linux-kernel - [PATCH] mm: mempolicy: fix policy_nodemask() for MPOL_PREFERRED

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Message-Id: <20220801084207.39086-1-songmuchun@bytedance.com>
Date:   Mon,  1 Aug 2022 16:42:07 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     akpm@...ux-foundation.org, bwidawsk@...nel.org, mhocko@...e.com,
        dave.hansen@...ux.intel.com, feng.tang@...el.com
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Muchun Song <songmuchun@...edance.com>
Subject: [PATCH] mm: mempolicy: fix policy_nodemask() for MPOL_PREFERRED_MANY case

policy_nodemask() is supposed to be returned a nodemask representing a mempolicy
for filtering nodes for page allocation, which is a hard restriction (see the user
of allowed_mems_nr() in hugetlb.c).  However, MPOL_PREFERRED_MANY is a preferred
mode not a hard restriction.  Now it breaks the user of HugeTLB.  Remove it from
policy_nodemask() to fix it, which will not affect current users of policy_nodemask()
since all of the users already have handled the case of MPOL_PREFERRED_MANY before
calling it.  BTW, it is found by code inspection.

Fixes: b27abaccf8e8 ("mm/mempolicy: add MPOL_PREFERRED_MANY for multiple preferred nodes")
Signed-off-by: Muchun Song <songmuchun@...edance.com>
---
 mm/mempolicy.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 6c27acb6cd63..4deec7e598c6 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1845,9 +1845,6 @@ nodemask_t *policy_nodemask(gfp_t gfp, struct mempolicy *policy)
 		cpuset_nodemask_valid_mems_allowed(&policy->nodes))
 		return &policy->nodes;

-	if (mode == MPOL_PREFERRED_MANY)
-		return &policy->nodes;
-
 	return NULL;
 }

-- 
2.11.0