From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Subject: mm/vmscan.c: add checks for incorrect handling of current->reclaim_state
Six sites are presently altering current->reclaim_state. There is a risk
that one function stomps on a caller's value. Use a helper function to
catch such errors.
Cc: Yafang Shao <laoar.shao@xxxxxxxxx>
Cc: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmscan.c | 37 ++++++++++++++++++++++++-------------
1 file changed, 24 insertions(+), 13 deletions(-)
--- a/mm/vmscan.c~mm-vmscanc-add-checks-for-incorrect-handling-of-current-reclaim_state
+++ a/mm/vmscan.c
@@ -241,6 +241,18 @@ static void unregister_memcg_shrinker(st
}
#endif /* CONFIG_MEMCG_KMEM */
+static void set_task_reclaim_state(struct task_struct *task,
+ struct reclaim_state *rs)
+{
+ /* Check for an overwrite */
+ WARN_ON_ONCE(rs && task->reclaim_state);
+
+ /* Check for the nulling of an already-nulled member */
+ WARN_ON_ONCE(!rs && !task->reclaim_state);
+
+ task->reclaim_state = rs;
+}
+
#ifdef CONFIG_MEMCG
static bool global_reclaim(struct scan_control *sc)
{
@@ -3194,13 +3206,13 @@ unsigned long try_to_free_pages(struct z
if (throttle_direct_reclaim(sc.gfp_mask, zonelist, nodemask))
return 1;
- current->reclaim_state = &sc.reclaim_state;
+ set_task_reclaim_state(current, &sc.reclaim_state);
trace_mm_vmscan_direct_reclaim_begin(order, sc.gfp_mask);
nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
- current->reclaim_state = NULL;
+ set_task_reclaim_state(current, NULL);
return nr_reclaimed;
}
@@ -3223,7 +3235,7 @@ unsigned long mem_cgroup_shrink_node(str
};
unsigned long lru_pages;
- current->reclaim_state = &sc.reclaim_state;
+ set_task_reclaim_state(current, &sc.reclaim_state);
sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
@@ -3241,7 +3253,7 @@ unsigned long mem_cgroup_shrink_node(str
trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
- current->reclaim_state = NULL;
+ set_task_reclaim_state(current, NULL);
*nr_scanned = sc.nr_scanned;
return sc.nr_reclaimed;
@@ -3270,7 +3282,7 @@ unsigned long try_to_free_mem_cgroup_pag
.may_shrinkslab = 1,
};
- current->reclaim_state = &sc.reclaim_state;
+ set_task_reclaim_state(current, &sc.reclaim_state);
/*
* Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
* take care of from where we get pages. So the node where we start the
@@ -3291,7 +3303,7 @@ unsigned long try_to_free_mem_cgroup_pag
psi_memstall_leave(&pflags);
trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
- current->reclaim_state = NULL;
+ set_task_reclaim_state(current, NULL);
return nr_reclaimed;
}
@@ -3493,7 +3505,7 @@ static int balance_pgdat(pg_data_t *pgda
.may_unmap = 1,
};
- current->reclaim_state = &sc.reclaim_state;
+ set_task_reclaim_state(current, &sc.reclaim_state);
psi_memstall_enter(&pflags);
__fs_reclaim_acquire();
@@ -3675,7 +3687,7 @@ out:
snapshot_refaults(NULL, pgdat);
__fs_reclaim_release();
psi_memstall_leave(&pflags);
- current->reclaim_state = NULL;
+ set_task_reclaim_state(current, NULL);
/*
* Return the order kswapd stopped reclaiming at as
@@ -3940,17 +3952,16 @@ unsigned long shrink_all_memory(unsigned
.hibernation_mode = 1,
};
struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
- struct task_struct *p = current;
unsigned long nr_reclaimed;
unsigned int noreclaim_flag;
fs_reclaim_acquire(sc.gfp_mask);
noreclaim_flag = memalloc_noreclaim_save();
- p->reclaim_state = &sc.reclaim_state;
+ set_task_reclaim_state(current, &sc.reclaim_state);
nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
- p->reclaim_state = NULL;
+ set_task_reclaim_state(current, NULL);
memalloc_noreclaim_restore(noreclaim_flag);
fs_reclaim_release(sc.gfp_mask);
@@ -4139,7 +4150,7 @@ static int __node_reclaim(struct pglist_
*/
noreclaim_flag = memalloc_noreclaim_save();
p->flags |= PF_SWAPWRITE;
- p->reclaim_state = &sc.reclaim_state;
+ set_task_reclaim_state(p, &sc.reclaim_state);
if (node_pagecache_reclaimable(pgdat) > pgdat->min_unmapped_pages) {
/*
@@ -4151,7 +4162,7 @@ static int __node_reclaim(struct pglist_
} while (sc.nr_reclaimed < nr_pages && --sc.priority >= 0);
}
- p->reclaim_state = NULL;
+ set_task_reclaim_state(p, NULL);
current->flags &= ~PF_SWAPWRITE;
memalloc_noreclaim_restore(noreclaim_flag);
fs_reclaim_release(sc.gfp_mask);
_
