From: ira.weiny@intel.com
To: Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@suse.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
"Jérôme Glisse" <jglisse@redhat.com>,
"Dan Williams" <dan.j.williams@intel.com>,
"John Hubbard" <jhubbard@nvidia.com>,
"Ira Weiny" <ira.weiny@intel.com>
Subject: [PATCH v4] mm/swap: Fix release_pages() when releasing devmap pages
Date: Wed, 5 Jun 2019 14:49:22 -0700 [thread overview]
Message-ID: <20190605214922.17684-1-ira.weiny@intel.com> (raw)
From: Ira Weiny <ira.weiny@intel.com>
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://lore.kernel.org/lkml/20190523172852.GA27175@iweiny-DESK2.sc.intel.com/
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
---
Changes from V3:
Update comment to the one provided by John
Changes from V2:
Update changelog for more clarity as requested by Michal
Update comment WRT "failing" of put_devmap_managed_page()
Changes from V1:
Add comment clarifying that put_devmap_managed_page() can still
fail.
Add Reviewed-by tags.
mm/swap.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/mm/swap.c b/mm/swap.c
index 7ede3eddc12a..607c48229a1d 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -740,15 +740,20 @@ 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);
- continue;
+ /*
+ * 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;
}
page = compound_head(page);
--
2.20.1
next reply other threads:[~2019-06-05 21:48 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-05 21:49 ira.weiny [this message]
2019-06-21 8:11 ` [PATCH v4] mm/swap: Fix release_pages() when releasing devmap pages Michal Hocko
2019-07-03 1:15 ` Jason Gunthorpe
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