//.........这里部分代码省略.........
			 * because we have a reference on the page.
			 */
			if (page->index > end) {
				/*
				 * can't be range_cyclic (1st pass) because
				 * end == -1 in that case.
				 */
				done = 1;
				break;
			}

			done_index = page->index + 1;
			//页面加锁
			lock_page(page);

			/*
			 * Page truncated or invalidated. We can freely skip it
			 * then, even for data integrity operations: the page
			 * has disappeared concurrently, so there could be no
			 * real expectation of this data interity operation
			 * even if there is now a new, dirty page at the same
			 * pagecache address.
			 */
			 /*由于在加锁过程中可能其它进程对页面做过改动，因此要做以下判断*/
			if (unlikely(page->mapping != mapping)) {//页面无效
continue_unlock:
				unlock_page(page);
				continue;
			}

			if (!PageDirty(page)) {//页面回写完成，I_DIRTY标志已经清除。
				/* someone wrote it for us */
				goto continue_unlock;
			}

			if (PageWriteback(page)) {//页面正在回写中，那要根据sync_mode采取策略
				if (wbc->sync_mode != WB_SYNC_NONE)
					wait_on_page_writeback(page);//要等待正在回写完成后才继续
				else
					goto continue_unlock;
			}

			BUG_ON(PageWriteback(page));
			if (!clear_page_dirty_for_io(page))
				goto continue_unlock;

			trace_wbc_writepage(wbc, mapping->backing_dev_info);
			//开始回写"脏"页面
			ret = (*writepage)(page, wbc, data);
			if (unlikely(ret)) {
				if (ret == AOP_WRITEPAGE_ACTIVATE) {
					unlock_page(page);
					ret = 0;
				} else {
					/*
					 * done_index is set past this page,
					 * so media errors will not choke
					 * background writeout for the entire
					 * file. This has consequences for
					 * range_cyclic semantics (ie. it may
					 * not be suitable for data integrity
					 * writeout).
					 */
					done = 1;
					break;
				}
			}

			/*
			 * We stop writing back only if we are not doing
			 * integrity sync. In case of integrity sync we have to
			 * keep going until we have written all the pages
			 * we tagged for writeback prior to entering this loop.
			 */
			/*页面写成功后，递减计数器*/
			if (--wbc->nr_to_write <= 0 &&
			    wbc->sync_mode == WB_SYNC_NONE) {
				done = 1;
				break;
			}
		}
		pagevec_release(&pvec);
		cond_resched();
	}
	if (!cycled && !done) {
		/*
		 * range_cyclic:
		 * We hit the last page and there is more work to be done: wrap
		 * back to the start of the file
		 */
		cycled = 1;
		index = 0;
		end = writeback_index - 1;
		goto retry;
	}
	if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
		mapping->writeback_index = done_index;

	return ret;
}

static int wrapfs_writepage(struct page *page, struct writeback_control *wbc)
{
        int err = -EIO;
        struct inode *inode;
        struct inode *lower_inode;
        struct page *lower_page;
        struct address_space *lower_mapping; /* lower inode mapping */
        gfp_t mask;

        /*printk(KERN_ALERT "in writepage() \n");*/

        BUG_ON(!PageUptodate(page));
        inode = page->mapping->host;
        /* if no lower inode, nothing to do */
        if (!inode || !WRAPFS_I(inode) || WRAPFS_I(inode)->lower_inode) {
                err = 0;
                goto out;
        }
        lower_inode = wrapfs_lower_inode(inode);
        lower_mapping = lower_inode->i_mapping;

        /*
         * find lower page (returns a locked page)
         *
         * We turn off __GFP_FS while we look for or create a new lower
         * page.  This prevents a recursion into the file system code, which
         * under memory pressure conditions could lead to a deadlock.  This
         * is similar to how the loop driver behaves (see loop_set_fd in
         * drivers/block/loop.c).  If we can't find the lower page, we
         * redirty our page and return "success" so that the VM will call us
         * again in the (hopefully near) future.
         */
        mask = mapping_gfp_mask(lower_mapping) & ~(__GFP_FS);
        lower_page = find_or_create_page(lower_mapping, page->index, mask);
        if (!lower_page) {
                err = 0;
                set_page_dirty(page);
                goto out;
        }

        /* copy page data from our upper page to the lower page */
        copy_highpage(lower_page, page);
        flush_dcache_page(lower_page);
        SetPageUptodate(lower_page);
        set_page_dirty(lower_page);

        /*
         * Call lower writepage (expects locked page).  However, if we are
         * called with wbc->for_reclaim, then the VFS/VM just wants to
         * reclaim our page.  Therefore, we don't need to call the lower
         * ->writepage: just copy our data to the lower page (already done
         * above), then mark the lower page dirty and unlock it, and return
         * success.
         */
        if (wbc->for_reclaim) {
                unlock_page(lower_page);
                goto out_release;
        }

        BUG_ON(!lower_mapping->a_ops->writepage);
        wait_on_page_writeback(lower_page); /* prevent multiple writers */
        clear_page_dirty_for_io(lower_page); /* emulate VFS behavior */
        err = lower_mapping->a_ops->writepage(lower_page, wbc);
        if (err < 0)
                goto out_release;

        /*
         * Lower file systems such as ramfs and tmpfs, may return
         * AOP_WRITEPAGE_ACTIVATE so that the VM won't try to (pointlessly)
         * write the page again for a while.  But those lower file systems
         * also set the page dirty bit back again.  Since we successfully
         * copied our page data to the lower page, then the VM will come
         * back to the lower page (directly) and try to flush it.  So we can
         * save the VM the hassle of coming back to our page and trying to
         * flush too.  Therefore, we don't re-dirty our own page, and we
         * never return AOP_WRITEPAGE_ACTIVATE back to the VM (we consider
         * this a success).
         *
         * We also unlock the lower page if the lower ->writepage returned
         * AOP_WRITEPAGE_ACTIVATE.  (This "anomalous" behaviour may be
         * addressed in future shmem/VM code.)
         */
        if (err == AOP_WRITEPAGE_ACTIVATE) {
                err = 0;
                unlock_page(lower_page);
        }

        /* all is well */

        /* lower mtimes have changed: update ours */
        /*	fsstack_copy_inode_size(dentry->d_inode,
				lower_file->f_path.dentry->d_inode);
        fsstack_copy_attr_times(dentry->d_inode,
				lower_file->f_path.dentry->d_inode);	
        */

out_release:
        /* b/c find_or_create_page increased refcnt */
        page_cache_release(lower_page);
out:
//.........这里部分代码省略.........

int f2fs_convert_inline_page(struct dnode_of_data *dn, struct page *page)
{
	struct f2fs_io_info fio = {
		.sbi = F2FS_I_SB(dn->inode),
		.type = DATA,
		.op = REQ_OP_WRITE,
		.op_flags = REQ_SYNC | REQ_PRIO,
		.page = page,
		.encrypted_page = NULL,
	};
	int dirty, err;

	if (!f2fs_exist_data(dn->inode))
		goto clear_out;

	err = f2fs_reserve_block(dn, 0);
	if (err)
		return err;

	f2fs_bug_on(F2FS_P_SB(page), PageWriteback(page));

	read_inline_data(page, dn->inode_page);
	set_page_dirty(page);

	/* clear dirty state */
	dirty = clear_page_dirty_for_io(page);

	/* write data page to try to make data consistent */
	set_page_writeback(page);
	fio.old_blkaddr = dn->data_blkaddr;
	set_inode_flag(dn->inode, FI_HOT_DATA);
	write_data_page(dn, &fio);
	f2fs_wait_on_page_writeback(page, DATA, true);
	if (dirty) {
		inode_dec_dirty_pages(dn->inode);
		remove_dirty_inode(dn->inode);
	}

	/* this converted inline_data should be recovered. */
	set_inode_flag(dn->inode, FI_APPEND_WRITE);

	/* clear inline data and flag after data writeback */
	truncate_inline_inode(dn->inode, dn->inode_page, 0);
	clear_inline_node(dn->inode_page);
clear_out:
	stat_dec_inline_inode(dn->inode);
	clear_inode_flag(dn->inode, FI_INLINE_DATA);
	f2fs_put_dnode(dn);
	return 0;
}

int f2fs_convert_inline_inode(struct inode *inode)
{
	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
	struct dnode_of_data dn;
	struct page *ipage, *page;
	int err = 0;

	if (!f2fs_has_inline_data(inode))
		return 0;

	page = f2fs_grab_cache_page(inode->i_mapping, 0, false);
	if (!page)
		return -ENOMEM;

	f2fs_lock_op(sbi);

	ipage = get_node_page(sbi, inode->i_ino);
	if (IS_ERR(ipage)) {
		err = PTR_ERR(ipage);
		goto out;
	}

	set_new_dnode(&dn, inode, ipage, ipage, 0);

	if (f2fs_has_inline_data(inode))
		err = f2fs_convert_inline_page(&dn, page);

	f2fs_put_dnode(&dn);
out:
	f2fs_unlock_op(sbi);

	f2fs_put_page(page, 1);

	f2fs_balance_fs(sbi, dn.node_changed);

	return err;
}

int f2fs_write_inline_data(struct inode *inode, struct page *page)
{
	void *src_addr, *dst_addr;
	struct dnode_of_data dn;
	int err;

	set_new_dnode(&dn, inode, NULL, NULL, 0);
	err = get_dnode_of_data(&dn, 0, LOOKUP_NODE);
	if (err)
		return err;

//.........这里部分代码省略.........

int write_one_page(struct page *page, int wait)
{
	struct address_space *mapping = page->mapping;
	int ret = 0;
	struct writeback_control wbc = {
		.sync_mode = WB_SYNC_ALL,
		.nr_to_write = 1,
	};

	BUG_ON(!PageLocked(page));

	if (wait)
		wait_on_page_writeback(page);

	if (clear_page_dirty_for_io(page)) {
		page_cache_get(page);
		ret = mapping->a_ops->writepage(page, &wbc);
		if (ret == 0 && wait) {
			wait_on_page_writeback(page);
			if (PageError(page))
				ret = -EIO;
		}
		page_cache_release(page);
	} else {
		unlock_page(page);
	}
	return ret;
}
EXPORT_SYMBOL(write_one_page);

int __set_page_dirty_no_writeback(struct page *page)
{
	if (!PageDirty(page))
		SetPageDirty(page);
	return 0;
}

void account_page_dirtied(struct page *page, struct address_space *mapping)
{
	if (mapping_cap_account_dirty(mapping)) {
		__inc_zone_page_state(page, NR_FILE_DIRTY);
		__inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
		task_dirty_inc(current);
		task_io_account_write(PAGE_CACHE_SIZE);
	}
}

int __set_page_dirty_nobuffers(struct page *page)
{
	if (!TestSetPageDirty(page)) {
		struct address_space *mapping = page_mapping(page);
		struct address_space *mapping2;

		if (!mapping)
			return 1;

		spin_lock_irq(&mapping->tree_lock);
		mapping2 = page_mapping(page);
		if (mapping2) { /* Race with truncate? */
			BUG_ON(mapping2 != mapping);
			WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page));
			account_page_dirtied(page, mapping);
			radix_tree_tag_set(&mapping->page_tree,
				page_index(page), PAGECACHE_TAG_DIRTY);
		}
		spin_unlock_irq(&mapping->tree_lock);
		if (mapping->host) {
			/* !PageAnon && !swapper_space */
			__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
		}
		return 1;
	}
	return 0;
}
EXPORT_SYMBOL(__set_page_dirty_nobuffers);

int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page)
{
	wbc->pages_skipped++;
	return __set_page_dirty_nobuffers(page);
}

static int gfs2_write_jdata_pagevec(struct address_space *mapping,
				    struct writeback_control *wbc,
				    struct pagevec *pvec,
				    int nr_pages, pgoff_t end,
				    pgoff_t *done_index)
{
	struct inode *inode = mapping->host;
	struct gfs2_sbd *sdp = GFS2_SB(inode);
	unsigned nrblocks = nr_pages * (PAGE_CACHE_SIZE/inode->i_sb->s_blocksize);
	int i;
	int ret;

	ret = gfs2_trans_begin(sdp, nrblocks, nrblocks);
	if (ret < 0)
		return ret;

	for(i = 0; i < nr_pages; i++) {
		struct page *page = pvec->pages[i];

		/*
		 * At this point, the page may be truncated or
		 * invalidated (changing page->mapping to NULL), or
		 * even swizzled back from swapper_space to tmpfs file
		 * mapping. However, page->index will not change
		 * because we have a reference on the page.
		 */
		if (page->index > end) {
			/*
			 * can't be range_cyclic (1st pass) because
			 * end == -1 in that case.
			 */
			ret = 1;
			break;
		}

		*done_index = page->index;

		lock_page(page);

		if (unlikely(page->mapping != mapping)) {
continue_unlock:
			unlock_page(page);
			continue;
		}

		if (!PageDirty(page)) {
			/* someone wrote it for us */
			goto continue_unlock;
		}

		if (PageWriteback(page)) {
			if (wbc->sync_mode != WB_SYNC_NONE)
				wait_on_page_writeback(page);
			else
				goto continue_unlock;
		}

		BUG_ON(PageWriteback(page));
		if (!clear_page_dirty_for_io(page))
			goto continue_unlock;

		trace_wbc_writepage(wbc, inode_to_bdi(inode));

		ret = __gfs2_jdata_writepage(page, wbc);
		if (unlikely(ret)) {
			if (ret == AOP_WRITEPAGE_ACTIVATE) {
				unlock_page(page);
				ret = 0;
			} else {

				/*
				 * done_index is set past this page,
				 * so media errors will not choke
				 * background writeout for the entire
				 * file. This has consequences for
				 * range_cyclic semantics (ie. it may
				 * not be suitable for data integrity
				 * writeout).
				 */
				*done_index = page->index + 1;
				ret = 1;
				break;
			}
		}

		/*
		 * We stop writing back only if we are not doing
		 * integrity sync. In case of integrity sync we have to
		 * keep going until we have written all the pages
		 * we tagged for writeback prior to entering this loop.
		 */
		if (--wbc->nr_to_write <= 0 && wbc->sync_mode == WB_SYNC_NONE) {
			ret = 1;
			break;
		}

	}
	gfs2_trans_end(sdp);
	return ret;
}

static int gfs2_write_jdata_pagevec(struct address_space *mapping,
				    struct writeback_control *wbc,
				    struct pagevec *pvec,
				    int nr_pages, pgoff_t end)
{
	struct inode *inode = mapping->host;
	struct gfs2_sbd *sdp = GFS2_SB(inode);
	loff_t i_size = i_size_read(inode);
	pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
	unsigned offset = i_size & (PAGE_CACHE_SIZE-1);
	unsigned nrblocks = nr_pages * (PAGE_CACHE_SIZE/inode->i_sb->s_blocksize);
	struct backing_dev_info *bdi = mapping->backing_dev_info;
	int i;
	int ret;

	ret = gfs2_trans_begin(sdp, nrblocks, nrblocks);
	if (ret < 0)
		return ret;

	for(i = 0; i < nr_pages; i++) {
		struct page *page = pvec->pages[i];

		lock_page(page);

		if (unlikely(page->mapping != mapping)) {
			unlock_page(page);
			continue;
		}

		if (!wbc->range_cyclic && page->index > end) {
			ret = 1;
			unlock_page(page);
			continue;
		}

		if (wbc->sync_mode != WB_SYNC_NONE)
			wait_on_page_writeback(page);

		if (PageWriteback(page) ||
		    !clear_page_dirty_for_io(page)) {
			unlock_page(page);
			continue;
		}

		/* Is the page fully outside i_size? (truncate in progress) */
		if (page->index > end_index || (page->index == end_index && !offset)) {
			page->mapping->a_ops->invalidatepage(page, 0);
			unlock_page(page);
			continue;
		}

		ret = __gfs2_jdata_writepage(page, wbc);

		if (ret || (--(wbc->nr_to_write) <= 0))
			ret = 1;
		if (wbc->nonblocking && bdi_write_congested(bdi)) {
			wbc->encountered_congestion = 1;
			ret = 1;
		}

	}
	gfs2_trans_end(sdp);
	return ret;
}

/*
 * It only removes the dentry from the dentry page,corresponding name
 * entry in name page does not need to be touched during deletion.
 */
void f2fs_delete_entry(struct f2fs_dir_entry *dentry, struct page *page,
						struct inode *inode)
{
	struct	f2fs_dentry_block *dentry_blk;
	unsigned int bit_pos;
	struct address_space *mapping = page->mapping;
	struct inode *dir = mapping->host;
	struct f2fs_sb_info *sbi = F2FS_SB(dir->i_sb);
	int slots = GET_DENTRY_SLOTS(le16_to_cpu(dentry->name_len));
	void *kaddr = page_address(page);
	int i;

	mutex_lock_op(sbi, DENTRY_OPS);

	lock_page(page);
	wait_on_page_writeback(page);

	dentry_blk = (struct f2fs_dentry_block *)kaddr;
	bit_pos = dentry - (struct f2fs_dir_entry *)dentry_blk->dentry;
	for (i = 0; i < slots; i++)
		test_and_clear_bit_le(bit_pos + i, &dentry_blk->dentry_bitmap);

	/* Let's check and deallocate this dentry page */
	bit_pos = find_next_bit_le(&dentry_blk->dentry_bitmap,
			NR_DENTRY_IN_BLOCK,
			0);
	kunmap(page); /* kunmap - pair of f2fs_find_entry */
	set_page_dirty(page);

	dir->i_ctime = dir->i_mtime = CURRENT_TIME;

	if (inode && S_ISDIR(inode->i_mode)) {
		drop_nlink(dir);
		f2fs_write_inode(dir, NULL);
	} else {
		mark_inode_dirty(dir);
	}

	if (inode) {
		inode->i_ctime = CURRENT_TIME;
		drop_nlink(inode);
		if (S_ISDIR(inode->i_mode)) {
			drop_nlink(inode);
			i_size_write(inode, 0);
		}
		f2fs_write_inode(inode, NULL);
		if (inode->i_nlink == 0)
			add_orphan_inode(sbi, inode->i_ino);
	}

	if (bit_pos == NR_DENTRY_IN_BLOCK) {
		truncate_hole(dir, page->index, page->index + 1);
		clear_page_dirty_for_io(page);
		ClearPageUptodate(page);
		dec_page_count(sbi, F2FS_DIRTY_DENTS);
		inode_dec_dirty_dents(dir);
	}
	f2fs_put_page(page, 1);

	mutex_unlock_op(sbi, DENTRY_OPS);
}

//.........这里部分代码省略.........
			}

			done_index = page->index + 1;

			lock_page(page);

			/*
			 * Page truncated or invalidated. We can freely skip it
			 * then, even for data integrity operations: the page
			 * has disappeared concurrently, so there could be no
			 * real expectation of this data interity operation
			 * even if there is now a new, dirty page at the same
			 * pagecache address.
			 */
			if (unlikely(page->mapping != mapping)) {
continue_unlock:
				unlock_page(page);
				continue;
			}

			if (!PageDirty(page)) {
				/* someone wrote it for us */
				goto continue_unlock;
			}

			if (PageWriteback(page)) {
				if (wbc->sync_mode != WB_SYNC_NONE)
					wait_on_page_writeback(page);
				else
					goto continue_unlock;
			}

			BUG_ON(PageWriteback(page));
			if (!clear_page_dirty_for_io(page))
				goto continue_unlock;

			pgs[pgidx++] = page;
		}

		/*trace_wbc_writepage(wbc, mapping->backing_dev_info);*/
		ret = ecryptfs_encrypt_pages(pgs, pgidx);
		//printk("[g-ecryptfs] Info: enc %d pages in writepages\n", pgidx);
		mapping_set_error(mapping, ret);

		for (i = 0; i < nr_pages; i++) {
			page = pvec.pages[i];

			if (unlikely(ret)) {
				if (ret == AOP_WRITEPAGE_ACTIVATE) {
					if (PageLocked(page))
						unlock_page(page);
					ret = 0;
				} else {
					/*
					 * done_index is set past this page,
					 * so media errors will not choke
					 * background writeout for the entire
					 * file. This has consequences for
					 * range_cyclic semantics (ie. it may
					 * not be suitable for data integrity
					 * writeout).
					 */
					done = 1;
					break;
				}
			}

//.........这里部分代码省略.........
			      min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1);
		if (nr_pages == 0) {
			done_index = 0;
			break;
		}

		for (i = 0; i < nr_pages; i++) {
			struct page *page = pvec.pages[i];

			/*
			 * At this point, the page may be truncated or
			 * invalidated (changing page->mapping to NULL), or
			 * even swizzled back from swapper_space to tmpfs file
			 * mapping. However, page->index will not change
			 * because we have a reference on the page.
			 */
			if (page->index > end) {
				/*
				 * can't be range_cyclic (1st pass) because
				 * end == -1 in that case.
				 */
				done = 1;
				break;
			}

			done_index = page->index + 1;

			lock_page(page);

			/*
			 * Page truncated or invalidated. We can freely skip it
			 * then, even for data integrity operations: the page
			 * has disappeared concurrently, so there could be no
			 * real expectation of this data interity operation
			 * even if there is now a new, dirty page at the same
			 * pagecache address.
			 */
			if (unlikely(page->mapping != mapping)) {
continue_unlock:
				unlock_page(page);
				continue;
			}

			if (!PageDirty(page)) {
				/* someone wrote it for us */
				goto continue_unlock;
			}

			if (PageWriteback(page)) {
				if (wbc->sync_mode != WB_SYNC_NONE)
					wait_on_page_writeback(page);
				else
					goto continue_unlock;
			}

			BUG_ON(PageWriteback(page));
			if (!clear_page_dirty_for_io(page))
				goto continue_unlock;

			trace_wbc_writepage(wbc, mapping->backing_dev_info);
			ret = (*writepage)(page, wbc, data);
			if (unlikely(ret)) {
				if (ret == AOP_WRITEPAGE_ACTIVATE) {
					unlock_page(page);
					ret = 0;
				} else {
					/*
					 * done_index is set past this page,
					 * so media errors will not choke
					 * background writeout for the entire
					 * file. This has consequences for
					 * range_cyclic semantics (ie. it may
					 * not be suitable for data integrity
					 * writeout).
					 */
					done = 1;
					break;
				}
			}

			/*
			 * We stop writing back only if we are not doing
			 * integrity sync. In case of integrity sync we have to
			 * keep going until we have written all the pages
			 * we tagged for writeback prior to entering this loop.
			 */
			if (--wbc->nr_to_write <= 0 &&
			    wbc->sync_mode == WB_SYNC_NONE) {
				done = 1;
				break;
			}
		}
		pagevec_release(&pvec);
		cond_resched();
	}
	if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
		mapping->writeback_index = done_index;

	return ret;
}

/*
 * write a region of pages back to the server
 */
static int afs_writepages_region(struct address_space *mapping,
				 struct writeback_control *wbc,
				 pgoff_t index, pgoff_t end, pgoff_t *_next)
{
	struct page *page;
	int ret, n;

	_enter(",,%lx,%lx,", index, end);

	do {
		n = find_get_pages_range_tag(mapping, &index, end,
					PAGECACHE_TAG_DIRTY, 1, &page);
		if (!n)
			break;

		_debug("wback %lx", page->index);

		/*
		 * at this point we hold neither the i_pages lock nor the
		 * page lock: the page may be truncated or invalidated
		 * (changing page->mapping to NULL), or even swizzled
		 * back from swapper_space to tmpfs file mapping
		 */
		ret = lock_page_killable(page);
		if (ret < 0) {
			put_page(page);
			_leave(" = %d", ret);
			return ret;
		}

		if (page->mapping != mapping || !PageDirty(page)) {
			unlock_page(page);
			put_page(page);
			continue;
		}

		if (PageWriteback(page)) {
			unlock_page(page);
			if (wbc->sync_mode != WB_SYNC_NONE)
				wait_on_page_writeback(page);
			put_page(page);
			continue;
		}

		if (!clear_page_dirty_for_io(page))
			BUG();
		ret = afs_write_back_from_locked_page(mapping, wbc, page, end);
		put_page(page);
		if (ret < 0) {
			_leave(" = %d", ret);
			return ret;
		}

		wbc->nr_to_write -= ret;

		cond_resched();
	} while (index < end && wbc->nr_to_write > 0);

	*_next = index;
	_leave(" = 0 [%lx]", *_next);
	return 0;
}

/*
 * Synchronously write back the locked page and any subsequent non-locked dirty
 * pages.
 */
static int afs_write_back_from_locked_page(struct address_space *mapping,
					   struct writeback_control *wbc,
					   struct page *primary_page,
					   pgoff_t final_page)
{
	struct afs_vnode *vnode = AFS_FS_I(mapping->host);
	struct page *pages[8], *page;
	unsigned long count, priv;
	unsigned n, offset, to, f, t;
	pgoff_t start, first, last;
	int loop, ret;

	_enter(",%lx", primary_page->index);

	count = 1;
	if (test_set_page_writeback(primary_page))
		BUG();

	/* Find all consecutive lockable dirty pages that have contiguous
	 * written regions, stopping when we find a page that is not
	 * immediately lockable, is not dirty or is missing, or we reach the
	 * end of the range.
	 */
	start = primary_page->index;
	priv = page_private(primary_page);
	offset = priv & AFS_PRIV_MAX;
	to = priv >> AFS_PRIV_SHIFT;
	trace_afs_page_dirty(vnode, tracepoint_string("store"),
			     primary_page->index, priv);

	WARN_ON(offset == to);
	if (offset == to)
		trace_afs_page_dirty(vnode, tracepoint_string("WARN"),
				     primary_page->index, priv);

	if (start >= final_page ||
	    (to < PAGE_SIZE && !test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags)))
		goto no_more;

	start++;
	do {
		_debug("more %lx [%lx]", start, count);
		n = final_page - start + 1;
		if (n > ARRAY_SIZE(pages))
			n = ARRAY_SIZE(pages);
		n = find_get_pages_contig(mapping, start, ARRAY_SIZE(pages), pages);
		_debug("fgpc %u", n);
		if (n == 0)
			goto no_more;
		if (pages[0]->index != start) {
			do {
				put_page(pages[--n]);
			} while (n > 0);
			goto no_more;
		}

		for (loop = 0; loop < n; loop++) {
			page = pages[loop];
			if (to != PAGE_SIZE &&
			    !test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags))
				break;
			if (page->index > final_page)
				break;
			if (!trylock_page(page))
				break;
			if (!PageDirty(page) || PageWriteback(page)) {
				unlock_page(page);
				break;
			}

			priv = page_private(page);
			f = priv & AFS_PRIV_MAX;
			t = priv >> AFS_PRIV_SHIFT;
			if (f != 0 &&
			    !test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags)) {
				unlock_page(page);
				break;
			}
			to = t;

			trace_afs_page_dirty(vnode, tracepoint_string("store+"),
					     page->index, priv);

			if (!clear_page_dirty_for_io(page))
				BUG();
			if (test_set_page_writeback(page))
				BUG();
			unlock_page(page);
			put_page(page);
		}
		count += loop;
		if (loop < n) {
			for (; loop < n; loop++)
				put_page(pages[loop]);
			goto no_more;
		}
//.........这里部分代码省略.........

/* Two pass sync: first using WB_SYNC_NONE, then WB_SYNC_ALL */
static int nfs_write_mapping(struct address_space *mapping, int how)
{
	struct writeback_control wbc = {
		.bdi = mapping->backing_dev_info,
		.sync_mode = WB_SYNC_ALL,
		.nr_to_write = LONG_MAX,
		.range_start = 0,
		.range_end = LLONG_MAX,
	};

	return __nfs_write_mapping(mapping, &wbc, how);
}

/*
 * flush the inode to disk.
 */
int nfs_wb_all(struct inode *inode)
{
	return nfs_write_mapping(inode->i_mapping, 0);
}

int nfs_wb_nocommit(struct inode *inode)
{
	return nfs_write_mapping(inode->i_mapping, FLUSH_NOCOMMIT);
}

int nfs_wb_page_cancel(struct inode *inode, struct page *page)
{
	struct nfs_page *req;
	loff_t range_start = page_offset(page);
	loff_t range_end = range_start + (loff_t)(PAGE_CACHE_SIZE - 1);
	struct writeback_control wbc = {
		.bdi = page->mapping->backing_dev_info,
		.sync_mode = WB_SYNC_ALL,
		.nr_to_write = LONG_MAX,
		.range_start = range_start,
		.range_end = range_end,
	};
	int ret = 0;

	BUG_ON(!PageLocked(page));
	for (;;) {
		req = nfs_page_find_request(page);
		if (req == NULL)
			goto out;
		if (test_bit(PG_CLEAN, &req->wb_flags)) {
			nfs_release_request(req);
			break;
		}
		if (nfs_lock_request_dontget(req)) {
			nfs_inode_remove_request(req);
			/*
			 * In case nfs_inode_remove_request has marked the
			 * page as being dirty
			 */
			cancel_dirty_page(page, PAGE_CACHE_SIZE);
			nfs_unlock_request(req);
			break;
		}
		ret = nfs_wait_on_request(req);
		if (ret < 0)
			goto out;
	}
	if (!PagePrivate(page))
		return 0;
	ret = nfs_sync_mapping_wait(page->mapping, &wbc, FLUSH_INVALIDATE);
out:
	return ret;
}

static int nfs_wb_page_priority(struct inode *inode, struct page *page,
				int how)
{
	loff_t range_start = page_offset(page);
	loff_t range_end = range_start + (loff_t)(PAGE_CACHE_SIZE - 1);
	struct writeback_control wbc = {
		.bdi = page->mapping->backing_dev_info,
		.sync_mode = WB_SYNC_ALL,
		.nr_to_write = LONG_MAX,
		.range_start = range_start,
		.range_end = range_end,
	};
	int ret;

	do {
		if (clear_page_dirty_for_io(page)) {
			ret = nfs_writepage_locked(page, &wbc);
			if (ret < 0)
				goto out_error;
		} else if (!PagePrivate(page))
			break;
		ret = nfs_sync_mapping_wait(page->mapping, &wbc, how);
		if (ret < 0)
			goto out_error;
	} while (PagePrivate(page));
	return 0;
out_error:
	__mark_inode_dirty(inode, I_DIRTY_PAGES);
	return ret;
//.........这里部分代码省略.........

//.........这里部分代码省略.........
			cycled = 0;
		end = -1;
	} else {
		index = wbc->range_start >> PAGE_CACHE_SHIFT;
		end = wbc->range_end >> PAGE_CACHE_SHIFT;
		if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
			range_whole = 1;
		cycled = 1; /* ignore range_cyclic tests */
	}
	if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
		tag = PAGECACHE_TAG_TOWRITE;
	else
		tag = PAGECACHE_TAG_DIRTY;
retry:
	if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
		tag_pages_for_writeback(mapping, index, end);
	done_index = index;
	while (!done && (index <= end)) {
		int i;

		nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, tag,
			      min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1);
		if (nr_pages == 0)
			break;

		for (i = 0; i < nr_pages; i++) {
			struct page *page = pvec.pages[i];

			if (page->index > end) {
				done = 1;
				break;
			}

			done_index = page->index;

			lock_page(page);

			if (unlikely(page->mapping != mapping)) {
continue_unlock:
				unlock_page(page);
				continue;
			}

			if (!PageDirty(page)) {
				/* someone wrote it for us */
				goto continue_unlock;
			}

			if (step == is_cold_data(page))
				goto continue_unlock;

			if (PageWriteback(page)) {
				if (wbc->sync_mode != WB_SYNC_NONE)
					f2fs_wait_on_page_writeback(page, DATA);
				else
					goto continue_unlock;
			}

			BUG_ON(PageWriteback(page));
			if (!clear_page_dirty_for_io(page))
				goto continue_unlock;

			ret = (*writepage)(page, wbc, data);
			if (unlikely(ret)) {
				if (ret == AOP_WRITEPAGE_ACTIVATE) {
					unlock_page(page);
					ret = 0;
				} else {
					done_index = page->index + 1;
					done = 1;
					break;
				}
			}

			if (--wbc->nr_to_write <= 0 &&
			    wbc->sync_mode == WB_SYNC_NONE) {
				done = 1;
				break;
			}
		}
		pagevec_release(&pvec);
		cond_resched();
	}

	if (step < 1) {
		step++;
		goto next;
	}

	if (!cycled && !done) {
		cycled = 1;
		index = 0;
		end = writeback_index - 1;
		goto retry;
	}
	if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
		mapping->writeback_index = done_index;

	return ret;
}

int f2fs_convert_inline_page(struct dnode_of_data *dn, struct page *page)
{
	void *src_addr, *dst_addr;
	struct f2fs_io_info fio = {
		.type = DATA,
		.rw = WRITE_SYNC | REQ_PRIO,
	};
	int dirty, err;

	f2fs_bug_on(F2FS_I_SB(dn->inode), page->index);

	if (!f2fs_exist_data(dn->inode))
		goto clear_out;

	err = f2fs_reserve_block(dn, 0);
	if (err)
		return err;

	f2fs_wait_on_page_writeback(page, DATA);

	if (PageUptodate(page))
		goto no_update;

	zero_user_segment(page, MAX_INLINE_DATA, PAGE_CACHE_SIZE);

	/* Copy the whole inline data block */
	src_addr = inline_data_addr(dn->inode_page);
	dst_addr = kmap_atomic(page);
	memcpy(dst_addr, src_addr, MAX_INLINE_DATA);
	flush_dcache_page(page);
	kunmap_atomic(dst_addr);
	SetPageUptodate(page);
no_update:
	/* clear dirty state */
	dirty = clear_page_dirty_for_io(page);

	/* write data page to try to make data consistent */
	set_page_writeback(page);
	fio.blk_addr = dn->data_blkaddr;
	write_data_page(page, dn, &fio);
	update_extent_cache(dn);
	f2fs_wait_on_page_writeback(page, DATA);
	if (dirty)
		inode_dec_dirty_pages(dn->inode);

	/* this converted inline_data should be recovered. */
	set_inode_flag(F2FS_I(dn->inode), FI_APPEND_WRITE);

	/* clear inline data and flag after data writeback */
	truncate_inline_data(dn->inode_page);
clear_out:
	stat_dec_inline_inode(dn->inode);
	f2fs_clear_inline_inode(dn->inode);
	sync_inode_page(dn);
	f2fs_put_dnode(dn);
	return 0;
}

int f2fs_convert_inline_inode(struct inode *inode)
{
	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
	struct dnode_of_data dn;
	struct page *ipage, *page;
	int err = 0;

	page = grab_cache_page(inode->i_mapping, 0);
	if (!page)
		return -ENOMEM;

	f2fs_lock_op(sbi);

	ipage = get_node_page(sbi, inode->i_ino);
	if (IS_ERR(ipage)) {
		err = PTR_ERR(ipage);
		goto out;
	}

	set_new_dnode(&dn, inode, ipage, ipage, 0);

	if (f2fs_has_inline_data(inode))
		err = f2fs_convert_inline_page(&dn, page);

	f2fs_put_dnode(&dn);
out:
	f2fs_unlock_op(sbi);

	f2fs_put_page(page, 1);
	return err;
}

int f2fs_write_inline_data(struct inode *inode, struct page *page)
{
	void *src_addr, *dst_addr;
	struct dnode_of_data dn;
	int err;

	set_new_dnode(&dn, inode, NULL, NULL, 0);
	err = get_dnode_of_data(&dn, 0, LOOKUP_NODE);
	if (err)
		return err;
//.........这里部分代码省略.........

/**
 * write_cache_pages - walk the list of dirty pages of the given address space and write all of them.
 * @mapping: address space structure to write
 * @wbc: subtract the number of written pages from *@wbc->nr_to_write
 * @writepage: function called for each page
 * @data: data passed to writepage function
 *
 * If a page is already under I/O, write_cache_pages() skips it, even
 * if it's dirty.  This is desirable behaviour for memory-cleaning writeback,
 * but it is INCORRECT for data-integrity system calls such as fsync().  fsync()
 * and msync() need to guarantee that all the data which was dirty at the time
 * the call was made get new I/O started against them.  If wbc->sync_mode is
 * WB_SYNC_ALL then we were called for data integrity and we must wait for
 * existing IO to complete.
 */
int write_cache_pages(struct address_space *mapping,
		      struct writeback_control *wbc, writepage_t writepage,
		      void *data)
{
	struct backing_dev_info *bdi = mapping->backing_dev_info;
	int ret = 0;
	int done = 0;
	struct pagevec pvec;
	int nr_pages;
	pgoff_t index;
	pgoff_t end;		/* Inclusive */
	int scanned = 0;
	int range_whole = 0;
	long nr_to_write = wbc->nr_to_write;

	if (wbc->nonblocking && bdi_write_congested(bdi)) {
		wbc->encountered_congestion = 1;
		return 0;
	}

	pagevec_init(&pvec, 0);
	if (wbc->range_cyclic) {
		index = mapping->writeback_index; /* Start from prev offset */
		end = -1;
	} else {
		index = wbc->range_start >> PAGE_CACHE_SHIFT;
		end = wbc->range_end >> PAGE_CACHE_SHIFT;
		if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
			range_whole = 1;
		scanned = 1;
	}
retry:
	while (!done && (index <= end) &&
	       (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
					      PAGECACHE_TAG_DIRTY,
					      min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1))) {
		unsigned i;

		scanned = 1;
		for (i = 0; i < nr_pages; i++) {
			struct page *page = pvec.pages[i];

			/*
			 * At this point we hold neither mapping->tree_lock nor
			 * lock on the page itself: the page may be truncated or
			 * invalidated (changing page->mapping to NULL), or even
			 * swizzled back from swapper_space to tmpfs file
			 * mapping
			 */
			lock_page(page);

			if (unlikely(page->mapping != mapping)) {
				unlock_page(page);
				continue;
			}

			if (!wbc->range_cyclic && page->index > end) {
				done = 1;
				unlock_page(page);
				continue;
			}

			if (wbc->sync_mode != WB_SYNC_NONE)
				wait_on_page_writeback(page);

			if (PageWriteback(page) ||
			    !clear_page_dirty_for_io(page)) {
				unlock_page(page);
				continue;
			}

			ret = (*writepage)(page, wbc, data);

			if (unlikely(ret == AOP_WRITEPAGE_ACTIVATE)) {
				unlock_page(page);
				ret = 0;
			}
			if (ret || (--nr_to_write <= 0))
				done = 1;
			if (wbc->nonblocking && bdi_write_congested(bdi)) {
				wbc->encountered_congestion = 1;
				done = 1;
			}
		}
		pagevec_release(&pvec);
//.........这里部分代码省略.........

static int wrapfs_writepage(struct page *page, struct writeback_control *wbc)
{
	int err = -EIO;
	struct inode *inode;
	struct inode *lower_inode;
	struct page *lower_page;
	struct address_space *lower_mapping; /* lower inode mapping */
	gfp_t mask;
	char *lower_page_data = NULL;
/*#ifdef WRAPFS_CRYPTO
	char *enc_buf = NULL;
#endif*/
	wrapfs_debug_aops(
		WRAPFS_SB(page->mapping->host->i_sb)->wrapfs_debug_a_ops, "");
	wrapfs_debug("");
	BUG_ON(!PageUptodate(page));
	wrapfs_debug("");
	inode = page->mapping->host;

	/* if no lower inode, nothing to do */
	if (!inode || !WRAPFS_I(inode) || WRAPFS_I(inode)->lower_inode) {
		err = 0;
		goto out;
	}
	lower_inode = wrapfs_lower_inode(inode);
	lower_mapping = lower_inode->i_mapping;

	/*
	 * find lower page (returns a locked page)
	 *
	 * We turn off __GFP_FS while we look for or create a new lower
	 * page.  This prevents a recursion into the file system code, which
	 * under memory pressure conditions could lead to a deadlock.  This
	 * is similar to how the loop driver behaves (see loop_set_fd in
	 * drivers/block/loop.c).  If we can't find the lower page, we
	 * redirty our page and return "success" so that the VM will call us
	 * again in the (hopefully near) future.
	 */
	mask = mapping_gfp_mask(lower_mapping) & ~(__GFP_FS);
	lower_page = find_or_create_page(lower_mapping, page->index, mask);
	if (!lower_page) {
		err = 0;
		set_page_dirty(page);
		goto out;
	}
	lower_page_data = (char *)kmap(lower_page);

	/* copy page data from our upper page to the lower page */
	copy_highpage(lower_page, page);
	flush_dcache_page(lower_page);
	SetPageUptodate(lower_page);
	set_page_dirty(lower_page);

/*#ifdef WRAPFS_CRYPTO
	enc_buf = kmalloc(PAGE_CACHE_SIZE, GFP_KERNEL);
	if (enc_buf == NULL) {
		wrapfs_debug("No memory!!");
		err = -ENOMEM;
		goto out_release;
	}
	err = my_encrypt(lower_page_data, PAGE_CACHE_SIZE, enc_buf,
			PAGE_CACHE_SIZE,
			WRAPFS_SB(inode->i_sb)->key,
			WRAPFS_CRYPTO_KEY_LEN);
	if (err < 0) {
		wrapfs_debug("encrypt error!!");
		kfree(enc_buf);
		err = -EINVAL;
		goto out_release;
	}
	memcpy(lower_page_data, enc_buf, PAGE_CACHE_SIZE);
	kfree(enc_buf);
#endif*/

	/*
	 * Call lower writepage (expects locked page).  However, if we are
	 * called with wbc->for_reclaim, then the VFS/VM just wants to
	 * reclaim our page.  Therefore, we don't need to call the lower
	 * ->writepage: just copy our data to the lower page (already done
	 * above), then mark the lower page dirty and unlock it, and return
	 * success.
	 */
	/*if (wbc->for_reclaim) {
		unlock_page(lower_page);
		goto out_release;
	}*/

	BUG_ON(!lower_mapping->a_ops->writepage);
	wait_on_page_writeback(lower_page); /* prevent multiple writers */
	clear_page_dirty_for_io(lower_page); /* emulate VFS behavior */
	err = lower_mapping->a_ops->writepage(lower_page, wbc);
	if (err < 0)
		goto out_release;

	/*
	 * Lower file systems such as ramfs and tmpfs, may return
	 * AOP_WRITEPAGE_ACTIVATE so that the VM won't try to (pointlessly)
	 * write the page again for a while.  But those lower file systems
	 * also set the page dirty bit back again.  Since we successfully
	 * copied our page data to the lower page, then the VM will come
//.........这里部分代码省略.........