[PATCH 1/3] mm: refactor __vunmap() to avoid duplicated call to find_vm_area()

[Roman Gushchin]

__vunmap() calls find_vm_area() twice without an obvious reason:
first directly to get the area pointer, second indirectly by calling
remove_vm_area(), which is again searching for the area.

To remove this redundancy, let's split remove_vm_area() into
__remove_vm_area(struct vmap_area *), which performs the actual area
removal, and remove_vm_area(const void *addr) wrapper, which can
be used everywhere, where it has been used before.

On my test setup, I've got up to 12% speed up on vfree()'ing 1000000
of 4-pages vmalloc blocks.

Signed-off-by: Roman Gushchin <g...@fb.com>
Acked-by: Johannes Weiner <han...@cmpxchg.org>
Reviewed-by: Matthew Wilcox <wi...@infradead.org>
---
 mm/vmalloc.c | 47 +++++++++++++++++++++++++++--------------------
 1 file changed, 27 insertions(+), 20 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 871e41c55e23..7660e3ef4133 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1462,6 +1462,24 @@ struct vm_struct *find_vm_area(const void *addr)
        return NULL;
 }
 
+static struct vm_struct *__remove_vm_area(struct vmap_area *va)
+{
+       struct vm_struct *vm = va->vm;
+
+       might_sleep();
+
+       spin_lock(&vmap_area_lock);
+       va->vm = NULL;
+       va->flags &= ~VM_VM_AREA;
+       va->flags |= VM_LAZY_FREE;
+       spin_unlock(&vmap_area_lock);
+
+       kasan_free_shadow(vm);
+       free_unmap_vmap_area(va);
+
+       return vm;
+}
+
 /**
  *     remove_vm_area  -  find and remove a continuous kernel virtual area
  *     @addr:          base address
@@ -1472,31 +1490,20 @@ struct vm_struct *find_vm_area(const void *addr)
  */
 struct vm_struct *remove_vm_area(const void *addr)
 {
+       struct vm_struct *vm = NULL;
        struct vmap_area *va;
 
-       might_sleep();
-
        va = find_vmap_area((unsigned long)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;
-               va->flags |= VM_LAZY_FREE;
-               spin_unlock(&vmap_area_lock);
-
-               kasan_free_shadow(vm);
-               free_unmap_vmap_area(va);
+       if (va && va->flags & VM_VM_AREA)
+               vm = __remove_vm_area(va);
 
-               return vm;
-       }
-       return NULL;
+       return vm;
 }
 
 static void __vunmap(const void *addr, int deallocate_pages)
 {
        struct vm_struct *area;
+       struct vmap_area *va;
 
        if (!addr)
                return;
@@ -1505,17 +1512,18 @@ static void __vunmap(const void *addr, int 
deallocate_pages)
                        addr))
                return;
 
-       area = find_vmap_area((unsigned long)addr)->vm;
-       if (unlikely(!area)) {
+       va = find_vmap_area((unsigned long)addr);
+       if (unlikely(!va || !va->vm)) {
                WARN(1, KERN_ERR "Trying to vfree() nonexistent vm area (%p)\n",
                                addr);
                return;
        }
 
+       area = va->vm;
        debug_check_no_locks_freed(area->addr, get_vm_area_size(area));
        debug_check_no_obj_freed(area->addr, get_vm_area_size(area));
 
-       remove_vm_area(addr);
+       __remove_vm_area(va);
        if (deallocate_pages) {
                int i;
 
@@ -1530,7 +1538,6 @@ static void __vunmap(const void *addr, int 
deallocate_pages)
        }
 
        kfree(area);
-       return;
 }
 
 static inline void __vfree_deferred(const void *addr)
-- 
2.19.2