From: Michal Hocko <mhocko@kernel.org>
To: Minchan Kim <minchan@kernel.org>
Cc: Oleksandr Natalenko <oleksandr@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Tim Murray <timmurray@google.com>,
Joel Fernandes <joel@joelfernandes.org>,
Suren Baghdasaryan <surenb@google.com>,
Daniel Colascione <dancol@google.com>,
Shakeel Butt <shakeelb@google.com>,
Sonny Rao <sonnyrao@google.com>,
Brian Geffon <bgeffon@google.com>
Subject: Re: [RFC 4/7] mm: factor out madvise's core functionality
Date: Tue, 21 May 2019 12:55:03 +0200 [thread overview]
Message-ID: <20190521105503.GQ32329@dhcp22.suse.cz> (raw)
In-Reply-To: <20190521104949.GE219653@google.com>
On Tue 21-05-19 19:49:49, Minchan Kim wrote:
> On Tue, May 21, 2019 at 08:36:28AM +0200, Oleksandr Natalenko wrote:
> > Hi.
> >
> > On Tue, May 21, 2019 at 10:26:49AM +0900, Minchan Kim wrote:
> > > On Mon, May 20, 2019 at 04:26:33PM +0200, Oleksandr Natalenko wrote:
> > > > Hi.
> > > >
> > > > On Mon, May 20, 2019 at 12:52:51PM +0900, Minchan Kim wrote:
> > > > > This patch factor out madvise's core functionality so that upcoming
> > > > > patch can reuse it without duplication.
> > > > >
> > > > > It shouldn't change any behavior.
> > > > >
> > > > > Signed-off-by: Minchan Kim <minchan@kernel.org>
> > > > > ---
> > > > > mm/madvise.c | 168 +++++++++++++++++++++++++++------------------------
> > > > > 1 file changed, 89 insertions(+), 79 deletions(-)
> > > > >
> > > > > diff --git a/mm/madvise.c b/mm/madvise.c
> > > > > index 9a6698b56845..119e82e1f065 100644
> > > > > --- a/mm/madvise.c
> > > > > +++ b/mm/madvise.c
> > > > > @@ -742,7 +742,8 @@ static long madvise_dontneed_single_vma(struct vm_area_struct *vma,
> > > > > return 0;
> > > > > }
> > > > >
> > > > > -static long madvise_dontneed_free(struct vm_area_struct *vma,
> > > > > +static long madvise_dontneed_free(struct task_struct *tsk,
> > > > > + struct vm_area_struct *vma,
> > > > > struct vm_area_struct **prev,
> > > > > unsigned long start, unsigned long end,
> > > > > int behavior)
> > > > > @@ -754,8 +755,8 @@ static long madvise_dontneed_free(struct vm_area_struct *vma,
> > > > > if (!userfaultfd_remove(vma, start, end)) {
> > > > > *prev = NULL; /* mmap_sem has been dropped, prev is stale */
> > > > >
> > > > > - down_read(¤t->mm->mmap_sem);
> > > > > - vma = find_vma(current->mm, start);
> > > > > + down_read(&tsk->mm->mmap_sem);
> > > > > + vma = find_vma(tsk->mm, start);
> > > > > if (!vma)
> > > > > return -ENOMEM;
> > > > > if (start < vma->vm_start) {
> > > > > @@ -802,7 +803,8 @@ static long madvise_dontneed_free(struct vm_area_struct *vma,
> > > > > * Application wants to free up the pages and associated backing store.
> > > > > * This is effectively punching a hole into the middle of a file.
> > > > > */
> > > > > -static long madvise_remove(struct vm_area_struct *vma,
> > > > > +static long madvise_remove(struct task_struct *tsk,
> > > > > + struct vm_area_struct *vma,
> > > > > struct vm_area_struct **prev,
> > > > > unsigned long start, unsigned long end)
> > > > > {
> > > > > @@ -836,13 +838,13 @@ static long madvise_remove(struct vm_area_struct *vma,
> > > > > get_file(f);
> > > > > if (userfaultfd_remove(vma, start, end)) {
> > > > > /* mmap_sem was not released by userfaultfd_remove() */
> > > > > - up_read(¤t->mm->mmap_sem);
> > > > > + up_read(&tsk->mm->mmap_sem);
> > > > > }
> > > > > error = vfs_fallocate(f,
> > > > > FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
> > > > > offset, end - start);
> > > > > fput(f);
> > > > > - down_read(¤t->mm->mmap_sem);
> > > > > + down_read(&tsk->mm->mmap_sem);
> > > > > return error;
> > > > > }
> > > > >
> > > > > @@ -916,12 +918,13 @@ static int madvise_inject_error(int behavior,
> > > > > #endif
> > > >
> > > > What about madvise_inject_error() and get_user_pages_fast() in it
> > > > please?
> > >
> > > Good point. Maybe, there more places where assume context is "current" so
> > > I'm thinking to limit hints we could allow from external process.
> > > It would be better for maintainance point of view in that we could know
> > > the workload/usecases when someone ask new advises from external process
> > > without making every hints works both contexts.
> >
> > Well, for madvise_inject_error() we still have a remote variant of
> > get_user_pages(), and that should work, no?
>
> Regardless of madvise_inject_error, it seems to be risky to expose all
> of hints for external process, I think. For example, MADV_DONTNEED with
> race, it's critical for stability. So, until we could get the way to
> prevent the race, I want to restrict hints.
Well, if you allow the full ptrace access then you can shoot the target
whatever you like.
> > Regarding restricting the hints, I'm definitely interested in having
> > remote MADV_MERGEABLE/MADV_UNMERGEABLE. But, OTOH, doing it via remote
> > madvise() introduces another issue with traversing remote VMAs reliably.
>
> How is it signifiact when the race happens? It could waste CPU cycle
> and make unncessary break of that merged pages but expect it should be
> rare so such non-desruptive hint could be exposed via process_madvise, I think.
>
> If the hint is critical for the race, yes, as Michal suggested, we need a way
> to close it and I guess non-cooperative userfaultfd with synchronous support
> would help private anonymous vma.
If we have a per vma fd approach then we can revalidate atomically and
make sure the operation is performed on the range that was really
requested. I do not think we want to provide a more specific guarantees.
Monitor process has to be careful same way ptrace doesn't want to harm
the target.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2019-05-21 10:55 UTC|newest]
Thread overview: 138+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-20 3:52 [RFC 0/7] introduce memory hinting API for external process Minchan Kim
2019-05-20 3:52 ` [RFC 1/7] mm: introduce MADV_COOL Minchan Kim
2019-05-20 8:16 ` Michal Hocko
2019-05-20 8:19 ` Michal Hocko
2019-05-20 15:08 ` Suren Baghdasaryan
2019-05-20 22:55 ` Minchan Kim
2019-05-20 22:54 ` Minchan Kim
2019-05-21 6:04 ` Michal Hocko
2019-05-21 9:11 ` Minchan Kim
2019-05-21 10:05 ` Michal Hocko
2019-05-28 8:53 ` Hillf Danton
2019-05-28 10:58 ` Minchan Kim
2019-05-20 3:52 ` [RFC 2/7] mm: change PAGEREF_RECLAIM_CLEAN with PAGE_REFRECLAIM Minchan Kim
2019-05-20 16:50 ` Johannes Weiner
2019-05-20 22:57 ` Minchan Kim
2019-05-20 3:52 ` [RFC 3/7] mm: introduce MADV_COLD Minchan Kim
2019-05-20 8:27 ` Michal Hocko
2019-05-20 23:00 ` Minchan Kim
2019-05-21 6:08 ` Michal Hocko
2019-05-21 9:13 ` Minchan Kim
2019-05-28 14:54 ` Hillf Danton
2019-05-30 0:45 ` Minchan Kim
2019-05-20 3:52 ` [RFC 4/7] mm: factor out madvise's core functionality Minchan Kim
2019-05-20 14:26 ` Oleksandr Natalenko
2019-05-21 1:26 ` Minchan Kim
2019-05-21 6:36 ` Oleksandr Natalenko
2019-05-21 6:50 ` Michal Hocko
2019-05-21 7:06 ` Oleksandr Natalenko
2019-05-21 10:52 ` Minchan Kim
2019-05-21 11:00 ` Michal Hocko
2019-05-21 11:24 ` Minchan Kim
2019-05-21 11:32 ` Michal Hocko
2019-05-21 10:49 ` Minchan Kim
2019-05-21 10:55 ` Michal Hocko [this message]
2019-05-20 3:52 ` [RFC 5/7] mm: introduce external memory hinting API Minchan Kim
2019-05-20 9:18 ` Michal Hocko
2019-05-21 2:41 ` Minchan Kim
2019-05-21 6:17 ` Michal Hocko
2019-05-21 10:32 ` Minchan Kim
2019-05-21 9:01 ` Christian Brauner
2019-05-21 11:35 ` Minchan Kim
2019-05-21 11:51 ` Christian Brauner
2019-05-21 15:31 ` Oleg Nesterov
2019-05-27 7:43 ` Minchan Kim
2019-05-27 15:12 ` Oleg Nesterov
2019-05-27 23:33 ` Minchan Kim
2019-05-28 7:23 ` Michal Hocko
2019-05-29 3:41 ` Hillf Danton
2019-05-30 0:38 ` Minchan Kim
2019-05-20 3:52 ` [RFC 6/7] mm: extend process_madvise syscall to support vector arrary Minchan Kim
2019-05-20 9:22 ` Michal Hocko
2019-05-21 2:48 ` Minchan Kim
2019-05-21 6:24 ` Michal Hocko
2019-05-21 10:26 ` Minchan Kim
2019-05-21 10:37 ` Michal Hocko
2019-05-27 7:49 ` Minchan Kim
2019-05-29 10:08 ` Daniel Colascione
2019-05-29 10:33 ` Michal Hocko
2019-05-30 2:17 ` Minchan Kim
2019-05-30 6:57 ` Michal Hocko
2019-05-30 8:02 ` Minchan Kim
2019-05-30 16:19 ` Daniel Colascione
2019-05-30 18:47 ` Michal Hocko
2019-05-29 4:14 ` Hillf Danton
2019-05-30 0:35 ` Minchan Kim
2019-05-20 3:52 ` [RFC 7/7] mm: madvise support MADV_ANONYMOUS_FILTER and MADV_FILE_FILTER Minchan Kim
2019-05-20 9:28 ` Michal Hocko
2019-05-21 2:55 ` Minchan Kim
2019-05-21 6:26 ` Michal Hocko
2019-05-27 7:58 ` Minchan Kim
2019-05-27 12:44 ` Michal Hocko
2019-05-28 3:26 ` Minchan Kim
2019-05-28 6:29 ` Michal Hocko
2019-05-28 8:13 ` Minchan Kim
2019-05-28 8:31 ` Daniel Colascione
2019-05-28 8:49 ` Minchan Kim
2019-05-28 9:08 ` Michal Hocko
2019-05-28 9:39 ` Daniel Colascione
2019-05-28 10:33 ` Michal Hocko
2019-05-28 11:21 ` Daniel Colascione
2019-05-28 11:49 ` Michal Hocko
2019-05-28 12:11 ` Daniel Colascione
2019-05-28 12:32 ` Michal Hocko
2019-05-28 10:32 ` Minchan Kim
2019-05-28 10:41 ` Michal Hocko
2019-05-28 11:12 ` Minchan Kim
2019-05-28 11:28 ` Michal Hocko
2019-05-28 11:42 ` Daniel Colascione
2019-05-28 11:56 ` Michal Hocko
2019-05-28 12:18 ` Daniel Colascione
2019-05-28 12:38 ` Michal Hocko
2019-05-28 12:10 ` Minchan Kim
2019-05-28 11:44 ` Minchan Kim
2019-05-28 11:51 ` Daniel Colascione
2019-05-28 12:06 ` Michal Hocko
2019-05-28 12:22 ` Minchan Kim
2019-05-28 11:28 ` Daniel Colascione
2019-05-21 15:33 ` Johannes Weiner
2019-05-22 1:50 ` Minchan Kim
2019-05-29 4:36 ` Hillf Danton
2019-05-30 1:00 ` Minchan Kim
2019-05-20 6:37 ` [RFC 0/7] introduce memory hinting API for external process Anshuman Khandual
2019-05-20 16:59 ` Tim Murray
2019-05-21 2:55 ` Anshuman Khandual
2019-05-21 5:14 ` Minchan Kim
2019-05-21 10:34 ` Michal Hocko
2019-05-28 10:50 ` Anshuman Khandual
2019-05-21 12:56 ` Shakeel Butt
2019-05-22 4:15 ` Brian Geffon
2019-05-22 4:23 ` Brian Geffon
2019-05-20 9:28 ` Michal Hocko
2019-05-20 14:42 ` Oleksandr Natalenko
2019-05-21 2:56 ` Minchan Kim
2019-05-20 16:46 ` Johannes Weiner
2019-05-21 4:39 ` Minchan Kim
2019-05-21 6:32 ` Michal Hocko
2019-05-21 1:44 ` Matthew Wilcox
2019-05-21 5:01 ` Minchan Kim
2019-05-21 6:34 ` Michal Hocko
2019-05-21 8:42 ` Christian Brauner
2019-05-21 11:05 ` Minchan Kim
2019-05-21 11:30 ` Christian Brauner
2019-05-21 11:39 ` Christian Brauner
2019-05-22 5:11 ` Daniel Colascione
2019-05-22 8:22 ` Christian Brauner
2019-05-22 13:16 ` Daniel Colascione
2019-05-22 14:52 ` Christian Brauner
2019-05-22 15:17 ` Daniel Colascione
2019-05-22 15:48 ` Christian Brauner
2019-05-22 15:57 ` Daniel Colascione
2019-05-22 16:01 ` Christian Brauner
2019-05-22 16:01 ` Daniel Colascione
2019-05-23 13:07 ` Minchan Kim
2019-05-27 8:06 ` Minchan Kim
2019-05-21 11:41 ` Minchan Kim
2019-05-21 12:04 ` Christian Brauner
2019-05-21 12:15 ` Oleksandr Natalenko
2019-05-21 12:53 ` Shakeel Butt
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