lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Date:   Fri, 14 Feb 2020 08:29:45 +0800
From:   Yang Shi <>
Subject: [PATCH] mm: migrate.c: migrate PG_readahead flag

Currently migration code doesn't migrate PG_readahead flag.
Theoretically this would incur slight performance loss as the
application might have to ramp its readahead back up again.  Even though
such problem happens, it might be hidden by something else since
migration is typically triggered by compaction and NUMA balancing, any
of which should be more noticeable.

Migrate the flag after end_page_writeback() since it may clear
PG_reclaim flag, which is the same bit as PG_readahead, for the new

Cc: Matthew Wilcox <>
Cc: Michal Hocko <>
Signed-off-by: Yang Shi <>
I didn't experience any real problem, found by visual inspection. And, this was
discussed in thread:

 mm/migrate.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/mm/migrate.c b/mm/migrate.c
index edf42ed..f3c492d 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -647,6 +647,14 @@ void migrate_page_states(struct page *newpage, struct page *page)
 	if (PageWriteback(newpage))
+	/*
+	 * PG_readahead share the same bit with PG_reclaim, the above
+	 * end_page_writeback() may clear PG_readahead mistakenly, so set
+	 * the bit after that.
+	 */
+	if (PageReadahead(page))
+		SetPageReadahead(newpage);
 	copy_page_owner(page, newpage);
 	mem_cgroup_migrate(page, newpage);

Powered by blists - more mailing lists