Commit 9808895e authored Apr 01, 2020 by Mina Almasry Committed by Linus Torvalds Apr 02, 2020

mm/hugetlb_cgroup: fix hugetlb_cgroup migration



Commit c32300516047 ("hugetlb_cgroup: add interface for charge/uncharge
hugetlb reservations") mistakingly doesn't handle the migration of *both*
the reservation hugetlb_cgroup and the fault hugetlb_cgroup correctly.

What should happen is that both cgroups shuold be queried from the old
page, then both set to NULL on the old page, then both inserted into the
new page.

The mistake also creates the following warning:

mm/hugetlb_cgroup.c: In function 'hugetlb_cgroup_migrate':
mm/hugetlb_cgroup.c:777:25: warning: variable 'h_cg' set but not used
[-Wunused-but-set-variable]
  struct hugetlb_cgroup *h_cg;
                         ^~~~

Solution is to add the missing steps, namly setting the reservation
hugetlb_cgroup to NULL on the old page, and setting the fault
hugetlb_cgroup on the new page.

Fixes: c32300516047 ("hugetlb_cgroup: add interface for charge/uncharge hugetlb reservations")
Reported-by: Qian Cai <cai@lca.pw>
Signed-off-by: Mina Almasry <almasrymina@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Sandipan Das <sandipan@linux.ibm.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Link: http://lkml.kernel.org/r/20200218194727.46995-1-almasrymina@google.com


Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 1adc4d41

mm/hugetlb_cgroup.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -797,8 +797,10 @@ void hugetlb_cgroup_migrate(struct page oldhpage, struct page newhpage)
		h_cg = hugetlb_cgroup_from_page(oldhpage);
		h_cg_rsvd = hugetlb_cgroup_from_page_rsvd(oldhpage);
		set_hugetlb_cgroup(oldhpage, NULL);
		set_hugetlb_cgroup_rsvd(oldhpage, NULL);

		/* move the h_cg details to new cgroup */
		set_hugetlb_cgroup(newhpage, h_cg);
		set_hugetlb_cgroup_rsvd(newhpage, h_cg_rsvd);
		list_move(&newhpage->lru, &h->hugepage_activelist);
		spin_unlock(&hugetlb_lock);

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