/* * mm/balloon_compaction.c * * Common interface for making balloon pages movable by compaction. * * Copyright (C) 2012, Red Hat, Inc. Rafael Aquini <aquini@redhat.com> */ #include <linux/mm.h> #include <linux/slab.h> #include <linux/export.h> #include <linux/balloon_compaction.h> /* * balloon_page_alloc - allocates a new page for insertion into the balloon * page list. * * Driver must call it to properly allocate a new enlisted balloon page. * Driver must call balloon_page_enqueue before definitively removing it from * the guest system. This function returns the page address for the recently * allocated page or NULL in the case we fail to allocate a new page this turn. */ struct page *balloon_page_alloc(void) { struct page *page = alloc_page(balloon_mapping_gfp_mask() | __GFP_NOMEMALLOC | __GFP_NORETRY); return page; } EXPORT_SYMBOL_GPL(balloon_page_alloc); /* * balloon_page_enqueue - allocates a new page and inserts it into the balloon * page list. * @b_dev_info: balloon device descriptor where we will insert a new page to * @page: new page to enqueue - allocated using balloon_page_alloc. * * Driver must call it to properly enqueue a new allocated balloon page * before definitively removing it from the guest system. * This function returns the page address for the recently enqueued page or * NULL in the case we fail to allocate a new page this turn. */ void balloon_page_enqueue(struct balloon_dev_info *b_dev_info, struct page *page) { unsigned long flags; /* * Block others from accessing the 'page' when we get around to * establishing additional references. We should be the only one * holding a reference to the 'page' at this point. */ BUG_ON(!trylock_page(page)); spin_lock_irqsave(&b_dev_info->pages_lock, flags); balloon_page_insert(b_dev_info, page); __count_vm_event(BALLOON_INFLATE); spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); unlock_page(page); } EXPORT_SYMBOL_GPL(balloon_page_enqueue); /* * balloon_page_dequeue - removes a page from balloon's page list and returns * the its address to allow the driver release the page. * @b_dev_info: balloon device decriptor where we will grab a page from. * * Driver must call it to properly de-allocate a previous enlisted balloon page * before definetively releasing it back to the guest system. * This function returns the page address for the recently dequeued page or * NULL in the case we find balloon's page list temporarily empty due to * compaction isolated pages. */ struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info) { struct page *page, *tmp; unsigned long flags; bool dequeued_page; dequeued_page = false; spin_lock_irqsave(&b_dev_info->pages_lock, flags); list_for_each_entry_safe(page, tmp, &b_dev_info->pages, lru) { /* * Block others from accessing the 'page' while we get around * establishing additional references and preparing the 'page' * to be released by the balloon driver. */ if (trylock_page(page)) { #ifdef CONFIG_BALLOON_COMPACTION if (PageIsolated(page)) { /* raced with isolation */ unlock_page(page); continue; } #endif balloon_page_delete(page); __count_vm_event(BALLOON_DEFLATE); unlock_page(page); dequeued_page = true; break; } } spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); if (!dequeued_page) { /* * If we are unable to dequeue a balloon page because the page * list is empty and there is no isolated pages, then something * went out of track and some balloon pages are lost. * BUG() here, otherwise the balloon driver may get stuck into * an infinite loop while attempting to release all its pages. */ spin_lock_irqsave(&b_dev_info->pages_lock, flags); if (unlikely(list_empty(&b_dev_info->pages) && !b_dev_info->isolated_pages)) BUG(); spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); page = NULL; } return page; } EXPORT_SYMBOL_GPL(balloon_page_dequeue); #ifdef CONFIG_BALLOON_COMPACTION bool balloon_page_isolate(struct page *page, isolate_mode_t mode) { struct balloon_dev_info *b_dev_info = balloon_page_device(page); unsigned long flags; spin_lock_irqsave(&b_dev_info->pages_lock, flags); list_del(&page->lru); b_dev_info->isolated_pages++; spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); return true; } void balloon_page_putback(struct page *page) { struct balloon_dev_info *b_dev_info = balloon_page_device(page); unsigned long flags; spin_lock_irqsave(&b_dev_info->pages_lock, flags); list_add(&page->lru, &b_dev_info->pages); b_dev_info->isolated_pages--; spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); } /* move_to_new_page() counterpart for a ballooned page */ int balloon_page_migrate(struct address_space *mapping, struct page *newpage, struct page *page, enum migrate_mode mode) { struct balloon_dev_info *balloon = balloon_page_device(page); /* * We can not easily support the no copy case here so ignore it as it * is unlikely to be use with ballon pages. See include/linux/hmm.h for * user of the MIGRATE_SYNC_NO_COPY mode. */ if (mode == MIGRATE_SYNC_NO_COPY) return -EINVAL; VM_BUG_ON_PAGE(!PageLocked(page), page); VM_BUG_ON_PAGE(!PageLocked(newpage), newpage); return balloon->migratepage(balloon, newpage, page, mode); } const struct address_space_operations balloon_aops = { .migratepage = balloon_page_migrate, .isolate_page = balloon_page_isolate, .putback_page = balloon_page_putback, }; EXPORT_SYMBOL_GPL(balloon_aops); #endif /* CONFIG_BALLOON_COMPACTION */