Subversion Repositories or1k_soc_on_altera_embedded_dev_kit

/*

 *  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 <linux/pagevec.h>

#include <linux/migrate.h>

#include <asm/pgtable.h>

/*

 * swapper_space is a fiction, retained to simplify the path through

 * vmscan's shrink_page_list, to make sync_page look nicer, and to allow

 * future use of radix_tree tags in the swap cache.

 */

static const struct address_space_operations swap_aops = {

        .writepage      = swap_writepage,

        .sync_page      = block_sync_page,

        .set_page_dirty = __set_page_dirty_nobuffers,

        .migratepage    = migrate_page,

};

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(swapper_space.tree_lock),

        .a_ops          = &swap_aops,

        .i_mmap_nonlinear = LIST_HEAD_INIT(swapper_space.i_mmap_nonlinear),

        .backing_dev_info = &swap_backing_dev_info,

};

#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,

                               gfp_t gfp_mask)

{

        int error;

        BUG_ON(!PageLocked(page));

        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);

                        SetPageSwapCache(page);

                        set_page_private(page, entry.val);

                        total_swapcache_pages++;

                        __inc_zone_page_state(page, NR_FILE_PAGES);

                }

                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;

        BUG_ON(PageLocked(page));

        if (!swap_duplicate(entry)) {

                INC_CACHE_INFO(noent_race);

                return -ENOENT;

        }

        SetPageLocked(page);

        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) {

                ClearPageLocked(page);

                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));

        BUG_ON(PagePrivate(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);

}

/**

 * 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;

        BUG_ON(!PageLocked(page));

        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 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;

        entry.val = page_private(page);

        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.

 */

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)

{

        struct page **pagep = pages;

        lru_add_drain();

        while (nr) {

                int todo = min(nr, PAGEVEC_SIZE);

                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_MOVABLE,

                                                                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;

}