[PATCH] mm/vmalloc: avoid bogus -Wmaybe-uninitialized warning

[Arnd Bergmann]

gcc gets confused in pcpu_get_vm_areas() because there are too many
branches that affect whether 'lva' was initialized before it gets
used:

mm/vmalloc.c: In function 'pcpu_get_vm_areas':
mm/vmalloc.c:991:4: error: 'lva' may be used uninitialized in this function 
[-Werror=maybe-uninitialized]
    insert_vmap_area_augment(lva, &va->rb_node,
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     &free_vmap_area_root, &free_vmap_area_list);
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mm/vmalloc.c:916:20: note: 'lva' was declared here
  struct vmap_area *lva;
                    ^~~

Add an intialization to NULL, and check whether this has changed
before the first use.

Fixes: 68ad4a330433 ("mm/vmalloc.c: keep track of free blocks for vmap 
allocation")
Signed-off-by: Arnd Bergmann <a...@arndb.de>
---
 mm/vmalloc.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index a9213fc3802d..42a6f795c3ee 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -913,7 +913,12 @@ adjust_va_to_fit_type(struct vmap_area *va,
        unsigned long nva_start_addr, unsigned long size,
        enum fit_type type)
 {
-       struct vmap_area *lva;
+       /*
+        * GCC cannot always keep track of whether this variable
+        * was initialized across many branches, therefore set
+        * it NULL here to avoid a warning.
+        */
+       struct vmap_area *lva = NULL;
 
        if (type == FL_FIT_TYPE) {
                /*
@@ -987,7 +992,7 @@ adjust_va_to_fit_type(struct vmap_area *va,
        if (type != FL_FIT_TYPE) {
                augment_tree_propagate_from(va);
 
-               if (type == NE_FIT_TYPE)
+               if (lva)
                        insert_vmap_area_augment(lva, &va->rb_node,
                                &free_vmap_area_root, &free_vmap_area_list);
        }
-- 
2.20.0