Commit c5d6c45e authored by Ira Weiny's avatar Ira Weiny Committed by Jason Gunthorpe
Browse files

mm/swap: fix release_pages() when releasing devmap pages

release_pages() is an optimized version of a loop around put_page().
Unfortunately for devmap pages the logic is not entirely correct in
release_pages().  This is because device pages can be more than type
MEMORY_DEVICE_PUBLIC.  There are in fact 4 types, private, public, FS DAX,
and PCI P2PDMA.  Some of these have specific needs to "put" the page while
others do not.

This logic to handle any special needs is contained in
put_devmap_managed_page().  Therefore all devmap pages should be processed
by this function where we can contain the correct logic for a page put.

Handle all device type pages within release_pages() by calling
put_devmap_managed_page() on all devmap pages.  If
put_devmap_managed_page() returns true the page has been put and we
continue with the next page.  A false return of put_devmap_managed_page()
means the page did not require special processing and should fall to
"normal" processing.

This was found via code inspection while determining if release_pages()
and the new put_user_pages() could be interchangeable.[1]

[1] https://lkml.kernel.org/r/20190523172852.GA27175@iweiny-DESK2.sc.intel.com

Link: https://lkml.kernel.org/r/20190605214922.17684-1-ira.weiny@intel.com


Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Reviewed-by: default avatarDan Williams <dan.j.williams@intel.com>
Reviewed-by: default avatarJohn Hubbard <jhubbard@nvidia.com>
Signed-off-by: default avatarIra Weiny <ira.weiny@intel.com>
Signed-off-by: default avatarJason Gunthorpe <jgg@mellanox.com>
parent 5a136b4a
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+9 −4
Original line number Diff line number Diff line
@@ -740,14 +740,19 @@ void release_pages(struct page **pages, int nr)
		if (is_huge_zero_page(page))
			continue;

		/* Device public page can not be huge page */
		if (is_device_public_page(page)) {
		if (is_zone_device_page(page)) {
			if (locked_pgdat) {
				spin_unlock_irqrestore(&locked_pgdat->lru_lock,
						       flags);
				locked_pgdat = NULL;
			}
			put_devmap_managed_page(page);
			/*
			 * ZONE_DEVICE pages that return 'false' from
			 * put_devmap_managed_page() do not require special
			 * processing, and instead, expect a call to
			 * put_page_testzero().
			 */
			if (put_devmap_managed_page(page))
				continue;
		}