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

[Brendan Jackman]

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@xxxxxxxxxx> 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@xxxxxxxxx/
>>
>> 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.
>>
>> 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.