mm/migrate: make migrate_misplaced_folio() return 0 on success

Patch series "mm/migrate: move NUMA hinting fault folio isolation + checks
under PTL".

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.

Link: https://lkml.kernel.org/r/20240620212935.656243-1-david@redhat.com
Link: https://lkml.kernel.org/r/20240620212935.656243-2-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Donet Tom <donettom@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index be598e9..69ca526 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1653,7 +1653,7 @@ 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);
@@ -1697,8 +1697,7 @@ 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 9e87932..395f6e7 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5357,7 +5357,7 @@ 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 72ca341..45e4712 100644 (file)
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2618,11 +2618,11 @@ 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 */