Re: [PATCH v6 3/5] vmcore: Introduce remap_oldmem_pfn_range()

From: Michael Holzheu <holzheu@linux.vnet.ibm.com>
To: Vivek Goyal <vgoyal@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>,
	kexec@lists.infradead.org, Jan Willeke <willeke@de.ibm.com>,
	linux-kernel@vger.kernel.org,
	HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>,
	Martin Schwidefsky <schwidefsky@de.ibm.com>
Subject: Re: [PATCH v6 3/5] vmcore: Introduce remap_oldmem_pfn_range()
Date: Mon, 15 Jul 2013 15:44:51 +0200	[thread overview]
Message-ID: <20130715154451.02a3a767@holzheu> (raw)
In-Reply-To: <20130702154214.GC22603@redhat.com>

On Tue, 2 Jul 2013 11:42:14 -0400
Vivek Goyal <vgoyal@redhat.com> wrote:

> On Mon, Jul 01, 2013 at 09:32:37PM +0200, Michael Holzheu wrote:
> > For zfcpdump we can't map the HSA storage because it is only available
> > via a read interface. Therefore, for the new vmcore mmap feature we have
> > introduce a new mechanism to create mappings on demand.
> > 
> > This patch introduces a new architecture function remap_oldmem_pfn_range()
> > that should be used to create mappings with remap_pfn_range() for oldmem
> > areas that can be directly mapped. For zfcpdump this is everything besides
> > of the HSA memory. For the areas that are not mapped by remap_oldmem_pfn_range()
> > a generic vmcore a new generic vmcore fault handler mmap_vmcore_fault()
> > is called.
> > 
> > This handler works as follows:
> > 
> > * Get already available or new page from page cache (find_or_create_page)
> > * Check if /proc/vmcore page is filled with data (PageUptodate)
> > * If yes:
> >   Return that page
> > * If no:
> >   Fill page using __vmcore_read(), set PageUptodate, and return page
> > 
> > Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
> 
> In general vmcore related changes look fine to me. I am not very familiar
> with the logic of finding pages in page cache and using page uptodate
> flag.
> 
> Hatayama, can you please review it.
> 
> Acked-by: Vivek Goyal <vgoyal@redhat.com>

Hello Vivek and Andrew,

We just realized that Hatayama's mmap patches went into v3.11-rc1. This currently
breaks s390 kdump because of the following two issues:

1) The copy_oldmem_page() is now used for copying to vmalloc memory
2) The mmap() implementation is not compatible with the current
   s390 crashkernel swap:
   See: http://marc.info/?l=kexec&m=136940802511603&w=2

The "kdump: Introduce ELF header in new memory feature" patch series will
fix both issues for s390.

There is the one small open discussion left:

http://www.mail-archive.com/linux-kernel@vger.kernel.org/msg464856.html

But once we have finished that, would it be possible to get the
patches in 3.11?

Michael

_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec