kexec-save-pg_head_mask-in-vmcoreinfo.patch

[Vivek Goyal]

On Tue, Jun 17, 2014 at 08:10:01AM +0200, Petr Tesarik wrote:
> On Thu, 12 Jun 2014 17:04:36 +0200
> Petr Tesarik <ptesarik at suse.cz> wrote:
> 
> > On Wed, 11 Jun 2014 13:24:22 -0400
> > Vivek Goyal <vgoyal at redhat.com> wrote:
> > 
> > > On Wed, Jun 11, 2014 at 01:20:42PM +0200, Petr Tesarik wrote:
> > > > On Tue, 10 Jun 2014 11:35:54 -0400
> > > > Vivek Goyal <vgoyal at redhat.com> wrote:
> > > > 
> > > > > On Mon, Jun 09, 2014 at 03:31:53PM -0700, Andrew Morton wrote:
> > > > > > 
> > > > > > 
> > > > > > Guys, could you please review this one?
> > > > > > 
> > > > > > Thanks.
> > > > > > 
> > > > > > 
> > > > > > From: Petr Tesarik <ptesarik at suse.cz>
> > > > > > Subject: kexec: save PG_head_mask in VMCOREINFO
> > > > > > 
> > > > > > To allow filtering of huge pages, makedumpfile must be able to identify
> > > > > > them in the dump.  This can be done by checking the appropriate page flag,
> > > > > > so communicate its value to makedumpfile through the VMCOREINFO interface.
> > > > > > 
> > > > > > There's only one small catch.  Depending on how many page flags are
> > > > > > available on a given architecture, this bit can be called PG_head or
> > > > > > PG_compound.
> > > > > > 
> > > > > > I sent a similar patch back in 2012, but Eric Biederman did not like using
> > > > > > an #ifdef.  So, this time I'm adding a common symbol (PG_head_mask)
> > > > > > instead.
> > > > > > 
> > > > > > See https://lkml.org/lkml/2012/11/28/91 for the previous version.
> > > > > > 
> > > > > 
> > > > > Hi Petr,
> > > > > 
> > > > > I went through previous conversation and personally I like that patch
> > > > > better.
> > > > > 
> > > > > We already have so many exports in vmcoreinfo which are conditional
> > > > > based on config options. Adding one more should be just fine. And as
> > > > > you said that it should not bitrot as it will most likely lead
> > > > > to complication failures if things shift around.
> > > > > 
> > > > > Does this patch compile with !CONFIG_PAGEFLAGS_EXTENDED. I did not see
> > > > > a definition of PG_head_mask in that case.
> > > > 
> > > > With !CONFIG_PAGEFLAGS_EXTENDED, the definition of PG_head_mask is
> > > > already there (and has been for quite some time).
> > > 
> > > Oh.., I had not noticed that. Thanks.
> > > 
> > > > 
> > > > > So I would say post your patch again, I will ack it. CC Eric and hopefully
> > > > > he does not have any objections to it.
> 
> Oh, it seems you're still waiting for Eric's opinion, but I didn't
> notice that he wasn't in Cc yet.

That was in the context of when I said repost the old patch. Later I
agreed to existing patch (The one with PG_head_mask) and I have acked it.

Thanks
Vivek