From: "Michael S. Tsirkin" <mst@redhat.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>,
Rafael Aquini <aquini@redhat.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org,
Rik van Riel <riel@redhat.com>, Mel Gorman <mel@csn.ul.ie>,
Andi Kleen <andi@firstfloor.org>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Minchan Kim <minchan@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: [PATCH v11 5/7] virtio_balloon: introduce migration primitives to balloon pages
Date: Sat, 10 Nov 2012 17:53:19 +0200 [thread overview]
Message-ID: <20121110155319.GA13846@redhat.com> (raw)
In-Reply-To: <20121107161146.b99dc4a8.akpm@linux-foundation.org>
On Wed, Nov 07, 2012 at 04:11:46PM -0800, Andrew Morton wrote:
> On Thu, 08 Nov 2012 09:32:18 +1030
> Rusty Russell <rusty@rustcorp.com.au> wrote:
>
> > Rafael Aquini <aquini@redhat.com> writes:
> > > + * virtballoon_migratepage - perform the balloon page migration on behalf of
> > > + * a compation thread. (called under page lock)
> >
> > > + if (!mutex_trylock(&vb->balloon_lock))
> > > + return -EAGAIN;
> >
> > Erk, OK...
>
> Not really. As is almost always the case with a trylock, it needs a
> comment explaining why we couldn't use the far superior mutex_lock().
> Data: this reader doesn't know!
>
> > > + /* balloon's page migration 1st step -- inflate "newpage" */
> > > + spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
> > > + balloon_page_insert(newpage, mapping, &vb_dev_info->pages);
> > > + vb_dev_info->isolated_pages--;
> > > + spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
> > > + vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
> > > + set_page_pfns(vb->pfns, newpage);
> > > + tell_host(vb, vb->inflate_vq);
> >
> > tell_host does wait_event(), so you can't call it under the page_lock.
> > Right?
>
> Sleeping inside lock_page() is OK. More problematic is that GFP_KERNEL
> allocation.
Do you mean this one:
if (virtqueue_add_buf(vq, &sg, 1, 0, vb, GFP_KERNEL) < 0)
?
In practice it never triggers an allocation, we can pass in
GFP_ATOMIC just as well.
--
MST
next prev parent reply other threads:[~2012-11-10 15:51 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-07 3:05 [PATCH v11 0/7] make balloon pages movable by compaction Rafael Aquini
2012-11-07 3:05 ` [PATCH v11 1/7] mm: adjust address_space_operations.migratepage() return code Rafael Aquini
2012-11-07 19:56 ` Andrew Morton
2012-11-07 21:39 ` Rafael Aquini
2012-11-07 3:05 ` [PATCH v11 2/7] mm: redefine address_space.assoc_mapping Rafael Aquini
2012-11-07 3:05 ` [PATCH v11 3/7] mm: introduce a common interface for balloon pages mobility Rafael Aquini
2012-11-07 21:02 ` Andrew Morton
2012-11-07 21:34 ` Rafael Aquini
2012-11-09 12:11 ` Mel Gorman
2012-11-09 14:53 ` Rafael Aquini
2012-11-09 16:23 ` Mel Gorman
2012-11-09 17:58 ` Rafael Aquini
2012-11-07 3:05 ` [PATCH v11 4/7] mm: introduce compaction and migration for ballooned pages Rafael Aquini
2012-11-09 12:16 ` Mel Gorman
2012-11-20 23:33 ` Andrew Morton
2012-11-27 11:59 ` Rafael Aquini
2012-11-07 3:05 ` [PATCH v11 5/7] virtio_balloon: introduce migration primitives to balloon pages Rafael Aquini
2012-11-07 19:58 ` Andrew Morton
2012-11-07 22:02 ` Rafael Aquini
2012-11-07 23:02 ` Rusty Russell
2012-11-08 0:11 ` Andrew Morton
2012-11-08 0:32 ` Rafael Aquini
2012-11-10 15:53 ` Michael S. Tsirkin [this message]
2012-11-08 0:34 ` Rafael Aquini
2012-11-12 7:49 ` Rusty Russell
2012-11-10 15:53 ` Michael S. Tsirkin
2012-11-07 3:05 ` [PATCH v11 6/7] mm: introduce putback_movable_pages() Rafael Aquini
2012-11-07 3:05 ` [PATCH v11 7/7] mm: add vm event counters for balloon pages compaction Rafael Aquini
2012-11-09 12:20 ` Mel Gorman
2012-11-09 14:58 ` Rafael Aquini
2012-11-20 23:29 ` Andrew Morton
2012-11-10 15:55 ` Michael S. Tsirkin
2012-11-11 19:22 ` Rafael Aquini
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