Re: [PATCH -next 1/2] PM: hibernate: fix spelling mistake for annotation

[TGSP]

在 2022/11/4 00:25, Rafael J. Wysocki 写道:
> On Tue, Nov 1, 2022 at 3:28 AM TGSP <tgsp002@xxxxxxxxx> wrote:
> > From: xiongxin <xiongxin@xxxxxxxxxx>
> >
> > The actual calculation formula in the code below is:
> >
> > max_size = (count - (size + PAGES_FOR_IO)) / 2
> >              - 2 * DIV_ROUND_UP(reserved_size, PAGE_SIZE);
> >
> > But function comments are written differently, the comment is wrong?
>
> It is, and it is more serious than just a spelling mistake.
>
> > By the way, what exactly do the "/ 2" and "2 *" mean?
>
> Every page in the image is a copy of an existing allocated page, so
> room needs to be made for the two, except for the "IO pages" and
> metadata pages that are not copied.  Hence, the division by 2.
>
> Now, the "reserved_size" pages will be allocated right before creating
> the image and there will be a copy of each of them in the image, so
> there needs to be room for twice as many.

According to your interpretation, the formula should be：
max_size = (count - 2 * DIV_ROUND_UP(reserved_size, PAGE_SIZE)
               - (size + PAGES_FOR_IO)) / 2

Am I right?

> I'll adjust the changelog and queue up the path for 6.2.
>
> > Cc: stable@xxxxxxxxxxxxxxx
>
> I'll add a Fixes tag instead.
>
> > Signed-off-by: xiongxin <xiongxin@xxxxxxxxxx>
> > ---
> >   kernel/power/snapshot.c | 4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
> > index 2a406753af90..c20ca5fb9adc 100644
> > --- a/kernel/power/snapshot.c
> > +++ b/kernel/power/snapshot.c
> > @@ -1723,8 +1723,8 @@ static unsigned long minimum_image_size(unsigned long saveable)
> >    * /sys/power/reserved_size, respectively).  To make this happen, we compute the
> >    * total number of available page frames and allocate at least
> >    *
> > - * ([page frames total] + PAGES_FOR_IO + [metadata pages]) / 2
> > - *  + 2 * DIV_ROUND_UP(reserved_size, PAGE_SIZE)
> > + * ([page frames total] - PAGES_FOR_IO - [metadata pages]) / 2
> > + *  - 2 * DIV_ROUND_UP(reserved_size, PAGE_SIZE)
> >    *
> >    * of them, which corresponds to the maximum size of a hibernation image.
> >    *
> > --
> > 2.25.1