linux-kernel - [PATCH v1 1/2] mm/migrate: make migrate_misplaced

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Date: Thu, 20 Jun 2024 23:29:34 +0200
From: David Hildenbrand <david@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org,
	David Hildenbrand <david@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH v1 1/2] mm/migrate: make migrate_misplaced_folio() return 0 on success

Let's just return 0 on success, which is less confusing.

... especially because we got it wrong in the migrate.h stub where we
have "return -EAGAIN; /* can't migrate now */" instead of "return 0;".
Likely this wrong return value doesn't currently matter, but it
certainly adds confusion.

We'll add migrate_misplaced_folio_prepare() next, where we want to use
the same "return 0 on success" approach, so let's just clean this up.

Signed-off-by: David Hildenbrand <david@...hat.com>
---
 mm/huge_memory.c | 5 ++---
 mm/memory.c      | 2 +-
 mm/migrate.c     | 4 ++--
 3 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 0fffaa58a47a..fc27dabcd8e3 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1652,7 +1652,7 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
 	unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
 	int nid = NUMA_NO_NODE;
 	int target_nid, last_cpupid = (-1 & LAST_CPUPID_MASK);
-	bool migrated = false, writable = false;
+	bool writable = false;
 	int flags = 0;
 
 	vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
@@ -1696,8 +1696,7 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
 	spin_unlock(vmf->ptl);
 	writable = false;
 
-	migrated = migrate_misplaced_folio(folio, vma, target_nid);
-	if (migrated) {
+	if (!migrate_misplaced_folio(folio, vma, target_nid)) {
 		flags |= TNF_MIGRATED;
 		nid = target_nid;
 	} else {
diff --git a/mm/memory.c b/mm/memory.c
index 00728ea95583..118660de5bcc 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5354,7 +5354,7 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf)
 	ignore_writable = true;
 
 	/* Migrate to the requested node */
-	if (migrate_misplaced_folio(folio, vma, target_nid)) {
+	if (!migrate_misplaced_folio(folio, vma, target_nid)) {
 		nid = target_nid;
 		flags |= TNF_MIGRATED;
 	} else {
diff --git a/mm/migrate.c b/mm/migrate.c
index 781979567f64..0307b54879a0 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2629,11 +2629,11 @@ int migrate_misplaced_folio(struct folio *folio, struct vm_area_struct *vma,
 					    nr_succeeded);
 	}
 	BUG_ON(!list_empty(&migratepages));
-	return isolated;
+	return isolated ? 0 : -EAGAIN;
 
 out:
 	folio_put(folio);
-	return 0;
+	return -EAGAIN;
 }
 #endif /* CONFIG_NUMA_BALANCING */
 #endif /* CONFIG_NUMA */
-- 
2.45.2