linux-kernel - [PATCH 07/12] mempolicy: mpol_shared_policy

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Date:   Mon, 25 Sep 2023 01:29:28 -0700 (PDT)
From:   Hugh Dickins <hughd@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
cc:     Andi Kleen <ak@...ux.intel.com>, Christoph Lameter <cl@...ux.com>,
        Matthew Wilcox <willy@...radead.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        David Hildenbrand <david@...hat.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Yang Shi <shy828301@...il.com>,
        Sidhartha Kumar <sidhartha.kumar@...cle.com>,
        Vishal Moola <vishal.moola@...il.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Tejun Heo <tj@...nel.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Michal Hocko <mhocko@...e.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: [PATCH 07/12] mempolicy: mpol_shared_policy_init() without
 pseudo-vma

mpol_shared_policy_init() does not need to use a pseudo-vma: it can use
sp_alloc() and sp_insert() directly, since the object's shared policy
tree is empty and inaccessible (needing no lock) at get_inode() time.

Signed-off-by: Hugh Dickins <hughd@...gle.com>
---
 mm/mempolicy.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 065e886ec9b6..a22b641cfd6b 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2749,7 +2749,7 @@ void mpol_shared_policy_init(struct shared_policy *sp, struct mempolicy *mpol)
 	rwlock_init(&sp->lock);
 
 	if (mpol) {
-		struct vm_area_struct pvma;
+		struct sp_node *n;
 		struct mempolicy *new;
 		NODEMASK_SCRATCH(scratch);
 
@@ -2766,11 +2766,10 @@ void mpol_shared_policy_init(struct shared_policy *sp, struct mempolicy *mpol)
 		if (ret)
 			goto put_new;
 
-		/* Create pseudo-vma that contains just the policy */
-		vma_init(&pvma, NULL);
-		pvma.vm_end = TASK_SIZE;	/* policy covers entire file */
-		mpol_set_shared_policy(sp, &pvma, new); /* adds ref */
-
+		/* alloc node covering entire file; adds ref to new */
+		n = sp_alloc(0, MAX_LFS_FILESIZE >> PAGE_SHIFT, new);
+		if (n)
+			sp_insert(sp, n);
 put_new:
 		mpol_put(new);			/* drop initial ref */
 free_scratch:
-- 
2.35.3