[RHEL6.8 Patch 18/19] s390/vmcore: implement remap_oldmem_pfn_range for s390

[Baoquan He <bhe@redhat.com>]

Resolves: bz1097904
https://bugzilla.redhat.com/show_bug.cgi?id=1097904

This is back ported from upstream.

commit 23df79da8eb97757e39af7625665c1c5cecc610b
Author: Jan Willeke <willeke@de.ibm.com>
Date:   Wed Sep 11 14:24:52 2013 -0700

    s390/vmcore: implement remap_oldmem_pfn_range for s390

    Introduce the s390 specific way to map pages from oldmem.  The memory area
    below OLDMEM_SIZE is mapped with offset OLDMEM_BASE.  The other old memory
    is mapped directly.

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

Signed-off-by: Baoquan He <bhe@redhat.com>
---
 arch/s390/kernel/crash_dump.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/arch/s390/kernel/crash_dump.c b/arch/s390/kernel/crash_dump.c
index 0f70217..1f38051 100644
--- a/arch/s390/kernel/crash_dump.c
+++ b/arch/s390/kernel/crash_dump.c
@@ -127,6 +127,32 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
 }
 
 /*
+ * Remap "oldmem"
+ *
+ * For the kdump reserved memory this functions performs a swap operation:
+ * [0 - OLDMEM_SIZE] is mapped to [OLDMEM_BASE - OLDMEM_BASE + OLDMEM_SIZE]
+ */
+int remap_oldmem_pfn_range(struct vm_area_struct *vma, unsigned long from,
+			   unsigned long pfn, unsigned long size, pgprot_t prot)
+{
+	unsigned long size_old;
+	int rc;
+
+	if (pfn < OLDMEM_SIZE >> PAGE_SHIFT) {
+		size_old = min(size, OLDMEM_SIZE - (pfn << PAGE_SHIFT));
+		rc = remap_pfn_range(vma, from,
+				     pfn + (OLDMEM_BASE >> PAGE_SHIFT),
+				     size_old, prot);
+		if (rc || size == size_old)
+			return rc;
+		size -= size_old;
+		from += size_old;
+		pfn += size_old >> PAGE_SHIFT;
+	}
+	return remap_pfn_range(vma, from, pfn, size, prot);
+}
+
+/*
  * Copy memory from old kernel
  */
 static int copy_from_oldmem(void *dest, void *src, size_t count)
-- 
2.1.0