On Tue, Mar 19, 2024 at 07:32:12PM +0100, Oscar Salvador wrote: > Upon migration, new allocated pages are being given the handle of the old > pages. This is problematic because it means that for the stack which > allocated the old page, we will be substracting the old page + the new one > when that page is freed, creating an accounting imbalance. > > Fix this by adding a new migrate_handle in the page_owner struct, and > record the handle that allocated the new page in __folio_copy_owner(). > Upon freeing, we check whether we have a migrate_handle, and if we do, > we use migrate_handle for dec_stack_record_count(), which will > subtract those pages from its right handle. Is this the right way to fix this problem? I would have thought we'd be better off accounting this as migration freeing the old page and allocating the new page. If I understand correctly, this is the code which says "This page was last allocated by X and freed by Y", and I would think that being last freed (or allocated) by the migration code would be a very nice hint about where a problem might stem from.
