Re: mm, slab/slub: Ensure kmem_cache_alloc_bulk() is available early

[Vlastimil Babka]

On 2/7/23 15:45, Vlastimil Babka wrote:
> On 2/7/23 15:16, Thomas Gleixner wrote:
>> The memory allocators are available during early boot even in the phase
>> where interrupts are disabled and scheduling is not yet possible.
>> 
>> The setup is so that GFP_KERNEL allocations work in this phase without
>> causing might_alloc() splats to be emitted because the system state is
>> SYSTEM_BOOTING at that point which prevents the warnings to trigger.
>> 
>> Most allocation/free functions use local_irq_save()/restore() or a lock
>> variant of that. But kmem_cache_alloc_bulk() and kmem_cache_free_bulk() use
>> local_[lock]_irq_disable()/enable(), which leads to a lockdep warning when
>> interrupts are enabled during the early boot phase.
>> 
>> This went unnoticed so far as there are no early users of these
>> interfaces. The upcoming conversion of the interrupt descriptor store from
>> radix_tree to maple_tree triggered this warning as maple_tree uses the bulk
>> interface.
>> 
>> Cure this by moving the kmem_cache_alloc/free() bulk variants of SLUB and
>> SLAB to local[_lock]_irq_save()/restore().
>> 
>> There is obviously no reclaim possible and required at this point so there
>> is no need to expand this coverage further.
>> 
>> No functional change.
>> 
>> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> 
> +Cc rest of slab folks
> 
> Thanks, added to slab/for-6.3/fixes

After your patch, I think it also makes sense to do the following:
----8<----