Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 7d5e3245 authored by Johannes Weiner's avatar Johannes Weiner Committed by Linus Torvalds
Browse files

mm: memcontrol: clarify migration where old page is uncharged 



Better explain re-entrant migration when compaction races with reclaim,
and also mention swapcache readahead pages as possible uncharged migration
sources.

Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Cc: Hugh Dickins <hughd@google.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent dfe0e773

mm/memcontrol.c

+6 −1
Original line number Original line Diff line number Diff line
@@ -6157,7 +6157,12 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage, 
	if (PageCgroupUsed(pc))

	if (PageCgroupUsed(pc))

		return;

		return;





	/* Re-entrant migration: old page already uncharged? */

	/*

	 * Swapcache readahead pages can get migrated before being

	 * charged, and migration from compaction can happen to an

	 * uncharged page when the PFN walker finds a page that

	 * reclaim just put back on the LRU but has not released yet.

	 */

	pc = lookup_page_cgroup(oldpage);

	pc = lookup_page_cgroup(oldpage);

	if (!PageCgroupUsed(pc))

	if (!PageCgroupUsed(pc))

		return;

		return;