xfs: move kmem_to_page()

Move it to the general xfs linux wrapper header file so we can
prepare to remove kmem.h

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

fs/xfs/kmem.h

@@ -20,15 +20,4 @@ static inline void  kmem_free(const void *ptr)
 	kvfree(ptr);
 }
 
-/*
- * Zone interfaces
- */
-static inline struct page *
-kmem_to_page(void *addr)
-{
-	if (is_vmalloc_addr(addr))
-		return vmalloc_to_page(addr);
-	return virt_to_page(addr);
-}
-
 #endif /* __XFS_SUPPORT_KMEM_H__ */

fs/xfs/xfs_linux.h

@@ -269,4 +269,15 @@ int xfs_rw_bdev(struct block_device *bdev, sector_t sector, unsigned int count,
 # define PTR_FMT "%p"
 #endif
 
+/*
+ * Helper for IO routines to grab backing pages from allocated kernel memory.
+ */
+static inline struct page *
+kmem_to_page(void *addr)
+{
+	if (is_vmalloc_addr(addr))
+		return vmalloc_to_page(addr);
+	return virt_to_page(addr);
+}
+
 #endif /* __XFS_LINUX__ */