mm/madvise: pass mm to do_madvise

mm/madvise: pass mm to do_madvise

Patch series "introduce memory hinting API for external process", v9.

Now, we have MADV_PAGEOUT and MADV_COLD as madvise hinting API.  With
that, application could give hints to kernel what memory range are
preferred to be reclaimed.  However, in some platform(e.g., Android), the
information required to make the hinting decision is not known to the app.
Instead, it is known to a centralized userspace daemon(e.g.,
ActivityManagerService), and that daemon must be able to initiate reclaim
on its own without any app involvement.

To solve the concern, this patch introduces new syscall -
process_madvise(2).  Bascially, it's same with madvise(2) syscall but it
has some differences.

1. It needs pidfd of target process to provide the hint

2. It supports only MADV_{COLD|PAGEOUT|MERGEABLE|UNMEREABLE} at this
   moment.  Other hints in madvise will be opened when there are explicit
   requests from community to prevent unexpected bugs we couldn't support.

3. Only privileged processes can do something for other process's
   address space.

For more detail of the new API, please see "mm: introduce external memory
hinting API" description in this patchset.

This patch (of 3):

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 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->mm as arguments of do_madvise so it shouldn't
change existing behavior but prepare next patch to make review easy.

[[email protected]: changelog tweak]
[[email protected]: use current->mm for io_uring]
Link: http://lkml.kernel.org/r/[email protected]
[[email protected]: fix it for upstream changes]
[[email protected]: whoops]
[[email protected]: add missing includes]

Signed-off-by: Minchan Kim <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Reviewed-by: Suren Baghdasaryan <[email protected]>
Reviewed-by: Vlastimil Babka <[email protected]>
Acked-by: David Rientjes <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: Jann Horn <[email protected]>
Cc: Tim Murray <[email protected]>
Cc: Daniel Colascione <[email protected]>
Cc: Sandeep Patil <[email protected]>
Cc: Sonny Rao <[email protected]>
Cc: Brian Geffon <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Shakeel Butt <[email protected]>
Cc: John Dias <[email protected]>
Cc: Joel Fernandes <[email protected]>
Cc: Alexander Duyck <[email protected]>
Cc: SeongJae Park <[email protected]>
Cc: Christian Brauner <[email protected]>
Cc: Kirill Tkhai <[email protected]>
Cc: Oleksandr Natalenko <[email protected]>
Cc: SeongJae Park <[email protected]>
Cc: Christian Brauner <[email protected]>
Cc: Florian Weimer <[email protected]>
Cc: <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
Link: http://lkml.kernel.org/r/[email protected]
Link: http://lkml.kernel.org/r/[email protected]
Link: http://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>