slab: prevent infinite loop in kmalloc_nolock() with debugging

In review of a followup work, Harry noticed a potential infinite loop.
Upon closed inspection, it already exists for kmalloc_nolock() on a
cache with debugging enabled, since commit af92793e52c3 ("slab:
Introduce kmalloc_nolock() and kfree_nolock().")

When alloc_single_from_new_slab() fails to trylock node list_lock, we
keep retrying to get partial slab or allocate a new slab. If we indeed
interrupted somebody holding the list_lock, the trylock fill fail
deterministically and we end up allocating and defer-freeing slabs
indefinitely with no progress.

To fix it, fail the allocation if spinning is not allowed. This is
acceptable in the restricted context of kmalloc_nolock(), especially
with debugging enabled.

Reported-by: Harry Yoo <[email protected]>
Closes: https://lore.kernel.org/all/aQLqZjjq1SPD3Fml@hyeyoo/
Fixes: af92793e52c3 ("slab: Introduce kmalloc_nolock() and kfree_nolock().")
Acked-by: Alexei Starovoitov <[email protected]>
Reviewed-by: Harry Yoo <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Vlastimil Babka <[email protected]>

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