linux-kernel - Re: [PATCH] arm64:free_initrd_mem should also free the memblock

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Date:	Mon, 15 Sep 2014 19:40:23 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Will Deacon <will.deacon@....com>
Cc:	"Wang, Yalin" <Yalin.Wang@...ymobile.com>,
	"'linux-kernel@...r.kernel.org'" <linux-kernel@...r.kernel.org>,
	"'linux-arm-kernel@...ts.infradead.org'" 
	<linux-arm-kernel@...ts.infradead.org>,
	"'linux-mm@...ck.org'" <linux-mm@...ck.org>
Subject: Re: [PATCH] arm64:free_initrd_mem should also free the memblock

On Mon, Sep 15, 2014 at 07:33:34PM +0100, Will Deacon wrote:
> On Fri, Sep 12, 2014 at 11:17:18AM +0100, Wang, Yalin wrote:
> > this patch fix the memblock statics for memblock
> > in file /sys/kernel/debug/memblock/reserved
> > if we don't call memblock_free the initrd will still
> > be marked as reserved, even they are freed.
> > 
> > Signed-off-by: Yalin Wang <yalin.wang@...ymobile.com>
> > ---
> >  arch/arm64/mm/init.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> > index 5472c24..34605c8 100644
> > --- a/arch/arm64/mm/init.c
> > +++ b/arch/arm64/mm/init.c
> > @@ -334,8 +334,10 @@ static int keep_initrd;
> >  
> >  void free_initrd_mem(unsigned long start, unsigned long end)
> >  {
> > -	if (!keep_initrd)
> > +	if (!keep_initrd) {
> >  		free_reserved_area((void *)start, (void *)end, 0, "initrd");
> > +		memblock_free(__pa(start), end - start);
> > +	}
> 
> I don't think it makes any technical difference, but doing the memblock_free
> before the free_reserved_area makes more sense to me.

A better question is... should we even be doing this.  The memblock
information is used as a method to bring up the kernel and provide
early allocation.  Once the memory is handed over from memblock to
the normal kernel page allocators, we no longer care what happens to
memblock.

There is no need to free the initrd memory back into memblock.  In
fact, seeing the initrd location in /sys/kernel/debug/memblock/reserved
can be useful debug information in itself.

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