[PATCH 3.4 47/88] mm: add kmap_to_page()

Greg Kroah-Hartman
2014-06-10T00:24:57Z

From: Ben Hutchings <ben@decadent.org.uk>

commit fcb8996728fb59eddf84678df7cb213b2c9a2e26 upstream.

This is extracted from Mel Gorman's commit 5a178119b0fb ('mm: add
support for direct_IO to highmem pages') upstream.

Required to backport commit b9cdc88df8e6 ('virtio: 9p: correctly pass
physical address to userspace for high pages').

Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Yijing Wang <wangyijing@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
include/linux/highmem.h | 7 +++++++
mm/highmem.c | 12 ++++++++++++
2 files changed, 19 insertions(+)

--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -39,10 +39,17 @@ extern unsigned long totalhigh_pages;

void kmap_flush_unused(void);

+struct page *kmap_to_page(void *addr);
+
#else /* CONFIG_HIGHMEM */

static inline unsigned int nr_free_highpages(void) { return 0; }

+static inline struct page *kmap_to_page(void *addr)
+{
+ return virt_to_page(addr);
+}
+
#define totalhigh_pages 0UL

#ifndef ARCH_HAS_KMAP
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -94,6 +94,18 @@ static DECLARE_WAIT_QUEUE_HEAD(pkmap_map
do { spin_unlock(&kmap_lock); (void)(flags); } while (0)
#endif

+struct page *kmap_to_page(void *vaddr)
+{
+ unsigned long addr = (unsigned long)vaddr;
+
+ if (addr >= PKMAP_ADDR(0) && addr <= PKMAP_ADDR(LAST_PKMAP)) {
+ int i = (addr - PKMAP_ADDR(0)) >> PAGE_SHIFT;
+ return pte_page(pkmap_page_table[i]);
+ }
+
+ return virt_to_page(addr);
+}
+
static void flush_all_zero_pkmaps(void)
{
int i;