On 05/11/2012 23:36, David Rientjes wrote:
> 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
I haven't seen these warning. Perhaps I used a different compiler
version, or the right flags.
>
> 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.
This solution looks great to me.
>
> Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
> ---
> mm/memory.c | 10 ++++------
> 1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -2527,9 +2527,8 @@ 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) {
> @@ -2708,8 +2707,7 @@ 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);
>
> /*
> @@ -2778,7 +2776,7 @@ 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) {
> /*
>
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