From: Wei Wang <[email protected]>
A #GP is reported in the guest when requesting balloon inflation via
virtio-balloon. The reason is that the virtio-balloon driver has
removed the page from its internal page list (via balloon_page_pop),
but balloon_page_enqueue_one also calls "list_del" to do the removal.
This is necessary when it's used from balloon_page_enqueue_list, but
not from balloon_page_enqueue.
Move list_del to balloon_page_enqueue, and update comments accordingly.
Fixes: 418a3ab1e778 (mm/balloon_compaction: List interfaces)
Signed-off-by: Wei Wang <[email protected]>
Signed-off-by: Michael S. Tsirkin <[email protected]>
---
mm/balloon_compaction.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c
index 83a7b614061f..d25664e1857b 100644
--- a/mm/balloon_compaction.c
+++ b/mm/balloon_compaction.c
@@ -21,7 +21,6 @@ static void balloon_page_enqueue_one(struct balloon_dev_info *b_dev_info,
* memory corruption is possible and we should stop execution.
*/
BUG_ON(!trylock_page(page));
- list_del(&page->lru);
balloon_page_insert(b_dev_info, page);
unlock_page(page);
__count_vm_event(BALLOON_INFLATE);
@@ -47,6 +46,7 @@ size_t balloon_page_list_enqueue(struct balloon_dev_info *b_dev_info,
spin_lock_irqsave(&b_dev_info->pages_lock, flags);
list_for_each_entry_safe(page, tmp, pages, lru) {
+ list_del(&page->lru);
balloon_page_enqueue_one(b_dev_info, page);
n_pages++;
}
@@ -128,13 +128,19 @@ struct page *balloon_page_alloc(void)
EXPORT_SYMBOL_GPL(balloon_page_alloc);
/*
- * balloon_page_enqueue - allocates a new page and inserts it into the balloon
- * page list.
+ * balloon_page_enqueue - inserts a new page 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.
+ *
+ * Drivers must not call balloon_page_enqueue on pages that have been
+ * pushed to a list with balloon_page_push before removing them with
+ * balloon_page_pop. To all pages on a list, use balloon_page_list_enqueue
+ * instead.
+ *
* 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.
*/
--
MST
Lots of comments bitrotted. Fix them up.
Fixes: 418a3ab1e778 (mm/balloon_compaction: List interfaces)
Signed-off-by: Michael S. Tsirkin <[email protected]>
---
mm/balloon_compaction.c | 73 +++++++++++++++++++++++------------------
1 file changed, 41 insertions(+), 32 deletions(-)
diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c
index d25664e1857b..9cb03da5bcea 100644
--- a/mm/balloon_compaction.c
+++ b/mm/balloon_compaction.c
@@ -32,10 +32,10 @@ static void balloon_page_enqueue_one(struct balloon_dev_info *b_dev_info,
* @b_dev_info: balloon device descriptor where we will insert a new page to
* @pages: pages to enqueue - allocated using balloon_page_alloc.
*
- * Driver must call it to properly enqueue a balloon pages before definitively
- * removing it from the guest system.
+ * Driver must call this function to properly enqueue balloon pages before
+ * definitively removing them from the guest system.
*
- * Return: number of pages that were enqueued.
+ * Returns: number of pages that were enqueued.
*/
size_t balloon_page_list_enqueue(struct balloon_dev_info *b_dev_info,
struct list_head *pages)
@@ -63,14 +63,15 @@ EXPORT_SYMBOL_GPL(balloon_page_list_enqueue);
* @n_req_pages: number of requested pages.
*
* Driver must call this function to properly de-allocate a previous enlisted
- * balloon pages before definetively releasing it back to the guest system.
+ * balloon pages before definitively releasing it back to the guest system.
* This function tries to remove @n_req_pages from the ballooned pages and
* return them to the caller in the @pages list.
*
- * Note that this function may fail to dequeue some pages temporarily empty due
- * to compaction isolated pages.
+ * Note that this function may fail to dequeue some pages even if the balloon
+ * isn't empty - since the page list can be temporarily empty due to compaction
+ * of isolated pages.
*
- * Return: number of pages that were added to the @pages list.
+ * Returns: number of pages that were added to the @pages list.
*/
size_t balloon_page_list_dequeue(struct balloon_dev_info *b_dev_info,
struct list_head *pages, size_t n_req_pages)
@@ -112,12 +113,14 @@ EXPORT_SYMBOL_GPL(balloon_page_list_dequeue);
/*
* balloon_page_alloc - allocates a new page for insertion into the balloon
- * page list.
+ * 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.
+ * Driver must call this function to properly allocate a new enlisted balloon page.
+ * Driver must call balloon_page_enqueue before definitively removing the page
+ * from the guest system.
+ *
+ * Returns: struct page address for the allocated page or NULL in case it fails
+ * to allocate a new page.
*/
struct page *balloon_page_alloc(void)
{
@@ -130,19 +133,15 @@ EXPORT_SYMBOL_GPL(balloon_page_alloc);
/*
* balloon_page_enqueue - inserts a new page into the balloon page list.
*
- * @b_dev_info: balloon device descriptor where we will insert a new page to
+ * @b_dev_info: balloon device descriptor where we will insert a new page
* @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.
+ * Drivers must call this function to properly enqueue a new allocated balloon
+ * page before definitively removing the page from the guest system.
*
- * Drivers must not call balloon_page_enqueue on pages that have been
- * pushed to a list with balloon_page_push before removing them with
- * balloon_page_pop. To all pages on a list, use balloon_page_list_enqueue
- * instead.
- *
- * 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.
+ * Drivers must not call balloon_page_enqueue on pages that have been pushed to
+ * a list with balloon_page_push before removing them with balloon_page_pop. To
+ * enqueue all pages on a list, use balloon_page_list_enqueue instead.
*/
void balloon_page_enqueue(struct balloon_dev_info *b_dev_info,
struct page *page)
@@ -157,14 +156,24 @@ 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.
+ * its address to allow the driver to 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.
+ * Driver must call this to properly dequeue a previously enqueued page
+ * before definitively releasing it back to the guest system.
+ *
+ * Caller must perform its own accounting to ensure that this
+ * function is called only if some pages are actually enqueued.
+ *
+ * Note that this function may fail to dequeue some pages even if there are
+ * some enqueued pages - since the page list can be temporarily empty due to
+ * the compaction of isolated pages.
+ *
+ * TODO: remove the caller accounting requirements, and allow caller to wait
+ * until all pages can be dequeued.
+ *
+ * Returns: struct page address for the dequeued page, or NULL if it fails to
+ * dequeue any pages.
*/
struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info)
{
@@ -177,9 +186,9 @@ struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info)
if (n_pages != 1) {
/*
* If we are unable to dequeue a balloon page because the page
- * list is empty and there is no isolated pages, then something
+ * list is empty and there are 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
+ * BUG() here, otherwise the balloon driver may get stuck in
* an infinite loop while attempting to release all its pages.
*/
spin_lock_irqsave(&b_dev_info->pages_lock, flags);
@@ -230,8 +239,8 @@ int balloon_page_migrate(struct address_space *mapping,
/*
* 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.
+ * is unlikely to be used with ballon pages. See include/linux/hmm.h for
+ * a user of the MIGRATE_SYNC_NO_COPY mode.
*/
if (mode == MIGRATE_SYNC_NO_COPY)
return -EINVAL;
--
MST
On Thursday, July 18, 2019 8:24 PM, Michael S. Tsirkin wrote:
> /*
> * balloon_page_alloc - allocates a new page for insertion into the balloon
> - * page list.
> + * 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.
> + * Driver must call this function to properly allocate a new enlisted balloon
> page.
Probably better to say "allocate a new balloon page to enlist" ?
"enlisted page" implies that the allocated page has been added to the list, which might
be misleading.
> + * Driver must call balloon_page_enqueue before definitively removing
> + the page
> + * from the guest system.
> + *
> + * Returns: struct page address for the allocated page or NULL in case it fails
> + * to allocate a new page.
> */
Returns: pointer to the page struct of the allocated page, or NULL if allocation fails.
> struct page *balloon_page_alloc(void)
> {
> @@ -130,19 +133,15 @@ EXPORT_SYMBOL_GPL(balloon_page_alloc);
> /*
> * balloon_page_enqueue - inserts a new page into the balloon page list.
> *
> - * @b_dev_info: balloon device descriptor where we will insert a new page
> to
> + * @b_dev_info: balloon device descriptor where we will insert a new
> + page
> * @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.
> + * Drivers must call this function to properly enqueue a new allocated
> + balloon
> + * page before definitively removing the page from the guest system.
> *
> - * Drivers must not call balloon_page_enqueue on pages that have been
> - * pushed to a list with balloon_page_push before removing them with
> - * balloon_page_pop. To all pages on a list, use balloon_page_list_enqueue
> - * instead.
> - *
> - * 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.
> + * Drivers must not call balloon_page_enqueue on pages that have been
> + pushed to
> + * a list with balloon_page_push before removing them with
> + balloon_page_pop. To
> + * enqueue all pages on a list, use balloon_page_list_enqueue instead.
"To enqueue a list of pages" ?
> */
> void balloon_page_enqueue(struct balloon_dev_info *b_dev_info,
> struct page *page)
> @@ -157,14 +156,24 @@ 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.
> + * its address to allow the driver to 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.
> + * Driver must call this to properly dequeue a previously enqueued page
"call this function"?
> + * before definitively releasing it back to the guest system.
> + *
> + * Caller must perform its own accounting to ensure that this
> + * function is called only if some pages are actually enqueued.
"only when" ?
> + *
> + * Note that this function may fail to dequeue some pages even if there
"even when" ?
> + are
> + * some enqueued pages - since the page list can be temporarily empty
> + due to
> + * the compaction of isolated pages.
> + *
> + * TODO: remove the caller accounting requirements, and allow caller to
> + wait
> + * until all pages can be dequeued.
> + *
> + * Returns: struct page address for the dequeued page, or NULL if it fails to
> + * dequeue any pages.
Returns: pointer to the page struct of the dequeued page, or NULL if no page gets dequeued.
> */
> struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info)
> { @@ -177,9 +186,9 @@ struct page *balloon_page_dequeue(struct
> balloon_dev_info *b_dev_info)
> if (n_pages != 1) {
> /*
> * If we are unable to dequeue a balloon page because the
> page
> - * list is empty and there is no isolated pages, then
> something
> + * list is empty and there are 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
> + * BUG() here, otherwise the balloon driver may get stuck in
> * an infinite loop while attempting to release all its pages.
> */
> spin_lock_irqsave(&b_dev_info->pages_lock, flags); @@ -
> 230,8 +239,8 @@ int balloon_page_migrate(struct address_space *mapping,
>
> /*
> * We can not easily support the no copy case here so ignore it as it
"cannot"
> - * is unlikely to be use with ballon pages. See include/linux/hmm.h
> for
> - * user of the MIGRATE_SYNC_NO_COPY mode.
> + * is unlikely to be used with ballon pages. See include/linux/hmm.h
"ballon" -> "balloon"
> for
> + * a user of the MIGRATE_SYNC_NO_COPY mode.
"for the usage of" ?
Other parts look good to me.
Reviewed-by: Wei Wang <[email protected]>
Best,
Wei
On Thu, Jul 18, 2019 at 01:47:40PM +0000, Wang, Wei W wrote:
> On Thursday, July 18, 2019 8:24 PM, Michael S. Tsirkin wrote:
> > /*
> > * balloon_page_alloc - allocates a new page for insertion into the balloon
> > - * page list.
> > + * 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.
> > + * Driver must call this function to properly allocate a new enlisted balloon
> > page.
>
> Probably better to say "allocate a new balloon page to enlist" ?
> "enlisted page" implies that the allocated page has been added to the list, which might
> be misleading.
right should be just a new balloon page.
>
> > + * Driver must call balloon_page_enqueue before definitively removing
> > + the page
> > + * from the guest system.
> > + *
> > + * Returns: struct page address for the allocated page or NULL in case it fails
> > + * to allocate a new page.
> > */
>
> Returns: pointer to the page struct of the allocated page, or NULL if allocation fails.
ok
>
>
> > struct page *balloon_page_alloc(void)
> > {
> > @@ -130,19 +133,15 @@ EXPORT_SYMBOL_GPL(balloon_page_alloc);
> > /*
> > * balloon_page_enqueue - inserts a new page into the balloon page list.
> > *
> > - * @b_dev_info: balloon device descriptor where we will insert a new page
> > to
> > + * @b_dev_info: balloon device descriptor where we will insert a new
> > + page
> > * @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.
> > + * Drivers must call this function to properly enqueue a new allocated
> > + balloon
> > + * page before definitively removing the page from the guest system.
> > *
> > - * Drivers must not call balloon_page_enqueue on pages that have been
> > - * pushed to a list with balloon_page_push before removing them with
> > - * balloon_page_pop. To all pages on a list, use balloon_page_list_enqueue
> > - * instead.
> > - *
> > - * 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.
> > + * Drivers must not call balloon_page_enqueue on pages that have been
> > + pushed to
> > + * a list with balloon_page_push before removing them with
> > + balloon_page_pop. To
> > + * enqueue all pages on a list, use balloon_page_list_enqueue instead.
>
> "To enqueue a list of pages" ?
ok
>
> > */
> > void balloon_page_enqueue(struct balloon_dev_info *b_dev_info,
> > struct page *page)
> > @@ -157,14 +156,24 @@ 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.
> > + * its address to allow the driver to 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.
> > + * Driver must call this to properly dequeue a previously enqueued page
>
> "call this function"?
ok
>
> > + * before definitively releasing it back to the guest system.
> > + *
> > + * Caller must perform its own accounting to ensure that this
> > + * function is called only if some pages are actually enqueued.
>
>
> "only when" ?
I think when would be confusing here since this function
is called significantly after pages are first enqueued.
> > + *
> > + * Note that this function may fail to dequeue some pages even if there
>
> "even when" ?
same
> > + are
> > + * some enqueued pages - since the page list can be temporarily empty
> > + due to
> > + * the compaction of isolated pages.
> > + *
> > + * TODO: remove the caller accounting requirements, and allow caller to
> > + wait
> > + * until all pages can be dequeued.
> > + *
> > + * Returns: struct page address for the dequeued page, or NULL if it fails to
> > + * dequeue any pages.
>
> Returns: pointer to the page struct of the dequeued page, or NULL if no page gets dequeued.
>
was dequeued.
> > */
> > struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info)
> > { @@ -177,9 +186,9 @@ struct page *balloon_page_dequeue(struct
> > balloon_dev_info *b_dev_info)
> > if (n_pages != 1) {
> > /*
> > * If we are unable to dequeue a balloon page because the
> > page
> > - * list is empty and there is no isolated pages, then
> > something
> > + * list is empty and there are 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
> > + * BUG() here, otherwise the balloon driver may get stuck in
> > * an infinite loop while attempting to release all its pages.
> > */
> > spin_lock_irqsave(&b_dev_info->pages_lock, flags); @@ -
> > 230,8 +239,8 @@ int balloon_page_migrate(struct address_space *mapping,
> >
> > /*
> > * We can not easily support the no copy case here so ignore it as it
>
> "cannot"
>
> > - * is unlikely to be use with ballon pages. See include/linux/hmm.h
> > for
> > - * user of the MIGRATE_SYNC_NO_COPY mode.
> > + * is unlikely to be used with ballon pages. See include/linux/hmm.h
>
>
> "ballon" -> "balloon"
ok
>
> > for
> > + * a user of the MIGRATE_SYNC_NO_COPY mode.
>
> "for the usage of" ?
Not really I think, it's an example user but does not document usage.
>
> Other parts look good to me.
> Reviewed-by: Wei Wang <[email protected]>
>
> Best,
> Wei