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path: root/mm/truncate.c

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/*
 * 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/dax.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/shmem_fs.h>
#include <linux/cleancache.h>
#include <linux/rmap.h>
#include "internal.h"

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

	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(&mapping->page_tree, node, slot, NULL,
			     workingset_update_node, mapping);
	mapping->nrexceptional--;
unlock:
	spin_unlock_irq(&mapping->tree_lock);
}

/*
 * Unconditionally remove exceptional entry. Usually called from truncate path.
 */
static void truncate_exceptional_entry(struct address_space *mapping,
				       pgoff_t index, void *entry)
{
	/* Handled by shmem itself */
	if (shmem_mapping(mapping))
		return;

	if (dax_mapping(mapping)) {
		dax_delete_mapping_entry(mapping, index);
		return;
	}
	clear_shadow_entry(mapping, index, entry);
}

/*
 * Invalidate exceptional entry if easily possible. This handles exceptional
 * entries for invalidate_inode_pages().
 */
static int invalidate_exceptional_entry(struct address_space *mapping,
					pgoff_t index, void *entry)
{
	/* Handled by shmem itself, or for DAX we do nothing. */
	if (shmem_mapping(mapping) || dax_mapping(mapping))
		return 1;
	clear_shadow_entry(mapping, index, entry);
	return 1;
}

/*
 * Invalidate exceptional entry if clean. This handles exceptional entries for
 * invalidate_inode_pages2() so for DAX it evicts only clean entries.
 */
static int invalidate_exceptional_entry2(struct address_space *mapping,
					 pgoff_t index, void *entry)
{
	/* Handled by shmem itself */
	if (shmem_mapping(mapping))
		return 1;
	if (dax_mapping(mapping))
		return dax_invalidate_mapping_entry_sync(mapping, index);
	clear_shadow_entry(mapping, index, entry);
	return 1;
}

/**
 * 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);
}

/*
 * 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_SIZE);

	/*
	 * Some filesystems seem to re-dirty the page even after
	 * the VM has canceled the dirty bit (eg ext3 journaling).
	 * Hence dirty accounting check is placed after invalidation.
	 */
	cancel_dirty_page(page);
	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)
{
	loff_t holelen;
	VM_BUG_ON_PAGE(PageTail(page), page);

	holelen = PageTransHuge(page) ? HPAGE_PMD_SIZE : PAGE_SIZE;
	if (page_mapped(page)) {
		unmap_mapping_range(mapping,
				   (loff_t)page->index << PAGE_SHIFT,
				   holelen, 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