On Wed 16-07-14 17:36:49, David Rientjes wrote:
> Setting vm_dirty_bytes and dirty_background_bytes is not protected by any
> serialization.
>
> Therefore, it's possible for either variable to change value after the
> test in global_dirty_limits() to determine whether available_memory needs
> to be initialized or not.
>
> Always ensure that available_memory is properly initialized.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
Makes sense to me
Acked-by: Michal Hocko <mhocko@xxxxxxx>
> ---
> mm/page-writeback.c | 5 +----
> 1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -261,14 +261,11 @@ static unsigned long global_dirtyable_memory(void)
> */
> void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty)
> {
> + const unsigned long available_memory = global_dirtyable_memory();
> unsigned long background;
> unsigned long dirty;
> - unsigned long uninitialized_var(available_memory);
> struct task_struct *tsk;
>
> - if (!vm_dirty_bytes || !dirty_background_bytes)
> - available_memory = global_dirtyable_memory();
> -
> if (vm_dirty_bytes)
> dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE);
> else
--
Michal Hocko
SUSE Labs
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