Re: [PATCH bpf-next 1/3] bpf: Add memory usage for arena

[bot+bpf-ci]

>     bpf: Add memory usage for arena
>
>     arena is the only map type whose map_mem_usage() still returns 0, so
>     "bpftool map show" and fdinfo always showed 0 memlock for an arena no
>     matter how many pages it had.
>
>     Count the pages that are actually mapped into the arena: bump a counter in
>     apply_range_set_cb() when a page goes in and drop it in
>     apply_range_clear_cb() when a page goes out, both under the arena spinlock.
>     map_mem_usage() then just returns nr_pages << PAGE_SHIFT.
>
>     Only real data pages are counted, not the scratch page.
>
>     Signed-off-by: Jiayuan Chen <jiayuan.chen@xxxxxxxxx>

This looks like a fix for a user-visible bug: arena's map_mem_usage()
always returned 0, so bpftool map show and fdinfo reported 0 memlock
regardless of how many pages the arena had.  The returns-0 stub was added
together with kernel/bpf/arena.c.  Should this include:

  Fixes: 317460317a02 ("bpf: Introduce bpf_arena.")


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