linux/drivers/virtio/virtio_balloon.c
Wei Wang c9a6820fc0 virtio_balloon: fix shrinker count
Instead of multiplying by page order, virtio balloon divided by page
order. The result is that it can return 0 if there are a bit less
than MAX_ORDER - 1 pages in use, and then shrinker scan won't be called.

Cc: stable@vger.kernel.org
Fixes: 71994620bb ("virtio_balloon: replace oom notifier with shrinker")
Signed-off-by: Wei Wang <wei.w.wang@intel.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
2019-11-20 02:15:57 -05:00

1058 lines
29 KiB
C

// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Virtio balloon implementation, inspired by Dor Laor and Marcelo
* Tosatti's implementations.
*
* Copyright 2008 Rusty Russell IBM Corporation
*/
#include <linux/virtio.h>
#include <linux/virtio_balloon.h>
#include <linux/swap.h>
#include <linux/workqueue.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/balloon_compaction.h>
#include <linux/wait.h>
#include <linux/mm.h>
#include <linux/mount.h>
#include <linux/magic.h>
#include <linux/pseudo_fs.h>
/*
* Balloon device works in 4K page units. So each page is pointed to by
* multiple balloon pages. All memory counters in this driver are in balloon
* page units.
*/
#define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
#define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256
#define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80
#define VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG (__GFP_NORETRY | __GFP_NOWARN | \
__GFP_NOMEMALLOC)
/* The order of free page blocks to report to host */
#define VIRTIO_BALLOON_FREE_PAGE_ORDER (MAX_ORDER - 1)
/* The size of a free page block in bytes */
#define VIRTIO_BALLOON_FREE_PAGE_SIZE \
(1 << (VIRTIO_BALLOON_FREE_PAGE_ORDER + PAGE_SHIFT))
#ifdef CONFIG_BALLOON_COMPACTION
static struct vfsmount *balloon_mnt;
#endif
enum virtio_balloon_vq {
VIRTIO_BALLOON_VQ_INFLATE,
VIRTIO_BALLOON_VQ_DEFLATE,
VIRTIO_BALLOON_VQ_STATS,
VIRTIO_BALLOON_VQ_FREE_PAGE,
VIRTIO_BALLOON_VQ_MAX
};
enum virtio_balloon_config_read {
VIRTIO_BALLOON_CONFIG_READ_CMD_ID = 0,
};
struct virtio_balloon {
struct virtio_device *vdev;
struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq;
/* Balloon's own wq for cpu-intensive work items */
struct workqueue_struct *balloon_wq;
/* The free page reporting work item submitted to the balloon wq */
struct work_struct report_free_page_work;
/* The balloon servicing is delegated to a freezable workqueue. */
struct work_struct update_balloon_stats_work;
struct work_struct update_balloon_size_work;
/* Prevent updating balloon when it is being canceled. */
spinlock_t stop_update_lock;
bool stop_update;
/* Bitmap to indicate if reading the related config fields are needed */
unsigned long config_read_bitmap;
/* The list of allocated free pages, waiting to be given back to mm */
struct list_head free_page_list;
spinlock_t free_page_list_lock;
/* The number of free page blocks on the above list */
unsigned long num_free_page_blocks;
/*
* The cmd id received from host.
* Read it via virtio_balloon_cmd_id_received to get the latest value
* sent from host.
*/
u32 cmd_id_received_cache;
/* The cmd id that is actively in use */
__virtio32 cmd_id_active;
/* Buffer to store the stop sign */
__virtio32 cmd_id_stop;
/* Waiting for host to ack the pages we released. */
wait_queue_head_t acked;
/* Number of balloon pages we've told the Host we're not using. */
unsigned int num_pages;
/*
* The pages we've told the Host we're not using are enqueued
* at vb_dev_info->pages list.
* Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
* to num_pages above.
*/
struct balloon_dev_info vb_dev_info;
/* Synchronize access/update to this struct virtio_balloon elements */
struct mutex balloon_lock;
/* The array of pfns we tell the Host about. */
unsigned int num_pfns;
__virtio32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];
/* Memory statistics */
struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
/* To register a shrinker to shrink memory upon memory pressure */
struct shrinker shrinker;
};
static struct virtio_device_id id_table[] = {
{ VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
{ 0 },
};
static u32 page_to_balloon_pfn(struct page *page)
{
unsigned long pfn = page_to_pfn(page);
BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
/* Convert pfn from Linux page size to balloon page size. */
return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
}
static void balloon_ack(struct virtqueue *vq)
{
struct virtio_balloon *vb = vq->vdev->priv;
wake_up(&vb->acked);
}
static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
{
struct scatterlist sg;
unsigned int len;
sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
/* We should always be able to add one buffer to an empty queue. */
virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
virtqueue_kick(vq);
/* When host has read buffer, this completes via balloon_ack */
wait_event(vb->acked, virtqueue_get_buf(vq, &len));
}
static void set_page_pfns(struct virtio_balloon *vb,
__virtio32 pfns[], struct page *page)
{
unsigned int i;
/*
* Set balloon pfns pointing at this page.
* Note that the first pfn points at start of the page.
*/
for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
pfns[i] = cpu_to_virtio32(vb->vdev,
page_to_balloon_pfn(page) + i);
}
static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
{
unsigned num_allocated_pages;
unsigned num_pfns;
struct page *page;
LIST_HEAD(pages);
/* We can only do one array worth at a time. */
num = min(num, ARRAY_SIZE(vb->pfns));
for (num_pfns = 0; num_pfns < num;
num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
struct page *page = balloon_page_alloc();
if (!page) {
dev_info_ratelimited(&vb->vdev->dev,
"Out of puff! Can't get %u pages\n",
VIRTIO_BALLOON_PAGES_PER_PAGE);
/* Sleep for at least 1/5 of a second before retry. */
msleep(200);
break;
}
balloon_page_push(&pages, page);
}
mutex_lock(&vb->balloon_lock);
vb->num_pfns = 0;
while ((page = balloon_page_pop(&pages))) {
balloon_page_enqueue(&vb->vb_dev_info, page);
set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
if (!virtio_has_feature(vb->vdev,
VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
adjust_managed_page_count(page, -1);
vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE;
}
num_allocated_pages = vb->num_pfns;
/* Did we get any? */
if (vb->num_pfns != 0)
tell_host(vb, vb->inflate_vq);
mutex_unlock(&vb->balloon_lock);
return num_allocated_pages;
}
static void release_pages_balloon(struct virtio_balloon *vb,
struct list_head *pages)
{
struct page *page, *next;
list_for_each_entry_safe(page, next, pages, lru) {
if (!virtio_has_feature(vb->vdev,
VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
adjust_managed_page_count(page, 1);
list_del(&page->lru);
put_page(page); /* balloon reference */
}
}
static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
{
unsigned num_freed_pages;
struct page *page;
struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
LIST_HEAD(pages);
/* We can only do one array worth at a time. */
num = min(num, ARRAY_SIZE(vb->pfns));
mutex_lock(&vb->balloon_lock);
/* We can't release more pages than taken */
num = min(num, (size_t)vb->num_pages);
for (vb->num_pfns = 0; vb->num_pfns < num;
vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
page = balloon_page_dequeue(vb_dev_info);
if (!page)
break;
set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
list_add(&page->lru, &pages);
vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
}
num_freed_pages = vb->num_pfns;
/*
* Note that if
* virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
* is true, we *have* to do it in this order
*/
if (vb->num_pfns != 0)
tell_host(vb, vb->deflate_vq);
release_pages_balloon(vb, &pages);
mutex_unlock(&vb->balloon_lock);
return num_freed_pages;
}
static inline void update_stat(struct virtio_balloon *vb, int idx,
u16 tag, u64 val)
{
BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag);
vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val);
}
#define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
static unsigned int update_balloon_stats(struct virtio_balloon *vb)
{
unsigned long events[NR_VM_EVENT_ITEMS];
struct sysinfo i;
unsigned int idx = 0;
long available;
unsigned long caches;
all_vm_events(events);
si_meminfo(&i);
available = si_mem_available();
caches = global_node_page_state(NR_FILE_PAGES);
#ifdef CONFIG_VM_EVENT_COUNTERS
update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
pages_to_bytes(events[PSWPIN]));
update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
pages_to_bytes(events[PSWPOUT]));
update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
#ifdef CONFIG_HUGETLB_PAGE
update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGALLOC,
events[HTLB_BUDDY_PGALLOC]);
update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGFAIL,
events[HTLB_BUDDY_PGALLOC_FAIL]);
#endif
#endif
update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
pages_to_bytes(i.freeram));
update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
pages_to_bytes(i.totalram));
update_stat(vb, idx++, VIRTIO_BALLOON_S_AVAIL,
pages_to_bytes(available));
update_stat(vb, idx++, VIRTIO_BALLOON_S_CACHES,
pages_to_bytes(caches));
return idx;
}
/*
* While most virtqueues communicate guest-initiated requests to the hypervisor,
* the stats queue operates in reverse. The driver initializes the virtqueue
* with a single buffer. From that point forward, all conversations consist of
* a hypervisor request (a call to this function) which directs us to refill
* the virtqueue with a fresh stats buffer. Since stats collection can sleep,
* we delegate the job to a freezable workqueue that will do the actual work via
* stats_handle_request().
*/
static void stats_request(struct virtqueue *vq)
{
struct virtio_balloon *vb = vq->vdev->priv;
spin_lock(&vb->stop_update_lock);
if (!vb->stop_update)
queue_work(system_freezable_wq, &vb->update_balloon_stats_work);
spin_unlock(&vb->stop_update_lock);
}
static void stats_handle_request(struct virtio_balloon *vb)
{
struct virtqueue *vq;
struct scatterlist sg;
unsigned int len, num_stats;
num_stats = update_balloon_stats(vb);
vq = vb->stats_vq;
if (!virtqueue_get_buf(vq, &len))
return;
sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
virtqueue_kick(vq);
}
static inline s64 towards_target(struct virtio_balloon *vb)
{
s64 target;
u32 num_pages;
virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages,
&num_pages);
/* Legacy balloon config space is LE, unlike all other devices. */
if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
num_pages = le32_to_cpu((__force __le32)num_pages);
target = num_pages;
return target - vb->num_pages;
}
/* Gives back @num_to_return blocks of free pages to mm. */
static unsigned long return_free_pages_to_mm(struct virtio_balloon *vb,
unsigned long num_to_return)
{
struct page *page;
unsigned long num_returned;
spin_lock_irq(&vb->free_page_list_lock);
for (num_returned = 0; num_returned < num_to_return; num_returned++) {
page = balloon_page_pop(&vb->free_page_list);
if (!page)
break;
free_pages((unsigned long)page_address(page),
VIRTIO_BALLOON_FREE_PAGE_ORDER);
}
vb->num_free_page_blocks -= num_returned;
spin_unlock_irq(&vb->free_page_list_lock);
return num_returned;
}
static void virtio_balloon_queue_free_page_work(struct virtio_balloon *vb)
{
if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
return;
/* No need to queue the work if the bit was already set. */
if (test_and_set_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
&vb->config_read_bitmap))
return;
queue_work(vb->balloon_wq, &vb->report_free_page_work);
}
static void virtballoon_changed(struct virtio_device *vdev)
{
struct virtio_balloon *vb = vdev->priv;
unsigned long flags;
spin_lock_irqsave(&vb->stop_update_lock, flags);
if (!vb->stop_update) {
queue_work(system_freezable_wq,
&vb->update_balloon_size_work);
virtio_balloon_queue_free_page_work(vb);
}
spin_unlock_irqrestore(&vb->stop_update_lock, flags);
}
static void update_balloon_size(struct virtio_balloon *vb)
{
u32 actual = vb->num_pages;
/* Legacy balloon config space is LE, unlike all other devices. */
if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
actual = (__force u32)cpu_to_le32(actual);
virtio_cwrite(vb->vdev, struct virtio_balloon_config, actual,
&actual);
}
static void update_balloon_stats_func(struct work_struct *work)
{
struct virtio_balloon *vb;
vb = container_of(work, struct virtio_balloon,
update_balloon_stats_work);
stats_handle_request(vb);
}
static void update_balloon_size_func(struct work_struct *work)
{
struct virtio_balloon *vb;
s64 diff;
vb = container_of(work, struct virtio_balloon,
update_balloon_size_work);
diff = towards_target(vb);
if (!diff)
return;
if (diff > 0)
diff -= fill_balloon(vb, diff);
else
diff += leak_balloon(vb, -diff);
update_balloon_size(vb);
if (diff)
queue_work(system_freezable_wq, work);
}
static int init_vqs(struct virtio_balloon *vb)
{
struct virtqueue *vqs[VIRTIO_BALLOON_VQ_MAX];
vq_callback_t *callbacks[VIRTIO_BALLOON_VQ_MAX];
const char *names[VIRTIO_BALLOON_VQ_MAX];
int err;
/*
* Inflateq and deflateq are used unconditionally. The names[]
* will be NULL if the related feature is not enabled, which will
* cause no allocation for the corresponding virtqueue in find_vqs.
*/
callbacks[VIRTIO_BALLOON_VQ_INFLATE] = balloon_ack;
names[VIRTIO_BALLOON_VQ_INFLATE] = "inflate";
callbacks[VIRTIO_BALLOON_VQ_DEFLATE] = balloon_ack;
names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate";
names[VIRTIO_BALLOON_VQ_STATS] = NULL;
names[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
names[VIRTIO_BALLOON_VQ_STATS] = "stats";
callbacks[VIRTIO_BALLOON_VQ_STATS] = stats_request;
}
if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
names[VIRTIO_BALLOON_VQ_FREE_PAGE] = "free_page_vq";
callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
}
err = vb->vdev->config->find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX,
vqs, callbacks, names, NULL, NULL);
if (err)
return err;
vb->inflate_vq = vqs[VIRTIO_BALLOON_VQ_INFLATE];
vb->deflate_vq = vqs[VIRTIO_BALLOON_VQ_DEFLATE];
if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
struct scatterlist sg;
unsigned int num_stats;
vb->stats_vq = vqs[VIRTIO_BALLOON_VQ_STATS];
/*
* Prime this virtqueue with one buffer so the hypervisor can
* use it to signal us later (it can't be broken yet!).
*/
num_stats = update_balloon_stats(vb);
sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
err = virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb,
GFP_KERNEL);
if (err) {
dev_warn(&vb->vdev->dev, "%s: add stat_vq failed\n",
__func__);
return err;
}
virtqueue_kick(vb->stats_vq);
}
if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
vb->free_page_vq = vqs[VIRTIO_BALLOON_VQ_FREE_PAGE];
return 0;
}
static u32 virtio_balloon_cmd_id_received(struct virtio_balloon *vb)
{
if (test_and_clear_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
&vb->config_read_bitmap))
virtio_cread(vb->vdev, struct virtio_balloon_config,
free_page_report_cmd_id,
&vb->cmd_id_received_cache);
return vb->cmd_id_received_cache;
}
static int send_cmd_id_start(struct virtio_balloon *vb)
{
struct scatterlist sg;
struct virtqueue *vq = vb->free_page_vq;
int err, unused;
/* Detach all the used buffers from the vq */
while (virtqueue_get_buf(vq, &unused))
;
vb->cmd_id_active = virtio32_to_cpu(vb->vdev,
virtio_balloon_cmd_id_received(vb));
sg_init_one(&sg, &vb->cmd_id_active, sizeof(vb->cmd_id_active));
err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_active, GFP_KERNEL);
if (!err)
virtqueue_kick(vq);
return err;
}
static int send_cmd_id_stop(struct virtio_balloon *vb)
{
struct scatterlist sg;
struct virtqueue *vq = vb->free_page_vq;
int err, unused;
/* Detach all the used buffers from the vq */
while (virtqueue_get_buf(vq, &unused))
;
sg_init_one(&sg, &vb->cmd_id_stop, sizeof(vb->cmd_id_stop));
err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_stop, GFP_KERNEL);
if (!err)
virtqueue_kick(vq);
return err;
}
static int get_free_page_and_send(struct virtio_balloon *vb)
{
struct virtqueue *vq = vb->free_page_vq;
struct page *page;
struct scatterlist sg;
int err, unused;
void *p;
/* Detach all the used buffers from the vq */
while (virtqueue_get_buf(vq, &unused))
;
page = alloc_pages(VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG,
VIRTIO_BALLOON_FREE_PAGE_ORDER);
/*
* When the allocation returns NULL, it indicates that we have got all
* the possible free pages, so return -EINTR to stop.
*/
if (!page)
return -EINTR;
p = page_address(page);
sg_init_one(&sg, p, VIRTIO_BALLOON_FREE_PAGE_SIZE);
/* There is always 1 entry reserved for the cmd id to use. */
if (vq->num_free > 1) {
err = virtqueue_add_inbuf(vq, &sg, 1, p, GFP_KERNEL);
if (unlikely(err)) {
free_pages((unsigned long)p,
VIRTIO_BALLOON_FREE_PAGE_ORDER);
return err;
}
virtqueue_kick(vq);
spin_lock_irq(&vb->free_page_list_lock);
balloon_page_push(&vb->free_page_list, page);
vb->num_free_page_blocks++;
spin_unlock_irq(&vb->free_page_list_lock);
} else {
/*
* The vq has no available entry to add this page block, so
* just free it.
*/
free_pages((unsigned long)p, VIRTIO_BALLOON_FREE_PAGE_ORDER);
}
return 0;
}
static int send_free_pages(struct virtio_balloon *vb)
{
int err;
u32 cmd_id_active;
while (1) {
/*
* If a stop id or a new cmd id was just received from host,
* stop the reporting.
*/
cmd_id_active = virtio32_to_cpu(vb->vdev, vb->cmd_id_active);
if (unlikely(cmd_id_active !=
virtio_balloon_cmd_id_received(vb)))
break;
/*
* The free page blocks are allocated and sent to host one by
* one.
*/
err = get_free_page_and_send(vb);
if (err == -EINTR)
break;
else if (unlikely(err))
return err;
}
return 0;
}
static void virtio_balloon_report_free_page(struct virtio_balloon *vb)
{
int err;
struct device *dev = &vb->vdev->dev;
/* Start by sending the received cmd id to host with an outbuf. */
err = send_cmd_id_start(vb);
if (unlikely(err))
dev_err(dev, "Failed to send a start id, err = %d\n", err);
err = send_free_pages(vb);
if (unlikely(err))
dev_err(dev, "Failed to send a free page, err = %d\n", err);
/* End by sending a stop id to host with an outbuf. */
err = send_cmd_id_stop(vb);
if (unlikely(err))
dev_err(dev, "Failed to send a stop id, err = %d\n", err);
}
static void report_free_page_func(struct work_struct *work)
{
struct virtio_balloon *vb = container_of(work, struct virtio_balloon,
report_free_page_work);
u32 cmd_id_received;
cmd_id_received = virtio_balloon_cmd_id_received(vb);
if (cmd_id_received == VIRTIO_BALLOON_CMD_ID_DONE) {
/* Pass ULONG_MAX to give back all the free pages */
return_free_pages_to_mm(vb, ULONG_MAX);
} else if (cmd_id_received != VIRTIO_BALLOON_CMD_ID_STOP &&
cmd_id_received !=
virtio32_to_cpu(vb->vdev, vb->cmd_id_active)) {
virtio_balloon_report_free_page(vb);
}
}
#ifdef CONFIG_BALLOON_COMPACTION
/*
* virtballoon_migratepage - perform the balloon page migration on behalf of
* a compation thread. (called under page lock)
* @vb_dev_info: the balloon device
* @newpage: page that will replace the isolated page after migration finishes.
* @page : the isolated (old) page that is about to be migrated to newpage.
* @mode : compaction mode -- not used for balloon page migration.
*
* After a ballooned page gets isolated by compaction procedures, this is the
* function that performs the page migration on behalf of a compaction thread
* The page migration for virtio balloon is done in a simple swap fashion which
* follows these two macro steps:
* 1) insert newpage into vb->pages list and update the host about it;
* 2) update the host about the old page removed from vb->pages list;
*
* This function preforms the balloon page migration task.
* Called through balloon_mapping->a_ops->migratepage
*/
static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
struct page *newpage, struct page *page, enum migrate_mode mode)
{
struct virtio_balloon *vb = container_of(vb_dev_info,
struct virtio_balloon, vb_dev_info);
unsigned long flags;
/*
* In order to avoid lock contention while migrating pages concurrently
* to leak_balloon() or fill_balloon() we just give up the balloon_lock
* this turn, as it is easier to retry the page migration later.
* This also prevents fill_balloon() getting stuck into a mutex
* recursion in the case it ends up triggering memory compaction
* while it is attempting to inflate the ballon.
*/
if (!mutex_trylock(&vb->balloon_lock))
return -EAGAIN;
get_page(newpage); /* balloon reference */
/* balloon's page migration 1st step -- inflate "newpage" */
spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
balloon_page_insert(vb_dev_info, newpage);
vb_dev_info->isolated_pages--;
__count_vm_event(BALLOON_MIGRATE);
spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
set_page_pfns(vb, vb->pfns, newpage);
tell_host(vb, vb->inflate_vq);
/* balloon's page migration 2nd step -- deflate "page" */
spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
balloon_page_delete(page);
spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
set_page_pfns(vb, vb->pfns, page);
tell_host(vb, vb->deflate_vq);
mutex_unlock(&vb->balloon_lock);
put_page(page); /* balloon reference */
return MIGRATEPAGE_SUCCESS;
}
static int balloon_init_fs_context(struct fs_context *fc)
{
return init_pseudo(fc, BALLOON_KVM_MAGIC) ? 0 : -ENOMEM;
}
static struct file_system_type balloon_fs = {
.name = "balloon-kvm",
.init_fs_context = balloon_init_fs_context,
.kill_sb = kill_anon_super,
};
#endif /* CONFIG_BALLOON_COMPACTION */
static unsigned long shrink_free_pages(struct virtio_balloon *vb,
unsigned long pages_to_free)
{
unsigned long blocks_to_free, blocks_freed;
pages_to_free = round_up(pages_to_free,
1 << VIRTIO_BALLOON_FREE_PAGE_ORDER);
blocks_to_free = pages_to_free >> VIRTIO_BALLOON_FREE_PAGE_ORDER;
blocks_freed = return_free_pages_to_mm(vb, blocks_to_free);
return blocks_freed << VIRTIO_BALLOON_FREE_PAGE_ORDER;
}
static unsigned long leak_balloon_pages(struct virtio_balloon *vb,
unsigned long pages_to_free)
{
return leak_balloon(vb, pages_to_free * VIRTIO_BALLOON_PAGES_PER_PAGE) /
VIRTIO_BALLOON_PAGES_PER_PAGE;
}
static unsigned long shrink_balloon_pages(struct virtio_balloon *vb,
unsigned long pages_to_free)
{
unsigned long pages_freed = 0;
/*
* One invocation of leak_balloon can deflate at most
* VIRTIO_BALLOON_ARRAY_PFNS_MAX balloon pages, so we call it
* multiple times to deflate pages till reaching pages_to_free.
*/
while (vb->num_pages && pages_freed < pages_to_free)
pages_freed += leak_balloon_pages(vb,
pages_to_free - pages_freed);
update_balloon_size(vb);
return pages_freed;
}
static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker,
struct shrink_control *sc)
{
unsigned long pages_to_free, pages_freed = 0;
struct virtio_balloon *vb = container_of(shrinker,
struct virtio_balloon, shrinker);
pages_to_free = sc->nr_to_scan;
if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
pages_freed = shrink_free_pages(vb, pages_to_free);
if (pages_freed >= pages_to_free)
return pages_freed;
pages_freed += shrink_balloon_pages(vb, pages_to_free - pages_freed);
return pages_freed;
}
static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker,
struct shrink_control *sc)
{
struct virtio_balloon *vb = container_of(shrinker,
struct virtio_balloon, shrinker);
unsigned long count;
count = vb->num_pages / VIRTIO_BALLOON_PAGES_PER_PAGE;
count += vb->num_free_page_blocks << VIRTIO_BALLOON_FREE_PAGE_ORDER;
return count;
}
static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb)
{
unregister_shrinker(&vb->shrinker);
}
static int virtio_balloon_register_shrinker(struct virtio_balloon *vb)
{
vb->shrinker.scan_objects = virtio_balloon_shrinker_scan;
vb->shrinker.count_objects = virtio_balloon_shrinker_count;
vb->shrinker.seeks = DEFAULT_SEEKS;
return register_shrinker(&vb->shrinker);
}
static int virtballoon_probe(struct virtio_device *vdev)
{
struct virtio_balloon *vb;
__u32 poison_val;
int err;
if (!vdev->config->get) {
dev_err(&vdev->dev, "%s failure: config access disabled\n",
__func__);
return -EINVAL;
}
vdev->priv = vb = kzalloc(sizeof(*vb), GFP_KERNEL);
if (!vb) {
err = -ENOMEM;
goto out;
}
INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func);
INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func);
spin_lock_init(&vb->stop_update_lock);
mutex_init(&vb->balloon_lock);
init_waitqueue_head(&vb->acked);
vb->vdev = vdev;
balloon_devinfo_init(&vb->vb_dev_info);
err = init_vqs(vb);
if (err)
goto out_free_vb;
#ifdef CONFIG_BALLOON_COMPACTION
balloon_mnt = kern_mount(&balloon_fs);
if (IS_ERR(balloon_mnt)) {
err = PTR_ERR(balloon_mnt);
goto out_del_vqs;
}
vb->vb_dev_info.migratepage = virtballoon_migratepage;
vb->vb_dev_info.inode = alloc_anon_inode(balloon_mnt->mnt_sb);
if (IS_ERR(vb->vb_dev_info.inode)) {
err = PTR_ERR(vb->vb_dev_info.inode);
kern_unmount(balloon_mnt);
goto out_del_vqs;
}
vb->vb_dev_info.inode->i_mapping->a_ops = &balloon_aops;
#endif
if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
/*
* There is always one entry reserved for cmd id, so the ring
* size needs to be at least two to report free page hints.
*/
if (virtqueue_get_vring_size(vb->free_page_vq) < 2) {
err = -ENOSPC;
goto out_del_vqs;
}
vb->balloon_wq = alloc_workqueue("balloon-wq",
WQ_FREEZABLE | WQ_CPU_INTENSIVE, 0);
if (!vb->balloon_wq) {
err = -ENOMEM;
goto out_del_vqs;
}
INIT_WORK(&vb->report_free_page_work, report_free_page_func);
vb->cmd_id_received_cache = VIRTIO_BALLOON_CMD_ID_STOP;
vb->cmd_id_active = cpu_to_virtio32(vb->vdev,
VIRTIO_BALLOON_CMD_ID_STOP);
vb->cmd_id_stop = cpu_to_virtio32(vb->vdev,
VIRTIO_BALLOON_CMD_ID_STOP);
spin_lock_init(&vb->free_page_list_lock);
INIT_LIST_HEAD(&vb->free_page_list);
if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) {
memset(&poison_val, PAGE_POISON, sizeof(poison_val));
virtio_cwrite(vb->vdev, struct virtio_balloon_config,
poison_val, &poison_val);
}
}
/*
* We continue to use VIRTIO_BALLOON_F_DEFLATE_ON_OOM to decide if a
* shrinker needs to be registered to relieve memory pressure.
*/
if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) {
err = virtio_balloon_register_shrinker(vb);
if (err)
goto out_del_balloon_wq;
}
virtio_device_ready(vdev);
if (towards_target(vb))
virtballoon_changed(vdev);
return 0;
out_del_balloon_wq:
if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
destroy_workqueue(vb->balloon_wq);
out_del_vqs:
vdev->config->del_vqs(vdev);
out_free_vb:
kfree(vb);
out:
return err;
}
static void remove_common(struct virtio_balloon *vb)
{
/* There might be pages left in the balloon: free them. */
while (vb->num_pages)
leak_balloon(vb, vb->num_pages);
update_balloon_size(vb);
/* Now we reset the device so we can clean up the queues. */
vb->vdev->config->reset(vb->vdev);
vb->vdev->config->del_vqs(vb->vdev);
}
static void virtballoon_remove(struct virtio_device *vdev)
{
struct virtio_balloon *vb = vdev->priv;
if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
virtio_balloon_unregister_shrinker(vb);
spin_lock_irq(&vb->stop_update_lock);
vb->stop_update = true;
spin_unlock_irq(&vb->stop_update_lock);
cancel_work_sync(&vb->update_balloon_size_work);
cancel_work_sync(&vb->update_balloon_stats_work);
if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
cancel_work_sync(&vb->report_free_page_work);
destroy_workqueue(vb->balloon_wq);
}
remove_common(vb);
#ifdef CONFIG_BALLOON_COMPACTION
if (vb->vb_dev_info.inode)
iput(vb->vb_dev_info.inode);
kern_unmount(balloon_mnt);
#endif
kfree(vb);
}
#ifdef CONFIG_PM_SLEEP
static int virtballoon_freeze(struct virtio_device *vdev)
{
struct virtio_balloon *vb = vdev->priv;
/*
* The workqueue is already frozen by the PM core before this
* function is called.
*/
remove_common(vb);
return 0;
}
static int virtballoon_restore(struct virtio_device *vdev)
{
struct virtio_balloon *vb = vdev->priv;
int ret;
ret = init_vqs(vdev->priv);
if (ret)
return ret;
virtio_device_ready(vdev);
if (towards_target(vb))
virtballoon_changed(vdev);
update_balloon_size(vb);
return 0;
}
#endif
static int virtballoon_validate(struct virtio_device *vdev)
{
if (!page_poisoning_enabled())
__virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON);
__virtio_clear_bit(vdev, VIRTIO_F_IOMMU_PLATFORM);
return 0;
}
static unsigned int features[] = {
VIRTIO_BALLOON_F_MUST_TELL_HOST,
VIRTIO_BALLOON_F_STATS_VQ,
VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
VIRTIO_BALLOON_F_FREE_PAGE_HINT,
VIRTIO_BALLOON_F_PAGE_POISON,
};
static struct virtio_driver virtio_balloon_driver = {
.feature_table = features,
.feature_table_size = ARRAY_SIZE(features),
.driver.name = KBUILD_MODNAME,
.driver.owner = THIS_MODULE,
.id_table = id_table,
.validate = virtballoon_validate,
.probe = virtballoon_probe,
.remove = virtballoon_remove,
.config_changed = virtballoon_changed,
#ifdef CONFIG_PM_SLEEP
.freeze = virtballoon_freeze,
.restore = virtballoon_restore,
#endif
};
module_virtio_driver(virtio_balloon_driver);
MODULE_DEVICE_TABLE(virtio, id_table);
MODULE_DESCRIPTION("Virtio balloon driver");
MODULE_LICENSE("GPL");