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32 results

page_alloc.c

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  • truncate.c 27.65 KiB
    // SPDX-License-Identifier: GPL-2.0-only
    /*
     * 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"
    
    /*
     * Regular page slots are stabilized by the page lock even without the tree
     * itself locked.  These unlocked entries need verification under the tree
     * lock.
     */
    static inline void __clear_shadow_entry(struct address_space *mapping,
    				pgoff_t index, void *entry)
    {
    	XA_STATE(xas, &mapping->i_pages, index);
    
    	xas_set_update(&xas, workingset_update_node);
    	if (xas_load(&xas) != entry)
    		return;
    	xas_store(&xas, NULL);
    	mapping->nrexceptional--;
    }
    
    static void clear_shadow_entry(struct address_space *mapping, pgoff_t index,
    			       void *entry)
    {
    	xa_lock_irq(&mapping->i_pages);
    	__clear_shadow_entry(mapping, index, entry);
    	xa_unlock_irq(&mapping->i_pages);
    }
    
    /*
     * Unconditionally remove exceptional entries. Usually called from truncate
     * path. Note that the pagevec may be altered by this function by removing
     * exceptional entries similar to what pagevec_remove_exceptionals does.
     */
    static void truncate_exceptional_pvec_entries(struct address_space *mapping,
    				struct pagevec *pvec, pgoff_t *indices,
    				pgoff_t end)
    {
    	int i, j;
    	bool dax, lock;
    
    	/* Handled by shmem itself */
    	if (shmem_mapping(mapping))
    		return;
    
    	for (j = 0; j < pagevec_count(pvec); j++)
    		if (xa_is_value(pvec->pages[j]))
    			break;
    
    	if (j == pagevec_count(pvec))
    		return;
    
    	dax = dax_mapping(mapping);
    	lock = !dax && indices[j] < end;
    	if (lock)
    		xa_lock_irq(&mapping->i_pages);
    
    	for (i = j; i < pagevec_count(pvec); i++) {
    		struct page *page = pvec->pages[i];
    		pgoff_t index = indices[i];
    
    		if (!xa_is_value(page)) {
    			pvec->pages[j++] = page;
    			continue;
    		}
    
    		if (index >= end)
    			continue;
    
    		if (unlikely(dax)) {
    			dax_delete_mapping_entry(mapping, index);
    			continue;
    		}
    
    		__clear_shadow_entry(mapping, index, page);
    	}
    
    	if (lock)
    		xa_unlock_irq(&mapping->i_pages);
    	pvec->nr = j;
    }
    
    /*
     * 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 bail 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_cleanup_page(struct address_space *mapping, struct page *page)
    {
    	if (page_mapped(page)) {
    		unsigned int nr = thp_nr_pages(page);
    		unmap_mapping_pages(mapping, page->index, nr, false);
    	}
    
    	if (page_has_private(page))
    		do_invalidatepage(page, 0, thp_size(page));
    
    	/*
    	 * 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);
    }
    
    /*
     * 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)
    {
    	VM_BUG_ON_PAGE(PageTail(page), page);
    
    	if (page->mapping != mapping)
    		return -EIO;
    
    	truncate_cleanup_page(mapping, page);
    	delete_from_page_cache(page);
    	return 0;
    }
    
    /*
     * 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;
    
    	if (mapping->nrpages == 0 && mapping->nrexceptional == 0)
    		goto out;
    
    	/* Offsets within partial pages */
    	partial_start = lstart & (PAGE_SIZE - 1);
    	partial_end = (lend + 1) & (PAGE_SIZE - 1);
    
    	/*
    	 * 'start' and 'end' always covers the range of pages to be fully
    	 * truncated. Partial pages are covered with 'partial_start' at the
    	 * start of the range and 'partial_end' at the end of the range.
    	 * Note that 'end' is exclusive while 'lend' is inclusive.
    	 */
    	start = (lstart + PAGE_SIZE - 1) >> PAGE_SHIFT;
    	if (lend == -1)
    		/*
    		 * lend == -1 indicates end-of-file so we have to set 'end'
    		 * to the highest possible pgoff_t and since the type is
    		 * unsigned we're using -1.
    		 */
    		end = -1;
    	else
    		end = (lend + 1) >> PAGE_SHIFT;
    
    	pagevec_init(&pvec);
    	index = start;
    	while (index < end && pagevec_lookup_entries(&pvec, mapping, index,
    			min(end - index, (pgoff_t)PAGEVEC_SIZE),
    			indices)) {
    		/*
    		 * Pagevec array has exceptional entries and we may also fail
    		 * to lock some pages. So we store pages that can be deleted
    		 * in a new pagevec.
    		 */
    		struct pagevec locked_pvec;
    
    		pagevec_init(&locked_pvec);
    		for (i = 0; i < pagevec_count(&pvec); i++) {
    			struct page *page = pvec.pages[i];
    
    			/* We rely upon deletion not changing page->index */
    			index = indices[i];
    			if (index >= end)
    				break;
    
    			if (xa_is_value(page))
    				continue;
    
    			if (!trylock_page(page))
    				continue;
    			WARN_ON(page_to_index(page) != index);
    			if (PageWriteback(page)) {
    				unlock_page(page);
    				continue;
    			}
    			if (page->mapping != mapping) {
    				unlock_page(page);
    				continue;
    			}
    			pagevec_add(&locked_pvec, page);
    		}
    		for (i = 0; i < pagevec_count(&locked_pvec); i++)
    			truncate_cleanup_page(mapping, locked_pvec.pages[i]);
    		delete_from_page_cache_batch(mapping, &locked_pvec);
    		for (i = 0; i < pagevec_count(&locked_pvec); i++)
    			unlock_page(locked_pvec.pages[i]);
    		truncate_exceptional_pvec_entries(mapping, &pvec, indices, end);
    		pagevec_release(&pvec);
    		cond_resched();
    		index++;
    	}
    	if (partial_start) {
    		struct page *page = find_lock_page(mapping, start - 1);
    		if (page) {
    			unsigned int top = PAGE_SIZE;
    			if (start > end) {
    				/* Truncation within a single page */
    				top = partial_end;
    				partial_end = 0;
    			}
    			wait_on_page_writeback(page);
    			zero_user_segment(page, partial_start, top);
    			cleancache_invalidate_page(mapping, page);
    			if (page_has_private(page))
    				do_invalidatepage(page, partial_start,
    						  top - partial_start);
    			unlock_page(page);
    			put_page(page);
    		}
    	}
    	if (partial_end) {
    		struct page *page = find_lock_page(mapping, end);
    		if (page) {
    			wait_on_page_writeback(page);
    			zero_user_segment(page, 0, partial_end);
    			cleancache_invalidate_page(mapping, page);
    			if (page_has_private(page))
    				do_invalidatepage(page, 0,
    						  partial_end);
    			unlock_page(page);
    			put_page(page);
    		}
    	}
    	/*
    	 * If the truncation happened within a single page no pages
    	 * will be released, just zeroed, so we can bail out now.
    	 */
    	if (start >= end)
    		goto out;
    
    	index = start;
    	for ( ; ; ) {
    		cond_resched();
    		if (!pagevec_lookup_entries(&pvec, mapping, index,
    			min(end - index, (pgoff_t)PAGEVEC_SIZE), indices)) {
    			/* If all gone from start onwards, we're done */
    			if (index == start)
    				break;
    			/* Otherwise restart to make sure all gone */
    			index = start;
    			continue;
    		}
    		if (index == start && indices[0] >= end) {
    			/* All gone out of hole to be punched, we're done */
    			pagevec_remove_exceptionals(&pvec);
    			pagevec_release(&pvec);
    			break;
    		}
    
    		for (i = 0; i < pagevec_count(&pvec); i++) {
    			struct page *page = pvec.pages[i];
    
    			/* We rely upon deletion not changing page->index */
    			index = indices[i];
    			if (index >= end) {
    				/* Restart punch to make sure all gone */
    				index = start - 1;
    				break;
    			}
    
    			if (xa_is_value(page))
    				continue;
    
    			lock_page(page);
    			WARN_ON(page_to_index(page) != index);
    			wait_on_page_writeback(page);
    			truncate_inode_page(mapping, page);
    			unlock_page(page);
    		}
    		truncate_exceptional_pvec_entries(mapping, &pvec, indices, end);
    		pagevec_release(&pvec);
    		index++;
    	}
    
    out:
    	cleancache_invalidate_inode(mapping);
    }
    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.
     *
     * Note: When this function returns, there can be a page in the process of
     * deletion (inside __delete_from_page_cache()) in the specified range.  Thus
     * mapping->nrpages can be non-zero when this function returns even after
     * truncation of the whole mapping.
     */
    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);
    
    /**
     * truncate_inode_pages_final - truncate *all* pages before inode dies
     * @mapping: mapping to truncate
     *
     * Called under (and serialized by) inode->i_mutex.
     *
     * Filesystems have to use this in the .evict_inode path to inform the
     * VM that this is the final truncate and the inode is going away.
     */
    void truncate_inode_pages_final(struct address_space *mapping)
    {
    	unsigned long nrexceptional;
    	unsigned long nrpages;
    
    	/*
    	 * Page reclaim can not participate in regular inode lifetime
    	 * management (can't call iput()) and thus can race with the
    	 * inode teardown.  Tell it when the address space is exiting,
    	 * so that it does not install eviction information after the
    	 * final truncate has begun.
    	 */
    	mapping_set_exiting(mapping);
    
    	/*
    	 * When reclaim installs eviction entries, it increases
    	 * nrexceptional first, then decreases nrpages.  Make sure we see
    	 * this in the right order or we might miss an entry.
    	 */
    	nrpages = mapping->nrpages;
    	smp_rmb();
    	nrexceptional = mapping->nrexceptional;
    
    	if (nrpages || nrexceptional) {
    		/*
    		 * As truncation uses a lockless tree lookup, cycle
    		 * the tree lock to make sure any ongoing tree
    		 * modification that does not see AS_EXITING is
    		 * completed before starting the final truncate.
    		 */
    		xa_lock_irq(&mapping->i_pages);
    		xa_unlock_irq(&mapping->i_pages);
    	}
    
    	/*
    	 * Cleancache needs notification even if there are no pages or shadow
    	 * entries.
    	 */
    	truncate_inode_pages(mapping, 0);
    }
    EXPORT_SYMBOL(truncate_inode_pages_final);
    
    static unsigned long __invalidate_mapping_pages(struct address_space *mapping,
    		pgoff_t start, pgoff_t end, unsigned long *nr_pagevec)
    {
    	pgoff_t indices[PAGEVEC_SIZE];
    	struct pagevec pvec;
    	pgoff_t index = start;
    	unsigned long ret;
    	unsigned long count = 0;
    	int i;
    
    	pagevec_init(&pvec);
    	while (index <= end && pagevec_lookup_entries(&pvec, mapping, index,
    			min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1,
    			indices)) {
    		for (i = 0; i < pagevec_count(&pvec); i++) {
    			struct page *page = pvec.pages[i];
    
    			/* We rely upon deletion not changing page->index */
    			index = indices[i];
    			if (index > end)
    				break;
    
    			if (xa_is_value(page)) {
    				invalidate_exceptional_entry(mapping, index,
    							     page);
    				continue;
    			}
    
    			if (!trylock_page(page))
    				continue;
    
    			WARN_ON(page_to_index(page) != index);
    
    			/* Middle of THP: skip */
    			if (PageTransTail(page)) {
    				unlock_page(page);
    				continue;
    			} else if (PageTransHuge(page)) {
    				index += HPAGE_PMD_NR - 1;
    				i += HPAGE_PMD_NR - 1;
    				/*
    				 * 'end' is in the middle of THP. Don't
    				 * invalidate the page as the part outside of
    				 * 'end' could be still useful.
    				 */
    				if (index > end) {
    					unlock_page(page);
    					continue;
    				}
    
    				/* Take a pin outside pagevec */
    				get_page(page);
    
    				/*
    				 * Drop extra pins before trying to invalidate
    				 * the huge page.
    				 */
    				pagevec_remove_exceptionals(&pvec);
    				pagevec_release(&pvec);
    			}
    
    			ret = invalidate_inode_page(page);
    			unlock_page(page);
    			/*
    			 * Invalidation is a hint that the page is no longer
    			 * of interest and try to speed up its reclaim.
    			 */
    			if (!ret) {
    				deactivate_file_page(page);
    				/* It is likely on the pagevec of a remote CPU */
    				if (nr_pagevec)
    					(*nr_pagevec)++;
    			}
    
    			if (PageTransHuge(page))
    				put_page(page);
    			count += ret;
    		}
    		pagevec_remove_exceptionals(&pvec);
    		pagevec_release(&pvec);
    		cond_resched();
    		index++;
    	}
    	return count;
    }
    
    /**
     * 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.
     *
     * Return: the number of the pages that were invalidated
     */
    unsigned long invalidate_mapping_pages(struct address_space *mapping,
    		pgoff_t start, pgoff_t end)
    {
    	return __invalidate_mapping_pages(mapping, start, end, NULL);
    }
    EXPORT_SYMBOL(invalidate_mapping_pages);
    
    /**
     * invalidate_mapping_pagevec - 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)
     * @nr_pagevec: invalidate failed page number for caller
     *
     * This helper is similar to invalidate_mapping_pages(), except that it accounts
     * for pages that are likely on a pagevec and counts them in @nr_pagevec, which
     * will be used by the caller.
     */
    void invalidate_mapping_pagevec(struct address_space *mapping,
    		pgoff_t start, pgoff_t end, unsigned long *nr_pagevec)
    {
    	__invalidate_mapping_pages(mapping, start, end, nr_pagevec);
    }
    
    /*
     * 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)
    {
    	unsigned long flags;
    
    	if (page->mapping != mapping)
    		return 0;
    
    	if (page_has_private(page) && !try_to_release_page(page, GFP_KERNEL))
    		return 0;
    
    	xa_lock_irqsave(&mapping->i_pages, flags);
    	if (PageDirty(page))
    		goto failed;
    
    	BUG_ON(page_has_private(page));
    	__delete_from_page_cache(page, NULL);
    	xa_unlock_irqrestore(&mapping->i_pages, flags);
    
    	if (mapping->a_ops->freepage)
    		mapping->a_ops->freepage(page);
    
    	put_page(page);	/* pagecache ref */
    	return 1;
    failed:
    	xa_unlock_irqrestore(&mapping->i_pages, flags);
    	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.
     *
     * Return: -EBUSY if any pages could not be invalidated.
     */
    int invalidate_inode_pages2_range(struct address_space *mapping,
    				  pgoff_t start, pgoff_t end)
    {
    	pgoff_t indices[PAGEVEC_SIZE];
    	struct pagevec pvec;
    	pgoff_t index;
    	int i;
    	int ret = 0;
    	int ret2 = 0;
    	int did_range_unmap = 0;
    
    	if (mapping->nrpages == 0 && mapping->nrexceptional == 0)
    		goto out;
    
    	pagevec_init(&pvec);
    	index = start;
    	while (index <= end && pagevec_lookup_entries(&pvec, mapping, index,
    			min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1,
    			indices)) {
    		for (i = 0; i < pagevec_count(&pvec); i++) {
    			struct page *page = pvec.pages[i];
    
    			/* We rely upon deletion not changing page->index */
    			index = indices[i];
    			if (index > end)
    				break;
    
    			if (xa_is_value(page)) {
    				if (!invalidate_exceptional_entry2(mapping,
    								   index, page))
    					ret = -EBUSY;
    				continue;
    			}
    
    			lock_page(page);
    			WARN_ON(page_to_index(page) != index);
    			if (page->mapping != mapping) {
    				unlock_page(page);
    				continue;
    			}
    			wait_on_page_writeback(page);
    			if (page_mapped(page)) {
    				if (!did_range_unmap) {
    					/*
    					 * Zap the rest of the file in one hit.
    					 */
    					unmap_mapping_pages(mapping, index,
    						(1 + end - index), false);
    					did_range_unmap = 1;
    				} else {
    					/*
    					 * Just zap this page
    					 */
    					unmap_mapping_pages(mapping, index,
    								1, false);
    				}
    			}
    			BUG_ON(page_mapped(page));
    			ret2 = do_launder_page(mapping, page);
    			if (ret2 == 0) {
    				if (!invalidate_complete_page2(mapping, page))
    					ret2 = -EBUSY;
    			}
    			if (ret2 < 0)
    				ret = ret2;
    			unlock_page(page);
    		}
    		pagevec_remove_exceptionals(&pvec);
    		pagevec_release(&pvec);
    		cond_resched();
    		index++;
    	}
    	/*
    	 * For DAX we invalidate page tables after invalidating page cache.  We
    	 * could invalidate page tables while invalidating each entry however
    	 * that would be expensive. And doing range unmapping before doesn't
    	 * work as we have no cheap way to find whether page cache entry didn't
    	 * get remapped later.
    	 */
    	if (dax_mapping(mapping)) {
    		unmap_mapping_pages(mapping, start, end - start + 1, false);
    	}
    out:
    	cleancache_invalidate_inode(mapping);
    	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.
     *
     * Return: -EBUSY 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);
    
    /**
     * truncate_pagecache - unmap and remove pagecache that has been truncated
     * @inode: inode
     * @newsize: new file size
     *
     * inode's new i_size must already be written before truncate_pagecache
     * is called.
     *
     * This function should typically be called before the filesystem
     * releases resources associated with the freed range (eg. deallocates
     * blocks). This way, pagecache will always stay logically coherent
     * with on-disk format, and the filesystem would not have to deal with
     * situations such as writepage being called for a page that has already
     * had its underlying blocks deallocated.
     */
    void truncate_pagecache(struct inode *inode, loff_t newsize)
    {
    	struct address_space *mapping = inode->i_mapping;
    	loff_t holebegin = round_up(newsize, PAGE_SIZE);
    
    	/*
    	 * unmap_mapping_range is called twice, first simply for
    	 * efficiency so that truncate_inode_pages does fewer
    	 * single-page unmaps.  However after this first call, and
    	 * before truncate_inode_pages finishes, it is possible for
    	 * private pages to be COWed, which remain after
    	 * truncate_inode_pages finishes, hence the second
    	 * unmap_mapping_range call must be made for correctness.
    	 */
    	unmap_mapping_range(mapping, holebegin, 0, 1);
    	truncate_inode_pages(mapping, newsize);
    	unmap_mapping_range(mapping, holebegin, 0, 1);
    }
    EXPORT_SYMBOL(truncate_pagecache);
    
    /**
     * truncate_setsize - update inode and pagecache for a new file size
     * @inode: inode
     * @newsize: new file size
     *
     * truncate_setsize updates i_size and performs pagecache truncation (if
     * necessary) to @newsize. It will be typically be called from the filesystem's
     * setattr function when ATTR_SIZE is passed in.
     *
     * Must be called with a lock serializing truncates and writes (generally
     * i_mutex but e.g. xfs uses a different lock) and before all filesystem
     * specific block truncation has been performed.
     */
    void truncate_setsize(struct inode *inode, loff_t newsize)
    {
    	loff_t oldsize = inode->i_size;
    
    	i_size_write(inode, newsize);
    	if (newsize > oldsize)
    		pagecache_isize_extended(inode, oldsize, newsize);
    	truncate_pagecache(inode, newsize);
    }
    EXPORT_SYMBOL(truncate_setsize);
    
    /**
     * pagecache_isize_extended - update pagecache after extension of i_size
     * @inode:	inode for which i_size was extended
     * @from:	original inode size
     * @to:		new inode size
     *
     * Handle extension of inode size either caused by extending truncate or by
     * write starting after current i_size. We mark the page straddling current
     * i_size RO so that page_mkwrite() is called on the nearest write access to
     * the page.  This way filesystem can be sure that page_mkwrite() is called on
     * the page before user writes to the page via mmap after the i_size has been
     * changed.
     *
     * The function must be called after i_size is updated so that page fault
     * coming after we unlock the page will already see the new i_size.
     * The function must be called while we still hold i_mutex - this not only
     * makes sure i_size is stable but also that userspace cannot observe new
     * i_size value before we are prepared to store mmap writes at new inode size.
     */
    void pagecache_isize_extended(struct inode *inode, loff_t from, loff_t to)
    {
    	int bsize = i_blocksize(inode);
    	loff_t rounded_from;
    	struct page *page;
    	pgoff_t index;
    
    	WARN_ON(to > inode->i_size);
    
    	if (from >= to || bsize == PAGE_SIZE)
    		return;
    	/* Page straddling @from will not have any hole block created? */
    	rounded_from = round_up(from, bsize);
    	if (to <= rounded_from || !(rounded_from & (PAGE_SIZE - 1)))
    		return;
    
    	index = from >> PAGE_SHIFT;
    	page = find_lock_page(inode->i_mapping, index);
    	/* Page not cached? Nothing to do */
    	if (!page)
    		return;
    	/*
    	 * See clear_page_dirty_for_io() for details why set_page_dirty()
    	 * is needed.
    	 */
    	if (page_mkclean(page))
    		set_page_dirty(page);
    	unlock_page(page);
    	put_page(page);
    }
    EXPORT_SYMBOL(pagecache_isize_extended);
    
    /**
     * truncate_pagecache_range - unmap and remove pagecache that is hole-punched
     * @inode: inode
     * @lstart: offset of beginning of hole
     * @lend: offset of last byte of hole
     *
     * This function should typically be called before the filesystem
     * releases resources associated with the freed range (eg. deallocates
     * blocks). This way, pagecache will always stay logically coherent
     * with on-disk format, and the filesystem would not have to deal with
     * situations such as writepage being called for a page that has already
     * had its underlying blocks deallocated.
     */
    void truncate_pagecache_range(struct inode *inode, loff_t lstart, loff_t lend)
    {
    	struct address_space *mapping = inode->i_mapping;
    	loff_t unmap_start = round_up(lstart, PAGE_SIZE);
    	loff_t unmap_end = round_down(1 + lend, PAGE_SIZE) - 1;
    	/*
    	 * This rounding is currently just for example: unmap_mapping_range
    	 * expands its hole outwards, whereas we want it to contract the hole
    	 * inwards.  However, existing callers of truncate_pagecache_range are
    	 * doing their own page rounding first.  Note that unmap_mapping_range
    	 * allows holelen 0 for all, and we allow lend -1 for end of file.
    	 */
    
    	/*
    	 * Unlike in truncate_pagecache, unmap_mapping_range is called only
    	 * once (before truncating pagecache), and without "even_cows" flag:
    	 * hole-punching should not remove private COWed pages from the hole.
    	 */
    	if ((u64)unmap_end > (u64)unmap_start)
    		unmap_mapping_range(mapping, unmap_start,
    				    1 + unmap_end - unmap_start, 0);
    	truncate_inode_pages_range(mapping, lstart, lend);
    }
    EXPORT_SYMBOL(truncate_pagecache_range);