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/*

 * mm/truncate.c - code for taking down pages from address_spaces

 *

 * Copyright (C) 2002, Linus Torvalds

 *

 * 10Sep2002    akpm@zip.com.au

 *              Initial version.

 */

#include <linux/kernel.h>

#include <linux/backing-dev.h>

#include <linux/mm.h>

#include <linux/swap.h>

#include <linux/module.h>

#include <linux/pagemap.h>

#include <linux/highmem.h>

#include <linux/pagevec.h>

#include <linux/task_io_accounting_ops.h>

#include <linux/buffer_head.h>  /* grr. try_to_release_page,

                                   do_invalidatepage */

/**

 * do_invalidatepage - invalidate part of all of a page

 * @page: the page which is affected

 * @offset: the index of the truncation point

 *

 * do_invalidatepage() is called when all or part of the page has become

 * invalidated by a truncate operation.

 *

 * do_invalidatepage() does not have to release all buffers, but it must

 * ensure that no dirty buffer is left outside @offset and that no I/O

 * is underway against any of the blocks which are outside the truncation

 * point.  Because the caller is about to free (and possibly reuse) those

 * blocks on-disk.

 */

void do_invalidatepage(struct page *page, unsigned long offset)

{

        void (*invalidatepage)(struct page *, unsigned long);

        invalidatepage = page->mapping->a_ops->invalidatepage;

#ifdef CONFIG_BLOCK

        if (!invalidatepage)

                invalidatepage = block_invalidatepage;

#endif

        if (invalidatepage)

                (*invalidatepage)(page, offset);

}

static inline void truncate_partial_page(struct page *page, unsigned partial)

{

        zero_user_page(page, partial, PAGE_CACHE_SIZE - partial, KM_USER0);

        if (PagePrivate(page))

                do_invalidatepage(page, partial);

}

/*

 * This cancels just the dirty bit on the kernel page itself, it

 * does NOT actually remove dirty bits on any mmap's that may be

 * around. It also leaves the page tagged dirty, so any sync

 * activity will still find it on the dirty lists, and in particular,

 * clear_page_dirty_for_io() will still look at the dirty bits in

 * the VM.

 *

 * Doing this should *normally* only ever be done when a page

 * is truncated, and is not actually mapped anywhere at all. However,

 * fs/buffer.c does this when it notices that somebody has cleaned

 * out all the buffers on a page without actually doing it through

 * the VM. Can you say "ext3 is horribly ugly"? Tought you could.

 */

void cancel_dirty_page(struct page *page, unsigned int account_size)

{

        if (TestClearPageDirty(page)) {

                struct address_space *mapping = page->mapping;

                if (mapping && mapping_cap_account_dirty(mapping)) {

                        dec_zone_page_state(page, NR_FILE_DIRTY);

                        dec_bdi_stat(mapping->backing_dev_info,

                                        BDI_RECLAIMABLE);

                        if (account_size)

                                task_io_account_cancelled_write(account_size);

                }

        }

}

EXPORT_SYMBOL(cancel_dirty_page);

/*

 * If truncate cannot remove the fs-private metadata from the page, the page

 * becomes anonymous.  It will be left on the LRU and may even be mapped into

 * user pagetables if we're racing with filemap_fault().

 *

 * We need to bale out if page->mapping is no longer equal to the original

 * mapping.  This happens a) when the VM reclaimed the page while we waited on

 * its lock, b) when a concurrent invalidate_mapping_pages got there first and

 * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.

 */

static void

truncate_complete_page(struct address_space *mapping, struct page *page)

{

        if (page->mapping != mapping)

                return;

        cancel_dirty_page(page, PAGE_CACHE_SIZE);

        if (PagePrivate(page))

                do_invalidatepage(page, 0);

        remove_from_page_cache(page);

        ClearPageUptodate(page);

        ClearPageMappedToDisk(page);

        page_cache_release(page);       /* pagecache ref */

}

/*

 * This is for invalidate_mapping_pages().  That function can be called at

 * any time, and is not supposed to throw away dirty pages.  But pages can

 * be marked dirty at any time too, so use remove_mapping which safely

 * discards clean, unused pages.

 *

 * Returns non-zero if the page was successfully invalidated.

 */

static int

invalidate_complete_page(struct address_space *mapping, struct page *page)

{

        int ret;

        if (page->mapping != mapping)

                return 0;

        if (PagePrivate(page) && !try_to_release_page(page, 0))

                return 0;

        ret = remove_mapping(mapping, page);

        return ret;

}

/**

 * truncate_inode_pages - truncate range of pages specified by start and

 * end byte offsets

 * @mapping: mapping to truncate

 * @lstart: offset from which to truncate

 * @lend: offset to which to truncate

 *

 * Truncate the page cache, removing the pages that are between

 * specified offsets (and zeroing out partial page

 * (if lstart is not page aligned)).

 *

 * Truncate takes two passes - the first pass is nonblocking.  It will not

 * block on page locks and it will not block on writeback.  The second pass

 * will wait.  This is to prevent as much IO as possible in the affected region.

 * The first pass will remove most pages, so the search cost of the second pass

 * is low.

 *

 * When looking at page->index outside the page lock we need to be careful to

 * copy it into a local to avoid races (it could change at any time).

 *

 * We pass down the cache-hot hint to the page freeing code.  Even if the

 * mapping is large, it is probably the case that the final pages are the most

 * recently touched, and freeing happens in ascending file offset order.

 */

void truncate_inode_pages_range(struct address_space *mapping,

                                loff_t lstart, loff_t lend)

{

        const pgoff_t start = (lstart + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;

        pgoff_t end;

        const unsigned partial = lstart & (PAGE_CACHE_SIZE - 1);

        struct pagevec pvec;

        pgoff_t next;

        int i;

        if (mapping->nrpages == 0)

                return;

        BUG_ON((lend & (PAGE_CACHE_SIZE - 1)) != (PAGE_CACHE_SIZE - 1));

        end = (lend >> PAGE_CACHE_SHIFT);

        pagevec_init(&pvec, 0);

        next = start;

        while (next <= end &&

               pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {

                for (i = 0; i < pagevec_count(&pvec); i++) {

                        struct page *page = pvec.pages[i];

                        pgoff_t page_index = page->index;

                        if (page_index > end) {

                                next = page_index;

                                break;

                        }

                        if (page_index > next)

                                next = page_index;

                        next++;

                        if (TestSetPageLocked(page))

                                continue;

                        if (PageWriteback(page)) {

                                unlock_page(page);

                                continue;

                        }

                        if (page_mapped(page)) {

                                unmap_mapping_range(mapping,

                                  (loff_t)page_index<<PAGE_CACHE_SHIFT,

                                  PAGE_CACHE_SIZE, 0);

                        }

                        truncate_complete_page(mapping, page);

                        unlock_page(page);

                }

                pagevec_release(&pvec);

                cond_resched();

        }

        if (partial) {

                struct page *page = find_lock_page(mapping, start - 1);

                if (page) {

                        wait_on_page_writeback(page);

                        truncate_partial_page(page, partial);

                        unlock_page(page);

                        page_cache_release(page);

                }

        }

        next = start;

        for ( ; ; ) {

                cond_resched();

                if (!pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {

                        if (next == start)

                                break;

                        next = start;

                        continue;

                }

                if (pvec.pages[0]->index > end) {

                        pagevec_release(&pvec);

                        break;

                }

                for (i = 0; i < pagevec_count(&pvec); i++) {

                        struct page *page = pvec.pages[i];

                        if (page->index > end)

                                break;

                        lock_page(page);

                        wait_on_page_writeback(page);

                        if (page_mapped(page)) {

                                unmap_mapping_range(mapping,

                                  (loff_t)page->index<<PAGE_CACHE_SHIFT,

                                  PAGE_CACHE_SIZE, 0);

                        }

                        if (page->index > next)

                                next = page->index;

                        next++;

                        truncate_complete_page(mapping, page);

                        unlock_page(page);

                }

                pagevec_release(&pvec);

        }

}

EXPORT_SYMBOL(truncate_inode_pages_range);

/**

 * truncate_inode_pages - truncate *all* the pages from an offset

 * @mapping: mapping to truncate

 * @lstart: offset from which to truncate

 *

 * Called under (and serialised by) inode->i_mutex.

 */

void truncate_inode_pages(struct address_space *mapping, loff_t lstart)

{

        truncate_inode_pages_range(mapping, lstart, (loff_t)-1);

}

EXPORT_SYMBOL(truncate_inode_pages);

unsigned long __invalidate_mapping_pages(struct address_space *mapping,

                                pgoff_t start, pgoff_t end, bool be_atomic)

{

        struct pagevec pvec;

        pgoff_t next = start;

        unsigned long ret = 0;

        int i;

        pagevec_init(&pvec, 0);

        while (next <= end &&

                        pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {

                for (i = 0; i < pagevec_count(&pvec); i++) {

                        struct page *page = pvec.pages[i];

                        pgoff_t index;

                        int lock_failed;

                        lock_failed = TestSetPageLocked(page);

                        /*

                         * We really shouldn't be looking at the ->index of an

                         * unlocked page.  But we're not allowed to lock these

                         * pages.  So we rely upon nobody altering the ->index

                         * of this (pinned-by-us) page.

                         */

                        index = page->index;

                        if (index > next)

                                next = index;

                        next++;

                        if (lock_failed)

                                continue;

                        if (PageDirty(page) || PageWriteback(page))

                                goto unlock;

                        if (page_mapped(page))

                                goto unlock;

                        ret += invalidate_complete_page(mapping, page);

unlock:

                        unlock_page(page);

                        if (next > end)

                                break;

                }

                pagevec_release(&pvec);

                if (likely(!be_atomic))

                        cond_resched();

        }

        return ret;

}

/**

 * invalidate_mapping_pages - Invalidate all the unlocked pages of one inode

 * @mapping: the address_space which holds the pages to invalidate

 * @start: the offset 'from' which to invalidate

 * @end: the offset 'to' which to invalidate (inclusive)

 *

 * This function only removes the unlocked pages, if you want to

 * remove all the pages of one inode, you must call truncate_inode_pages.

 *

 * invalidate_mapping_pages() will not block on IO activity. It will not

 * invalidate pages which are dirty, locked, under writeback or mapped into

 * pagetables.

 */

unsigned long invalidate_mapping_pages(struct address_space *mapping,

                                pgoff_t start, pgoff_t end)

{

        return __invalidate_mapping_pages(mapping, start, end, false);

}

EXPORT_SYMBOL(invalidate_mapping_pages);

/*

 * This is like invalidate_complete_page(), except it ignores the page's

 * refcount.  We do this because invalidate_inode_pages2() needs stronger

 * invalidation guarantees, and cannot afford to leave pages behind because

 * shrink_page_list() has a temp ref on them, or because they're transiently

 * sitting in the lru_cache_add() pagevecs.

 */

static int

invalidate_complete_page2(struct address_space *mapping, struct page *page)

{

        if (page->mapping != mapping)

                return 0;

        if (PagePrivate(page) && !try_to_release_page(page, GFP_KERNEL))

                return 0;

        write_lock_irq(&mapping->tree_lock);

        if (PageDirty(page))

                goto failed;

        BUG_ON(PagePrivate(page));

        __remove_from_page_cache(page);

        write_unlock_irq(&mapping->tree_lock);

        ClearPageUptodate(page);

        page_cache_release(page);       /* pagecache ref */

        return 1;

failed:

        write_unlock_irq(&mapping->tree_lock);

        return 0;

}

static int do_launder_page(struct address_space *mapping, struct page *page)

{

        if (!PageDirty(page))

                return 0;

        if (page->mapping != mapping || mapping->a_ops->launder_page == NULL)

                return 0;

        return mapping->a_ops->launder_page(page);

}

/**

 * invalidate_inode_pages2_range - remove range of pages from an address_space

 * @mapping: the address_space

 * @start: the page offset 'from' which to invalidate

 * @end: the page offset 'to' which to invalidate (inclusive)

 *

 * Any pages which are found to be mapped into pagetables are unmapped prior to

 * invalidation.

 *

 * Returns -EIO if any pages could not be invalidated.

 */

int invalidate_inode_pages2_range(struct address_space *mapping,

                                  pgoff_t start, pgoff_t end)

{

        struct pagevec pvec;

        pgoff_t next;

        int i;

        int ret = 0;

        int did_range_unmap = 0;

        int wrapped = 0;

        pagevec_init(&pvec, 0);

        next = start;

        while (next <= end && !wrapped &&

                pagevec_lookup(&pvec, mapping, next,

                        min(end - next, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {

                for (i = 0; i < pagevec_count(&pvec); i++) {

                        struct page *page = pvec.pages[i];

                        pgoff_t page_index;

                        lock_page(page);

                        if (page->mapping != mapping) {

                                unlock_page(page);

                                continue;

                        }

                        page_index = page->index;

                        next = page_index + 1;

                        if (next == 0)

                                wrapped = 1;

                        if (page_index > end) {

                                unlock_page(page);

                                break;

                        }

                        wait_on_page_writeback(page);

                        if (page_mapped(page)) {

                                if (!did_range_unmap) {

                                        /*

                                         * Zap the rest of the file in one hit.

                                         */

                                        unmap_mapping_range(mapping,

                                           (loff_t)page_index<<PAGE_CACHE_SHIFT,

                                           (loff_t)(end - page_index + 1)

                                                        << PAGE_CACHE_SHIFT,

                                            0);

                                        did_range_unmap = 1;

                                } else {

                                        /*

                                         * Just zap this page

                                         */

                                        unmap_mapping_range(mapping,

                                          (loff_t)page_index<<PAGE_CACHE_SHIFT,

                                          PAGE_CACHE_SIZE, 0);

                                }

                        }

                        BUG_ON(page_mapped(page));

                        ret = do_launder_page(mapping, page);

                        if (ret == 0 && !invalidate_complete_page2(mapping, page))

                                ret = -EIO;

                        unlock_page(page);

                }

                pagevec_release(&pvec);

                cond_resched();

        }

        return ret;

}

EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range);

/**

 * invalidate_inode_pages2 - remove all pages from an address_space

 * @mapping: the address_space

 *

 * Any pages which are found to be mapped into pagetables are unmapped prior to

 * invalidation.

 *

 * Returns -EIO if any pages could not be invalidated.

 */

int invalidate_inode_pages2(struct address_space *mapping)

{

        return invalidate_inode_pages2_range(mapping, 0, -1);

}

EXPORT_SYMBOL_GPL(invalidate_inode_pages2);