From: zhong jiang <zhongjiang@xxxxxxxxxx>
Subject: mm/mempolicy.c: fix an incorrect rebind node in mpol_rebind_nodemask
mpol_rebind_nodemask() is called for MPOL_BIND and MPOL_INTERLEAVE
mempoclicies when the tasks's cpuset's mems_allowed changes. For
policies created without MPOL_F_STATIC_NODES or MPOL_F_RELATIVE_NODES,
it works by remapping the policy's allowed nodes (stored in v.nodes)
using the previous value of mems_allowed (stored in
w.cpuset_mems_allowed) as the domain of map and the new mems_allowed
(passed as nodes) as the range of the map (see the comment of
bitmap_remap() for details).
The result of remapping is stored back as policy's nodemask in v.nodes,
and the new value of mems_allowed should be stored in
w.cpuset_mems_allowed to facilitate the next rebind, if it happens.
However, 213980c0f23b ("mm, mempolicy: simplify rebinding mempolicies
when updating cpusets") introduced a bug where the result of remapping
is stored in w.cpuset_mems_allowed instead. Thus, a mempolicy's
allowed nodes can evolve in an unexpected way after a series of
rebinding due to cpuset mems_allowed changes, possibly binding to a
wrong node or a smaller number of nodes which may e.g. overload them.
This patch fixes the bug so rebinding again works as intended.
[vbabka@xxxxxxx: new changlog]
Link: http://lkml.kernel.org/r/ef6a69c6-c052-b067-8f2c-9d615c619bb9@xxxxxxx
Link: http://lkml.kernel.org/r/1558768043-23184-1-git-send-email-zhongjiang@xxxxxxxxxx
Fixes: 213980c0f23b ("mm, mempolicy: simplify rebinding mempolicies when updating cpusets")
Signed-off-by: zhong jiang <zhongjiang@xxxxxxxxxx>
Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Anshuman Khandual <khandual@xxxxxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Ralph Campbell <rcampbell@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/mempolicy.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/mempolicy.c~mm-mempolicy-fix-an-incorrect-rebind-node-in-mpol_rebind_nodemask
+++ a/mm/mempolicy.c
@@ -306,7 +306,7 @@ static void mpol_rebind_nodemask(struct
else {
nodes_remap(tmp, pol->v.nodes,pol->w.cpuset_mems_allowed,
*nodes);
- pol->w.cpuset_mems_allowed = tmp;
+ pol->w.cpuset_mems_allowed = *nodes;
}
if (nodes_empty(tmp))
_
