Commit d1656c5a authored by Vlastimil Babka's avatar Vlastimil Babka Committed by Greg Kroah-Hartman

mm, page_alloc: fix fast-path race with cpuset update or removal

commit 16096c25 upstream.

Ganapatrao Kulkarni reported that the LTP test cpuset01 in stress mode
triggers OOM killer in few seconds, despite lots of free memory.  The
test attempts to repeatedly fault in memory in one process in a cpuset,
while changing allowed nodes of the cpuset between 0 and 1 in another
process.

One possible cause is that in the fast path we find the preferred
zoneref according to current mems_allowed, so that it points to the
middle of the zonelist, skipping e.g.  zones of node 1 completely.  If
the mems_allowed is updated to contain only node 1, we never reach it in
the zonelist, and trigger OOM before checking the cpuset_mems_cookie.

This patch fixes the particular case by redoing the preferred zoneref
search if we switch back to the original nodemask.  The condition is
also slightly changed so that when the last non-root cpuset is removed,
we don't miss it.

Note that this is not a full fix, and more patches will follow.

Link: http://lkml.kernel.org/r/20170120103843.24587-3-vbabka@suse.cz
Fixes: 682a3385 ("mm, page_alloc: inline the fast path of the zonelist iterator")
Signed-off-by: default avatarVlastimil Babka <vbabka@suse.cz>
Reported-by: default avatarGanapatrao Kulkarni <gpkulkarni@gmail.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Acked-by: default avatarMel Gorman <mgorman@techsingularity.net>
Acked-by: default avatarHillf Danton <hillf.zj@alibaba-inc.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent ade7afe9
...@@ -3783,9 +3783,17 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, ...@@ -3783,9 +3783,17 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
/* /*
* Restore the original nodemask if it was potentially replaced with * Restore the original nodemask if it was potentially replaced with
* &cpuset_current_mems_allowed to optimize the fast-path attempt. * &cpuset_current_mems_allowed to optimize the fast-path attempt.
* Also recalculate the starting point for the zonelist iterator or
* we could end up iterating over non-eligible zones endlessly.
*/ */
if (cpusets_enabled()) if (unlikely(ac.nodemask != nodemask)) {
ac.nodemask = nodemask; ac.nodemask = nodemask;
ac.preferred_zoneref = first_zones_zonelist(ac.zonelist,
ac.high_zoneidx, ac.nodemask);
if (!ac.preferred_zoneref->zone)
goto no_zone;
}
page = __alloc_pages_slowpath(alloc_mask, order, &ac); page = __alloc_pages_slowpath(alloc_mask, order, &ac);
no_zone: no_zone:
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment