bpf: Use try_alloc_pages() to allocate pages for bpf needs.

Use try_alloc_pages() and free_pages_nolock() for BPF needs when context doesn't allow using normal alloc_pages. This is a prerequisite for further work. Signed-off-by: Alexei Starovoitov <[email protected]>
kernel-patches · Feb 26, 2025 · aa71457 · aa71457
1 parent 038c427
commit aa71457
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Showing 3 changed files with 23 additions and 7 deletions.
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
@@ -2354,7 +2354,7 @@ int  generic_map_delete_batch(struct bpf_map *map,
 struct bpf_map *bpf_map_get_curr_or_next(u32 *id);
 struct bpf_prog *bpf_prog_get_curr_or_next(u32 *id);
 
-int bpf_map_alloc_pages(const struct bpf_map *map, gfp_t gfp, int nid,
+int bpf_map_alloc_pages(const struct bpf_map *map, int nid,
 			unsigned long nr_pages, struct page **page_array);
 #ifdef CONFIG_MEMCG
 void *bpf_map_kmalloc_node(const struct bpf_map *map, size_t size, gfp_t flags,

diff --git a/kernel/bpf/arena.c b/kernel/bpf/arena.c
@@ -287,7 +287,7 @@ static vm_fault_t arena_vm_fault(struct vm_fault *vmf)
 		return VM_FAULT_SIGSEGV;
 
 	/* Account into memcg of the process that created bpf_arena */
-	ret = bpf_map_alloc_pages(map, GFP_KERNEL | __GFP_ZERO, NUMA_NO_NODE, 1, &page);
+	ret = bpf_map_alloc_pages(map, NUMA_NO_NODE, 1, &page);
 	if (ret) {
 		range_tree_set(&arena->rt, vmf->pgoff, 1);
 		return VM_FAULT_SIGSEGV;
@@ -465,8 +465,7 @@ static long arena_alloc_pages(struct bpf_arena *arena, long uaddr, long page_cnt
 	if (ret)
 		goto out_free_pages;
 
-	ret = bpf_map_alloc_pages(&arena->map, GFP_KERNEL | __GFP_ZERO,
-				  node_id, page_cnt, pages);
+	ret = bpf_map_alloc_pages(&arena->map, node_id, page_cnt, pages);
 	if (ret)
 		goto out;
 

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
@@ -569,7 +569,24 @@ static void bpf_map_release_memcg(struct bpf_map *map)
 }
 #endif
 
-int bpf_map_alloc_pages(const struct bpf_map *map, gfp_t gfp, int nid,
+static bool can_alloc_pages(void)
+{
+	return preempt_count() == 0 && !irqs_disabled() &&
+		!IS_ENABLED(CONFIG_PREEMPT_RT);
+}
+
+static struct page *__bpf_alloc_page(int nid)
+{
+	if (!can_alloc_pages())
+		return try_alloc_pages(nid, 0);
+
+	return alloc_pages_node(nid,
+				GFP_KERNEL | __GFP_ZERO | __GFP_ACCOUNT
+				| __GFP_NOWARN,
+				0);
+}
+
+int bpf_map_alloc_pages(const struct bpf_map *map, int nid,
 			unsigned long nr_pages, struct page **pages)
 {
 	unsigned long i, j;
@@ -582,14 +599,14 @@ int bpf_map_alloc_pages(const struct bpf_map *map, gfp_t gfp, int nid,
 	old_memcg = set_active_memcg(memcg);
 #endif
 	for (i = 0; i < nr_pages; i++) {
-		pg = alloc_pages_node(nid, gfp | __GFP_ACCOUNT, 0);
+		pg = __bpf_alloc_page(nid);
 
 		if (pg) {
 			pages[i] = pg;
 			continue;
 		}
 		for (j = 0; j < i; j++)
-			__free_page(pages[j]);
+			free_pages_nolock(pages[j], 0);
 		ret = -ENOMEM;
 		break;
 	}