mm, vmalloc: protect va->vm by vmap_area_lock

Inserting and removing an entry to vmlist is linear time complexity, so
it is inefficient.  Following patches will try to remove vmlist
entirely.  This patch is preparing step for it.

For removing vmlist, iterating vmlist codes should be changed to
iterating a vmap_area_list.  Before implementing that, we should make
sure that when we iterate a vmap_area_list, accessing to va->vm doesn't
cause a race condition.  This patch ensure that when iterating a
vmap_area_list, there is no race condition for accessing to vm_struct.

Signed-off-by: Joonsoo Kim <[email protected]>
Signed-off-by: Joonsoo Kim <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Atsushi Kumagai <[email protected]>
Cc: Chris Metcalf <[email protected]>
Cc: Dave Anderson <[email protected]>
Cc: Eric Biederman <[email protected]>
Cc: Guan Xuetao <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Vivek Goyal <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 1d9878b7cf52e08bbcc0c335dc97365a9901413c..1bf94ad452b6ab3c47b1ccce4d83422f2cb42cb9 100644 (file)
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1290,12 +1290,14 @@ struct vm_struct *vmlist;
 static void setup_vmalloc_vm(struct vm_struct *vm, struct vmap_area *va,
                              unsigned long flags, const void *caller)
 {
+       spin_lock(&vmap_area_lock);
        vm->flags = flags;
        vm->addr = (void *)va->va_start;
        vm->size = va->va_end - va->va_start;
        vm->caller = caller;
        va->vm = vm;
        va->flags |= VM_VM_AREA;
+       spin_unlock(&vmap_area_lock);
 }
 
 static void insert_vmalloc_vmlist(struct vm_struct *vm)
@@ -1447,6 +1449,11 @@ struct vm_struct *remove_vm_area(const void *addr)
        if (va && va->flags & VM_VM_AREA) {
                struct vm_struct *vm = va->vm;
 
+               spin_lock(&vmap_area_lock);
+               va->vm = NULL;
+               va->flags &= ~VM_VM_AREA;
+               spin_unlock(&vmap_area_lock);
+
                if (!(vm->flags & VM_UNLIST)) {
                        struct vm_struct *tmp, **p;
                        /*