mm/vmalloc.c: avoid bogus -Wmaybe-uninitialized warning

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.

[akpm@linux-foundation.org: tweak comments]
Link: http://lkml.kernel.org/r/20190618092650.2943749-1-arnd@arndb.de
Fixes: 68ad4a330433 ("mm/vmalloc.c: keep track of free blocks for vmap allocation")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Cc: Joel Fernandes <joelaf@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 4c9e150..0f76cca 100644 (file)
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -913,7 +913,7 @@ 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;
+       struct vmap_area *lva = NULL;
 
        if (type == FL_FIT_TYPE) {
                /*
@@ -972,7 +972,7 @@ 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)        /* type == NE_FIT_TYPE */
                        insert_vmap_area_augment(lva, &va->rb_node,
                                &free_vmap_area_root, &free_vmap_area_list);
        }