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* [PATCH bpf-next 1/2] bpf: Add open coded version of kmem_cache iterator
@ 2024-10-17  8:06 Namhyung Kim
  2024-10-17  8:06 ` [PATCH bpf-next 2/2] selftests/bpf: Add a test for open coded kmem_cache iter Namhyung Kim
                   ` (2 more replies)
  0 siblings, 3 replies; 11+ messages in thread
From: Namhyung Kim @ 2024-10-17  8:06 UTC (permalink / raw)
  To: Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko
  Cc: Martin KaFai Lau, Eduard Zingerman, Song Liu, Yonghong Song,
	John Fastabend, KP Singh, Stanislav Fomichev, Hao Luo, Jiri Olsa,
	LKML, bpf, Andrew Morton, Christoph Lameter, Pekka Enberg,
	David Rientjes, Joonsoo Kim, Vlastimil Babka, Roman Gushchin,
	Hyeonggon Yoo, linux-mm, Arnaldo Carvalho de Melo, Kees Cook

Add a new open coded iterator for kmem_cache which can be called from a
BPF program like below.  It doesn't take any argument and traverses all
kmem_cache entries.

  struct kmem_cache *pos;

  bpf_for_each(kmem_cache, pos) {
      ...
  }

As it needs to grab slab_mutex, it should be called from sleepable BPF
programs only.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
 kernel/bpf/helpers.c         |  3 ++
 kernel/bpf/kmem_cache_iter.c | 87 ++++++++++++++++++++++++++++++++++++
 2 files changed, 90 insertions(+)

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 073e6f04f4d765ff..d1dfa4f335577914 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -3111,6 +3111,9 @@ BTF_ID_FLAGS(func, bpf_iter_bits_next, KF_ITER_NEXT | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_iter_bits_destroy, KF_ITER_DESTROY)
 BTF_ID_FLAGS(func, bpf_copy_from_user_str, KF_SLEEPABLE)
 BTF_ID_FLAGS(func, bpf_get_kmem_cache)
+BTF_ID_FLAGS(func, bpf_iter_kmem_cache_new, KF_ITER_NEW | KF_SLEEPABLE)
+BTF_ID_FLAGS(func, bpf_iter_kmem_cache_next, KF_ITER_NEXT | KF_RET_NULL | KF_SLEEPABLE)
+BTF_ID_FLAGS(func, bpf_iter_kmem_cache_destroy, KF_ITER_DESTROY | KF_SLEEPABLE)
 BTF_KFUNCS_END(common_btf_ids)
 
 static const struct btf_kfunc_id_set common_kfunc_set = {
diff --git a/kernel/bpf/kmem_cache_iter.c b/kernel/bpf/kmem_cache_iter.c
index ebc101d7da51b57c..31ddaf452b20a458 100644
--- a/kernel/bpf/kmem_cache_iter.c
+++ b/kernel/bpf/kmem_cache_iter.c
@@ -145,6 +145,93 @@ static const struct bpf_iter_seq_info kmem_cache_iter_seq_info = {
 	.seq_ops		= &kmem_cache_iter_seq_ops,
 };
 
+/* open-coded version */
+struct bpf_iter_kmem_cache {
+	__u64 __opaque[1];
+} __attribute__((aligned(8)));
+
+struct bpf_iter_kmem_cache_kern {
+	struct kmem_cache *pos;
+} __attribute__((aligned(8)));
+
+__bpf_kfunc_start_defs();
+
+__bpf_kfunc int bpf_iter_kmem_cache_new(struct bpf_iter_kmem_cache *it)
+{
+	struct bpf_iter_kmem_cache_kern *kit = (void *)it;
+
+	BUILD_BUG_ON(sizeof(*kit) > sizeof(*it));
+	BUILD_BUG_ON(__alignof__(*kit) != __alignof__(*it));
+
+	kit->pos = NULL;
+	return 0;
+}
+
+__bpf_kfunc struct kmem_cache *bpf_iter_kmem_cache_next(struct bpf_iter_kmem_cache *it)
+{
+	struct bpf_iter_kmem_cache_kern *kit = (void *)it;
+	struct kmem_cache *prev = kit->pos;
+	struct kmem_cache *next;
+	bool destroy = false;
+
+	mutex_lock(&slab_mutex);
+
+	if (list_empty(&slab_caches)) {
+		mutex_unlock(&slab_mutex);
+		return NULL;
+	}
+
+	if (prev == NULL)
+		next = list_first_entry(&slab_caches, struct kmem_cache, list);
+	else if (list_last_entry(&slab_caches, struct kmem_cache, list) == prev)
+		next = NULL;
+	else
+		next = list_next_entry(prev, list);
+
+	/* boot_caches have negative refcount, don't touch them */
+	if (next && next->refcount > 0)
+		next->refcount++;
+
+	/* Skip kmem_cache_destroy() for active entries */
+	if (prev && prev->refcount > 1)
+		prev->refcount--;
+	else if (prev && prev->refcount == 1)
+		destroy = true;
+
+	mutex_unlock(&slab_mutex);
+
+	if (destroy)
+		kmem_cache_destroy(prev);
+
+	kit->pos = next;
+	return next;
+}
+
+__bpf_kfunc void bpf_iter_kmem_cache_destroy(struct bpf_iter_kmem_cache *it)
+{
+	struct bpf_iter_kmem_cache_kern *kit = (void *)it;
+	struct kmem_cache *s = kit->pos;
+	bool destroy = false;
+
+	if (s == NULL)
+		return;
+
+	mutex_lock(&slab_mutex);
+
+	/* Skip kmem_cache_destroy() for active entries */
+	if (s->refcount > 1)
+		s->refcount--;
+	else if (s->refcount == 1)
+		destroy = true;
+
+	mutex_unlock(&slab_mutex);
+
+	if (destroy)
+		kmem_cache_destroy(s);
+}
+
+__bpf_kfunc_end_defs();
+
 static void bpf_iter_kmem_cache_show_fdinfo(const struct bpf_iter_aux_info *aux,
 					    struct seq_file *seq)
 {
-- 
2.47.0.rc1.288.g06298d1525-goog



^ permalink raw reply	[flat|nested] 11+ messages in thread
end of thread, other threads:[~2024-10-24  7:44 UTC | newest]

Thread overview: 11+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2024-10-17  8:06 [PATCH bpf-next 1/2] bpf: Add open coded version of kmem_cache iterator Namhyung Kim
2024-10-17  8:06 ` [PATCH bpf-next 2/2] selftests/bpf: Add a test for open coded kmem_cache iter Namhyung Kim
2024-10-18 18:46   ` Martin KaFai Lau
2024-10-22 17:51     ` Namhyung Kim
2024-10-21 23:36   ` Andrii Nakryiko
2024-10-22 17:52     ` Namhyung Kim
2024-10-24  7:44     ` Namhyung Kim
2024-10-18 18:22 ` [PATCH bpf-next 1/2] bpf: Add open coded version of kmem_cache iterator Martin KaFai Lau
2024-10-22 17:47   ` Namhyung Kim
2024-10-21 23:32 ` Andrii Nakryiko
2024-10-22 17:50   ` Namhyung Kim

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