linux-kernel - Re: [PATCH 7/8] initramfs: proide a generic free_initrd

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Date:   Wed, 13 Feb 2019 23:41:15 +0200
From:   Mike Rapoport <rppt@...ux.ibm.com>
To:     Christoph Hellwig <hch@....de>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Guan Xuetao <gxt@....edu.cn>,
        linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org,
        linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 7/8] initramfs: proide a generic free_initrd_mem
 implementation

On Wed, Feb 13, 2019 at 07:44:48PM +0100, Christoph Hellwig wrote:
> On Wed, Feb 13, 2019 at 08:41:40PM +0200, Mike Rapoport wrote:
> > csky seems to open-code free_reserved_page with the only
> > difference that it's also increments totalram_pages for the freed pages,
> > which doesn't seem correct anyway...
> > 
> > That said, I suppose arch/csky can be also added to the party.
> 
> Yes, I noticed that.  But I'd rather move it over manually in
> another patch post rc1 or for the next merge window.

Fair enough.
 
> > > +void __weak free_initrd_mem(unsigned long start, unsigned long end)
> > > +{
> > > +	free_reserved_area((void *)start, (void *)end, -1, "initrd");
> > 
> > Some architectures have pr_info("Freeing initrd memory..."), I'd add it for
> > the generic version as well.
> 
> Well, if we think such a printk is useful it should probably be
> moved to the caller in init/initramfs.c instead.  I can include a
> patch for that in the next iteration of the series.

I found it useful during board bring ups, this gave some starting point
when everything hangs and you are out to catch the lion in the desert.

> > Another thing that I was thinking of is that x86 has all those memory
> > protection calls in its free_initrd_mem, maybe it'd make sense to have them
> > in the generic version as well?
> 
> Maybe.  But I'd rather keep it out of the initial series as it looks
> a little more complicated.  Having a single implementation
> of free_initrd_mem would be great, though.

Ok.

BTW, the memblock_free() arm64 does, seems to be relevant for architectures
with CONFIG_ARCH_DISCARD_MEMBLOCK=n.
On powerpc the freed initrd region shows up in
/sys/kernel/debug/memblock/reserved.

-- 
Sincerely yours,
Mike.