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Message-Id: <e5f3c6d456f04adeac9fd714a6278424d71a97a0.1341353014.git.aquini@redhat.com>
Date: Tue, 3 Jul 2012 20:48:50 -0300
From: Rafael Aquini <aquini@...hat.com>
To: linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org,
virtualization@...ts.linux-foundation.org,
Rusty Russell <rusty@...tcorp.com.au>,
"Michael S. Tsirkin" <mst@...hat.com>,
Rik van Riel <riel@...hat.com>, Mel Gorman <mel@....ul.ie>,
Andi Kleen <andi@...stfloor.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
Minchan Kim <minchan@...nel.org>,
Rafael Aquini <aquini@...hat.com>
Subject: [PATCH v3 2/4] virtio_balloon: handle concurrent accesses to virtio_balloon struct elements
This patch introduces access sychronization to critical elements of struct
virtio_balloon, in order to allow the thread concurrency compaction/migration
bits might ended up imposing to the balloon driver on several situations.
Signed-off-by: Rafael Aquini <aquini@...hat.com>
---
drivers/virtio/virtio_balloon.c | 45 +++++++++++++++++++++++++++++----------
1 file changed, 34 insertions(+), 11 deletions(-)
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index bfbc15c..d47c5c2 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -51,6 +51,10 @@ struct virtio_balloon
/* Number of balloon pages we've told the Host we're not using. */
unsigned int num_pages;
+
+ /* Protect 'pages', 'pfns' & 'num_pnfs' against concurrent updates */
+ spinlock_t pfn_list_lock;
+
/*
* The pages we've told the Host we're not using.
* Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
@@ -97,21 +101,23 @@ static void balloon_ack(struct virtqueue *vq)
complete(&vb->acked);
}
-static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
-{
- struct scatterlist sg;
-
- sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
+/* Protection for concurrent accesses to balloon virtqueues and vb->acked */
+DEFINE_MUTEX(vb_queue_completion);
+static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq,
+ struct scatterlist *sg)
+{
+ mutex_lock(&vb_queue_completion);
init_completion(&vb->acked);
/* We should always be able to add one buffer to an empty queue. */
- if (virtqueue_add_buf(vq, &sg, 1, 0, vb, GFP_KERNEL) < 0)
+ if (virtqueue_add_buf(vq, sg, 1, 0, vb, GFP_KERNEL) < 0)
BUG();
virtqueue_kick(vq);
/* When host has read buffer, this completes via balloon_ack */
wait_for_completion(&vb->acked);
+ mutex_unlock(&vb_queue_completion);
}
static void set_page_pfns(u32 pfns[], struct page *page)
@@ -126,9 +132,12 @@ static void set_page_pfns(u32 pfns[], struct page *page)
static void fill_balloon(struct virtio_balloon *vb, size_t num)
{
+ struct scatterlist sg;
+ int alloc_failed = 0;
/* We can only do one array worth at a time. */
num = min(num, ARRAY_SIZE(vb->pfns));
+ spin_lock(&vb->pfn_list_lock);
for (vb->num_pfns = 0; vb->num_pfns < num;
vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
struct page *page = alloc_page(GFP_HIGHUSER | __GFP_NORETRY |
@@ -138,8 +147,7 @@ static void fill_balloon(struct virtio_balloon *vb, size_t num)
dev_printk(KERN_INFO, &vb->vdev->dev,
"Out of puff! Can't get %zu pages\n",
num);
- /* Sleep for at least 1/5 of a second before retry. */
- msleep(200);
+ alloc_failed = 1;
break;
}
set_page_pfns(vb->pfns + vb->num_pfns, page);
@@ -149,10 +157,19 @@ static void fill_balloon(struct virtio_balloon *vb, size_t num)
}
/* Didn't get any? Oh well. */
- if (vb->num_pfns == 0)
+ if (vb->num_pfns == 0) {
+ spin_unlock(&vb->pfn_list_lock);
return;
+ }
+
+ sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
+ spin_unlock(&vb->pfn_list_lock);
- tell_host(vb, vb->inflate_vq);
+ /* alloc_page failed, sleep for at least 1/5 of a sec before retry. */
+ if (alloc_failed)
+ msleep(200);
+
+ tell_host(vb, vb->inflate_vq, &sg);
}
static void release_pages_by_pfn(const u32 pfns[], unsigned int num)
@@ -169,10 +186,12 @@ static void release_pages_by_pfn(const u32 pfns[], unsigned int num)
static void leak_balloon(struct virtio_balloon *vb, size_t num)
{
struct page *page;
+ struct scatterlist sg;
/* We can only do one array worth at a time. */
num = min(num, ARRAY_SIZE(vb->pfns));
+ spin_lock(&vb->pfn_list_lock);
for (vb->num_pfns = 0; vb->num_pfns < num;
vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
page = list_first_entry(&vb->pages, struct page, lru);
@@ -180,13 +199,15 @@ static void leak_balloon(struct virtio_balloon *vb, size_t num)
set_page_pfns(vb->pfns + vb->num_pfns, page);
vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
}
+ sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
+ spin_unlock(&vb->pfn_list_lock);
/*
* Note that if
* virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
* is true, we *have* to do it in this order
*/
- tell_host(vb, vb->deflate_vq);
+ tell_host(vb, vb->deflate_vq, &sg);
release_pages_by_pfn(vb->pfns, vb->num_pfns);
}
@@ -356,6 +377,8 @@ static int virtballoon_probe(struct virtio_device *vdev)
}
INIT_LIST_HEAD(&vb->pages);
+ spin_lock_init(&vb->pfn_list_lock);
+
vb->num_pages = 0;
init_waitqueue_head(&vb->config_change);
vb->vdev = vdev;
--
1.7.10.4
--
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