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Subject[PATCH v9 38/61] mm: Convert page migration to XArray
Date
From: Matthew Wilcox <mawilcox@microsoft.com>

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
---
mm/migrate.c | 41 ++++++++++++++++-------------------------
1 file changed, 16 insertions(+), 25 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index 740b71857898..9a15d27768a0 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -322,7 +322,7 @@ void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
page = migration_entry_to_page(entry);

/*
- * Once radix-tree replacement of page migration started, page_count
+ * Once page cache replacement of page migration started, page_count
* *must* be zero. And, we don't want to call wait_on_page_locked()
* against a page without get_page().
* So, we use get_page_unless_zero(), here. Even failed, page fault
@@ -437,10 +437,10 @@ int migrate_page_move_mapping(struct address_space *mapping,
struct buffer_head *head, enum migrate_mode mode,
int extra_count)
{
+ XA_STATE(xas, &mapping->i_pages, page_index(page));
struct zone *oldzone, *newzone;
int dirty;
int expected_count = 1 + extra_count;
- void **pslot;

/*
* Device public or private pages have an extra refcount as they are
@@ -466,21 +466,16 @@ int migrate_page_move_mapping(struct address_space *mapping,
oldzone = page_zone(page);
newzone = page_zone(newpage);

- xa_lock_irq(&mapping->i_pages);
-
- pslot = radix_tree_lookup_slot(&mapping->i_pages,
- page_index(page));
+ xas_lock_irq(&xas);

expected_count += 1 + page_has_private(page);
- if (page_count(page) != expected_count ||
- radix_tree_deref_slot_protected(pslot,
- &mapping->i_pages.xa_lock) != page) {
- xa_unlock_irq(&mapping->i_pages);
+ if (page_count(page) != expected_count || xas_load(&xas) != page) {
+ xas_unlock_irq(&xas);
return -EAGAIN;
}

if (!page_ref_freeze(page, expected_count)) {
- xa_unlock_irq(&mapping->i_pages);
+ xas_unlock_irq(&xas);
return -EAGAIN;
}

@@ -494,7 +489,7 @@ int migrate_page_move_mapping(struct address_space *mapping,
if (mode == MIGRATE_ASYNC && head &&
!buffer_migrate_lock_buffers(head, mode)) {
page_ref_unfreeze(page, expected_count);
- xa_unlock_irq(&mapping->i_pages);
+ xas_unlock_irq(&xas);
return -EAGAIN;
}

@@ -522,7 +517,7 @@ int migrate_page_move_mapping(struct address_space *mapping,
SetPageDirty(newpage);
}

- radix_tree_replace_slot(&mapping->i_pages, pslot, newpage);
+ xas_store(&xas, newpage);

/*
* Drop cache reference from old page by unfreezing
@@ -531,7 +526,7 @@ int migrate_page_move_mapping(struct address_space *mapping,
*/
page_ref_unfreeze(page, expected_count - 1);

- xa_unlock(&mapping->i_pages);
+ xas_unlock(&xas);
/* Leave irq disabled to prevent preemption while updating stats */

/*
@@ -571,22 +566,18 @@ EXPORT_SYMBOL(migrate_page_move_mapping);
int migrate_huge_page_move_mapping(struct address_space *mapping,
struct page *newpage, struct page *page)
{
+ XA_STATE(xas, &mapping->i_pages, page_index(page));
int expected_count;
- void **pslot;
-
- xa_lock_irq(&mapping->i_pages);
-
- pslot = radix_tree_lookup_slot(&mapping->i_pages, page_index(page));

+ xas_lock_irq(&xas);
expected_count = 2 + page_has_private(page);
- if (page_count(page) != expected_count ||
- radix_tree_deref_slot_protected(pslot, &mapping->i_pages.xa_lock) != page) {
- xa_unlock_irq(&mapping->i_pages);
+ if (page_count(page) != expected_count || xas_load(&xas) != page) {
+ xas_unlock_irq(&xas);
return -EAGAIN;
}

if (!page_ref_freeze(page, expected_count)) {
- xa_unlock_irq(&mapping->i_pages);
+ xas_unlock_irq(&xas);
return -EAGAIN;
}

@@ -595,11 +586,11 @@ int migrate_huge_page_move_mapping(struct address_space *mapping,

get_page(newpage);

- radix_tree_replace_slot(&mapping->i_pages, pslot, newpage);
+ xas_store(&xas, newpage);

page_ref_unfreeze(page, expected_count - 1);

- xa_unlock_irq(&mapping->i_pages);
+ xas_unlock_irq(&xas);

return MIGRATEPAGE_SUCCESS;
}
--
2.16.1
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