This is a note to let you know that I've just added the patch titled
libbpf: Only create rx and tx XDP rings when necessary
to the 5.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
libbpf-only-create-rx-and-tx-xdp-rings-when-necessary.patch
and it can be found in the queue-5.11 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From ca7a83e2487ad0bc9a3e0e7a8645354aa1782f13 Mon Sep 17 00:00:00 2001
From: Ciara Loftus <ciara.loftus@xxxxxxxxx>
Date: Wed, 31 Mar 2021 06:12:18 +0000
Subject: libbpf: Only create rx and tx XDP rings when necessary
From: Ciara Loftus <ciara.loftus@xxxxxxxxx>
commit ca7a83e2487ad0bc9a3e0e7a8645354aa1782f13 upstream.
Prior to this commit xsk_socket__create(_shared) always attempted to create
the rx and tx rings for the socket. However this causes an issue when the
socket being setup is that which shares the fd with the UMEM. If a
previous call to this function failed with this socket after the rings were
set up, a subsequent call would always fail because the rings are not torn
down after the first call and when we try to set them up again we encounter
an error because they already exist. Solve this by remembering whether the
rings were set up by introducing new bools to struct xsk_umem which
represent the ring setup status and using them to determine whether or
not to set up the rings.
Fixes: 1cad07884239 ("libbpf: add support for using AF_XDP sockets")
Signed-off-by: Ciara Loftus <ciara.loftus@xxxxxxxxx>
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Link: https://lore.kernel.org/bpf/20210331061218.1647-4-ciara.loftus@xxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
tools/lib/bpf/xsk.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
--- a/tools/lib/bpf/xsk.c
+++ b/tools/lib/bpf/xsk.c
@@ -54,6 +54,8 @@ struct xsk_umem {
int fd;
int refcount;
struct list_head ctx_list;
+ bool rx_ring_setup_done;
+ bool tx_ring_setup_done;
};
struct xsk_ctx {
@@ -782,6 +784,7 @@ int xsk_socket__create_shared(struct xsk
struct xsk_ctx *ctx;
int err, ifindex;
bool unmap = umem->fill_save != fill;
+ bool rx_setup_done = false, tx_setup_done = false;
if (!umem || !xsk_ptr || !(rx || tx))
return -EFAULT;
@@ -809,6 +812,8 @@ int xsk_socket__create_shared(struct xsk
}
} else {
xsk->fd = umem->fd;
+ rx_setup_done = umem->rx_ring_setup_done;
+ tx_setup_done = umem->tx_ring_setup_done;
}
ctx = xsk_get_ctx(umem, ifindex, queue_id);
@@ -827,7 +832,7 @@ int xsk_socket__create_shared(struct xsk
}
xsk->ctx = ctx;
- if (rx) {
+ if (rx && !rx_setup_done) {
err = setsockopt(xsk->fd, SOL_XDP, XDP_RX_RING,
&xsk->config.rx_size,
sizeof(xsk->config.rx_size));
@@ -835,8 +840,10 @@ int xsk_socket__create_shared(struct xsk
err = -errno;
goto out_put_ctx;
}
+ if (xsk->fd == umem->fd)
+ umem->rx_ring_setup_done = true;
}
- if (tx) {
+ if (tx && !tx_setup_done) {
err = setsockopt(xsk->fd, SOL_XDP, XDP_TX_RING,
&xsk->config.tx_size,
sizeof(xsk->config.tx_size));
@@ -844,6 +851,8 @@ int xsk_socket__create_shared(struct xsk
err = -errno;
goto out_put_ctx;
}
+ if (xsk->fd == umem->fd)
+ umem->rx_ring_setup_done = true;
}
err = xsk_get_mmap_offsets(xsk->fd, &off);
Patches currently in stable-queue which might be from ciara.loftus@xxxxxxxxx are
queue-5.11/libbpf-only-create-rx-and-tx-xdp-rings-when-necessary.patch
queue-5.11/libbpf-ensure-umem-pointer-is-non-null-before-dereferencing.patch
queue-5.11/libbpf-restore-umem-state-after-socket-create-failure.patch
