[PATCH] slab: Fix using this_cpu_ptr() in preemptible context

ranxiaokai627
2025-09-30T08:34:34Z

From: Ran Xiaokai <ran.xiaokai@zte.com.cn>

defer_free() maybe called in preemptible context, this will
trigger the below warning message:

BUG: using smp_processor_id() in preemptible [00000000] code: swapper/0/1
caller is defer_free+0x1b/0x60
Call Trace:
<TASK>
dump_stack_lvl+0xac/0xc0
check_preemption_disabled+0xbe/0xe0
defer_free+0x1b/0x60
kfree_nolock+0x1eb/0x2b0
alloc_slab_obj_exts+0x356/0x390
__alloc_tagging_slab_alloc_hook+0xa0/0x300
__kmalloc_cache_noprof+0x1c4/0x5c0
__set_page_owner+0x10d/0x1c0
post_alloc_hook+0x84/0xf0
get_page_from_freelist+0x73b/0x1380
__alloc_frozen_pages_noprof+0x110/0x2c0
alloc_pages_mpol+0x44/0x140
alloc_slab_page+0xac/0x150
allocate_slab+0x78/0x3a0
___slab_alloc+0x76b/0xed0
__slab_alloc.constprop.0+0x5a/0xb0
__kmalloc_noprof+0x3dc/0x6d0
__list_lru_init+0x6c/0x210
alloc_super+0x3b6/0x470
sget_fc+0x5f/0x3a0
get_tree_nodev+0x27/0x90
vfs_get_tree+0x26/0xc0
vfs_kern_mount.part.0+0xb6/0x140
kern_mount+0x24/0x40
init_pipe_fs+0x4f/0x70
do_one_initcall+0x62/0x2e0
kernel_init_freeable+0x25b/0x4b0
kernel_init+0x1a/0x1c0
ret_from_fork+0x290/0x2e0
ret_from_fork_asm+0x11/0x20
</TASK>

Replace this_cpu_ptr with raw_cpu_ptr to eliminate
the above warning message.

Fixes: af92793e52c3 ("slab: Introduce kmalloc_nolock() and kfree_nolock().")
Signed-off-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
---
mm/slub.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 1433f5b988f7..67c57f1b5a86 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -6432,7 +6432,7 @@ static void free_deferred_objects(struct irq_work *work)

static void defer_free(struct kmem_cache *s, void *head)
{
- struct defer_free *df = this_cpu_ptr(&defer_free_objects);
+ struct defer_free *df = raw_cpu_ptr(&defer_free_objects);

if (llist_add(head + s->offset, &df->objects))
irq_work_queue(&df->work);
@@ -6440,7 +6440,7 @@ static void defer_free(struct kmem_cache *s, void *head)

static void defer_deactivate_slab(struct slab *slab, void *flush_freelist)
{
- struct defer_free *df = this_cpu_ptr(&defer_free_objects);
+ struct defer_free *df = raw_cpu_ptr(&defer_free_objects);

slab->flush_freelist = flush_freelist;
if (llist_add(&slab->llnode, &df->slabs))
--
2.25.1