MPOL_MF_LAZY was added by commit b24f53a0bea3 ("mm: mempolicy: Add
MPOL_MF_LAZY"), then it was disabled by commit a720094ded8c ("mm:
mempolicy: Hide MPOL_NOOP and MPOL_MF_LAZY from userspace for now")
right away in 2012.  So, it is never ever exported to userspace.

And, it looks nobody is interested in revisiting it since it was
disabled 7 years ago.  So, it sounds pointless to still keep it around.

Cc: Mel Gorman <mgor...@techsingularity.net>
Cc: Michal Hocko <mho...@suse.com>
Cc: Vlastimil Babka <vba...@suse.cz>
Signed-off-by: Yang Shi <yang....@linux.alibaba.com>
---
Hi folks,
I'm not sure if you still would like to revisit it later. And, I may be
not the first one to try to remvoe it. IMHO, it sounds pointless to still
keep it around if nobody is interested in it.

 include/uapi/linux/mempolicy.h |  3 +--
 mm/mempolicy.c                 | 13 -------------
 2 files changed, 1 insertion(+), 15 deletions(-)

diff --git a/include/uapi/linux/mempolicy.h b/include/uapi/linux/mempolicy.h
index 3354774..eb52a7a 100644
--- a/include/uapi/linux/mempolicy.h
+++ b/include/uapi/linux/mempolicy.h
@@ -45,8 +45,7 @@ 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_INTERNAL (1<<4)        /* Internal flags start here */
+#define MPOL_MF_INTERNAL (1<<3)        /* Internal flags start here */
 
 #define MPOL_MF_VALID  (MPOL_MF_STRICT   |     \
                         MPOL_MF_MOVE     |     \
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index af171cc..67886f4 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -593,15 +593,6 @@ static int queue_pages_test_walk(unsigned long start, 
unsigned long end,
 
        qp->prev = vma;
 
-       if (flags & MPOL_MF_LAZY) {
-               /* Similar to task_numa_work, skip inaccessible VMAs */
-               if (!is_vm_hugetlb_page(vma) &&
-                       (vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)) &&
-                       !(vma->vm_flags & VM_MIXEDMAP))
-                       change_prot_numa(vma, start, endvma);
-               return 1;
-       }
-
        /* queue pages from current vma */
        if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL))
                return 0;
@@ -1181,9 +1172,6 @@ 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
@@ -1226,7 +1214,6 @@ static long do_mbind(unsigned long start, unsigned long 
len,
                int nr_failed = 0;
 
                if (!list_empty(&pagelist)) {
-                       WARN_ON_ONCE(flags & MPOL_MF_LAZY);
                        nr_failed = migrate_pages(&pagelist, new_page, NULL,
                                start, MIGRATE_SYNC, MR_MEMPOLICY_MBIND);
                        if (nr_failed)
-- 
1.8.3.1

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