The main virtio_balloon state structure contains the fields num_pfns and
array 'pfns'. Although they are stored here persistently, the lifetime of
useful data in there is never more than one function - they're essentially
used as though they were local variables.
For the pfns buffer, used to communicate a batch of pfns this is useful to
avoid either transient kmalloc()s or putting too much data on the stack.
For num_pfns, there is no reason it should not be a local, though.
This patch cleans things up by making num_pfns a local in the functions it
is used in. The pfns array remains, but the comment is updated to clarify
that it contains no truly persistent data.
Signed-off-by: David Gibson <david@xxxxxxxxxxxxxxxxxxxxx>
---
drivers/virtio/virtio_balloon.c | 28 ++++++++++++++++------------
1 file changed, 16 insertions(+), 12 deletions(-)
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 05f0a80..6c07793 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -46,8 +46,8 @@ struct virtio_balloon
unsigned int num_pages;
struct list_head pages;
- /* The array of pfns we tell the Host about. */
- unsigned int num_pfns;
+ /* Temporary buffer of pfns to pass to the host */
+ /* Store this here to avoid a too-large local array */
u32 pfns[256];
/* Memory statistics */
@@ -79,11 +79,12 @@ static void balloon_ack(struct virtqueue *vq)
complete(&vb->acked);
}
-static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
+static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq,
+ unsigned int n)
{
struct scatterlist sg;
- sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
+ sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * n);
init_completion(&vb->acked);
@@ -98,10 +99,12 @@ static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
static void fill_balloon(struct virtio_balloon *vb, size_t num)
{
+ unsigned int n;
+
/* We can only do one array worth at a time. */
num = min(num, ARRAY_SIZE(vb->pfns));
- for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) {
+ for (n = 0; n < num; n++) {
struct page *page = alloc_page(GFP_HIGHUSER | __GFP_NORETRY |
__GFP_NOMEMALLOC | __GFP_NOWARN);
if (!page) {
@@ -113,17 +116,17 @@ static void fill_balloon(struct virtio_balloon *vb, size_t num)
msleep(200);
break;
}
- vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page);
+ vb->pfns[n] = page_to_balloon_pfn(page);
totalram_pages--;
vb->num_pages++;
list_add(&page->lru, &vb->pages);
}
/* Didn't get any? Oh well. */
- if (vb->num_pfns == 0)
+ if (n == 0)
return;
- tell_host(vb, vb->inflate_vq);
+ tell_host(vb, vb->inflate_vq, n);
}
static void release_pages_by_pfn(const u32 pfns[], unsigned int num)
@@ -139,14 +142,15 @@ 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;
+ unsigned int n;
/* We can only do one array worth at a time. */
num = min(num, ARRAY_SIZE(vb->pfns));
- for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) {
+ for (n = 0; n < num; n++) {
page = list_first_entry(&vb->pages, struct page, lru);
list_del(&page->lru);
- vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page);
+ vb->pfns[n] = page_to_balloon_pfn(page);
vb->num_pages--;
}
@@ -155,8 +159,8 @@ static void leak_balloon(struct virtio_balloon *vb, size_t num)
* 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);
- release_pages_by_pfn(vb->pfns, vb->num_pfns);
+ tell_host(vb, vb->deflate_vq, n);
+ release_pages_by_pfn(vb->pfns, n);
}
static inline void update_stat(struct virtio_balloon *vb, int idx,
--
1.7.9.5
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