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xen-balloon: Add interface to retrieve ballooned pages

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Pages that have been ballooned are useful for other Xen drivers doing
grant table actions, because these pages have valid struct page/PFNs but
have no valid MFN so are available for remapping.

Acked-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
[v2: Deal with rebasing on top of modified balloon code]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
Konrad Rzeszutek Wilk 2011-03-15 10:23:57 -04:00
parent 803eb047a2
commit b6f3067985
2 changed files with 70 additions and 6 deletions
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73
drivers/xen/balloon.c
View file

@ -128,14 +128,17 @@ static void balloon_append(struct page *page)
}
/* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
static struct page *balloon_retrieve(void)
static struct page *balloon_retrieve(bool prefer_highmem)
{
struct page *page;
if (list_empty(&ballooned_pages))
return NULL;
page = list_entry(ballooned_pages.next, struct page, lru);
if (prefer_highmem)
page = list_entry(ballooned_pages.prev, struct page, lru);
else
page = list_entry(ballooned_pages.next, struct page, lru);
list_del(&page->lru);
if (PageHighMem(page)) {
@ -233,7 +236,7 @@ static enum bp_state increase_reservation(unsigned long nr_pages)
return BP_EAGAIN;
for (i = 0; i < rc; i++) {
page = balloon_retrieve();
page = balloon_retrieve(false);
BUG_ON(page == NULL);
pfn = page_to_pfn(page);
@ -263,7 +266,7 @@ static enum bp_state increase_reservation(unsigned long nr_pages)
return BP_DONE;
}
static enum bp_state decrease_reservation(unsigned long nr_pages)
static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
{
enum bp_state state = BP_DONE;
unsigned long pfn, i;
@ -279,7 +282,7 @@ static enum bp_state decrease_reservation(unsigned long nr_pages)
nr_pages = ARRAY_SIZE(frame_list);
for (i = 0; i < nr_pages; i++) {
if ((page = alloc_page(GFP_BALLOON)) == NULL) {
if ((page = alloc_page(gfp)) == NULL) {
nr_pages = i;
state = BP_EAGAIN;
break;
@ -340,7 +343,7 @@ static void balloon_process(struct work_struct *work)
state = increase_reservation(credit);
if (credit < 0)
state = decrease_reservation(-credit);
state = decrease_reservation(-credit, GFP_BALLOON);
state = update_schedule(state);
@ -366,6 +369,64 @@ void balloon_set_new_target(unsigned long target)
}
EXPORT_SYMBOL_GPL(balloon_set_new_target);
/**
* alloc_xenballooned_pages - get pages that have been ballooned out
* @nr_pages: Number of pages to get
* @pages: pages returned
* @return 0 on success, error otherwise
*/
int alloc_xenballooned_pages(int nr_pages, struct page** pages)
{
int pgno = 0;
struct page* page;
mutex_lock(&balloon_mutex);
while (pgno < nr_pages) {
page = balloon_retrieve(true);
if (page) {
pages[pgno++] = page;
} else {
enum bp_state st;
st = decrease_reservation(nr_pages - pgno, GFP_HIGHUSER);
if (st != BP_DONE)
goto out_undo;
}
}
mutex_unlock(&balloon_mutex);
return 0;
out_undo:
while (pgno)
balloon_append(pages[--pgno]);
/* Free the memory back to the kernel soon */
schedule_delayed_work(&balloon_worker, 0);
mutex_unlock(&balloon_mutex);
return -ENOMEM;
}
EXPORT_SYMBOL(alloc_xenballooned_pages);
/**
* free_xenballooned_pages - return pages retrieved with get_ballooned_pages
* @nr_pages: Number of pages
* @pages: pages to return
*/
void free_xenballooned_pages(int nr_pages, struct page** pages)
{
int i;
mutex_lock(&balloon_mutex);
for (i = 0; i < nr_pages; i++) {
if (pages[i])
balloon_append(pages[i]);
}
/* The balloon may be too large now. Shrink it if needed. */
if (current_target() != balloon_stats.current_pages)
schedule_delayed_work(&balloon_worker, 0);
mutex_unlock(&balloon_mutex);
}
EXPORT_SYMBOL(free_xenballooned_pages);
static int __init balloon_init(void)
{
unsigned long pfn, extra_pfn_end;

3
include/xen/balloon.h
View file

@ -20,3 +20,6 @@ struct balloon_stats {
extern struct balloon_stats balloon_stats;
void balloon_set_new_target(unsigned long target);
int alloc_xenballooned_pages(int nr_pages, struct page** pages);
void free_xenballooned_pages(int nr_pages, struct page** pages);