path: root/mm/truncate.c

/*
 * mm/truncate.c - code for taking down pages from address_spaces
 *
 * Copyright (C) 2002, Linus Torvalds
 *
 * 10Sep2002	Andrew Morton
 *		Initial version.
 */

#include <linux/kernel.h>
#include <linux/backing-dev.h>
#include <linux/gfp.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/export.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 */
#include <linux/cleancache.h>
#include "internal.h"

static void clear_exceptional_entry(struct address_space *mapping,
				    pgoff_t index, void *entry)
{
	struct radix_tree_node *node;
	void **slot;

	/* Handled by shmem itself */
	if (shmem_mapping(mapping))
		return;

	spin_lock_irq(&mapping->tree_lock);
	/*
	 * Regular page slots are stabilized by the page lock even
	 * without the tree itself locked.  These unlocked entries
	 * need verification under the tree lock.
	 */
	if (!__radix_tree_lookup(&mapping->page_tree, index, &node, &slot))
		goto unlock;
	if (*slot != entry)
		goto unlock;
	radix_tree_replace_slot(slot, NULL);
	mapping->nrshadows--;
	if (!node)
		goto unlock;
	workingset_node_shadows_dec(node);
	/*
	 * Don't track node without shadow entries.
	 *
	 * Avoid acquiring the list_lru lock if already untracked.
	 * The list_empty() test is safe as node->private_list is
	 * protected by mapping->tree_lock.
	 */
	if (!workingset_node_shadows(node) &&
	    !list_empty(&node->private_list))
		list_lru_del(&workingset_shadow_nodes, &node->private_list);
	__radix_tree_delete_node(&mapping->page_tree, node);
unlock:
	spin_unlock_irq(&mapping->tree_lock);
}

/**
 * do_invalidatepage - invalidate part or all of a page
 * @page: the page which is affected
 * @offset: start of the range to invalidate
 * @length: length of the range to invalidate
 *
 * 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 int offset,
		       unsigned int length)
{
	void (*invalidatepage)(struct page *, unsigned int, unsigned int);

	invalidatepage = page->mapping->a_ops->invalidatepage;
#ifdef CONFIG_BLOCK
	if (!invalidatepage)
		invalidatepage = block_invalidatepage;
#endif
	if (invalidatepage)
		(*invalidatepage)(page, offset, length);
}

/*
 * 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 orphaned.  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 int
truncate_complete_page(struct address_space *mapping, struct page *page)
{
	if (page->mapping != mapping)
		return -EIO;

	if (page_has_private(page))
		do_invalidatepage(page, 0, PAGE_CACHE_SIZE);

	cancel_dirty_page(page, PAGE_CACHE_SIZE);

	ClearPageMappedToDisk(page);
	delete_from_page_cache(page);
	return 0;
}

/*
 * 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 (page_has_private(page) && !try_to_release_page(page, 0))
		return 0;

	ret = remove_mapping(mapping, page);

	return ret;
}

int truncate_inode_page(struct address_space *mapping, struct page *page)
{
	if (page_mapped(page)) {
		unmap_mapping_range(mapping,
				   (loff_t)page->index << PAGE_CACHE_SHIFT,
				   PAGE_CACHE_SIZE, 0);
	}
	return truncate_complete_page(mapping, page);
}

/*
 * Used to get rid of pages on hardware memory corruption.
 */
int generic_error_remove_page(struct address_space *mapping, struct page *page)
{
	if (!mapping)
		return -EINVAL;
	/*
	 * Only punch for normal data pages for now.
	 * Handling other types like directories would need more auditing.
	 */
	if (!S_ISREG(mapping->host->i_mode))
		return -EIO;
	return truncate_inode_page(mapping, page);
}
EXPORT_SYMBOL(generic_error_remove_page);

/*
 * Safely invalidate one page from its pagecache mapping.
 * It only drops clean, unused pages. The page must be locked.
 *
 * Returns 1 if the page is successfully invalidated, otherwise 0.
 */
int invalidate_inode_page(struct page *page)
{
	struct address_space *mapping = page_mapping(page);
	if (!mapping)
		return 0;
	if (PageDirty(page) || PageWriteback(page))
		return 0;
	if (page_mapped(page))
		return 0;
	return invalidate_complete_page(mapping, page);
}

/**
 * truncate_inode_pages_range - truncate range of pages specified by start & end byte offsets
 * @mapping: mapping to truncate
 * @lstart: offset from which to truncate
 * @lend: offset to which to truncate (inclusive)
 *
 * Truncate the page cache, removing the pages that are between
 * specified offsets (and zeroing out partial pages
 * if lstart or lend + 1 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.
 *
 * 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.
 *
 * Note that since ->invalidatepage() accepts range to invalidate
 * truncate_inode_pages_range is able to handle cases where lend + 1 is not
 * page aligned properly.
 */
void truncate_inode_pages_range(struct address_space *mapping,
				loff_t lstart, loff_t lend)
{
	pgoff_t		start;		/* inclusive */
	pgoff_t		end;		/* exclusive */
	unsigned int	partial_start;	/* inclusive */
	unsigned int	partial_end;	/* exclusive */
	struct pagevec	pvec;
	pgoff_t		indices[PAGEVEC_SIZE];
	pgoff_t		index;
	int		i;

	cleancache_invalidate_inode(mapping