org>
CC:     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()



> -----Original Message-----
> From: Mike Rapoport [mailto:rppt@...ux.ibm.com]
> Sent: Wednesday, February 13, 2019 1:09 PM
> 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-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.

Thanks for the info. I will update this patch to use free_reserved_area().

Regards,
Anup