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Date: Tue, 2 Sep 2014 09:09:01 -0400
From: Rafael Aquini <aquini@...hat.com>
To: Konstantin Khlebnikov <koct9i@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Konstantin Khlebnikov <k.khlebnikov@...sung.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
linux-mm@...ck.org, Andrey Ryabinin <ryabinin.a.a@...il.com>,
Sasha Levin <sasha.levin@...cle.com>
Subject: Re: [PATCH v2 6/6] mm/balloon_compaction: general cleanup
On Sat, Aug 30, 2014 at 08:41:27PM +0400, Konstantin Khlebnikov wrote:
> From: Konstantin Khlebnikov <k.khlebnikov@...sung.com>
>
> * move special branch for balloon migraion into migrate_pages
> * remove special mapping for balloon and its flag AS_BALLOON_MAP
> * embed struct balloon_dev_info into struct virtio_balloon
> * cleanup balloon_page_dequeue, kill balloon_page_free
>
> Signed-off-by: Konstantin Khlebnikov <k.khlebnikov@...sung.com>
> ---
> drivers/virtio/virtio_balloon.c | 77 ++++---------
> include/linux/balloon_compaction.h | 127 ++++++---------------
> include/linux/migrate.h | 11 --
> include/linux/pagemap.h | 18 ---
> mm/balloon_compaction.c | 214 ++++++++++++------------------------
> mm/migrate.c | 29 +----
> 6 files changed, 134 insertions(+), 342 deletions(-)
>
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> index 25ebe8e..c84d6a8 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -59,7 +59,7 @@ struct virtio_balloon
> * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
> * to num_pages above.
> */
> - struct balloon_dev_info *vb_dev_info;
> + struct balloon_dev_info vb_dev_info;
>
> /* Synchronize access/update to this struct virtio_balloon elements */
> struct mutex balloon_lock;
> @@ -127,7 +127,7 @@ static void set_page_pfns(u32 pfns[], struct page *page)
>
> static void fill_balloon(struct virtio_balloon *vb, size_t num)
> {
> - struct balloon_dev_info *vb_dev_info = vb->vb_dev_info;
> + struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
>
> /* We can only do one array worth at a time. */
> num = min(num, ARRAY_SIZE(vb->pfns));
> @@ -163,15 +163,15 @@ static void release_pages_by_pfn(const u32 pfns[], unsigned int num)
> /* Find pfns pointing at start of each page, get pages and free them. */
> for (i = 0; i < num; i += VIRTIO_BALLOON_PAGES_PER_PAGE) {
> struct page *page = balloon_pfn_to_page(pfns[i]);
> - balloon_page_free(page);
> adjust_managed_page_count(page, 1);
> + put_page(page);
> }
> }
>
> static void leak_balloon(struct virtio_balloon *vb, size_t num)
> {
> struct page *page;
> - struct balloon_dev_info *vb_dev_info = vb->vb_dev_info;
> + struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
>
> /* We can only do one array worth at a time. */
> num = min(num, ARRAY_SIZE(vb->pfns));
> @@ -353,12 +353,11 @@ static int init_vqs(struct virtio_balloon *vb)
> return 0;
> }
>
> -static const struct address_space_operations virtio_balloon_aops;
> #ifdef CONFIG_BALLOON_COMPACTION
> /*
> * virtballoon_migratepage - perform the balloon page migration on behalf of
> * a compation thread. (called under page lock)
> - * @mapping: the page->mapping which will be assigned to the new migrated page.
> + * @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.
> @@ -373,17 +372,13 @@ static const struct address_space_operations virtio_balloon_aops;
> * This function preforms the balloon page migration task.
> * Called through balloon_mapping->a_ops->migratepage
> */
> -static int virtballoon_migratepage(struct address_space *mapping,
> +static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
> struct page *newpage, struct page *page, enum migrate_mode mode)
> {
> - struct balloon_dev_info *vb_dev_info = balloon_page_device(page);
> - struct virtio_balloon *vb;
> + struct virtio_balloon *vb = container_of(vb_dev_info,
> + struct virtio_balloon, vb_dev_info);
> unsigned long flags;
>
> - BUG_ON(!vb_dev_info);
> -
> - vb = vb_dev_info->balloon_device;
> -
> /*
> * In order to avoid lock contention while migrating pages concurrently
> * to leak_balloon() or fill_balloon() we just give up the balloon_lock
> @@ -395,42 +390,34 @@ static int virtballoon_migratepage(struct address_space *mapping,
> 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(newpage, mapping, &vb_dev_info->pages);
> + balloon_page_insert(vb_dev_info, newpage);
> vb_dev_info->isolated_pages--;
> spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
> vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
> set_page_pfns(vb->pfns, newpage);
> tell_host(vb, vb->inflate_vq);
>
> - /*
> - * balloon's page migration 2nd step -- deflate "page"
> - *
> - * It's safe to delete page->lru here because this page is at
> - * an isolated migration list, and this step is expected to happen here
> - */
> - balloon_page_delete(page);
> + /* balloon's page migration 2nd step -- deflate "page" */
> + balloon_page_delete(page, true);
> vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
> set_page_pfns(vb->pfns, page);
> tell_host(vb, vb->deflate_vq);
>
> mutex_unlock(&vb->balloon_lock);
>
> - return MIGRATEPAGE_BALLOON_SUCCESS;
> -}
> + put_page(page); /* balloon reference */
>
> -/* define the balloon_mapping->a_ops callback to allow balloon page migration */
> -static const struct address_space_operations virtio_balloon_aops = {
> - .migratepage = virtballoon_migratepage,
> -};
> + return MIGRATEPAGE_SUCCESS;
> +}
> #endif /* CONFIG_BALLOON_COMPACTION */
>
> static int virtballoon_probe(struct virtio_device *vdev)
> {
> struct virtio_balloon *vb;
> - struct address_space *vb_mapping;
> - struct balloon_dev_info *vb_devinfo;
> int err;
>
> vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
> @@ -446,30 +433,14 @@ static int virtballoon_probe(struct virtio_device *vdev)
> vb->vdev = vdev;
> vb->need_stats_update = 0;
>
> - vb_devinfo = balloon_devinfo_alloc(vb);
> - if (IS_ERR(vb_devinfo)) {
> - err = PTR_ERR(vb_devinfo);
> - goto out_free_vb;
> - }
> -
> - vb_mapping = balloon_mapping_alloc(vb_devinfo,
> - (balloon_compaction_check()) ?
> - &virtio_balloon_aops : NULL);
> - if (IS_ERR(vb_mapping)) {
> - /*
> - * IS_ERR(vb_mapping) && PTR_ERR(vb_mapping) == -EOPNOTSUPP
> - * This means !CONFIG_BALLOON_COMPACTION, otherwise we get off.
> - */
> - err = PTR_ERR(vb_mapping);
> - if (err != -EOPNOTSUPP)
> - goto out_free_vb_devinfo;
> - }
> -
> - vb->vb_dev_info = vb_devinfo;
> + balloon_devinfo_init(&vb->vb_dev_info);
> +#ifdef CONFIG_BALLOON_COMPACTION
> + vb->vb_dev_info.migratepage = virtballoon_migratepage;
> +#endif
>
> err = init_vqs(vb);
> if (err)
> - goto out_free_vb_mapping;
> + goto out_free_vb;
>
> vb->thread = kthread_run(balloon, vb, "vballoon");
> if (IS_ERR(vb->thread)) {
> @@ -481,10 +452,6 @@ static int virtballoon_probe(struct virtio_device *vdev)
>
> out_del_vqs:
> vdev->config->del_vqs(vdev);
> -out_free_vb_mapping:
> - balloon_mapping_free(vb_mapping);
> -out_free_vb_devinfo:
> - balloon_devinfo_free(vb_devinfo);
> out_free_vb:
> kfree(vb);
> out:
> @@ -510,8 +477,6 @@ static void virtballoon_remove(struct virtio_device *vdev)
>
> kthread_stop(vb->thread);
> remove_common(vb);
> - balloon_mapping_free(vb->vb_dev_info->mapping);
> - balloon_devinfo_free(vb->vb_dev_info);
> kfree(vb);
> }
>
> diff --git a/include/linux/balloon_compaction.h b/include/linux/balloon_compaction.h
> index 09f8c5a..ad112fcc6 100644
> --- a/include/linux/balloon_compaction.h
> +++ b/include/linux/balloon_compaction.h
> @@ -56,96 +56,58 @@
> * balloon driver as a page book-keeper for its registered balloon devices.
> */
> struct balloon_dev_info {
> - void *balloon_device; /* balloon device descriptor */
> - struct address_space *mapping; /* balloon special page->mapping */
> unsigned long isolated_pages; /* # of isolated pages for migration */
> spinlock_t pages_lock; /* Protection to pages list */
> struct list_head pages; /* Pages enqueued & handled to Host */
> + int (*migratepage)(struct balloon_dev_info *, struct page *newpage,
> + struct page *page, enum migrate_mode mode);
> };
>
> -extern struct page *balloon_page_enqueue(struct balloon_dev_info *b_dev_info);
> -extern struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info);
> -extern struct balloon_dev_info *balloon_devinfo_alloc(
> - void *balloon_dev_descriptor);
> -
> -static inline void balloon_devinfo_free(struct balloon_dev_info *b_dev_info)
> +static inline void balloon_devinfo_init(struct balloon_dev_info *b_dev_info)
> {
> - kfree(b_dev_info);
> + b_dev_info->isolated_pages = 0;
> + spin_lock_init(&b_dev_info->pages_lock);
> + INIT_LIST_HEAD(&b_dev_info->pages);
> + b_dev_info->migratepage = NULL;
> }
>
> -/*
> - * balloon_page_free - release a balloon page back to the page free lists
> - * @page: ballooned page to be set free
> - *
> - * This function must be used to properly set free an isolated/dequeued balloon
> - * page at the end of a sucessful page migration, or at the balloon driver's
> - * page release procedure.
> - */
> -static inline void balloon_page_free(struct page *page)
> -{
> - /*
> - * Balloon pages always get an extra refcount before being isolated
> - * and before being dequeued to help on sorting out fortuite colisions
> - * between a thread attempting to isolate and another thread attempting
> - * to release the very same balloon page.
> - *
> - * Before we handle the page back to Buddy, lets drop its extra refcnt.
> - */
> - put_page(page);
> - __free_page(page);
> -}
> +extern struct page *balloon_page_enqueue(struct balloon_dev_info *b_dev_info);
> +extern struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info);
>
> /*
> - * balloon_page_insert - insert a page into the balloon's page list and make
> - * the page->mapping assignment accordingly.
> - * @page : page to be assigned as a 'balloon page'
> - * @mapping : allocated special 'balloon_mapping'
> - * @head : balloon's device page list head
> + * balloon_page_insert - insert a page into the balloon's page list,
> + * mark and account it accordingly.
> + * @b_dev_info : pinter to ballon device
> + * @page : page to be assigned as a 'balloon page'
> *
> * Caller must ensure the page is locked and the spin_lock protecting balloon
> * pages list is held before inserting a page into the balloon device.
> */
> -static inline void balloon_page_insert(struct page *page,
> - struct address_space *mapping,
> - struct list_head *head)
> +static inline void
> +balloon_page_insert(struct balloon_dev_info *b_dev_info, struct page *page)
> {
> __SetPageBalloon(page);
> inc_zone_page_state(page, NR_BALLOON_PAGES);
> - page->mapping = mapping;
> - list_add(&page->lru, head);
> + set_page_private(page, (unsigned long)b_dev_info);
> + list_add(&page->lru, &b_dev_info->pages);
> }
>
> /*
> * balloon_page_delete - delete a page from balloon's page list and clear
> - * the page->mapping assignement accordingly.
> + * the ballon page mark accordingly.
> * @page : page to be released from balloon's page list
> + * @isolated: already isolated, do not delete from list
> *
> * Caller must ensure the page is locked and the spin_lock protecting balloon
> * pages list is held before deleting a page from the balloon device.
> */
> -static inline void balloon_page_delete(struct page *page)
> +static inline void balloon_page_delete(struct page *page, bool isolated)
> {
> __ClearPageBalloon(page);
> dec_zone_page_state(page, NR_BALLOON_PAGES);
> - page->mapping = NULL;
> - list_del(&page->lru);
> -}
> -
> -#endif /* CONFIG_MEMORY_BALLOON */
> -
> -#ifdef CONFIG_BALLOON_COMPACTION
> -
> -extern bool balloon_page_isolate(struct page *page);
> -extern void balloon_page_putback(struct page *page);
> -extern int balloon_page_migrate(struct page *newpage,
> - struct page *page, enum migrate_mode mode);
> -extern struct address_space
> -*balloon_mapping_alloc(struct balloon_dev_info *b_dev_info,
> - const struct address_space_operations *a_ops);
> -
> -static inline void balloon_mapping_free(struct address_space *balloon_mapping)
> -{
> - kfree(balloon_mapping);
> + set_page_private(page, 0);
> + if (!isolated)
> + list_del(&page->lru);
> }
>
> /*
> @@ -154,35 +116,25 @@ static inline void balloon_mapping_free(struct address_space *balloon_mapping)
> */
> static inline struct balloon_dev_info *balloon_page_device(struct page *page)
> {
> - struct address_space *mapping = page->mapping;
> - if (likely(mapping))
> - return mapping->private_data;
> -
> - return NULL;
> + return (struct balloon_dev_info *)page_private(page);
> }
>
> -static inline gfp_t balloon_mapping_gfp_mask(void)
> -{
> - return GFP_HIGHUSER_MOVABLE;
> -}
> +#endif /* CONFIG_MEMORY_BALLOON */
>
> -static inline bool balloon_compaction_check(void)
> -{
> - return true;
> -}
> +#ifdef CONFIG_BALLOON_COMPACTION
> +extern bool balloon_page_isolate(struct page *page);
> +extern void balloon_page_putback(struct page *page);
>
> -#else /* !CONFIG_BALLOON_COMPACTION */
> +int balloon_page_migrate(new_page_t get_new_page, free_page_t put_new_page,
> + unsigned long private, struct page *page,
> + int force, enum migrate_mode mode);
>
> -static inline void *balloon_mapping_alloc(void *balloon_device,
> - const struct address_space_operations *a_ops)
> +static inline gfp_t balloon_mapping_gfp_mask(void)
> {
> - return ERR_PTR(-EOPNOTSUPP);
> + return GFP_HIGHUSER_MOVABLE;
> }
>
> -static inline void balloon_mapping_free(struct address_space *balloon_mapping)
> -{
> - return;
> -}
> +#else /* !CONFIG_BALLOON_COMPACTION */
>
> static inline bool balloon_page_isolate(struct page *page)
> {
> @@ -194,10 +146,11 @@ static inline void balloon_page_putback(struct page *page)
> return;
> }
>
> -static inline int balloon_page_migrate(struct page *newpage,
> - struct page *page, enum migrate_mode mode)
> +static inline int balloon_page_migrate(new_page_t get_new_page,
> + free_page_t put_new_page, unsigned long private,
> + struct page *page, int force, enum migrate_mode mode)
> {
> - return 0;
> + return -EAGAIN;
> }
>
> static inline gfp_t balloon_mapping_gfp_mask(void)
> @@ -205,9 +158,5 @@ static inline gfp_t balloon_mapping_gfp_mask(void)
> return GFP_HIGHUSER;
> }
>
> -static inline bool balloon_compaction_check(void)
> -{
> - return false;
> -}
> #endif /* CONFIG_BALLOON_COMPACTION */
> #endif /* _LINUX_BALLOON_COMPACTION_H */
> diff --git a/include/linux/migrate.h b/include/linux/migrate.h
> index 0a4604a..cf90776 100644
> --- a/include/linux/migrate.h
> +++ b/include/linux/migrate.h
> @@ -13,18 +13,9 @@ typedef void free_page_t(struct page *page, unsigned long private);
> * Return values from addresss_space_operations.migratepage():
> * - negative errno on page migration failure;
> * - zero on page migration success;
> - *
> - * The balloon page migration introduces this special case where a 'distinct'
> - * return code is used to flag a successful page migration to unmap_and_move().
> - * This approach is necessary because page migration can race against balloon
> - * deflation procedure, and for such case we could introduce a nasty page leak
> - * if a successfully migrated balloon page gets released concurrently with
> - * migration's unmap_and_move() wrap-up steps.
> */
> #define MIGRATEPAGE_SUCCESS 0
> -#define MIGRATEPAGE_BALLOON_SUCCESS 1 /* special ret code for balloon page
> - * sucessful migration case.
> - */
> +
> enum migrate_reason {
> MR_COMPACTION,
> MR_MEMORY_FAILURE,
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index 5ba1813..210b46b 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -24,8 +24,7 @@ enum mapping_flags {
> AS_ENOSPC = __GFP_BITS_SHIFT + 1, /* ENOSPC on async write */
> AS_MM_ALL_LOCKS = __GFP_BITS_SHIFT + 2, /* under mm_take_all_locks() */
> AS_UNEVICTABLE = __GFP_BITS_SHIFT + 3, /* e.g., ramdisk, SHM_LOCK */
> - AS_BALLOON_MAP = __GFP_BITS_SHIFT + 4, /* balloon page special map */
> - AS_EXITING = __GFP_BITS_SHIFT + 5, /* final truncate in progress */
> + AS_EXITING = __GFP_BITS_SHIFT + 4, /* final truncate in progress */
> };
>
> static inline void mapping_set_error(struct address_space *mapping, int error)
> @@ -55,21 +54,6 @@ static inline int mapping_unevictable(struct address_space *mapping)
> return !!mapping;
> }
>
> -static inline void mapping_set_balloon(struct address_space *mapping)
> -{
> - set_bit(AS_BALLOON_MAP, &mapping->flags);
> -}
> -
> -static inline void mapping_clear_balloon(struct address_space *mapping)
> -{
> - clear_bit(AS_BALLOON_MAP, &mapping->flags);
> -}
> -
> -static inline int mapping_balloon(struct address_space *mapping)
> -{
> - return mapping && test_bit(AS_BALLOON_MAP, &mapping->flags);
> -}
> -
> static inline void mapping_set_exiting(struct address_space *mapping)
> {
> set_bit(AS_EXITING, &mapping->flags);
> diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c
> index a942081..3c8cb7a 100644
> --- a/mm/balloon_compaction.c
> +++ b/mm/balloon_compaction.c
> @@ -11,32 +11,6 @@
> #include <linux/balloon_compaction.h>
>
> /*
> - * balloon_devinfo_alloc - allocates a balloon device information descriptor.
> - * @balloon_dev_descriptor: pointer to reference the balloon device which
> - * this struct balloon_dev_info will be servicing.
> - *
> - * Driver must call it to properly allocate and initialize an instance of
> - * struct balloon_dev_info which will be used to reference a balloon device
> - * as well as to keep track of the balloon device page list.
> - */
> -struct balloon_dev_info *balloon_devinfo_alloc(void *balloon_dev_descriptor)
> -{
> - struct balloon_dev_info *b_dev_info;
> - b_dev_info = kmalloc(sizeof(*b_dev_info), GFP_KERNEL);
> - if (!b_dev_info)
> - return ERR_PTR(-ENOMEM);
> -
> - b_dev_info->balloon_device = balloon_dev_descriptor;
> - b_dev_info->mapping = NULL;
> - b_dev_info->isolated_pages = 0;
> - spin_lock_init(&b_dev_info->pages_lock);
> - INIT_LIST_HEAD(&b_dev_info->pages);
> -
> - return b_dev_info;
> -}
> -EXPORT_SYMBOL_GPL(balloon_devinfo_alloc);
> -
> -/*
> * balloon_page_enqueue - allocates a new page and inserts it into the balloon
> * page list.
> * @b_dev_info: balloon device decriptor where we will insert a new page to
> @@ -61,7 +35,7 @@ struct page *balloon_page_enqueue(struct balloon_dev_info *b_dev_info)
> */
> BUG_ON(!trylock_page(page));
> spin_lock_irqsave(&b_dev_info->pages_lock, flags);
> - balloon_page_insert(page, b_dev_info->mapping, &b_dev_info->pages);
> + balloon_page_insert(b_dev_info, page);
> spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
> unlock_page(page);
> return page;
> @@ -81,12 +55,10 @@ EXPORT_SYMBOL_GPL(balloon_page_enqueue);
> */
> struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info)
> {
> - struct page *page, *tmp;
> + struct page *page;
> unsigned long flags;
> - bool dequeued_page;
>
> - dequeued_page = false;
> - list_for_each_entry_safe(page, tmp, &b_dev_info->pages, lru) {
> + list_for_each_entry(page, &b_dev_info->pages, lru) {
> /*
> * Block others from accessing the 'page' while we get around
> * establishing additional references and preparing the 'page'
> @@ -94,98 +66,32 @@ struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info)
> */
> if (trylock_page(page)) {
> spin_lock_irqsave(&b_dev_info->pages_lock, flags);
> - /*
> - * Raise the page refcount here to prevent any wrong
> - * attempt to isolate this page, in case of coliding
> - * with balloon_page_isolate() just after we release
> - * the page lock.
> - *
> - * balloon_page_free() will take care of dropping
> - * this extra refcount later.
> - */
> - get_page(page);
> - balloon_page_delete(page);
> + balloon_page_delete(page, false);
> spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
> unlock_page(page);
> - dequeued_page = true;
> - break;
> + return page;
> }
> }
>
> - 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;
> + /*
> + * 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);
> + BUG_ON(list_empty(&b_dev_info->pages) && !b_dev_info->isolated_pages);
> + spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
> + return NULL;
> }
> EXPORT_SYMBOL_GPL(balloon_page_dequeue);
>
> #ifdef CONFIG_BALLOON_COMPACTION
> -/*
> - * balloon_mapping_alloc - allocates a special ->mapping for ballooned pages.
> - * @b_dev_info: holds the balloon device information descriptor.
> - * @a_ops: balloon_mapping address_space_operations descriptor.
> - *
> - * Driver must call it to properly allocate and initialize an instance of
> - * struct address_space which will be used as the special page->mapping for
> - * balloon device enlisted page instances.
> - */
> -struct address_space *balloon_mapping_alloc(struct balloon_dev_info *b_dev_info,
> - const struct address_space_operations *a_ops)
> -{
> - struct address_space *mapping;
> -
> - mapping = kmalloc(sizeof(*mapping), GFP_KERNEL);
> - if (!mapping)
> - return ERR_PTR(-ENOMEM);
> -
> - /*
> - * Give a clean 'zeroed' status to all elements of this special
> - * balloon page->mapping struct address_space instance.
> - */
> - address_space_init_once(mapping);
> -
> - /*
> - * Set mapping->flags appropriately, to allow balloon pages
> - * ->mapping identification.
> - */
> - mapping_set_balloon(mapping);
> - mapping_set_gfp_mask(mapping, balloon_mapping_gfp_mask());
> -
> - /* balloon's page->mapping->a_ops callback descriptor */
> - mapping->a_ops = a_ops;
> -
> - /*
> - * Establish a pointer reference back to the balloon device descriptor
> - * this particular page->mapping will be servicing.
> - * This is used by compaction / migration procedures to identify and
> - * access the balloon device pageset while isolating / migrating pages.
> - *
> - * As some balloon drivers can register multiple balloon devices
> - * for a single guest, this also helps compaction / migration to
> - * properly deal with multiple balloon pagesets, when required.
> - */
> - mapping->private_data = b_dev_info;
> - b_dev_info->mapping = mapping;
> -
> - return mapping;
> -}
> -EXPORT_SYMBOL_GPL(balloon_mapping_alloc);
>
> static inline void __isolate_balloon_page(struct page *page)
> {
> - struct balloon_dev_info *b_dev_info = page->mapping->private_data;
> + 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);
> @@ -195,7 +101,7 @@ static inline void __isolate_balloon_page(struct page *page)
>
> static inline void __putback_balloon_page(struct page *page)
> {
> - struct balloon_dev_info *b_dev_info = page->mapping->private_data;
> + 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);
> @@ -203,12 +109,6 @@ static inline void __putback_balloon_page(struct page *page)
> spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
> }
>
> -static inline int __migrate_balloon_page(struct address_space *mapping,
> - struct page *newpage, struct page *page, enum migrate_mode mode)
> -{
> - return page->mapping->a_ops->migratepage(mapping, newpage, page, mode);
> -}
> -
> /* __isolate_lru_page() counterpart for a ballooned page */
> bool balloon_page_isolate(struct page *page)
> {
> @@ -251,6 +151,57 @@ bool balloon_page_isolate(struct page *page)
> return false;
> }
>
> +int balloon_page_migrate(new_page_t get_new_page, free_page_t put_new_page,
> + unsigned long private, struct page *page,
> + int force, enum migrate_mode mode)
> +{
> + struct balloon_dev_info *balloon = balloon_page_device(page);
> + struct page *newpage;
> + int *result = NULL;
> + int rc = -EAGAIN;
> +
> + if (!balloon || !balloon->migratepage)
> + return -EAGAIN;
> +
> + newpage = get_new_page(page, private, &result);
> + if (!newpage)
> + return -ENOMEM;
> +
> + if (!trylock_page(newpage))
> + BUG();
> +
> + if (!trylock_page(page)) {
> + if (!force || mode != MIGRATE_SYNC)
> + goto out;
> + lock_page(page);
> + }
> +
> + rc = balloon->migratepage(balloon, newpage, page, mode);
> +
> + unlock_page(page);
> +out:
> + unlock_page(newpage);
> +
> + if (rc != -EAGAIN) {
> + dec_zone_page_state(page, NR_ISOLATED_FILE);
> + list_del(&page->lru);
> + put_page(page);
> + }
> +
> + if (rc != MIGRATEPAGE_SUCCESS && put_new_page)
> + put_new_page(newpage, private);
> + else
> + put_page(newpage);
> +
> + if (result) {
> + if (rc)
> + *result = rc;
> + else
> + *result = page_to_nid(newpage);
> + }
> + return rc;
> +}
> +
> /* putback_lru_page() counterpart for a ballooned page */
> void balloon_page_putback(struct page *page)
> {
> @@ -271,31 +222,4 @@ void balloon_page_putback(struct page *page)
> unlock_page(page);
> }
>
> -/* move_to_new_page() counterpart for a ballooned page */
> -int balloon_page_migrate(struct page *newpage,
> - struct page *page, enum migrate_mode mode)
> -{
> - struct address_space *mapping;
> - int rc = -EAGAIN;
> -
> - /*
> - * Block others from accessing the 'newpage' when we get around to
> - * establishing additional references. We should be the only one
> - * holding a reference to the 'newpage' at this point.
> - */
> - BUG_ON(!trylock_page(newpage));
> -
> - if (WARN_ON(!PageBalloon(page))) {
> - dump_page(page, "not movable balloon page");
> - unlock_page(newpage);
> - return rc;
> - }
> -
> - mapping = page->mapping;
> - if (mapping)
> - rc = __migrate_balloon_page(mapping, newpage, page, mode);
> -
> - unlock_page(newpage);
> - return rc;
> -}
> #endif /* CONFIG_BALLOON_COMPACTION */
> diff --git a/mm/migrate.c b/mm/migrate.c
> index a4939b1..e6d0d2d 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -873,18 +873,6 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
> }
> }
>
> - if (unlikely(PageBalloon(page))) {
> - /*
> - * A ballooned page does not need any special attention from
> - * physical to virtual reverse mapping procedures.
> - * Skip any attempt to unmap PTEs or to remap swap cache,
> - * in order to avoid burning cycles at rmap level, and perform
> - * the page migration right away (proteced by page lock).
> - */
> - rc = balloon_page_migrate(newpage, page, mode);
> - goto out_unlock;
> - }
> -
> /*
> * Corner case handling:
> * 1. When a new swap-cache page is read into, it is added to the LRU
> @@ -952,19 +940,6 @@ static int unmap_and_move(new_page_t get_new_page, free_page_t put_new_page,
>
> rc = __unmap_and_move(page, newpage, force, mode);
>
> -#ifdef CONFIG_MEMORY_BALLOON
> - if (unlikely(rc == MIGRATEPAGE_BALLOON_SUCCESS)) {
> - /*
> - * A ballooned page has been migrated already.
> - * Now, it's the time to wrap-up counters,
> - * handle the page back to Buddy and return.
> - */
> - dec_zone_page_state(page, NR_ISOLATED_ANON +
> - page_is_file_cache(page));
> - balloon_page_free(page);
> - return MIGRATEPAGE_SUCCESS;
> - }
> -#endif
> out:
> if (rc != -EAGAIN) {
> /*
> @@ -1139,6 +1114,10 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
> rc = unmap_and_move_huge_page(get_new_page,
> put_new_page, private, page,
> pass > 2, mode);
> + else if (PageBalloon(page))
> + rc = balloon_page_migrate(get_new_page,
> + put_new_page, private,
> + page, pass > 2, mode);
> else
> rc = unmap_and_move(get_new_page, put_new_page,
> private, page, pass > 2, mode);
>
Acked-by: Rafael Aquini <aquini@...hat.com>
--
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