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From: Minchan Kim <minchan@kernel.org>
To: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-mm <linux-mm@kvack.org>,
	linux-api@vger.kernel.org, oleksandr@redhat.com,
	Suren Baghdasaryan <surenb@google.com>,
	Tim Murray <timmurray@google.com>,
	Daniel Colascione <dancol@google.com>,
	Sandeep Patil <sspatil@google.com>,
	Sonny Rao <sonnyrao@google.com>,
	Brian Geffon <bgeffon@google.com>, Michal Hocko <mhocko@suse.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Shakeel Butt <shakeelb@google.com>,
	John Dias <joaodias@google.com>,
	christian.brauner@ubuntu.com, sjpark@amazon.de,
	"Kirill A. Shutemov" <kirill@shutemov.name>
Subject: Re: [PATCH v2 1/5] mm: factor out madvise's core functionality
Date: Fri, 17 Jan 2020 10:14:13 -0800	[thread overview]
Message-ID: <20200117181413.GC140922@google.com> (raw)
In-Reply-To: <d3b8431d-fa3d-6a16-8af1-a68b3ac8ca58@virtuozzo.com>

On Fri, Jan 17, 2020 at 01:02:34PM +0300, Kirill Tkhai wrote:
> On 17.01.2020 02:59, 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 | 194 +++++++++++++++++++++++++++++----------------------
> >  1 file changed, 111 insertions(+), 83 deletions(-)
> > 
> > diff --git a/mm/madvise.c b/mm/madvise.c
> > index bcdb6a042787..0c901de531e4 100644
> > --- a/mm/madvise.c
> > +++ b/mm/madvise.c
> > @@ -35,6 +35,7 @@
> >  struct madvise_walk_private {
> >  	struct mmu_gather *tlb;
> >  	bool pageout;
> > +	struct task_struct *task;
> >  };
> >  
> >  /*
> > @@ -306,12 +307,13 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
> >  	bool pageout = private->pageout;
> >  	struct mm_struct *mm = tlb->mm;
> >  	struct vm_area_struct *vma = walk->vma;
> > +	struct task_struct *task = private->task;
> >  	pte_t *orig_pte, *pte, ptent;
> >  	spinlock_t *ptl;
> >  	struct page *page = NULL;
> >  	LIST_HEAD(page_list);
> >  
> > -	if (fatal_signal_pending(current))
> > +	if (fatal_signal_pending(task))
> >  		return -EINTR;
> 
> This EINTR may confuse userspace. Users will think the syscall was interrupted,
> and it may be restarted, but this is not true.

madvise_[pageout|cold] doesn't propagate the error to userspace.

> 
> What we care here? Current task received fatal signal, while walk_page_range(..&cold_walk_ops..)
> is a long cycle. So, this check allows to break the cycle faster.
> 
> Iteration over remote task's mm may also be long, and we still may need to break
> it if current received a signal.
> 
> So, we'd better left fatal_signal_pending(current) here.
> 
> Maybe we need both tasks fatal_signal_pending() checks and different retvals here,
> but it's up to you.

Yub, let's check both processes here to bail out.

Thanks for the review!

  reply	other threads:[~2020-01-17 18:14 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-16 23:59 [PATCH v2 0/5] introduce memory hinting API for external process Minchan Kim
2020-01-16 23:59 ` [PATCH v2 1/5] mm: factor out madvise's core functionality Minchan Kim
2020-01-17 10:02   ` Kirill Tkhai
2020-01-17 18:14     ` Minchan Kim [this message]
2020-01-16 23:59 ` [PATCH v2 2/5] mm: introduce external memory hinting API Minchan Kim
2020-01-17 11:52   ` Michal Hocko
2020-01-17 15:58     ` Kirill A. Shutemov
2020-01-17 17:32       ` Minchan Kim
2020-01-17 21:26         ` Kirill A. Shutemov
2020-01-18  9:40           ` SeongJae Park
2020-01-19 16:14           ` sspatil
2020-01-20  7:58             ` Michal Hocko
2020-01-20 10:39               ` Kirill Tkhai
2020-01-21 18:32               ` Minchan Kim
2020-01-22  8:28                 ` Michal Hocko
2020-01-22  9:36                   ` SeongJae Park
2020-01-22 10:02                     ` Michal Hocko
2020-01-22 13:28                       ` SeongJae Park
2020-01-23  1:41                   ` Minchan Kim
2020-01-23  9:13                     ` Michal Hocko
2020-01-21 18:11           ` Minchan Kim
2020-01-22 10:44             ` Oleksandr Natalenko
2020-01-23  1:43               ` Minchan Kim
2020-01-23  7:29                 ` Oleksandr Natalenko
2020-01-17 17:25     ` Minchan Kim
2020-01-20  8:03       ` Michal Hocko
2020-01-20 10:24     ` Kirill Tkhai
2020-01-20 11:27       ` Michal Hocko
2020-01-20 12:39         ` Kirill A. Shutemov
2020-01-20 13:24           ` Michal Hocko
2020-01-20 14:21             ` Kirill A. Shutemov
2020-01-20 15:44               ` Michal Hocko
2020-01-21 18:43             ` Minchan Kim
2020-01-16 23:59 ` [PATCH v2 3/5] mm/madvise: employ mmget_still_valid for write lock Minchan Kim
2020-01-16 23:59 ` [PATCH v2 4/5] mm/madvise: allow KSM hints for remote API Minchan Kim
2020-01-17 10:13   ` Kirill Tkhai
2020-01-17 12:34     ` Oleksandr Natalenko
2020-01-21 17:45       ` Minchan Kim
2020-01-16 23:59 ` [PATCH v2 5/5] mm: support both pid and pidfd for process_madvise Minchan Kim

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