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@linux.dev>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Link: https://lore.kernel.org/bpf/20260717114117.350851-3-jiayuan.chen@linux.dev
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>

0 files changed, 0 insertions, 0 deletions