diff options
author | Linus Torvalds | 2005-04-16 15:20:36 -0700 |
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committer | Linus Torvalds | 2005-04-16 15:20:36 -0700 |
commit | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch) | |
tree | 0bba044c4ce775e45a88a51686b5d9f90697ea9d /mm/swap_state.c |
Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Diffstat (limited to 'mm/swap_state.c')
-rw-r--r-- | mm/swap_state.c | 382 |
1 files changed, 382 insertions, 0 deletions
diff --git a/mm/swap_state.c b/mm/swap_state.c new file mode 100644 index 000000000000..a063a902ed03 --- /dev/null +++ b/mm/swap_state.c @@ -0,0 +1,382 @@ +/* + * linux/mm/swap_state.c + * + * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds + * Swap reorganised 29.12.95, Stephen Tweedie + * + * Rewritten to use page cache, (C) 1998 Stephen Tweedie + */ +#include <linux/module.h> +#include <linux/mm.h> +#include <linux/kernel_stat.h> +#include <linux/swap.h> +#include <linux/init.h> +#include <linux/pagemap.h> +#include <linux/buffer_head.h> +#include <linux/backing-dev.h> + +#include <asm/pgtable.h> + +/* + * swapper_space is a fiction, retained to simplify the path through + * vmscan's shrink_list, to make sync_page look nicer, and to allow + * future use of radix_tree tags in the swap cache. + */ +static struct address_space_operations swap_aops = { + .writepage = swap_writepage, + .sync_page = block_sync_page, + .set_page_dirty = __set_page_dirty_nobuffers, +}; + +static struct backing_dev_info swap_backing_dev_info = { + .capabilities = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK, + .unplug_io_fn = swap_unplug_io_fn, +}; + +struct address_space swapper_space = { + .page_tree = RADIX_TREE_INIT(GFP_ATOMIC|__GFP_NOWARN), + .tree_lock = RW_LOCK_UNLOCKED, + .a_ops = &swap_aops, + .i_mmap_nonlinear = LIST_HEAD_INIT(swapper_space.i_mmap_nonlinear), + .backing_dev_info = &swap_backing_dev_info, +}; +EXPORT_SYMBOL(swapper_space); + +#define INC_CACHE_INFO(x) do { swap_cache_info.x++; } while (0) + +static struct { + unsigned long add_total; + unsigned long del_total; + unsigned long find_success; + unsigned long find_total; + unsigned long noent_race; + unsigned long exist_race; +} swap_cache_info; + +void show_swap_cache_info(void) +{ + printk("Swap cache: add %lu, delete %lu, find %lu/%lu, race %lu+%lu\n", + swap_cache_info.add_total, swap_cache_info.del_total, + swap_cache_info.find_success, swap_cache_info.find_total, + swap_cache_info.noent_race, swap_cache_info.exist_race); + printk("Free swap = %lukB\n", nr_swap_pages << (PAGE_SHIFT - 10)); + printk("Total swap = %lukB\n", total_swap_pages << (PAGE_SHIFT - 10)); +} + +/* + * __add_to_swap_cache resembles add_to_page_cache 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 gfp_mask) +{ + int error; + + BUG_ON(PageSwapCache(page)); + BUG_ON(PagePrivate(page)); + error = radix_tree_preload(gfp_mask); + if (!error) { + write_lock_irq(&swapper_space.tree_lock); + error = radix_tree_insert(&swapper_space.page_tree, + entry.val, page); + if (!error) { + page_cache_get(page); + SetPageLocked(page); + SetPageSwapCache(page); + page->private = entry.val; + total_swapcache_pages++; + pagecache_acct(1); + } + write_unlock_irq(&swapper_space.tree_lock); + radix_tree_preload_end(); + } + return error; +} + +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; +} + +/* + * 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)); + + radix_tree_delete(&swapper_space.page_tree, page->private); + page->private = 0; + ClearPageSwapCache(page); + total_swapcache_pages--; + pagecache_acct(-1); + INC_CACHE_INFO(del_total); +} + +/** + * 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) +{ + swp_entry_t entry; + int pf_flags; + int err; + + if (!PageLocked(page)) + BUG(); + + for (;;) { + entry = get_swap_page(); + if (!entry.val) + return 0; + + /* Radix-tree node allocations are performing + * GFP_ATOMIC allocations under PF_MEMALLOC. + * They can completely exhaust the page allocator. + * + * So PF_MEMALLOC is dropped here. This causes the slab + * allocations to fail earlier, so radix-tree nodes will + * then be allocated from the mempool reserves. + * + * We're still using __GFP_HIGH for radix-tree node + * allocations, so some of the emergency pools are available, + * just not all of them. + */ + + pf_flags = current->flags; + current->flags &= ~PF_MEMALLOC; + + /* + * Add it to the swap cache and mark it dirty + */ + err = __add_to_swap_cache(page, entry, GFP_ATOMIC|__GFP_NOWARN); + + if (pf_flags & PF_MEMALLOC) + current->flags |= PF_MEMALLOC; + + 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 and locked. + * It will never put the page into the free list, + * the caller has a reference on the page. + */ +void delete_from_swap_cache(struct page *page) +{ + swp_entry_t entry; + + BUG_ON(!PageSwapCache(page)); + BUG_ON(!PageLocked(page)); + BUG_ON(PageWriteback(page)); + BUG_ON(PagePrivate(page)); + + entry.val = page->private; + + write_lock_irq(&swapper_space.tree_lock); + __delete_from_swap_cache(page); + write_unlock_irq(&swapper_space.tree_lock); + + swap_free(entry); + page_cache_release(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; +} + +/* + * Strange swizzling function for shmem_getpage (and shmem_unuse) + */ +int move_from_swap_cache(struct page *page, unsigned long index, + struct address_space *mapping) +{ + int err = add_to_page_cache(page, mapping, index, GFP_ATOMIC); + if (!err) { + delete_from_swap_cache(page); + /* shift page from clean_pages to dirty_pages list */ + ClearPageDirty(page); + set_page_dirty(page); + } + return err; +} + +/* + * If we are the only user, then try to free up the swap cache. + * + * Its ok to check for PageSwapCache without the page lock + * here because we are going to recheck again inside + * exclusive_swap_page() _with_ the lock. + * - Marcelo + */ +static inline void free_swap_cache(struct page *page) +{ + if (PageSwapCache(page) && !TestSetPageLocked(page)) { + remove_exclusive_swap_page(page); + unlock_page(page); + } +} + +/* + * Perform a free_page(), also freeing any swap cache associated with + * this page if it is the last user of the page. Can not do a lock_page, + * as we are holding the page_table_lock spinlock. + */ +void free_page_and_swap_cache(struct page *page) +{ + free_swap_cache(page); + page_cache_release(page); +} + +/* + * Passed an array of pages, drop them all from swapcache and then release + * them. They are removed from the LRU and freed if this is their last use. + */ +void free_pages_and_swap_cache(struct page **pages, int nr) +{ + int chunk = 16; + struct page **pagep = pages; + + lru_add_drain(); + while (nr) { + int todo = min(chunk, nr); + int i; + + for (i = 0; i < todo; i++) + free_swap_cache(pagep[i]); + release_pages(pagep, todo, 0); + pagep += todo; + nr -= todo; + } +} + +/* + * 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; +} + +/* + * Locate a page of swap in physical memory, reserving swap cache space + * and reading the disk if it is not already cached. + * A failure return means that either the page allocation failed or that + * the swap entry is no longer in use. + */ +struct page *read_swap_cache_async(swp_entry_t entry, + struct vm_area_struct *vma, unsigned long addr) +{ + struct page *found_page, *new_page = NULL; + int err; + + do { + /* + * First check the swap cache. Since this is normally + * called after lookup_swap_cache() failed, re-calling + * that would confuse statistics. + */ + found_page = find_get_page(&swapper_space, entry.val); + if (found_page) + break; + + /* + * Get a new page to read into from swap. + */ + if (!new_page) { + new_page = alloc_page_vma(GFP_HIGHUSER, vma, addr); + if (!new_page) + break; /* Out of memory */ + } + + /* + * Associate the page with swap entry in the swap cache. + * May fail (-ENOENT) if swap entry has been freed since + * our caller observed it. May fail (-EEXIST) if there + * is already a page associated with this entry in the + * swap cache: added by a racing read_swap_cache_async, + * or by try_to_swap_out (or shmem_writepage) re-using + * the just freed swap entry for an existing page. + * May fail (-ENOMEM) if radix-tree node allocation failed. + */ + err = add_to_swap_cache(new_page, entry); + if (!err) { + /* + * Initiate read into locked page and return. + */ + lru_cache_add_active(new_page); + swap_readpage(NULL, new_page); + return new_page; + } + } while (err != -ENOENT && err != -ENOMEM); + + if (new_page) + page_cache_release(new_page); + return found_page; +} |