On Mon, 15 Jul 2013 10:27:08 -0400 Vivek Goyal <vgoyal at redhat.com> wrote: > On Mon, Jul 15, 2013 at 03:44:51PM +0200, Michael Holzheu wrote: > > On Tue, 2 Jul 2013 11:42:14 -0400 > > Vivek Goyal <vgoyal at 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 at 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 at 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 at vger.kernel.org/msg464856.html > > > > But once we have finished that, would it be possible to get the > > patches in 3.11? > > How about taking mmap() fault handler patches in 3.12. And in 3.11, deny > mmap() on s390 forcing makedumpfile to fall back on read() interface. That > way there will be no regression and mmap() related speedup will show up > in next release on s390. Hello Vivek and Hatayama, But then we still would have to somehow fix the copy_oldmem_page() issue (1). We would prefer to add the current patch series with "#ifndef CONFIG_S390" in the fault handler. @Vivek: Since you are the kdump maintainer, could you tell us which of the both variants you would like to have? static int mmap_vmcore_fault(struct vm_area_struct *vma, struct vm_fault *vmf) { ... #ifndef CONFIG_S390 return VM_FAULT_SIGBUS; #endif or #ifndef CONFIG_S390 WARN_ONCE(1, "vmcore: Unexpected call of mmap_vmcore_fault()"); #endif For all architectures besides of s390 this would implement the requested behavior. Regards, Michael
