Re: [PATCH] mm/page_alloc: unify __alloc_frozen_pages[_nolock]_noprof()

[Hao Ge <hao.ge@linux.dev>]

On 2026/6/18 01:14, Brendan Jackman wrote:
> On Wed Jun 17, 2026 at 4:49 PM UTC, Suren Baghdasaryan wrote:
>> On Wed, Jun 17, 2026 at 9:39 AM Vlastimil Babka (SUSE)
>> <vbabka@kernel.org> wrote:
>>> +Cc Alexei
>>>
>>> On 6/17/26 17:29, Brendan Jackman wrote:
>>>> Currently the core allocator code is controlled by ALLOC_NOLOCK, but the
>>> It's not, it's ALLOC_TRYLOCK! Thanks for proving that we need to rename it
>>> to ALLOC_NOLOCK:
>>>
>>> https://lore.kernel.org/all/DJ9QPTO2WXNB.10E88ZHWRDHB0@gmail.com/
>>>
>>> So you just won the job to do the rename :) I think it should be done before
>>> this patch, so that the new usages and other _trylock names introduced here
>>> can be done as _nolock outright.
> Ack. I'll aim to send that tomorrow once Sashiko has caught up.
>
>>>> main entry point function is significantly different from the normal
>>>> __alloc_frozen_pages_nolock(), this is tiring when reading the code.
>>>>
>>>> Plumb the ALLOC_NOLOCK control one layer up in the call stack: create
>>>> an alloc_flags argument to __alloc_frozen_pages_nolock() (which is only
>>>> exposed to mm/) and then turn the nolock variant into a thin wrapper
>>>> that just sets that flag (as well as handling NUMA_NO_NODE, similar to
>>>> how some of the wrappers in gfp.h do).
>>>>
>>>> Rationale that this doesn't change anything:
>>>>
>>>> 1. Simple bits: A bunch of the nolock-specific handling is just moved to
>>>>     the new alloc_order_allowed(), alloc_trylock_allowed() and
>>>>     gfp_trylock.
>>>>
>>>> 2. __alloc_frozen_pages_noprof() has some extra logic that wasn't
>>>>     previously in the nolock variant:
>>>>
>>>>     a. Application of gfp_allowed_mask; this only affects early boot, and
>>>>        only flags that affect the slowpath get changed here.
>>>>
>>>>     b. Application of current_gfp_context() - also only affects the
>>>>        slowpath
>>>>
>>>> 3. The slowpath itself: this is now just explicitly skipped under
>>>>     !ALLOC_TRYLOCK.
>>> I'll have to ponder it more closely.
>>>
>>>> Ulterior motive: adding an alloc_flags arg to the allocator's
>>>> mm-internal entrypoint can later be used to do more allocation
>>>> customisation without needing to create new GFP flags.
>>> Ack.
>> I think this change might also help us in removing __GFP_NO_CODETAG
> Nice, this actually looks trivial? I can probably just tack it onto the
> v2 for this patch/series.
>
>> introduced in [1] and being the only user of __GFP_NO_OBJ_EXT once
>> Vlastimil's patchset removing other __GFP_NO_OBJ_EXT users lands.
>> CC'ing Hao as he is brainstorming ways to remove __GFP_NO_CODETAG, and
>> this might be the answer.


Hi Brendan, Suren,

Thanks for CC'ing me, Suren. This is indeed a viable approach

and I believe it brings us one step closer to removing

__GFP_NO_CODETAG entirely.


Brendan, I'd actually put together a rough local implementation

earlier with mostly the same core idea as yours, and this change

would indeed be minimal based on your patch.

Thanks a lot for being interested in tacking this into your v2 patch series.


Thanks

Best Regards

Hao


>>> Besides the need to ponder unintended effects, mostly LGTM. Just not a fan
>>> of the hardcoded '0' passed at various places. In the slab variant of this
>>> (the thread I've linked above) I went with SLAB_ALLOC_DEFAULT, so you can do
>>> e.g. ALLOC_DEFAULT here?
> Yup ALLOC_DEFAULT sounds fine to me.
>
> Thanks for the reviews as always.