[PATCH v4 2/3] mm: replace migrate_[prep|finish] with lru_cache_[disable|enable]

Minchan Kim
2021-03-19T17:52:45Z

Currently, migrate_[prep|finish] is merely a wrapper of
lru_cache_[disable|enable]. There is not much to gain from
having additional abstraction.

Use lru_cache_[disable|enable] instead of migrate_[prep|finish],
which would be more descriptive.

note: migrate_prep_local in compaction.c changed into lru_add_drain
to avoid CPU schedule cost with involving many other CPUs to keep
keep old behavior.

Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>
---
include/linux/migrate.h | 7 -------
mm/compaction.c | 3 ++-
mm/mempolicy.c | 8 ++++----
mm/migrate.c | 28 ++--------------------------
mm/page_alloc.c | 4 ++--
5 files changed, 10 insertions(+), 40 deletions(-)

diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index 9e4a2dc8622c..6155d97ec76c 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -45,9 +45,6 @@ extern struct page *alloc_migration_target(struct page *page, unsigned long priv
extern int isolate_movable_page(struct page *page, isolate_mode_t mode);
extern void putback_movable_page(struct page *page);

-extern void migrate_prep(void);
-extern void migrate_finish(void);
-extern void migrate_prep_local(void);
extern void migrate_page_states(struct page *newpage, struct page *page);
extern void migrate_page_copy(struct page *newpage, struct page *page);
extern int migrate_huge_page_move_mapping(struct address_space *mapping,
@@ -67,10 +64,6 @@ static inline struct page *alloc_migration_target(struct page *page,
static inline int isolate_movable_page(struct page *page, isolate_mode_t mode)
{ return -EBUSY; }

-static inline int migrate_prep(void) { return -ENOSYS; }
-static inline int migrate_finish(void) { return -ENOSYS; }
-static inline int migrate_prep_local(void) { return -ENOSYS; }
-
static inline void migrate_page_states(struct page *newpage, struct page *page)
{
}
diff --git a/mm/compaction.c b/mm/compaction.c
index e04f4476e68e..3be017ececc0 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -2319,7 +2319,8 @@ compact_zone(struct compact_control *cc, struct capture_control *capc)
trace_mm_compaction_begin(start_pfn, cc->migrate_pfn,
cc->free_pfn, end_pfn, sync);

- migrate_prep_local();
+ /* lru_add_drain_all could be expensive with involving other CPUs */
+ lru_add_drain();

while ((ret = compact_finished(cc)) == COMPACT_CONTINUE) {
int err;
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 495b43a4b0f8..6daf9cc4c843 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1124,7 +1124,7 @@ int do_migrate_pages(struct mm_struct *mm, const nodemask_t *from,
int err = 0;
nodemask_t tmp;

- migrate_prep();
+ lru_cache_disable();

mmap_read_lock(mm);

@@ -1209,7 +1209,7 @@ int do_migrate_pages(struct mm_struct *mm, const nodemask_t *from,
}
mmap_read_unlock(mm);

- migrate_finish();
+ lru_cache_enable();
if (err < 0)
return err;
return busy;
@@ -1325,7 +1325,7 @@ static long do_mbind(unsigned long start, unsigned long len,

if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) {

- migrate_prep();
+ lru_cache_disable();
}
{
NODEMASK_SCRATCH(scratch);
@@ -1374,7 +1374,7 @@ static long do_mbind(unsigned long start, unsigned long len,
mpol_out:
mpol_put(new);
if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL))
- migrate_finish();
+ lru_cache_enable();
return err;
}

diff --git a/mm/migrate.c b/mm/migrate.c
index 4d6c306d41c6..acc9913e4303 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -57,30 +57,6 @@

#include "internal.h"

-/*
- * migrate_prep() needs to be called before we start compiling a list of pages
- * to be migrated using isolate_lru_page(). If scheduling work on other CPUs is
- * undesirable, use migrate_prep_local()
- */
-void migrate_prep(void)
-{
- /*
- * Clear the LRU lists so pages can be isolated.
- */
- lru_cache_disable();
-}
-
-void migrate_finish(void)
-{
- lru_cache_enable();
-}
-
-/* Do the necessary work of migrate_prep but not if it involves other CPUs */
-void migrate_prep_local(void)
-{
- lru_add_drain();
-}
-
int isolate_movable_page(struct page *page, isolate_mode_t mode)
{
struct address_space *mapping;
@@ -1771,7 +1747,7 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
int start, i;
int err = 0, err1;

- migrate_prep();
+ lru_cache_disable();

for (i = start = 0; i < nr_pages; i++) {
const void __user *p;
@@ -1840,7 +1816,7 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
if (err >= 0)
err = err1;
out:
- migrate_finish();
+ lru_cache_enable();
return err;
}

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index af5d4eeb2999..bf1606c7965a 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -8467,7 +8467,7 @@ static int __alloc_contig_migrate_range(struct compact_control *cc,
.gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL,
};

- migrate_prep();
+ lru_cache_disable();

while (pfn < end || !list_empty(&cc->migratepages)) {
if (fatal_signal_pending(current)) {
@@ -8496,7 +8496,7 @@ static int __alloc_contig_migrate_range(struct compact_control *cc,
NULL, (unsigned long)&mtc, cc->mode, MR_CONTIG_RANGE);
}

- migrate_finish();
+ lru_cache_enable();
if (ret < 0) {
putback_movable_pages(&cc->migratepages);
return ret;
--
2.31.0.rc2.261.g7f71774620-goog