Re: [PATCH v4 bpf-next 1/2] bpf: introduce helper bpf_find_vma

On 11/4/21 2:31 PM, Song Liu wrote:

In some profiler use cases, it is necessary to map an address to the
backing file, e.g., a shared library. bpf_find_vma helper provides a
flexible way to achieve this. bpf_find_vma maps an address of a task to
the vma (vm_area_struct) for this address, and feed the vma to an callback
BPF function. The callback function is necessary here, as we need to
ensure mmap_sem is unlocked.

It is necessary to lock mmap_sem for find_vma. To lock and unlock mmap_sem
safely when irqs are disable, we use the same mechanism as stackmap with
build_id. Specifically, when irqs are disabled, the unlocked is postponed
in an irq_work. Refactor stackmap.c so that the irq_work is shared among
bpf_find_vma and stackmap helpers.

Reported-by: kernel test robot <redacted>

You don't need the above "Reported-by".

Signed-off-by: Song Liu <redacted>

LGTM.

Acked-by: Yonghong Song <redacted>