linux-kernel - [PATCH v2 07/12] mempolicy: mpol_shared_policy

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Message-ID: <3bef62d8-ae78-4c2-533-56a44ae425c@google.com>
Date:   Tue, 3 Oct 2023 02:22:59 -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>,
        "Huang, Ying" <ying.huang@...el.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: [PATCH v2 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 | 28 ++++++++++++++--------------
 1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 1d3f9e1ecbb8..5d99fd5cd60b 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2756,30 +2756,30 @@ void mpol_shared_policy_init(struct shared_policy *sp, struct mempolicy *mpol)
 	rwlock_init(&sp->lock);
 
 	if (mpol) {
-		struct vm_area_struct pvma;
-		struct mempolicy *new;
+		struct sp_node *sn;
+		struct mempolicy *npol;
 		NODEMASK_SCRATCH(scratch);
 
 		if (!scratch)
 			goto put_mpol;
-		/* contextualize the tmpfs mount point mempolicy */
-		new = mpol_new(mpol->mode, mpol->flags, &mpol->w.user_nodemask);
-		if (IS_ERR(new))
+
+		/* contextualize the tmpfs mount point mempolicy to this file */
+		npol = mpol_new(mpol->mode, mpol->flags, &mpol->w.user_nodemask);
+		if (IS_ERR(npol))
 			goto free_scratch; /* no valid nodemask intersection */
 
 		task_lock(current);
-		ret = mpol_set_nodemask(new, &mpol->w.user_nodemask, scratch);
+		ret = mpol_set_nodemask(npol, &mpol->w.user_nodemask, scratch);
 		task_unlock(current);
 		if (ret)
-			goto put_new;
+			goto put_npol;
 
-		/* 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 */
-
-put_new:
-		mpol_put(new);			/* drop initial ref */
+		/* alloc node covering entire file; adds ref to file's npol */
+		sn = sp_alloc(0, MAX_LFS_FILESIZE >> PAGE_SHIFT, npol);
+		if (sn)
+			sp_insert(sp, sn);
+put_npol:
+		mpol_put(npol);	/* drop initial ref on file's npol */
 free_scratch:
 		NODEMASK_SCRATCH_FREE(scratch);
 put_mpol:
-- 
2.35.3