linux-kernel - [PATCH 5/7] io_uring/bpf_filter: add ref counts to struct io_bpf

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Message-ID: <20260127183311.86505-6-axboe@kernel.dk>
Date: Tue, 27 Jan 2026 11:30:00 -0700
From: Jens Axboe <axboe@...nel.dk>
To: io-uring@...r.kernel.org
Cc: brauner@...nel.org,
	cyphar@...har.com,
	jannh@...gle.com,
	kees@...nel.org,
	linux-kernel@...r.kernel.org,
	Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 5/7] io_uring/bpf_filter: add ref counts to struct io_bpf_filter

In preparation for allowing inheritance of BPF filters and filter
tables, add a reference count to the filter. This allows multiple tables
to safely include the same filter.

Reviewed-by: Christian Brauner <brauner@...nel.org>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
---
 io_uring/bpf_filter.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/io_uring/bpf_filter.c b/io_uring/bpf_filter.c
index 1409d625b686..b94944ab8442 100644
--- a/io_uring/bpf_filter.c
+++ b/io_uring/bpf_filter.c
@@ -15,6 +15,7 @@
 #include "openclose.h"
 
 struct io_bpf_filter {
+	refcount_t		refs;
 	struct bpf_prog		*prog;
 	struct io_bpf_filter	*next;
 };
@@ -125,6 +126,11 @@ static void io_free_bpf_filters(struct rcu_head *head)
 			 */
 			if (f == &dummy_filter)
 				break;
+
+			/* Someone still holds a ref, stop iterating. */
+			if (!refcount_dec_and_test(&f->refs))
+				break;
+
 			bpf_prog_destroy(f->prog);
 			kfree(f);
 			f = next;
@@ -298,6 +304,7 @@ int io_register_bpf_filter(struct io_restriction *res,
 		ret = -ENOMEM;
 		goto err;
 	}
+	refcount_set(&filter->refs, 1);
 	filter->prog = prog;
 	res->bpf_filters = filters;
 
-- 
2.51.0