参照元†
- struct address_space *mapping
- struct page *newpage
- struct page *page
- struct buffer_head *head
- enum migrate_mode mode
- int extra_count
返り値†
/*
* Replace the page in the mapping.
*
* The number of remaining references must be:
* 1 for anonymous pages without a mapping
* 2 for pages with a mapping
* 3 for pages with a mapping and PagePrivate/PagePrivate2 set.
*/
int migrate_page_move_mapping(struct address_space *mapping,
struct page *newpage, struct page *page,
struct buffer_head *head, enum migrate_mode mode,
int extra_count)
{
struct zone *oldzone, *newzone;
int dirty;
int expected_count = 1 + extra_count;
void **pslot;
if (!mapping) {
/* Anonymous page without mapping */
if (page_count(page) != expected_count)
return -EAGAIN;
/* No turning back from here */
set_page_memcg(newpage, page_memcg(page));
newpage->index = page->index;
newpage->mapping = page->mapping;
if (PageSwapBacked(page))
SetPageSwapBacked(newpage);
return MIGRATEPAGE_SUCCESS;
}
oldzone = page_zone(page);
newzone = page_zone(newpage);
spin_lock_irq(&mapping->tree_lock);
pslot = radix_tree_lookup_slot(&mapping->page_tree,
page_index(page));
expected_count += 1 + page_has_private(page);
if (page_count(page) != expected_count ||
radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) {
spin_unlock_irq(&mapping->tree_lock);
return -EAGAIN;
}
if (!page_freeze_refs(page, expected_count)) {
spin_unlock_irq(&mapping->tree_lock);
return -EAGAIN;
}
/*
* In the async migration case of moving a page with buffers, lock the
* buffers using trylock before the mapping is moved. If the mapping
* was moved, we later failed to lock the buffers and could not move
* the mapping back due to an elevated page count, we would have to
* block waiting on other references to be dropped.
*/
if (mode == MIGRATE_ASYNC && head &&
!buffer_migrate_lock_buffers(head, mode)) {
page_unfreeze_refs(page, expected_count);
spin_unlock_irq(&mapping->tree_lock);
return -EAGAIN;
}
/*
* Now we know that no one else is looking at the page:
* no turning back from here.
*/
set_page_memcg(newpage, page_memcg(page));
newpage->index = page->index;
newpage->mapping = page->mapping;
if (PageSwapBacked(page))
SetPageSwapBacked(newpage);
get_page(newpage); /* add cache reference */
if (PageSwapCache(page)) {
SetPageSwapCache(newpage);
set_page_private(newpage, page_private(page));
}
/* Move dirty while page refs frozen and newpage not yet exposed */
dirty = PageDirty(page);
if (dirty) {
ClearPageDirty(page);
SetPageDirty(newpage);
}
radix_tree_replace_slot(pslot, newpage);
/*
* Drop cache reference from old page by unfreezing
* to one less reference.
* We know this isn't the last reference.
*/
page_unfreeze_refs(page, expected_count - 1);
spin_unlock(&mapping->tree_lock);
/* Leave irq disabled to prevent preemption while updating stats */
/*
* If moved to a different zone then also account
* the page for that zone. Other VM counters will be
* taken care of when we establish references to the
* new page and drop references to the old page.
*
* Note that anonymous pages are accounted for
* via NR_FILE_PAGES and NR_ANON_PAGES if they
* are mapped to swap space.
*/
if (newzone != oldzone) {
__dec_zone_state(oldzone, NR_FILE_PAGES);
__inc_zone_state(newzone, NR_FILE_PAGES);
if (PageSwapBacked(page) && !PageSwapCache(page)) {
__dec_zone_state(oldzone, NR_SHMEM);
__inc_zone_state(newzone, NR_SHMEM);
}
if (dirty && mapping_cap_account_dirty(mapping)) {
__dec_zone_state(oldzone, NR_FILE_DIRTY);
__inc_zone_state(newzone, NR_FILE_DIRTY);
}
}
local_irq_enable();
return MIGRATEPAGE_SUCCESS;
}
コメント†
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