[RFC PATCH 16/25] exchange page: Add THP exchange support.

From: Zi Yan
Date: Wed Apr 03 2019 - 22:10:36 EST

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From: Zi Yan <ziy@xxxxxxxxxx>

Enable exchange THPs in the process. It also need to take care of
exchanging PTE-mapped THPs.

Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
---
include/linux/exchange.h | 2 ++
mm/exchange.c | 73 +++++++++++++++++++++++++++++++++++++-----------
mm/migrate.c | 2 +-
3 files changed, 60 insertions(+), 17 deletions(-)

diff --git a/include/linux/exchange.h b/include/linux/exchange.h
index 20d2184..8785d08 100644
--- a/include/linux/exchange.h
+++ b/include/linux/exchange.h
@@ -14,6 +14,8 @@ struct exchange_page_info {
int from_page_was_mapped;
int to_page_was_mapped;

+ pgoff_t from_index, to_index;
+
struct list_head list;
};

diff --git a/mm/exchange.c b/mm/exchange.c
index 555a72c..45c7013 100644
--- a/mm/exchange.c
+++ b/mm/exchange.c
@@ -51,7 +51,8 @@ struct page_flags {
unsigned int page_swapcache:1;
unsigned int page_writeback:1;
unsigned int page_private:1;
- unsigned int __pad:3;
+ unsigned int page_doublemap:1;
+ unsigned int __pad:2;
};

@@ -127,20 +128,23 @@ static void exchange_huge_page(struct page *dst, struct page *src)
static void exchange_page_flags(struct page *to_page, struct page *from_page)
{
int from_cpupid, to_cpupid;
- struct page_flags from_page_flags, to_page_flags;
+ struct page_flags from_page_flags = {0}, to_page_flags = {0};
struct mem_cgroup *to_memcg = page_memcg(to_page),
*from_memcg = page_memcg(from_page);

from_cpupid = page_cpupid_xchg_last(from_page, -1);

- from_page_flags.page_error = TestClearPageError(from_page);
+ from_page_flags.page_error = PageError(from_page);
+ if (from_page_flags.page_error)
+ ClearPageError(from_page);
from_page_flags.page_referenced = TestClearPageReferenced(from_page);
from_page_flags.page_uptodate = PageUptodate(from_page);
ClearPageUptodate(from_page);
from_page_flags.page_active = TestClearPageActive(from_page);
from_page_flags.page_unevictable = TestClearPageUnevictable(from_page);
from_page_flags.page_checked = PageChecked(from_page);
- ClearPageChecked(from_page);
+ if (from_page_flags.page_checked)
+ ClearPageChecked(from_page);
from_page_flags.page_mappedtodisk = PageMappedToDisk(from_page);
ClearPageMappedToDisk(from_page);
from_page_flags.page_dirty = PageDirty(from_page);
@@ -150,18 +154,22 @@ static void exchange_page_flags(struct page *to_page, struct page *from_page)
clear_page_idle(from_page);
from_page_flags.page_swapcache = PageSwapCache(from_page);
from_page_flags.page_writeback = test_clear_page_writeback(from_page);
+ from_page_flags.page_doublemap = PageDoubleMap(from_page);

to_cpupid = page_cpupid_xchg_last(to_page, -1);

- to_page_flags.page_error = TestClearPageError(to_page);
+ to_page_flags.page_error = PageError(to_page);
+ if (to_page_flags.page_error)
+ ClearPageError(to_page);
to_page_flags.page_referenced = TestClearPageReferenced(to_page);
to_page_flags.page_uptodate = PageUptodate(to_page);
ClearPageUptodate(to_page);
to_page_flags.page_active = TestClearPageActive(to_page);
to_page_flags.page_unevictable = TestClearPageUnevictable(to_page);
to_page_flags.page_checked = PageChecked(to_page);
- ClearPageChecked(to_page);
+ if (to_page_flags.page_checked)
+ ClearPageChecked(to_page);
to_page_flags.page_mappedtodisk = PageMappedToDisk(to_page);
ClearPageMappedToDisk(to_page);
to_page_flags.page_dirty = PageDirty(to_page);
@@ -171,6 +179,7 @@ static void exchange_page_flags(struct page *to_page, struct page *from_page)
clear_page_idle(to_page);
to_page_flags.page_swapcache = PageSwapCache(to_page);
to_page_flags.page_writeback = test_clear_page_writeback(to_page);
+ to_page_flags.page_doublemap = PageDoubleMap(to_page);

/* set to_page */
if (from_page_flags.page_error)
@@ -197,6 +206,8 @@ static void exchange_page_flags(struct page *to_page, struct page *from_page)
set_page_young(to_page);
if (from_page_flags.page_is_idle)
set_page_idle(to_page);
+ if (from_page_flags.page_doublemap)
+ SetPageDoubleMap(to_page);

/* set from_page */
if (to_page_flags.page_error)
@@ -223,6 +234,8 @@ static void exchange_page_flags(struct page *to_page, struct page *from_page)
set_page_young(from_page);
if (to_page_flags.page_is_idle)
set_page_idle(from_page);
+ if (to_page_flags.page_doublemap)
+ SetPageDoubleMap(from_page);

/*
* Copy NUMA information to the new page, to prevent over-eager
@@ -599,7 +612,6 @@ static int unmap_and_exchange(struct page *from_page, struct page *to_page,

from_index = from_page->index;
to_index = to_page->index;
-
/*
* Corner case handling:
* 1. When a new swap-cache page is read into, it is added to the LRU
@@ -673,8 +685,6 @@ static int unmap_and_exchange(struct page *from_page, struct page *to_page,
swap(from_page->index, from_index);
}

-
-
out_unlock_both:
if (to_anon_vma)
put_anon_vma(to_anon_vma);
@@ -689,6 +699,23 @@ static int unmap_and_exchange(struct page *from_page, struct page *to_page,
return rc;
}

+static bool can_be_exchanged(struct page *from, struct page *to)
+{
+ if (PageCompound(from) != PageCompound(to))
+ return false;
+
+ if (PageHuge(from) != PageHuge(to))
+ return false;
+
+ if (PageHuge(from) || PageHuge(to))
+ return false;
+
+ if (compound_order(from) != compound_order(to))
+ return false;
+
+ return true;
+}
+
/*
* Exchange pages in the exchange_list
*
@@ -745,7 +772,8 @@ int exchange_pages(struct list_head *exchange_list,
}

/* TODO: compound page not supported */
- if (PageCompound(from_page) || page_mapping(from_page)) {
+ if (!can_be_exchanged(from_page, to_page) ||
+ page_mapping(from_page)) {
++failed;
goto putback;
}
@@ -784,6 +812,8 @@ static int unmap_pair_pages_concur(struct exchange_page_info *one_pair,
struct page *from_page = one_pair->from_page;
struct page *to_page = one_pair->to_page;

+ one_pair->from_index = from_page->index;
+ one_pair->to_index = to_page->index;
/* from_page lock down */
if (!trylock_page(from_page)) {
if (!force || ((mode & MIGRATE_MODE_MASK) == MIGRATE_ASYNC))
@@ -903,7 +933,6 @@ static int exchange_page_mapping_concur(struct list_head *unmapped_list_ptr,
struct list_head *exchange_list_ptr,
enum migrate_mode mode)
{
- int rc = -EBUSY;
int nr_failed = 0;
struct address_space *to_page_mapping, *from_page_mapping;
struct exchange_page_info *one_pair, *one_pair2;
@@ -911,6 +940,7 @@ static int exchange_page_mapping_concur(struct list_head *unmapped_list_ptr,
list_for_each_entry_safe(one_pair, one_pair2, unmapped_list_ptr, list) {
struct page *from_page = one_pair->from_page;
struct page *to_page = one_pair->to_page;
+ int rc = -EBUSY;

VM_BUG_ON_PAGE(!PageLocked(from_page), from_page);
VM_BUG_ON_PAGE(!PageLocked(to_page), to_page);
@@ -926,8 +956,9 @@ static int exchange_page_mapping_concur(struct list_head *unmapped_list_ptr,
BUG_ON(PageWriteback(to_page));

/* actual page mapping exchange */
- rc = exchange_page_move_mapping(to_page_mapping, from_page_mapping,
- to_page, from_page, NULL, NULL, mode, 0, 0);
+ if (!page_mapped(from_page) && !page_mapped(to_page))
+ rc = exchange_page_move_mapping(to_page_mapping, from_page_mapping,
+ to_page, from_page, NULL, NULL, mode, 0, 0);

if (rc) {
if (one_pair->from_page_was_mapped)
@@ -954,7 +985,7 @@ static int exchange_page_mapping_concur(struct list_head *unmapped_list_ptr,
one_pair->from_page = NULL;
one_pair->to_page = NULL;

- list_move(&one_pair->list, exchange_list_ptr);
+ list_del(&one_pair->list);
++nr_failed;
}
}
@@ -1026,8 +1057,18 @@ static int remove_migration_ptes_concur(struct list_head *unmapped_list_ptr)
struct exchange_page_info *iterator;

list_for_each_entry(iterator, unmapped_list_ptr, list) {
- remove_migration_ptes(iterator->from_page, iterator->to_page, false);
- remove_migration_ptes(iterator->to_page, iterator->from_page, false);
+ struct page *from_page = iterator->from_page;
+ struct page *to_page = iterator->to_page;
+
+ swap(from_page->index, iterator->from_index);
+ if (iterator->from_page_was_mapped)
+ remove_migration_ptes(iterator->from_page, iterator->to_page, false);
+ swap(from_page->index, iterator->from_index);
+
+ swap(to_page->index, iterator->to_index);
+ if (iterator->to_page_was_mapped)
+ remove_migration_ptes(iterator->to_page, iterator->from_page, false);
+ swap(to_page->index, iterator->to_index);

if (iterator->from_anon_vma)
diff --git a/mm/migrate.c b/mm/migrate.c
index a0ca817..da7af68 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -229,7 +229,7 @@ static bool remove_migration_pte(struct page *page, struct vm_area_struct *vma,
if (PageKsm(page))
new = page;
else
- new = page - pvmw.page->index +
+ new = page - page->index +
linear_page_index(vma, pvmw.address);

#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
--
2.7.4

Next message: Zi Yan: "[RFC PATCH 09/25] mm: migrate: Add copy_page_lists_dma_always to support copy a list of pages."
Previous message: Zi Yan: "[RFC PATCH 18/25] memcg: Add per node memory usage&max stats in memcg."
In reply to: Zi Yan: "[RFC PATCH 18/25] memcg: Add per node memory usage&max stats in memcg."
Next in thread: Zi Yan: "[RFC PATCH 09/25] mm: migrate: Add copy_page_lists_dma_always to support copy a list of pages."
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