Re: [PATCH 1/3] mm/vma: miss to restore vmi.index on expansion failure

[Lorenzo Stoakes <lorenzo.stoakes@oracle.com>]

On Fri, Oct 25, 2024 at 08:54:09AM +0000, Wei Yang wrote:
> On Fri, Oct 25, 2024 at 09:51:12AM +0100, Lorenzo Stoakes wrote:
> >On Fri, Oct 25, 2024 at 08:49:19AM +0000, Wei Yang wrote:
> >> On Fri, Oct 25, 2024 at 09:40:25AM +0100, Lorenzo Stoakes wrote:
> >> >On Fri, Oct 25, 2024 at 08:32:27AM +0000, Wei Yang wrote:
> >> >
> >> >>
> >> >> But I have a question on your introduction of VMG_FLAG_JUST_EXPAND.
> >> >>
> >> >> Lets say just_expand is true and can_merge_left is true. Now we will adjust
> >> >> vmg->start/vma/pgoff in if (can_merge_left). If we fail expansion, we won't
> >> >> restore vmg->vma/start/pgoff, since just_expand is true.
> >> >>
> >> >> Is this what you expect?
> >> >
> >> >Yes, I explicitly wrote it to do that so it'd be a bit odd if I didn't
> >> >realise :)
> >> >
> >> >Actually at this point, I don't think we need a follow up patch, sorry.
> >> >
> >> >As I think perhaps I will make this change as part of an existing series
> >> >where I am reworking mmap_region(), since this is the only place where it
> >> >matters, and it would make everything a hell of a lot clearer.
> >> >
> >> >Thanks for pointing this out, it's very useful (and an embarrassing
> >> >oversight on my part...!), but I think it'd be better reworked this way.
> >> >
> >> >Thanks!
> >>
> >> Ok, for now I would just remove these two lines with the change log you
> >> suggested.
> >
> >NO! Sorry I've not been clear - don't send any series.
> >
> >I am going to make a change that eliminates the need for your change (sorry, but
> >in discussing this I've realised that's the best way forward).
> >
>
> Sure, go ahead.

Thanks, apologies I know it sucks, to be clear I very much appreciate your
input here!

For more detail - we are refactoring how the '2nd attempt' at a merge
works, also avoiding any abuse of vmg-> fields to keep track of start/end
of a range, so it becomes better to just open-code 'reset' of these fields
precisely at the point we need them.

Do please let us know if you notice any other silly mistakes like this :>)

Thanks, Lorenzo

>
> >>
> >> --
> >> Wei Yang
> >> Help you, Help me
> >>
>
> --
> Wei Yang
> Help you, Help me
>