bpf: Use kmalloc_nolock() in range tree

The range tree uses bpf_mem_alloc() that is safe to be called from all
contexts and uses a pre-allocated pool of memory to serve these
allocations.

Replace bpf_mem_alloc() with kmalloc_nolock() as it can be called safely
from all contexts and is more scalable than bpf_mem_alloc().

Remove the migrate_disable/enable pairs as they were only needed for
bpf_mem_alloc() as it does per-cpu operations, kmalloc_nolock() doesn't
need this.

Signed-off-by: Puranjay Mohan <puranjay@kernel.org>

Author: puranjaymohan

kernel/bpf/range_tree.c

@@ -2,7 +2,6 @@
 /* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */
 #include <linux/interval_tree_generic.h>
 #include <linux/slab.h>
-#include <linux/bpf_mem_alloc.h>
 #include <linux/bpf.h>
 #include "range_tree.h"
 
@@ -21,7 +20,7 @@
  * in commit 6772fcc8890a ("xfs: convert xbitmap to interval tree").
  *
  * The implementation relies on external lock to protect rbtree-s.
- * The alloc/free of range_node-s is done via bpf_mem_alloc.
+ * The alloc/free of range_node-s is done via kmalloc_nolock().
  *
  * bpf arena is using range_tree to represent unallocated slots.
  * At init time:
@@ -150,9 +149,8 @@ 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();
+			new_rn = kmalloc_nolock(sizeof(struct range_node), __GFP_ACCOUNT,
+						NUMA_NO_NODE);
 			if (!new_rn)
 				return -ENOMEM;
 			new_rn->rn_start = last + 1;
@@ -172,9 +170,7 @@ 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();
+			kfree_nolock(rn);
 		}
 	}
 	return 0;
@@ -227,9 +223,7 @@ 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();
+		kfree_nolock(right);
 	} else if (left) {
 		/* Combine with the left range */
 		range_it_remove(left, rt);
@@ -241,9 +235,7 @@ 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();
+		left = kmalloc_nolock(sizeof(struct range_node), __GFP_ACCOUNT, NUMA_NO_NODE);
 		if (!left)
 			return -ENOMEM;
 		left->rn_start = start;
@@ -259,7 +251,7 @@ void range_tree_destroy(struct range_tree *rt)
 
 	while ((rn = range_it_iter_first(rt, 0, -1U))) {
 		range_it_remove(rn, rt);
-		bpf_mem_free(&bpf_global_ma, rn);
+		kfree_nolock(rn);
 	}
 }