Merge branch 'Enable non-atomic allocations in local storage'

Joanne Koong says:

====================

From: Joanne Koong <joannelkoong@gmail.com>

Currently, local storage memory can only be allocated atomically
(GFP_ATOMIC). This restriction is too strict for sleepable bpf
programs.

In this patchset, sleepable programs can allocate memory in local
storage using GFP_KERNEL, while non-sleepable programs always default to
GFP_ATOMIC.

v3 <- v2:
* Add extra case to local_storage.c selftest to test associating multiple
elements with the local storage, which triggers a GFP_KERNEL allocation in
local_storage_update().
* Cast gfp_t to __s32 in verifier to fix the sparse warnings

v2 <- v1:
* Allocate the memory before/after the raw_spin_lock_irqsave, depending
on the gfp flags
* Rename mem_flags to gfp_flags
* Reword the comment "*mem_flags* is set by the bpf verifier" to
"*gfp_flags* is a hidden argument provided by the verifier"
* Add a sentence to the commit message about existing local storage
selftests covering both the GFP_ATOMIC and GFP_KERNEL paths in
bpf_local_storage_update.
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>