mm/mempool: Untangle CONFIG_SLUB_DEBUG_ON abuse and switch to static key

The mempool subsystem historically wrapped its debugging logic inside an
merely defines compile-time defaults for SLUB and caused two flaws:

1. On production kernels where CONFIG_SLUB_DEBUG=y but
   CONFIG_SLUB_DEBUG_ON=n, mempool debugging was completely compiled out
   at compile time.
2. On kernels with CONFIG_SLUB_DEBUG_ON=y, mempool debugging stayed active
   even if a user explicitly disabled slub debugging at boot time.

Clean up this mess by removing the #ifdef and switching to a runtime static
key (mempool_debug_enabled), allowing mempool debugging to be toggled
cleanly via its own boot parameter.

Suggested-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Signed-off-by: Li RongQing <lirongqing@baidu.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Harry Yoo <harry@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Hao Li <hao.li@linux.dev>
Cc: Christoph Lameter <cl@gentwo.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Usama Arif <usama.arif@linux.dev>
Reviewed-by: SeongJae Park <sj@kernel.org>
Reviewed-by: Harry Yoo (Oracle) <harry@kernel.org>
Link: https://patch.msgid.link/20260604110318.2089-1-lirongqing@baidu.com
Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>

0 files changed, 0 insertions, 0 deletions