Merge series "slab: Re-entrant kmalloc_nolock()"

Merge series "slab: Re-entrant kmalloc_nolock()"

From the cover letter [1]:

This patch set introduces kmalloc_nolock() which is the next logical
step towards any context allocation necessary to remove bpf_mem_alloc
and get rid of preallocation requirement in BPF infrastructure.

In production BPF maps grew to gigabytes in size. Preallocation wastes
memory. Alloc from any context addresses this issue for BPF and other
subsystems that are forced to preallocate too.

This long task started with introduction of alloc_pages_nolock(), then
memcg and objcg were converted to operate from any context including
NMI, this set completes the task with kmalloc_nolock() that builds on
top of alloc_pages_nolock() and memcg changes.

After that BPF subsystem will gradually adopt it everywhere.

Link: https://lore.kernel.org/all/20250909010007.1660-1-alexei.starovoitov@gmail.com/