LKML Archive on
 help / color / Atom feed
To: Andrew Morton <>,
	Michal Hocko <>
	"Jérôme Glisse" <>,
	"Dan Williams" <>,
	"John Hubbard" <>,
	"Ira Weiny" <>
Subject: [PATCH v4] mm/swap: Fix release_pages() when releasing devmap pages
Date: Wed,  5 Jun 2019 14:49:22 -0700
Message-ID: <> (raw)

From: Ira Weiny <>

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]


Cc: Jérôme Glisse <>
Cc: Michal Hocko <>
Reviewed-by: Dan Williams <>
Reviewed-by: John Hubbard <>
Signed-off-by: Ira Weiny <>

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
	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))
-		/* Device public page can not be huge page */
-		if (is_device_public_page(page)) {
+		if (is_zone_device_page(page)) {
 			if (locked_pgdat) {
 				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);

             reply index

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 ` Michal Hocko
2019-07-03  1:15 ` Jason Gunthorpe

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \ \ \ \ \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

LKML Archive on

Archives are clonable:
	git clone --mirror lkml/git/0.git
	git clone --mirror lkml/git/1.git
	git clone --mirror lkml/git/2.git
	git clone --mirror lkml/git/3.git
	git clone --mirror lkml/git/4.git
	git clone --mirror lkml/git/5.git
	git clone --mirror lkml/git/6.git
	git clone --mirror lkml/git/7.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 lkml lkml/ \
	public-inbox-index lkml

Newsgroup available over NNTP:

AGPL code for this site: git clone public-inbox