Re: [PATCH v7 1/7] mm: pass task and mm to do_madvise

On 3/2/20 8:36 PM, Minchan Kim wrote:

In upcoming patches, do_madvise will be called from external process
context so we shouldn't asssume "current" is always hinted process's
task_struct.

Furthermore, we couldn't access mm_struct via task->mm
once it's verified by access_mm which will be introduced in next
patch[1].

I would suggest to replace with:

Furthermore, we must not access mm_struct via task->mm, but obtain it via
access_mm() once (in the following patch) and only use that pointer [1], so pass
it to do_madvise() as well. Note the vma->vm_mm pointers are safe, so we can use
them further down the call stack.

And let's pass *current* and current->mm as arguments of
do_madvise so it shouldn't change existing behavior but prepare
next patch to make review easy.

Note: io_madvise pass NULL as target_task argument of do_madvise
because it couldn't know who is target.

             can't

[1] http://lore.kernel.org/r/CAG48ez27=pwm5m_N_988xT1huO7g7h6arTQL44zev6TD-h-7Tg@mail.gmail.com (local)

Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jann Horn <jannh@google.com>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>

Reviewed-by: Vlastimil Babka <redacted>

Nit:

This looks stray and unrelated.