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

["Brendan Jackman" <brendan.jackman@linux.dev>]

On Thu Jun 18, 2026 at 2:22 AM UTC, Hao Ge wrote:
>
> 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.

Oh, I just took a look and it's a bit more fiddly than I thought because
alloc_tag.c is actually in lib/ not mm/. 

How did you tackle that, can you share your implementation? It would be
nice if we can avoid exposing alloc_flags in gfp.h.