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Commit b6f30679 authored by Konrad Rzeszutek Wilk's avatar Konrad Rzeszutek Wilk
Browse files

xen-balloon: Add interface to retrieve ballooned pages 



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: default avatarIan Campbell <ian.campbell@citrix.com>
Signed-off-by: default avatarDaniel De Graaf <dgdegra@tycho.nsa.gov>
[v2: Deal with rebasing on top of modified balloon code]
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent 803eb047

drivers/xen/balloon.c

+67 −6
Original line number Diff line number Diff line
@@ -128,13 +128,16 @@ 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;



	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);
@@ -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;

include/xen/balloon.h

+3 −0
Original line number Diff line number Diff line
@@ -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);