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mm/mempolicy.c: fix an incorrect rebind node in mpol_rebind_nodemask

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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, 213980c0f2 ("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@suse.cz: new changlog]
  Link: http://lkml.kernel.org/r/ef6a69c6-c052-b067-8f2c-9d615c619bb9@suse.cz
Link: http://lkml.kernel.org/r/1558768043-23184-1-git-send-email-zhongjiang@huawei.com
Fixes: 213980c0f2 ("mm, mempolicy: simplify rebinding mempolicies when updating cpusets")
Signed-off-by: zhong jiang <zhongjiang@huawei.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
zhong jiang 2019-06-28 12:06:43 -07:00 committed by Linus Torvalds
parent cb8f381f16
commit 29b190fa77
1 changed files with 1 additions and 1 deletions
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2
mm/mempolicy.c
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@ -306,7 +306,7 @@ static void mpol_rebind_nodemask(struct mempolicy *pol, const nodemask_t *nodes)
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))