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/[email protected]/
links to a previous request to remove MPOL_MF_LAZY.
Signed-off-by: Hugh Dickins <[email protected]>
---
include/uapi/linux/mempolicy.h | 2 +-
mm/mempolicy.c | 18 ------------------
2 files changed, 1 insertion(+), 19 deletions(-)
diff --git a/include/uapi/linux/mempolicy.h b/include/uapi/linux/mempolicy.h
index 046d0ccba4cd..a8963f7ef4c2 100644
--- a/include/uapi/linux/mempolicy.h
+++ b/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 | \
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index a22b641cfd6b..7ab6102d7da4 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -632,12 +632,6 @@ unsigned long change_prot_numa(struct vm_area_struct *vma,
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,
@@ -676,14 +670,6 @@ static int queue_pages_test_walk(unsigned long start, unsigned long end,
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.
@@ -1271,9 +1257,6 @@ static long do_mbind(unsigned long start, unsigned long len,
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
@@ -1318,7 +1301,6 @@ static long do_mbind(unsigned long start, unsigned long len,
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);
}
--
2.35.3
On Mon, Sep 25, 2023 at 01:30:51AM -0700, Hugh Dickins wrote:
> 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/[email protected]/
> links to a previous request to remove MPOL_MF_LAZY.
>
> Signed-off-by: Hugh Dickins <[email protected]>
Reviewed-by: Matthew Wilcox (Oracle) <[email protected]>