vmap: add flag to allow lazy unmap to be disabled at runtime

Add a flag to force lazy_max_pages() to zero to prevent any outstanding
mapped pages.  We'll need this for Xen.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Nick Piggin <npiggin@suse.de>

2 files changed, 6 insertions, 0 deletions

diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index 227c2a585e4f..b840fdaf438c 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -7,6 +7,8 @@
 
 struct vm_area_struct;          /* vma defining user mapping in mm_types.h */
 
+extern bool vmap_lazy_unmap;
+
 /* bits in flags of vmalloc's vm_struct below */
 #define VM_IOREMAP      0x00000001      /* ioremap() and friends */
 #define VM_ALLOC        0x00000002      /* vmalloc() */
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index ae007462b7f6..7f35fe2cf9e7 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -31,6 +31,7 @@
 #include <asm/tlbflush.h>
 #include <asm/shmparam.h>
 
+bool vmap_lazy_unmap __read_mostly = true;
 
 /*** Page table manipulation functions ***/
 
@@ -502,6 +503,9 @@ static unsigned long lazy_max_pages(void)
 {
         unsigned int log;
 
+        if (!vmap_lazy_unmap)
+                return 0;
+
         log = fls(num_online_cpus());
 
         return log * (32UL * 1024 * 1024 / PAGE_SIZE);