Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757924Ab2FYX07 (ORCPT ); Mon, 25 Jun 2012 19:26:59 -0400 Received: from mx1.redhat.com ([209.132.183.28]:52723 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757722Ab2FYX0N (ORCPT ); Mon, 25 Jun 2012 19:26:13 -0400 From: Rafael Aquini To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Rusty Russell , "Michael S. Tsirkin" , Rik van Riel , Rafael Aquini Subject: [PATCH 2/4] virtio_balloon: handle concurrent accesses to virtio_balloon struct elements Date: Mon, 25 Jun 2012 20:25:57 -0300 Message-Id: In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4917 Lines: 146 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 --- 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; -- 1.7.10.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/