mm: fix build warning for uninitialized value

do_wp_page() sets mmun_called if mmun_start and mmun_end were initialized
and, if so, may call mmu_notifier_invalidate_range_end() with these
values.  This doesn't prevent gcc from emitting a build warning though:

mm/memory.c: In function `do_wp_page':
mm/memory.c:2530: warning: `mmun_start' may be used uninitialized in this function
mm/memory.c:2531: warning: `mmun_end' may be used uninitialized in this function

It's much easier to initialize the variables to impossible values and do a
simple comparison to determine if they were initialized to remove the bool
entirely.

Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/memory.c b/mm/memory.c
index b197b19d540073017d0cb68614066789ac81b1fe..9b7acd685b36abf13f94318cdd977833e383b518 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2572,9 +2572,8 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
        int ret = 0;
        int page_mkwrite = 0;
        struct page *dirty_page = NULL;
-       unsigned long mmun_start;       /* For mmu_notifiers */
-       unsigned long mmun_end;         /* For mmu_notifiers */
-       bool mmun_called = false;       /* For mmu_notifiers */
+       unsigned long mmun_start = 0;   /* For mmu_notifiers */
+       unsigned long mmun_end = 0;     /* For mmu_notifiers */
 
        old_page = vm_normal_page(vma, address, orig_pte);
        if (!old_page) {
@@ -2753,8 +2752,7 @@ gotten:
                goto oom_free_new;
 
        mmun_start  = address & PAGE_MASK;
-       mmun_end    = (address & PAGE_MASK) + PAGE_SIZE;
-       mmun_called = true;
+       mmun_end    = mmun_start + PAGE_SIZE;
        mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
 
        /*
@@ -2823,7 +2821,7 @@ gotten:
                page_cache_release(new_page);
 unlock:
        pte_unmap_unlock(page_table, ptl);
-       if (mmun_called)
+       if (mmun_end > mmun_start)
                mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
        if (old_page) {
                /*