vmcore: introduce remap_oldmem_pfn_range()

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>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Cc: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
Cc: Jan Willeke <willeke@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/crash_dump.h b/include/linux/crash_dump.h
index 6571f828e313..fe68a5a98583 100644
--- a/include/linux/crash_dump.h
+++ b/include/linux/crash_dump.h
@@ -17,6 +17,9 @@ extern int __weak elfcorehdr_alloc(unsigned long long *addr,
 extern void __weak elfcorehdr_free(unsigned long long addr);
 extern ssize_t __weak elfcorehdr_read(char *buf, size_t count, u64 *ppos);
 extern ssize_t __weak elfcorehdr_read_notes(char *buf, size_t count, u64 *ppos);
+extern int __weak remap_oldmem_pfn_range(struct vm_area_struct *vma,
+                                         unsigned long from, unsigned long pfn,
+                                         unsigned long size, pgprot_t prot);
 
 extern ssize_t copy_oldmem_page(unsigned long, char *, size_t,
                                                 unsigned long, int);