linux-kernel - [PATCH 4.14 17/43] mm/mempolicy.c: fix an incorrect rebind node in mpol_rebind

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Message-Id: <20190702080124.674463671@linuxfoundation.org>
Date:   Tue,  2 Jul 2019 10:01:57 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, zhong jiang <zhongjiang@...wei.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Oscar Salvador <osalvador@...e.de>,
        Anshuman Khandual <khandual@...ux.vnet.ibm.com>,
        Michal Hocko <mhocko@...e.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Ralph Campbell <rcampbell@...dia.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 4.14 17/43] mm/mempolicy.c: fix an incorrect rebind node in mpol_rebind_nodemask

From: zhong jiang <zhongjiang@...wei.com>

commit 29b190fa774dd1b72a1a6f19687d55dc72ea83be upstream.

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@...e.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: 213980c0f23b ("mm, mempolicy: simplify rebinding mempolicies when updating cpusets")
Signed-off-by: zhong jiang <zhongjiang@...wei.com>
Reviewed-by: Vlastimil Babka <vbabka@...e.cz>
Cc: Oscar Salvador <osalvador@...e.de>
Cc: Anshuman Khandual <khandual@...ux.vnet.ibm.com>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Mel Gorman <mgorman@...hsingularity.net>
Cc: Andrea Arcangeli <aarcange@...hat.com>
Cc: Ralph Campbell <rcampbell@...dia.com>
Cc: <stable@...r.kernel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 mm/mempolicy.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -305,7 +305,7 @@ 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))