mm: increment gen # before restarting traversal

The generation number in struct mem_cgroup_reclaim_iter should be
incremented on every round-trip.  Currently, it is possible for a
concurrent reclaimer to jump in at the end of the hierarchy, causing a
traversal restart (resetting the iteration position) without incrementing
the generation number.

By resetting the position without incrementing the generation, it's
possible for another ongoing mem_cgroup_iter() thread to walk the tree
twice.

Move the traversal restart such that the generation number is
incremented before the restart.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Kinsey Ho <[email protected]>
Reviewed-by: T.J. Mercier <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Michal Koutný <[email protected]>
Cc: Muchun Song <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Shakeel Butt <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Yosry Ahmed <[email protected]>
Cc: Zefan Li <[email protected]>
Cc: Hugh Dickins <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions