mm: add kmap_to_page()
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>
diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index d3999b4..e186e3c 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -39,10 +39,17 @@
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
diff --git a/mm/highmem.c b/mm/highmem.c
index 57d82c6..d517cd1 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -94,6 +94,18 @@
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;