linux-kernel - [PATCH bpf] libbpf: unmap rings when umem deleted

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Date:   Tue, 1 Mar 2022 13:26:23 +0000
From:   lic121 <lic121@...natelecom.cn>
To:     bpf@...r.kernel.org
Cc:     Björn Töpel <bjorn@...nel.org>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        lic121@...natelecom.cn
Subject: [PATCH bpf] libbpf: unmap rings when umem deleted

xsk_umem__create() does mmap for fill/comp rings, but xsk_umem__delete()
doesn't do the unmap. This works fine for regular cases, because
xsk_socket__delete() does unmap for the rings. But for the case that
xsk_socket__create_shared() fails, umem rings are not unmapped.

fill_save/comp_save are checked to determine if rings have already be
unmapped by xsk. If fill_save and comp_save are NULL, it means that the
rings have already been used by xsk. Then they are supposed to be
unmapped by xsk_socket__delete(). Otherwise, xsk_umem__delete() does the
unmap.

Fixes: 2f6324a3937f ("libbpf: Support shared umems between queues and devices")
Signed-off-by: lic121 <lic121@...natelecom.cn>
---
 tools/lib/bpf/xsk.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
index edafe56..32a2f57 100644
--- a/tools/lib/bpf/xsk.c
+++ b/tools/lib/bpf/xsk.c
@@ -1193,12 +1193,23 @@ int xsk_socket__create(struct xsk_socket **xsk_ptr, const char *ifname,
 
 int xsk_umem__delete(struct xsk_umem *umem)
 {
+	struct xdp_mmap_offsets off;
+	int err;
+
 	if (!umem)
 		return 0;
 
 	if (umem->refcount)
 		return -EBUSY;
 
+	err = xsk_get_mmap_offsets(umem->fd, &off);
+	if (!err && umem->fill_save && umem->comp_save) {
+		munmap(umem->fill_save->ring - off.fr.desc,
+		       off.fr.desc + umem->config.fill_size * sizeof(__u64));
+		munmap(umem->comp_save->ring - off.cr.desc,
+		       off.cr.desc + umem->config.comp_size * sizeof(__u64));
+	}
+
 	close(umem->fd);
 	free(umem);
 
-- 
1.8.3.1