The patch titled
Subject: mempolicy: remove confusing MPOL_MF_LAZY dead code
has been added to the -mm mm-unstable branch. Its filename is
mempolicy-remove-confusing-mpol_mf_lazy-dead-code.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mempolicy-remove-confusing-mpol_mf_lazy-dead-code.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: mempolicy: remove confusing MPOL_MF_LAZY dead code
Date: Tue, 3 Oct 2023 02:24:18 -0700 (PDT)
v3.8 commit b24f53a0bea3 ("mm: mempolicy: Add MPOL_MF_LAZY") introduced
MPOL_MF_LAZY, and included it in the MPOL_MF_VALID flags; but a720094ded8
("mm: mempolicy: Hide MPOL_NOOP and MPOL_MF_LAZY from userspace for now")
immediately removed it from MPOL_MF_VALID flags, pending further review.
"This will need to be revisited", but it has not been reinstated.
The present state is confusing: there is dead code in mm/mempolicy.c to
handle MPOL_MF_LAZY cases which can never occur. Remove that: it can be
resurrected later if necessary. But keep the definition of MPOL_MF_LAZY,
which must remain in the UAPI, even though it always fails with EINVAL.
https://lore.kernel.org/linux-mm/1553041659-46787-1-git-send-email-yang.shi@xxxxxxxxxxxxxxxxx/
links to a previous request to remove MPOL_MF_LAZY.
Link: https://lkml.kernel.org/r/80c9665c-1c3f-17ba-21a3-f6115cebf7d@xxxxxxxxxx
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Reviewed-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Reviewed-by: Yang Shi <shy828301@xxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: "Huang, Ying" <ying.huang@xxxxxxxxx>
Cc: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Nhat Pham <nphamcs@xxxxxxxxx>
Cc: Sidhartha Kumar <sidhartha.kumar@xxxxxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Tejun heo <tj@xxxxxxxxxx>
Cc: Vishal Moola (Oracle) <vishal.moola@xxxxxxxxx>
Cc: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/uapi/linux/mempolicy.h | 2 +-
mm/mempolicy.c | 18 ------------------
2 files changed, 1 insertion(+), 19 deletions(-)
--- a/include/uapi/linux/mempolicy.h~mempolicy-remove-confusing-mpol_mf_lazy-dead-code
+++ a/include/uapi/linux/mempolicy.h
@@ -48,7 +48,7 @@ enum {
#define MPOL_MF_MOVE (1<<1) /* Move pages owned by this process to conform
to policy */
#define MPOL_MF_MOVE_ALL (1<<2) /* Move every page to conform to policy */
-#define MPOL_MF_LAZY (1<<3) /* Modifies '_MOVE: lazy migrate on fault */
+#define MPOL_MF_LAZY (1<<3) /* UNSUPPORTED FLAG: Lazy migrate on fault */
#define MPOL_MF_INTERNAL (1<<4) /* Internal flags start here */
#define MPOL_MF_VALID (MPOL_MF_STRICT | \
--- a/mm/mempolicy.c~mempolicy-remove-confusing-mpol_mf_lazy-dead-code
+++ a/mm/mempolicy.c
@@ -636,12 +636,6 @@ unsigned long change_prot_numa(struct vm
return nr_updated;
}
-#else
-static unsigned long change_prot_numa(struct vm_area_struct *vma,
- unsigned long addr, unsigned long end)
-{
- return 0;
-}
#endif /* CONFIG_NUMA_BALANCING */
static int queue_pages_test_walk(unsigned long start, unsigned long end,
@@ -680,14 +674,6 @@ static int queue_pages_test_walk(unsigne
if (endvma > end)
endvma = end;
- if (flags & MPOL_MF_LAZY) {
- /* Similar to task_numa_work, skip inaccessible VMAs */
- if (!is_vm_hugetlb_page(vma) && vma_is_accessible(vma) &&
- !(vma->vm_flags & VM_MIXEDMAP))
- change_prot_numa(vma, start, endvma);
- return 1;
- }
-
/*
* Check page nodes, and queue pages to move, in the current vma.
* But if no moving, and no strict checking, the scan can be skipped.
@@ -1254,9 +1240,6 @@ static long do_mbind(unsigned long start
if (IS_ERR(new))
return PTR_ERR(new);
- if (flags & MPOL_MF_LAZY)
- new->flags |= MPOL_F_MOF;
-
/*
* If we are using the default policy then operation
* on discontinuous address spaces is okay after all
@@ -1301,7 +1284,6 @@ static long do_mbind(unsigned long start
if (!err) {
if (!list_empty(&pagelist)) {
- WARN_ON_ONCE(flags & MPOL_MF_LAZY);
nr_failed |= migrate_pages(&pagelist, new_folio, NULL,
start, MIGRATE_SYNC, MR_MEMPOLICY_MBIND, NULL);
}
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
hugetlbfs-drop-shared-numa-mempolicy-pretence.patch
kernfs-drop-shared-numa-mempolicy-hooks.patch
mempolicy-fix-migrate_pages2-syscall-return-nr_failed.patch
mempolicy-trivia-delete-those-ancient-pr_debugs.patch
mempolicy-trivia-slightly-more-consistent-naming.patch
mempolicy-trivia-use-pgoff_t-in-shared-mempolicy-tree.patch
mempolicy-mpol_shared_policy_init-without-pseudo-vma.patch
mempolicy-remove-confusing-mpol_mf_lazy-dead-code.patch
mm-add-page_rmappable_folio-wrapper.patch
mempolicy-alloc_pages_mpol-for-numa-policy-without-vma.patch
mempolicy-mmap_lock-is-not-needed-while-migrating-folios.patch
mempolicy-migration-attempt-to-match-interleave-nodes.patch
