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Subject[RFC PATCH] mm: mempolicy: remove MPOL_MF_LAZY
Date
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 <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Yang Shi <yang.shi@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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