[PATCH bpf-next v2] bpf: Add necessary migrate_{disable,enable} in range_tree

[Yonghong Song <yonghong.song@xxxxxxxxx>]

When running bpf selftest (./test_progs -j), the following warnings
showed up:

  $ ./test_progs -t arena_atomics
  ...
  BUG: using smp_processor_id() in preemptible [00000000] code: kworker/u19:0/12501
  caller is bpf_mem_free+0x128/0x330
  ...
  Call Trace:
   <TASK>
   dump_stack_lvl
   check_preemption_disabled
   bpf_mem_free
   range_tree_destroy
   arena_map_free
   bpf_map_free_deferred
   process_scheduled_works
   ...

For selftests arena_htab and arena_list, similar smp_process_id() BUGs are
dumped, and the following are two stack trace:

   <TASK>
   dump_stack_lvl
   check_preemption_disabled
   bpf_mem_alloc
   range_tree_set
   arena_map_alloc
   map_create
   ...

   <TASK>
   dump_stack_lvl
   check_preemption_disabled
   bpf_mem_alloc
   range_tree_clear
   arena_vm_fault
   do_pte_missing
   handle_mm_fault
   do_user_addr_fault
   ...

Adding migrate_{disable,enable}() around related bpf_mem_{alloc,free}()
calls can fix the issue.

Fixes: b795379757eb ("bpf: Introduce range_tree data structure and use it in bpf arena")
Signed-off-by: Yonghong Song <yonghong.song@xxxxxxxxx>
---
 kernel/bpf/range_tree.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/kernel/bpf/range_tree.c b/kernel/bpf/range_tree.c
index f7915ab0a6d3..5bdf9aadca3a 100644
--- a/kernel/bpf/range_tree.c
+++ b/kernel/bpf/range_tree.c
@@ -150,7 +150,9 @@ int range_tree_clear(struct range_tree *rt, u32 start, u32 len)
 			range_it_insert(rn, rt);
 
 			/* Add a range */
+			migrate_disable();
 			new_rn = bpf_mem_alloc(&bpf_global_ma, sizeof(struct range_node));
+			migrate_enable();
 			if (!new_rn)
 				return -ENOMEM;
 			new_rn->rn_start = last + 1;
@@ -170,7 +172,9 @@ int range_tree_clear(struct range_tree *rt, u32 start, u32 len)
 		} else {
 			/* in the middle of the clearing range */
 			range_it_remove(rn, rt);
+			migrate_disable();
 			bpf_mem_free(&bpf_global_ma, rn);
+			migrate_enable();
 		}
 	}
 	return 0;
@@ -223,7 +227,9 @@ int range_tree_set(struct range_tree *rt, u32 start, u32 len)
 		range_it_remove(right, rt);
 		left->rn_last = right->rn_last;
 		range_it_insert(left, rt);
+		migrate_disable();
 		bpf_mem_free(&bpf_global_ma, right);
+		migrate_enable();
 	} else if (left) {
 		/* Combine with the left range */
 		range_it_remove(left, rt);
@@ -235,7 +241,9 @@ int range_tree_set(struct range_tree *rt, u32 start, u32 len)
 		right->rn_start = start;
 		range_it_insert(right, rt);
 	} else {
+		migrate_disable();
 		left = bpf_mem_alloc(&bpf_global_ma, sizeof(struct range_node));
+		migrate_enable();
 		if (!left)
 			return -ENOMEM;
 		left->rn_start = start;
@@ -251,7 +259,9 @@ void range_tree_destroy(struct range_tree *rt)
 
 	while ((rn = range_it_iter_first(rt, 0, -1U))) {
 		range_it_remove(rn, rt);
+		migrate_disable();
 		bpf_mem_free(&bpf_global_ma, rn);
+		migrate_enable();
 	}
 }
 
-- 
2.43.5