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mm/balloon_compaction: centralize basic page migration handling

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Let's update the balloon page references, the balloon page list, the
BALLOON_MIGRATE counter and the isolated-pages counter in
balloon_page_migrate(), after letting the balloon->migratepage() callback
deal with the actual inflation+deflation.

Note that we now perform the balloon list modifications outside of any
implementation-specific locks: which is fine, there is nothing special
about these page actions that the lock would be protecting.

The old page is already no longer in the list (isolated) and the new page
is not yet in the list.

Let's use -ENOENT to communicate the special "inflation of new page failed
after already deflating the old page" to balloon_page_migrate() so it can
handle it accordingly.

While at it, rename balloon->b_dev_info to make it match the other
functions.  Also, drop the comment above balloon_page_migrate(), which
seems unnecessary.

Link: https://lkml.kernel.org/r/20260119230133.3551867-6-david@kernel.org
Signed-off-by: David Hildenbrand (Red Hat) <david@kernel.org>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Eugenio Pérez <eperezma@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Jerrin Shaji George <jerrin.shaji-george@broadcom.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: SeongJae Park <sj@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
David Hildenbrand (Red Hat)
2026-01-20 00:01:13 +01:00
committed by Andrew Morton
parent 6af05dfe9a
commit 1258460bd3
4 changed files with 35 additions and 73 deletions
Download Patch File Download Diff File Expand all files Collapse all files

49
drivers/misc/vmw_balloon.c
View File

@@ -1724,18 +1724,17 @@ static inline void vmballoon_debugfs_exit(struct vmballoon *b)
* @page: a ballooned page that should be migrated.
* @mode: migration mode, ignored.
*
* This function is really open-coded, but that is according to the interface
* that balloon_compaction provides.
*
* Return: zero on success, -EAGAIN when migration cannot be performed
* momentarily, and -EBUSY if migration failed and should be retried
* with that specific page.
* momentarily, -EBUSY if migration failed and should be retried
* with that specific page, and -ENOENT when deflating @page
* succeeded but inflating @newpage failed, effectively deflating
* the balloon.
*/
static int vmballoon_migratepage(struct balloon_dev_info *b_dev_info,
struct page *newpage, struct page *page,
enum migrate_mode mode)
{
unsigned long status, flags;
unsigned long status;
struct vmballoon *b;
int ret = 0;
@@ -1773,14 +1772,6 @@ static int vmballoon_migratepage(struct balloon_dev_info *b_dev_info,
goto out_unlock;
}
/*
* The page is isolated, so it is safe to delete it without holding
* @pages_lock . We keep holding @comm_lock since we will need it in a
* second.
*/
balloon_page_finalize(page);
put_page(page);
/* Inflate */
vmballoon_add_page(b, 0, newpage);
status = vmballoon_lock_op(b, 1, VMW_BALLOON_4K_PAGE,
@@ -1799,36 +1790,12 @@ static int vmballoon_migratepage(struct balloon_dev_info *b_dev_info,
* change.
*/
atomic64_dec(&b->size);
} else {
/*
* Success. Take a reference for the page, and we will add it to
* the list after acquiring the lock.
* Tell the core that we're deflating the old page and don't
* need the new page.
*/
get_page(newpage);
ret = -ENOENT;
}
/* Update the balloon list under the @pages_lock */
spin_lock_irqsave(&b->b_dev_info.pages_lock, flags);
/*
* On inflation success, we already took a reference for the @newpage.
* If we succeed just insert it to the list and update the statistics
* under the lock.
*/
if (status == VMW_BALLOON_SUCCESS) {
balloon_page_insert(&b->b_dev_info, newpage);
__count_vm_event(BALLOON_MIGRATE);
} else {
__count_vm_event(BALLOON_DEFLATE);
}
/*
* We deflated successfully, so regardless to the inflation success, we
* need to reduce the number of isolated_pages.
*/
b->b_dev_info.isolated_pages--;
spin_unlock_irqrestore(&b->b_dev_info.pages_lock, flags);
out_unlock:
up_read(&b->conf_sem);
return ret;