/*
* Lookup a swap entry in the swap cache. A found page will be returned
* unlocked and with its refcount incremented - we rely on the kernel
* lock getting page table operations atomic even if we drop the page
* lock before returning.
*/
struct page * lookup_swap_cache(swp_entry_t entry)
{
struct page *page;
page = find_get_page(&swapper_space, entry.val);
if (page)
INC_CACHE_INFO(find_success);
INC_CACHE_INFO(find_total);
return page;
}
/*
* Strange swizzling function only for use by shmem_writepage
*/
int move_to_swap_cache(struct page *page, swp_entry_t entry)
{
int err = __add_to_swap_cache(page, entry, GFP_ATOMIC);
if (!err) {
remove_from_page_cache(page);
page_cache_release(page); /* pagecache ref */
if (!swap_duplicate(entry))
BUG();
SetPageDirty(page);
INC_CACHE_INFO(add_total);
} else if (err == -EEXIST)
INC_CACHE_INFO(exist_race);
return err;
}
/*
* Lookup a swap entry in the swap cache. A found page will be returned
* unlocked and with its refcount incremented - we rely on the kernel
* lock getting page table operations atomic even if we drop the page
* lock before returning.
*/
struct page * lookup_swap_cache(swp_entry_t entry)
{
struct page *page;
page = find_get_page(swap_address_space(entry), entry.val);
if (page) {
INC_CACHE_INFO(find_success);
if (TestClearPageReadahead(page))
atomic_inc(&swapin_readahead_hits);
}
INC_CACHE_INFO(find_total);
return page;
}
/*
* Lookup a swap entry in the swap cache. A found page will be returned
* unlocked and with its refcount incremented - we rely on the kernel
* lock getting page table operations atomic even if we drop the page
* lock before returning.
*/
struct page * lookup_swap_cache(swp_entry_t entry)
{
struct page *page;
page = find_get_page(swap_address_space(entry), swp_offset(entry));
if (page && likely(!PageTransCompound(page))) {
INC_CACHE_INFO(find_success);
if (TestClearPageReadahead(page))
atomic_inc(&swapin_readahead_hits);
}
INC_CACHE_INFO(find_total);
return page;
}
/*
* add_to_swap_cache resembles add_to_page_cache_locked on swapper_space,
* but sets SwapCache flag and private instead of mapping and index.
*/
int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask)
{
int error;
VM_BUG_ON(!PageLocked(page));
VM_BUG_ON(PageSwapCache(page));
VM_BUG_ON(!PageSwapBacked(page));
error = radix_tree_preload(gfp_mask);
if (!error) {
page_cache_get(page);
SetPageSwapCache(page);
set_page_private(page, entry.val);
spin_lock_irq(&swapper_space.tree_lock);
error = radix_tree_insert(&swapper_space.page_tree,
entry.val, page);
if (likely(!error)) {
total_swapcache_pages++;
__inc_zone_page_state(page, NR_FILE_PAGES);
INC_CACHE_INFO(add_total);
}
spin_unlock_irq(&swapper_space.tree_lock);
radix_tree_preload_end();
if (unlikely(error)) {
set_page_private(page, 0UL);
ClearPageSwapCache(page);
page_cache_release(page);
}
}
return error;
}
/*
* __add_to_swap_cache resembles add_to_page_cache_locked on swapper_space,
* but sets SwapCache flag and private instead of mapping and index.
*/
static int __add_to_swap_cache(struct page *page, swp_entry_t entry)
{
int error;
VM_BUG_ON(!PageLocked(page));
VM_BUG_ON(PageSwapCache(page));
VM_BUG_ON(!PageSwapBacked(page));
page_cache_get(page);
SetPageSwapCache(page);
set_page_private(page, entry.val);
spin_lock_irq(&swapper_space.tree_lock);
error = radix_tree_insert(&swapper_space.page_tree, entry.val, page);
if (likely(!error)) {
total_swapcache_pages++;
__inc_zone_page_state(page, NR_FILE_PAGES);
INC_CACHE_INFO(add_total);
}
spin_unlock_irq(&swapper_space.tree_lock);
if (unlikely(error)) {
/*
* Only the context which have set SWAP_HAS_CACHE flag
* would call add_to_swap_cache().
* So add_to_swap_cache() doesn't returns -EEXIST.
*/
VM_BUG_ON(error == -EEXIST);
set_page_private(page, 0UL);
ClearPageSwapCache(page);
page_cache_release(page);
}
return error;
}
/*
* Lookup a swap entry in the swap cache. A found page will be returned
* unlocked and with its refcount incremented - we rely on the kernel
* lock getting page table operations atomic even if we drop the page
* lock before returning.
*/
struct page * lookup_swap_cache(swp_entry_t entry)
{
struct page *found;
found = find_get_page(&swapper_space, entry.val);
/*
* Unsafe to assert PageSwapCache and mapping on page found:
* if SMP nothing prevents swapoff from deleting this page from
* the swap cache at this moment. find_lock_page would prevent
* that, but no need to change: we _have_ got the right page.
*/
INC_CACHE_INFO(find_total);
if (found)
INC_CACHE_INFO(find_success);
return found;
}
/**
* add_to_swap - allocate swap space for a page
* @page: page we want to move to swap
*
* Allocate swap space for the page and add the page to the
* swap cache. Caller needs to hold the page lock.
*/
int add_to_swap(struct page * page, gfp_t gfp_mask)
{
swp_entry_t entry;
int err;
if (!PageLocked(page))
BUG();
for (;;) {
entry = get_swap_page();
if (!entry.val)
return 0;
/*
* Radix-tree node allocations from PF_MEMALLOC contexts could
* completely exhaust the page allocator. __GFP_NOMEMALLOC
* stops emergency reserves from being allocated.
*
* TODO: this could cause a theoretical memory reclaim
* deadlock in the swap out path.
*/
/*
* Add it to the swap cache and mark it dirty
*/
err = __add_to_swap_cache(page, entry,
gfp_mask|__GFP_NOMEMALLOC|__GFP_NOWARN);
switch (err) {
case 0: /* Success */
SetPageUptodate(page);
SetPageDirty(page);
INC_CACHE_INFO(add_total);
return 1;
case -EEXIST:
/* Raced with "speculative" read_swap_cache_async */
INC_CACHE_INFO(exist_race);
swap_free(entry);
continue;
default:
/* -ENOMEM radix-tree allocation failure */
swap_free(entry);
return 0;
}
}
}
/*
* This must be called only on pages that have
* been verified to be in the swap cache.
*/
void __delete_from_swap_cache(struct page *page)
{
if (!PageLocked(page))
BUG();
if (!PageSwapCache(page))
BUG();
ClearPageDirty(page);
__remove_inode_page(page);
INC_CACHE_INFO(del_total);
}
static int add_to_swap_cache(struct page *page, swp_entry_t entry)
{
int error;
if (!swap_duplicate(entry)) {
INC_CACHE_INFO(noent_race);
return -ENOENT;
}
error = __add_to_swap_cache(page, entry, GFP_KERNEL);
/*
* Anon pages are already on the LRU, we don't run lru_cache_add here.
*/
if (error) {
swap_free(entry);
if (error == -EEXIST)
INC_CACHE_INFO(exist_race);
return error;
}
INC_CACHE_INFO(add_total);
return 0;
}
int add_to_swap_cache(struct page *page, swp_entry_t entry)
{
if (page->mapping)
BUG();
if (!swap_duplicate(entry)) {
INC_CACHE_INFO(noent_race);
return -ENOENT;
}
if (add_to_page_cache_unique(page, &swapper_space, entry.val,
page_hash(&swapper_space, entry.val)) != 0) {
swap_free(entry);
INC_CACHE_INFO(exist_race);
return -EEXIST;
}
if (!PageLocked(page))
BUG();
if (!PageSwapCache(page))
BUG();
INC_CACHE_INFO(add_total);
return 0;
}
/**
* __delete_from_swap_cache:page从交换区高速缓存中删去
*/
void __delete_from_swap_cache(struct page *page)
{
VM_BUG_ON(!PageLocked(page));
VM_BUG_ON(!PageSwapCache(page));
VM_BUG_ON(PageWriteback(page));
radix_tree_delete(&swapper_space.page_tree, page_private(page));
set_page_private(page, 0);
ClearPageSwapCache(page);
total_swapcache_pages--;
__dec_zone_page_state(page, NR_FILE_PAGES);
INC_CACHE_INFO(del_total);
}
/*
* This must be called only on pages that have
* been verified to be in the swap cache.
*/
void __delete_from_swap_cache(struct page *page)
{
BUG_ON(!PageLocked(page));
BUG_ON(!PageSwapCache(page));
BUG_ON(PageWriteback(page));
BUG_ON(PagePrivate(page));
radix_tree_delete(&swapper_space.page_tree, page_private(page));
set_page_private(page, 0);
ClearPageSwapCache(page);
total_swapcache_pages--;
pagecache_acct(-1);
INC_CACHE_INFO(del_total);
}
/*
* This must be called only on pages that have
* been verified to be in the swap cache.
*/
void __delete_from_swap_cache(struct page *page)
{
swp_entry_t entry;
struct address_space *address_space;
VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_PAGE(!PageSwapCache(page), page);
VM_BUG_ON_PAGE(PageWriteback(page), page);
entry.val = page_private(page);
address_space = swap_address_space(entry);
radix_tree_delete(&address_space->page_tree, page_private(page));
set_page_private(page, 0);
ClearPageSwapCache(page);
address_space->nrpages--;
__dec_zone_page_state(page, NR_FILE_PAGES);
INC_CACHE_INFO(del_total);
}
/*
* __add_to_swap_cache resembles add_to_page_cache_locked on swapper_space,
* but sets SwapCache flag and private instead of mapping and index.
*/
int __add_to_swap_cache(struct page *page, swp_entry_t entry)
{
int error;
struct address_space *address_space;
VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_PAGE(PageSwapCache(page), page);
VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
get_page(page);
SetPageSwapCache(page);
set_page_private(page, entry.val);
address_space = swap_address_space(entry);
spin_lock_irq(&address_space->tree_lock);
error = radix_tree_insert(&address_space->page_tree,
entry.val, page);
if (likely(!error)) {
address_space->nrpages++;
__inc_zone_page_state(page, NR_FILE_PAGES);
INC_CACHE_INFO(add_total);
}
spin_unlock_irq(&address_space->tree_lock);
if (unlikely(error)) {
/*
* Only the context which have set SWAP_HAS_CACHE flag
* would call add_to_swap_cache().
* So add_to_swap_cache() doesn't returns -EEXIST.
*/
VM_BUG_ON(error == -EEXIST);
set_page_private(page, 0UL);
ClearPageSwapCache(page);
put_page(page);
}
return error;
}
