netdev - Re: [PATCH iproute2] lib: bpf_legacy: fix bpffs mount when /sys/fs/bpf exists

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Date:   Tue, 21 Sep 2021 12:04:12 +0200
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Andrea Claudi <aclaudi@...hat.com>, netdev@...r.kernel.org
Cc:     stephen@...workplumber.org, dsahern@...il.com
Subject: Re: [PATCH iproute2] lib: bpf_legacy: fix bpffs mount when
 /sys/fs/bpf exists

Andrea Claudi <aclaudi@...hat.com> writes:

> bpf selftests using iproute2 fails with:
>
> $ ip link set dev veth0 xdp object ../bpf/xdp_dummy.o section xdp_dummy
> Continuing without mounted eBPF fs. Too old kernel?
> mkdir (null)/globals failed: No such file or directory
> Unable to load program
>
> This happens when the /sys/fs/bpf directory exists. In this case, mkdir
> in bpf_mnt_check_target() fails with errno == EEXIST, and the function
> returns -1. Thus bpf_get_work_dir() does not call bpf_mnt_fs() and the
> bpffs is not mounted.
>
> Fix this in bpf_mnt_check_target(), returning 0 when the mountpoint
> exists.
>
> Fixes: d4fcdbbec9df ("lib/bpf: Fix and simplify bpf_mnt_check_target()")
> Reported-by: Mingyu Shi <mshi@...hat.com>
> Reported-by: Jiri Benc <jbenc@...hat.com>
> Suggested-by: Jiri Benc <jbenc@...hat.com>
> Signed-off-by: Andrea Claudi <aclaudi@...hat.com>

Reviewed-by: Toke Høiland-Jørgensen <toke@...hat.com>