The patch titled
Subject: mm, page_alloc: fix build_zonerefs_node()
has been added to the -mm tree. Its filename is
mm-page_alloc-fix-build_zonerefs_node.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-page_alloc-fix-build_zonerefs_node.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-page_alloc-fix-build_zonerefs_node.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Juergen Gross <jgross@xxxxxxxx>
Subject: mm, page_alloc: fix build_zonerefs_node()
Since commit 6aa303defb74 ("mm, vmscan: only allocate and reclaim from
zones with pages managed by the buddy allocator") only zones with free
memory are included in a built zonelist. This is problematic when e.g.
all memory of a zone has been ballooned out when zonelists are being
rebuilt.
The decision whether to rebuild the zonelists when onlining new memory is
done based on populated_zone() returning 0 for the zone the memory will be
added to. The new zone is added to the zonelists only, if it has free
memory pages (managed_zone() returns a non-zero value) after the memory
has been onlined. This implies, that onlining memory will always free the
added pages to the allocator immediately, but this is not true in all
cases: when e.g. running as a Xen guest the onlined new memory will be
added only to the ballooned memory list, it will be freed only when the
guest is being ballooned up afterwards.
Another problem with using managed_zone() for the decision whether a zone
is being added to the zonelists is, that a zone with all memory used will
in fact be removed from all zonelists in case the zonelists happen to be
rebuilt.
Use populated_zone() when building a zonelist as it has been done before
that commit.
Link: https://lkml.kernel.org/r/20220407120637.9035-1-jgross@xxxxxxxx
Fixes: 6aa303defb74 ("mm, vmscan: only allocate and reclaim from zones with pages managed by the buddy allocator")
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Reported-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/page_alloc.c~mm-page_alloc-fix-build_zonerefs_node
+++ a/mm/page_alloc.c
@@ -6131,7 +6131,7 @@ static int build_zonerefs_node(pg_data_t
do {
zone_type--;
zone = pgdat->node_zones + zone_type;
- if (managed_zone(zone)) {
+ if (populated_zone(zone)) {
zoneref_set_zone(zone, &zonerefs[nr_zones++]);
check_highest_zone(zone_type);
}
_
Patches currently in -mm which might be from jgross@xxxxxxxx are
mm-page_alloc-fix-build_zonerefs_node.patch
