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Subject[PATCH] mm/vmalloc: avoid bogus -Wmaybe-uninitialized warning
Date
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 <arnd@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
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