linux-kernel - Re: [PATCH v3 0/5] page allocation tag compression

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Message-ID: <CAJuCfpHo=gu-JJ-N_nU_3hX4HEsfsQ6=ff19vU=NCrp1y3abiw@mail.gmail.com>
Date: Mon, 14 Oct 2024 18:48:45 -0700
From: Suren Baghdasaryan <surenb@...gle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: kent.overstreet@...ux.dev, corbet@....net, arnd@...db.de, 
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Subject: Re: [PATCH v3 0/5] page allocation tag compression

On Mon, Oct 14, 2024 at 4:32 PM Andrew Morton <akpm@...ux-foundation.org> wrote:
>
> On Mon, 14 Oct 2024 13:36:41 -0700 Suren Baghdasaryan <surenb@...gle.com> wrote:
>
> > Patch #2 copies module tags into virtually contiguous memory which
> > serves two purposes:
> > - Lets us deal with the situation when module is unloaded while there
> > are still live allocations from that module. Since we are using a copy
> > version of the tags we can safely unload the module. Space and gaps in
> > this contiguous memory are managed using a maple tree.
>
> Does this make "lib: alloc_tag_module_unload must wait for pending
> kfree_rcu calls" unneeded?

With this change we can unload a module even when tags from that
module are still in use. However "lib: alloc_tag_module_unload must
wait for pending kfree_rcu calls" would still be useful because it
will allow us to release the memory occupied by module's tags and let
other modules use that memory.

>  If so, that patch was cc:stable (justifyably), so what to do about that?

Now that I posted this patchset I'll work on backporting "lib:
alloc_tag_module_unload must wait for pending kfree_rcu calls" and its
prerequisites to 6.10 and 6.11. I'll try to get backports out
tomorrow.
I don't think we need to backport this patchset to pre-6.12 kernels
since this is an improvement and not a bug fix. But if it's needed I
can backport it as well.
Thanks,
Suren.