fs/f2fs/data.c - maze/linux - Git at Google

 /**
  * fs/f2fs/data.c
  *
  * Copyright (c) 2012 Samsung Electronics Co., Ltd.
  *             http://www.samsung.com/
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  */
 #include <linux/fs.h>
 #include <linux/f2fs_fs.h>
 #include <linux/buffer_head.h>
 #include <linux/mpage.h>
 #include <linux/writeback.h>
 #include <linux/backing-dev.h>
 #include <linux/blkdev.h>
 #include <linux/bio.h>

 #include "f2fs.h"
 #include "node.h"
 #include "segment.h"

 /**
  * Lock ordering for the change of data block address:
  * ->data_page
  *  ->node_page
  *    update block addresses in the node page
  */
 static void __set_data_blkaddr(struct dnode_of_data *dn, block_t new_addr)
 {
 	struct f2fs_node *rn;
 	__le32 *addr_array;
 	struct page *node_page = dn->node_page;
 	unsigned int ofs_in_node = dn->ofs_in_node;

 	wait_on_page_writeback(node_page);

 	rn = (struct f2fs_node *)page_address(node_page);

 	/* Get physical address of data block */
 	addr_array = blkaddr_in_node(rn);
 	addr_array[ofs_in_node] = cpu_to_le32(new_addr);
 	set_page_dirty(node_page);
 }

 int reserve_new_block(struct dnode_of_data *dn)
 {
 	struct f2fs_sb_info *sbi = F2FS_SB(dn->inode->i_sb);

 	if (is_inode_flag_set(F2FS_I(dn->inode), FI_NO_ALLOC))
 		return -EPERM;
 	if (!inc_valid_block_count(sbi, dn->inode, 1))
 		return -ENOSPC;

 	__set_data_blkaddr(dn, NEW_ADDR);
 	dn->data_blkaddr = NEW_ADDR;
 	sync_inode_page(dn);
 	return 0;
 }

 static int check_extent_cache(struct inode *inode, pgoff_t pgofs,
 					struct buffer_head *bh_result)
 {
 	struct f2fs_inode_info *fi = F2FS_I(inode);
 	struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
 	pgoff_t start_fofs, end_fofs;
 	block_t start_blkaddr;

 	read_lock(&fi->ext.ext_lock);
 	if (fi->ext.len == 0) {
 		read_unlock(&fi->ext.ext_lock);
 		return 0;
 	}

 	sbi->total_hit_ext++;
 	start_fofs = fi->ext.fofs;
 	end_fofs = fi->ext.fofs + fi->ext.len - 1;
 	start_blkaddr = fi->ext.blk_addr;

 	if (pgofs >= start_fofs && pgofs <= end_fofs) {
 		unsigned int blkbits = inode->i_sb->s_blocksize_bits;
 		size_t count;

 		clear_buffer_new(bh_result);
 		map_bh(bh_result, inode->i_sb,
 				start_blkaddr + pgofs - start_fofs);
 		count = end_fofs - pgofs + 1;
 		if (count < (UINT_MAX >> blkbits))
 			bh_result->b_size = (count << blkbits);
 		else
 			bh_result->b_size = UINT_MAX;

 		sbi->read_hit_ext++;
 		read_unlock(&fi->ext.ext_lock);
 		return 1;
 	}
 	read_unlock(&fi->ext.ext_lock);
 	return 0;
 }

 void update_extent_cache(block_t blk_addr, struct dnode_of_data *dn)
 {
 	struct f2fs_inode_info *fi = F2FS_I(dn->inode);
 	pgoff_t fofs, start_fofs, end_fofs;
 	block_t start_blkaddr, end_blkaddr;

 	BUG_ON(blk_addr == NEW_ADDR);
 	fofs = start_bidx_of_node(ofs_of_node(dn->node_page)) + dn->ofs_in_node;

 	/* Update the page address in the parent node */
 	__set_data_blkaddr(dn, blk_addr);

 	write_lock(&fi->ext.ext_lock);

 	start_fofs = fi->ext.fofs;
 	end_fofs = fi->ext.fofs + fi->ext.len - 1;
 	start_blkaddr = fi->ext.blk_addr;
 	end_blkaddr = fi->ext.blk_addr + fi->ext.len - 1;

 	/* Drop and initialize the matched extent */
 	if (fi->ext.len == 1 && fofs == start_fofs)
 		fi->ext.len = 0;

 	/* Initial extent */
 	if (fi->ext.len == 0) {
 		if (blk_addr != NULL_ADDR) {
 			fi->ext.fofs = fofs;
 			fi->ext.blk_addr = blk_addr;
 			fi->ext.len = 1;
 		}
 		goto end_update;
 	}

 	/* Frone merge */
 	if (fofs == start_fofs - 1 && blk_addr == start_blkaddr - 1) {
 		fi->ext.fofs--;
 		fi->ext.blk_addr--;
 		fi->ext.len++;
 		goto end_update;
 	}

 	/* Back merge */
 	if (fofs == end_fofs + 1 && blk_addr == end_blkaddr + 1) {
 		fi->ext.len++;
 		goto end_update;
 	}

 	/* Split the existing extent */
 	if (fi->ext.len > 1 &&
 		fofs >= start_fofs && fofs <= end_fofs) {
 		if ((end_fofs - fofs) < (fi->ext.len >> 1)) {
 			fi->ext.len = fofs - start_fofs;
 		} else {
 			fi->ext.fofs = fofs + 1;
 			fi->ext.blk_addr = start_blkaddr +
 					fofs - start_fofs + 1;
 			fi->ext.len -= fofs - start_fofs + 1;
 		}
 		goto end_update;
 	}
 	write_unlock(&fi->ext.ext_lock);
 	return;

 end_update:
 	write_unlock(&fi->ext.ext_lock);
 	sync_inode_page(dn);
 	return;
 }

 struct page *find_data_page(struct inode *inode, pgoff_t index)
 {
 	struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
 	struct address_space *mapping = inode->i_mapping;
 	struct dnode_of_data dn;
 	struct page *page;
 	int err;

 	page = find_get_page(mapping, index);
 	if (page && PageUptodate(page))
 		return page;
 	f2fs_put_page(page, 0);

 	set_new_dnode(&dn, inode, NULL, NULL, 0);
 	err = get_dnode_of_data(&dn, index, RDONLY_NODE);
 	if (err)
 		return ERR_PTR(err);
 	f2fs_put_dnode(&dn);

 	if (dn.data_blkaddr == NULL_ADDR)
 		return ERR_PTR(-ENOENT);

 	/* By fallocate(), there is no cached page, but with NEW_ADDR */
 	if (dn.data_blkaddr == NEW_ADDR)
 		return ERR_PTR(-EINVAL);

 	page = grab_cache_page(mapping, index);
 	if (!page)
 		return ERR_PTR(-ENOMEM);

 	err = f2fs_readpage(sbi, page, dn.data_blkaddr, READ_SYNC);
 	if (err) {
 		f2fs_put_page(page, 1);
 		return ERR_PTR(err);
 	}
 	unlock_page(page);
 	return page;
 }

 /**
  * If it tries to access a hole, return an error.
  * Because, the callers, functions in dir.c and GC, should be able to know
  * whether this page exists or not.
  */
 struct page *get_lock_data_page(struct inode *inode, pgoff_t index)
 {
 	struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
 	struct address_space *mapping = inode->i_mapping;
 	struct dnode_of_data dn;
 	struct page *page;
 	int err;

 	set_new_dnode(&dn, inode, NULL, NULL, 0);
 	err = get_dnode_of_data(&dn, index, RDONLY_NODE);
 	if (err)
 		return ERR_PTR(err);
 	f2fs_put_dnode(&dn);

 	if (dn.data_blkaddr == NULL_ADDR)
 		return ERR_PTR(-ENOENT);

 	page = grab_cache_page(mapping, index);
 	if (!page)
 		return ERR_PTR(-ENOMEM);

 	if (PageUptodate(page))
 		return page;

 	BUG_ON(dn.data_blkaddr == NEW_ADDR);
 	BUG_ON(dn.data_blkaddr == NULL_ADDR);

 	err = f2fs_readpage(sbi, page, dn.data_blkaddr, READ_SYNC);
 	if (err) {
 		f2fs_put_page(page, 1);
 		return ERR_PTR(err);
 	}
 	return page;
 }

 /**
  * Caller ensures that this data page is never allocated.
  * A new zero-filled data page is allocated in the page cache.
  */
 struct page *get_new_data_page(struct inode *inode, pgoff_t index,
 						bool new_i_size)
 {
 	struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
 	struct address_space *mapping = inode->i_mapping;
 	struct page *page;
 	struct dnode_of_data dn;
 	int err;

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

 	if (dn.data_blkaddr == NULL_ADDR) {
 		if (reserve_new_block(&dn)) {
 			f2fs_put_dnode(&dn);
 			return ERR_PTR(-ENOSPC);
 		}
 	}
 	f2fs_put_dnode(&dn);

 	page = grab_cache_page(mapping, index);
 	if (!page)
 		return ERR_PTR(-ENOMEM);

 	if (PageUptodate(page))
 		return page;

 	if (dn.data_blkaddr == NEW_ADDR) {
 		zero_user_segment(page, 0, PAGE_CACHE_SIZE);
 	} else {
 		err = f2fs_readpage(sbi, page, dn.data_blkaddr, READ_SYNC);
 		if (err) {
 			f2fs_put_page(page, 1);
 			return ERR_PTR(err);
 		}
 	}
 	SetPageUptodate(page);

 	if (new_i_size &&
 		i_size_read(inode) < ((index + 1) << PAGE_CACHE_SHIFT)) {
 		i_size_write(inode, ((index + 1) << PAGE_CACHE_SHIFT));
 		mark_inode_dirty_sync(inode);
 	}
 	return page;
 }

 static void read_end_io(struct bio *bio, int err)
 {
 	const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
 	struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;

 	do {
 		struct page *page = bvec->bv_page;

 		if (--bvec >= bio->bi_io_vec)
 			prefetchw(&bvec->bv_page->flags);

 		if (uptodate) {
 			SetPageUptodate(page);
 		} else {
 			ClearPageUptodate(page);
 			SetPageError(page);
 		}
 		unlock_page(page);
 	} while (bvec >= bio->bi_io_vec);
 	kfree(bio->bi_private);
 	bio_put(bio);
 }

 /**
  * Fill the locked page with data located in the block address.
  * Read operation is synchronous, and caller must unlock the page.
  */
 int f2fs_readpage(struct f2fs_sb_info *sbi, struct page *page,
 					block_t blk_addr, int type)
 {
 	struct block_device *bdev = sbi->sb->s_bdev;
 	bool sync = (type == READ_SYNC);
 	struct bio *bio;

 	/* This page can be already read by other threads */
 	if (PageUptodate(page)) {
 		if (!sync)
 			unlock_page(page);
 		return 0;
 	}

 	down_read(&sbi->bio_sem);

 	/* Allocate a new bio */
 	bio = f2fs_bio_alloc(bdev, blk_addr << (sbi->log_blocksize - 9),
 				1, GFP_NOFS | __GFP_HIGH);

 	/* Initialize the bio */
 	bio->bi_end_io = read_end_io;
 	if (bio_add_page(bio, page, PAGE_CACHE_SIZE, 0) < PAGE_CACHE_SIZE) {
 		kfree(bio->bi_private);
 		bio_put(bio);
 		up_read(&sbi->bio_sem);
 		return -EFAULT;
 	}

 	submit_bio(type, bio);
 	up_read(&sbi->bio_sem);

 	/* wait for read completion if sync */
 	if (sync) {
 		lock_page(page);
 		if (PageError(page))
 			return -EIO;
 	}
 	return 0;
 }

 /**
  * This function should be used by the data read flow only where it
  * does not check the "create" flag that indicates block allocation.
  * The reason for this special functionality is to exploit VFS readahead
  * mechanism.
  */
 static int get_data_block_ro(struct inode *inode, sector_t iblock,
 			struct buffer_head *bh_result, int create)
 {
 	unsigned int blkbits = inode->i_sb->s_blocksize_bits;
 	unsigned maxblocks = bh_result->b_size >> blkbits;
 	struct dnode_of_data dn;
 	pgoff_t pgofs;
 	int err;

 	/* Get the page offset from the block offset(iblock) */
 	pgofs =	(pgoff_t)(iblock >> (PAGE_CACHE_SHIFT - blkbits));

 	if (check_extent_cache(inode, pgofs, bh_result))
 		return 0;

 	/* When reading holes, we need its node page */
 	set_new_dnode(&dn, inode, NULL, NULL, 0);
 	err = get_dnode_of_data(&dn, pgofs, RDONLY_NODE);
 	if (err)
 		return (err == -ENOENT) ? 0 : err;

 	/* It does not support data allocation */
 	BUG_ON(create);

 	if (dn.data_blkaddr != NEW_ADDR && dn.data_blkaddr != NULL_ADDR) {
 		int i;
 		unsigned int end_offset;

 		end_offset = IS_INODE(dn.node_page) ?
 				ADDRS_PER_INODE :
 				ADDRS_PER_BLOCK;

 		clear_buffer_new(bh_result);

 		/* Give more consecutive addresses for the read ahead */
 		for (i = 0; i < end_offset - dn.ofs_in_node; i++)
 			if (((datablock_addr(dn.node_page,
 							dn.ofs_in_node + i))
 				!= (dn.data_blkaddr + i)) || maxblocks == i)
 				break;
 		map_bh(bh_result, inode->i_sb, dn.data_blkaddr);
 		bh_result->b_size = (i << blkbits);
 	}
 	f2fs_put_dnode(&dn);
 	return 0;
 }

 static int f2fs_read_data_page(struct file *file, struct page *page)
 {
 	return mpage_readpage(page, get_data_block_ro);
 }

 static int f2fs_read_data_pages(struct file *file,
 			struct address_space *mapping,
 			struct list_head *pages, unsigned nr_pages)
 {
 	return mpage_readpages(mapping, pages, nr_pages, get_data_block_ro);
 }

 int do_write_data_page(struct page *page)
 {
 	struct inode *inode = page->mapping->host;
 	struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
 	block_t old_blk_addr, new_blk_addr;
 	struct dnode_of_data dn;
 	int err = 0;

 	set_new_dnode(&dn, inode, NULL, NULL, 0);
 	err = get_dnode_of_data(&dn, page->index, RDONLY_NODE);
 	if (err)
 		return err;

 	old_blk_addr = dn.data_blkaddr;

 	/* This page is already truncated */
 	if (old_blk_addr == NULL_ADDR)
 		goto out_writepage;

 	set_page_writeback(page);

 	/*
 	 * If current allocation needs SSR,
 	 * it had better in-place writes for updated data.
 	 */
 	if (old_blk_addr != NEW_ADDR && !is_cold_data(page) &&
 				need_inplace_update(inode)) {
 		rewrite_data_page(F2FS_SB(inode->i_sb), page,
 						old_blk_addr);
 	} else {
 		write_data_page(inode, page, &dn,
 				old_blk_addr, &new_blk_addr);
 		update_extent_cache(new_blk_addr, &dn);
 		F2FS_I(inode)->data_version =
 			le64_to_cpu(F2FS_CKPT(sbi)->checkpoint_ver);
 	}
 out_writepage:
 	f2fs_put_dnode(&dn);
 	return err;
 }

 static int f2fs_write_data_page(struct page *page,
 					struct writeback_control *wbc)
 {
 	struct inode *inode = page->mapping->host;
 	struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
 	loff_t i_size = i_size_read(inode);
 	const pgoff_t end_index = ((unsigned long long) i_size)
 							>> PAGE_CACHE_SHIFT;
 	unsigned offset;
 	int err = 0;

 	if (page->index < end_index)
 		goto out;

 	/*
 	 * If the offset is out-of-range of file size,
 	 * this page does not have to be written to disk.
 	 */
 	offset = i_size & (PAGE_CACHE_SIZE - 1);
 	if ((page->index >= end_index + 1) || !offset) {
 		if (S_ISDIR(inode->i_mode)) {
 			dec_page_count(sbi, F2FS_DIRTY_DENTS);
 			inode_dec_dirty_dents(inode);
 		}
 		goto unlock_out;
 	}

 	zero_user_segment(page, offset, PAGE_CACHE_SIZE);
 out:
 	if (sbi->por_doing)
 		goto redirty_out;

 	if (wbc->for_reclaim && !S_ISDIR(inode->i_mode) && !is_cold_data(page))
 		goto redirty_out;

 	mutex_lock_op(sbi, DATA_WRITE);
 	if (S_ISDIR(inode->i_mode)) {
 		dec_page_count(sbi, F2FS_DIRTY_DENTS);
 		inode_dec_dirty_dents(inode);
 	}
 	err = do_write_data_page(page);
 	if (err && err != -ENOENT) {
 		wbc->pages_skipped++;
 		set_page_dirty(page);
 	}
 	mutex_unlock_op(sbi, DATA_WRITE);

 	if (wbc->for_reclaim)
 		f2fs_submit_bio(sbi, DATA, true);

 	if (err == -ENOENT)
 		goto unlock_out;

 	clear_cold_data(page);
 	unlock_page(page);

 	if (!wbc->for_reclaim && !S_ISDIR(inode->i_mode))
 		f2fs_balance_fs(sbi);
 	return 0;

 unlock_out:
 	unlock_page(page);
 	return (err == -ENOENT) ? 0 : err;

 redirty_out:
 	wbc->pages_skipped++;
 	set_page_dirty(page);
 	return AOP_WRITEPAGE_ACTIVATE;
 }

 #define MAX_DESIRED_PAGES_WP	4096

 static int f2fs_write_data_pages(struct address_space *mapping,
 			    struct writeback_control *wbc)
 {
 	struct inode *inode = mapping->host;
 	struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
 	int ret;
 	long excess_nrtw = 0, desired_nrtw;

 	if (wbc->nr_to_write < MAX_DESIRED_PAGES_WP) {
 		desired_nrtw = MAX_DESIRED_PAGES_WP;
 		excess_nrtw = desired_nrtw - wbc->nr_to_write;
 		wbc->nr_to_write = desired_nrtw;
 	}

 	if (!S_ISDIR(inode->i_mode))
 		mutex_lock(&sbi->writepages);
 	ret = generic_writepages(mapping, wbc);
 	if (!S_ISDIR(inode->i_mode))
 		mutex_unlock(&sbi->writepages);
 	f2fs_submit_bio(sbi, DATA, (wbc->sync_mode == WB_SYNC_ALL));

 	remove_dirty_dir_inode(inode);

 	wbc->nr_to_write -= excess_nrtw;
 	return ret;
 }

 static int f2fs_write_begin(struct file *file, struct address_space *mapping,
 		loff_t pos, unsigned len, unsigned flags,
 		struct page **pagep, void **fsdata)
 {
 	struct inode *inode = mapping->host;
 	struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
 	struct page *page;
 	pgoff_t index = ((unsigned long long) pos) >> PAGE_CACHE_SHIFT;
 	struct dnode_of_data dn;
 	int err = 0;

 	/* for nobh_write_end */
 	*fsdata = NULL;

 	f2fs_balance_fs(sbi);

 	page = grab_cache_page_write_begin(mapping, index, flags);
 	if (!page)
 		return -ENOMEM;
 	*pagep = page;

 	mutex_lock_op(sbi, DATA_NEW);

 	set_new_dnode(&dn, inode, NULL, NULL, 0);
 	err = get_dnode_of_data(&dn, index, 0);
 	if (err) {
 		mutex_unlock_op(sbi, DATA_NEW);
 		f2fs_put_page(page, 1);
 		return err;
 	}

 	if (dn.data_blkaddr == NULL_ADDR) {
 		err = reserve_new_block(&dn);
 		if (err) {
 			f2fs_put_dnode(&dn);
 			mutex_unlock_op(sbi, DATA_NEW);
 			f2fs_put_page(page, 1);
 			return err;
 		}
 	}
 	f2fs_put_dnode(&dn);

 	mutex_unlock_op(sbi, DATA_NEW);

 	if ((len == PAGE_CACHE_SIZE) || PageUptodate(page))
 		return 0;

 	if ((pos & PAGE_CACHE_MASK) >= i_size_read(inode)) {
 		unsigned start = pos & (PAGE_CACHE_SIZE - 1);
 		unsigned end = start + len;

 		/* Reading beyond i_size is simple: memset to zero */
 		zero_user_segments(page, 0, start, end, PAGE_CACHE_SIZE);
 		return 0;
 	}

 	if (dn.data_blkaddr == NEW_ADDR) {
 		zero_user_segment(page, 0, PAGE_CACHE_SIZE);
 	} else {
 		err = f2fs_readpage(sbi, page, dn.data_blkaddr, READ_SYNC);
 		if (err) {
 			f2fs_put_page(page, 1);
 			return err;
 		}
 	}
 	SetPageUptodate(page);
 	clear_cold_data(page);
 	return 0;
 }

 static ssize_t f2fs_direct_IO(int rw, struct kiocb *iocb,
 		const struct iovec *iov, loff_t offset, unsigned long nr_segs)
 {
 	struct file *file = iocb->ki_filp;
 	struct inode *inode = file->f_mapping->host;

 	if (rw == WRITE)
 		return 0;

 	/* Needs synchronization with the cleaner */
 	return blockdev_direct_IO(rw, iocb, inode, iov, offset, nr_segs,
 						  get_data_block_ro);
 }

 static void f2fs_invalidate_data_page(struct page *page, unsigned long offset)
 {
 	struct inode *inode = page->mapping->host;
 	struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
 	if (S_ISDIR(inode->i_mode) && PageDirty(page)) {
 		dec_page_count(sbi, F2FS_DIRTY_DENTS);
 		inode_dec_dirty_dents(inode);
 	}
 	ClearPagePrivate(page);
 }

 static int f2fs_release_data_page(struct page *page, gfp_t wait)
 {
 	ClearPagePrivate(page);
 	return 0;
 }

 static int f2fs_set_data_page_dirty(struct page *page)
 {
 	struct address_space *mapping = page->mapping;
 	struct inode *inode = mapping->host;

 	SetPageUptodate(page);
 	if (!PageDirty(page)) {
 		__set_page_dirty_nobuffers(page);
 		set_dirty_dir_page(inode, page);
 		return 1;
 	}
 	return 0;
 }

 const struct address_space_operations f2fs_dblock_aops = {
 	.readpage	= f2fs_read_data_page,
 	.readpages	= f2fs_read_data_pages,
 	.writepage	= f2fs_write_data_page,
 	.writepages	= f2fs_write_data_pages,
 	.write_begin	= f2fs_write_begin,
 	.write_end	= nobh_write_end,
 	.set_page_dirty	= f2fs_set_data_page_dirty,
 	.invalidatepage	= f2fs_invalidate_data_page,
 	.releasepage	= f2fs_release_data_page,
 	.direct_IO	= f2fs_direct_IO,
 };
	/**
	* fs/f2fs/data.c
	*
	* Copyright (c) 2012 Samsung Electronics Co., Ltd.
	* http://www.samsung.com/
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 as
	* published by the Free Software Foundation.
	*/
	#include <linux/fs.h>
	#include <linux/f2fs_fs.h>
	#include <linux/buffer_head.h>
	#include <linux/mpage.h>
	#include <linux/writeback.h>
	#include <linux/backing-dev.h>
	#include <linux/blkdev.h>
	#include <linux/bio.h>

	#include "f2fs.h"
	#include "node.h"
	#include "segment.h"

	/**
	* Lock ordering for the change of data block address:
	* ->data_page
	* ->node_page
	* update block addresses in the node page
	*/
	static void __set_data_blkaddr(struct dnode_of_data *dn, block_t new_addr)
	{
	struct f2fs_node *rn;
	__le32 *addr_array;
	struct page *node_page = dn->node_page;
	unsigned int ofs_in_node = dn->ofs_in_node;

	wait_on_page_writeback(node_page);

	rn = (struct f2fs_node *)page_address(node_page);

	/* Get physical address of data block */
	addr_array = blkaddr_in_node(rn);
	addr_array[ofs_in_node] = cpu_to_le32(new_addr);
	set_page_dirty(node_page);
	}

	int reserve_new_block(struct dnode_of_data *dn)
	{
	struct f2fs_sb_info *sbi = F2FS_SB(dn->inode->i_sb);

	if (is_inode_flag_set(F2FS_I(dn->inode), FI_NO_ALLOC))
	return -EPERM;
	if (!inc_valid_block_count(sbi, dn->inode, 1))
	return -ENOSPC;

	__set_data_blkaddr(dn, NEW_ADDR);
	dn->data_blkaddr = NEW_ADDR;
	sync_inode_page(dn);
	return 0;
	}

	static int check_extent_cache(struct inode *inode, pgoff_t pgofs,
	struct buffer_head *bh_result)
	{
	struct f2fs_inode_info *fi = F2FS_I(inode);
	struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
	pgoff_t start_fofs, end_fofs;
	block_t start_blkaddr;

	read_lock(&fi->ext.ext_lock);
	if (fi->ext.len == 0) {
	read_unlock(&fi->ext.ext_lock);
	return 0;
	}

	sbi->total_hit_ext++;
	start_fofs = fi->ext.fofs;
	end_fofs = fi->ext.fofs + fi->ext.len - 1;
	start_blkaddr = fi->ext.blk_addr;

	if (pgofs >= start_fofs && pgofs <= end_fofs) {
	unsigned int blkbits = inode->i_sb->s_blocksize_bits;
	size_t count;

	clear_buffer_new(bh_result);
	map_bh(bh_result, inode->i_sb,
	start_blkaddr + pgofs - start_fofs);
	count = end_fofs - pgofs + 1;
	if (count < (UINT_MAX >> blkbits))
	bh_result->b_size = (count << blkbits);
	else
	bh_result->b_size = UINT_MAX;

	sbi->read_hit_ext++;
	read_unlock(&fi->ext.ext_lock);
	return 1;
	}
	read_unlock(&fi->ext.ext_lock);
	return 0;
	}

	void update_extent_cache(block_t blk_addr, struct dnode_of_data *dn)
	{
	struct f2fs_inode_info *fi = F2FS_I(dn->inode);
	pgoff_t fofs, start_fofs, end_fofs;
	block_t start_blkaddr, end_blkaddr;

	BUG_ON(blk_addr == NEW_ADDR);
	fofs = start_bidx_of_node(ofs_of_node(dn->node_page)) + dn->ofs_in_node;

	/* Update the page address in the parent node */
	__set_data_blkaddr(dn, blk_addr);

	write_lock(&fi->ext.ext_lock);

	start_fofs = fi->ext.fofs;
	end_fofs = fi->ext.fofs + fi->ext.len - 1;
	start_blkaddr = fi->ext.blk_addr;
	end_blkaddr = fi->ext.blk_addr + fi->ext.len - 1;

	/* Drop and initialize the matched extent */
	if (fi->ext.len == 1 && fofs == start_fofs)
	fi->ext.len = 0;

	/* Initial extent */
	if (fi->ext.len == 0) {
	if (blk_addr != NULL_ADDR) {
	fi->ext.fofs = fofs;
	fi->ext.blk_addr = blk_addr;
	fi->ext.len = 1;
	}
	goto end_update;
	}

	/* Frone merge */
	if (fofs == start_fofs - 1 && blk_addr == start_blkaddr - 1) {
	fi->ext.fofs--;
	fi->ext.blk_addr--;
	fi->ext.len++;
	goto end_update;
	}

	/* Back merge */
	if (fofs == end_fofs + 1 && blk_addr == end_blkaddr + 1) {
	fi->ext.len++;
	goto end_update;
	}

	/* Split the existing extent */
	if (fi->ext.len > 1 &&
	fofs >= start_fofs && fofs <= end_fofs) {
	if ((end_fofs - fofs) < (fi->ext.len >> 1)) {
	fi->ext.len = fofs - start_fofs;
	} else {
	fi->ext.fofs = fofs + 1;
	fi->ext.blk_addr = start_blkaddr +
	fofs - start_fofs + 1;
	fi->ext.len -= fofs - start_fofs + 1;
	}
	goto end_update;
	}
	write_unlock(&fi->ext.ext_lock);
	return;

	end_update:
	write_unlock(&fi->ext.ext_lock);
	sync_inode_page(dn);
	return;
	}

	struct page find_data_page(struct inode inode, pgoff_t index)
	{
	struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
	struct address_space *mapping = inode->i_mapping;
	struct dnode_of_data dn;
	struct page *page;
	int err;

	page = find_get_page(mapping, index);
	if (page && PageUptodate(page))
	return page;
	f2fs_put_page(page, 0);

	set_new_dnode(&dn, inode, NULL, NULL, 0);
	err = get_dnode_of_data(&dn, index, RDONLY_NODE);
	if (err)
	return ERR_PTR(err);
	f2fs_put_dnode(&dn);

	if (dn.data_blkaddr == NULL_ADDR)
	return ERR_PTR(-ENOENT);

	/* By fallocate(), there is no cached page, but with NEW_ADDR */
	if (dn.data_blkaddr == NEW_ADDR)
	return ERR_PTR(-EINVAL);

	page = grab_cache_page(mapping, index);
	if (!page)
	return ERR_PTR(-ENOMEM);

	err = f2fs_readpage(sbi, page, dn.data_blkaddr, READ_SYNC);
	if (err) {
	f2fs_put_page(page, 1);
	return ERR_PTR(err);
	}
	unlock_page(page);
	return page;
	}

	/**
	* If it tries to access a hole, return an error.
	* Because, the callers, functions in dir.c and GC, should be able to know
	* whether this page exists or not.
	*/
	struct page get_lock_data_page(struct inode inode, pgoff_t index)
	{
	struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
	struct address_space *mapping = inode->i_mapping;
	struct dnode_of_data dn;
	struct page *page;
	int err;

	set_new_dnode(&dn, inode, NULL, NULL, 0);
	err = get_dnode_of_data(&dn, index, RDONLY_NODE);
	if (err)
	return ERR_PTR(err);
	f2fs_put_dnode(&dn);

	if (dn.data_blkaddr == NULL_ADDR)
	return ERR_PTR(-ENOENT);

	page = grab_cache_page(mapping, index);
	if (!page)
	return ERR_PTR(-ENOMEM);

	if (PageUptodate(page))
	return page;

	BUG_ON(dn.data_blkaddr == NEW_ADDR);
	BUG_ON(dn.data_blkaddr == NULL_ADDR);

	err = f2fs_readpage(sbi, page, dn.data_blkaddr, READ_SYNC);
	if (err) {
	f2fs_put_page(page, 1);
	return ERR_PTR(err);
	}
	return page;
	}

	/**
	* Caller ensures that this data page is never allocated.
	* A new zero-filled data page is allocated in the page cache.
	*/
	struct page get_new_data_page(struct inode inode, pgoff_t index,
	bool new_i_size)
	{
	struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
	struct address_space *mapping = inode->i_mapping;
	struct page *page;
	struct dnode_of_data dn;
	int err;

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

	if (dn.data_blkaddr == NULL_ADDR) {
	if (reserve_new_block(&dn)) {
	f2fs_put_dnode(&dn);
	return ERR_PTR(-ENOSPC);
	}
	}
	f2fs_put_dnode(&dn);

	page = grab_cache_page(mapping, index);
	if (!page)
	return ERR_PTR(-ENOMEM);

	if (PageUptodate(page))
	return page;

	if (dn.data_blkaddr == NEW_ADDR) {
	zero_user_segment(page, 0, PAGE_CACHE_SIZE);
	} else {
	err = f2fs_readpage(sbi, page, dn.data_blkaddr, READ_SYNC);
	if (err) {
	f2fs_put_page(page, 1);
	return ERR_PTR(err);
	}
	}
	SetPageUptodate(page);

	if (new_i_size &&
	i_size_read(inode) < ((index + 1) << PAGE_CACHE_SHIFT)) {
	i_size_write(inode, ((index + 1) << PAGE_CACHE_SHIFT));
	mark_inode_dirty_sync(inode);
	}
	return page;
	}

	static void read_end_io(struct bio *bio, int err)
	{
	const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
	struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;

	do {
	struct page *page = bvec->bv_page;

	if (--bvec >= bio->bi_io_vec)
	prefetchw(&bvec->bv_page->flags);

	if (uptodate) {
	SetPageUptodate(page);
	} else {
	ClearPageUptodate(page);
	SetPageError(page);
	}
	unlock_page(page);
	} while (bvec >= bio->bi_io_vec);
	kfree(bio->bi_private);
	bio_put(bio);
	}

	/**
	* Fill the locked page with data located in the block address.
	* Read operation is synchronous, and caller must unlock the page.
	*/
	int f2fs_readpage(struct f2fs_sb_info sbi, struct page page,
	block_t blk_addr, int type)
	{
	struct block_device *bdev = sbi->sb->s_bdev;
	bool sync = (type == READ_SYNC);
	struct bio *bio;

	/* This page can be already read by other threads */
	if (PageUptodate(page)) {
	if (!sync)
	unlock_page(page);
	return 0;
	}

	down_read(&sbi->bio_sem);

	/* Allocate a new bio */
	bio = f2fs_bio_alloc(bdev, blk_addr << (sbi->log_blocksize - 9),
	1, GFP_NOFS \| __GFP_HIGH);

	/* Initialize the bio */
	bio->bi_end_io = read_end_io;
	if (bio_add_page(bio, page, PAGE_CACHE_SIZE, 0) < PAGE_CACHE_SIZE) {
	kfree(bio->bi_private);
	bio_put(bio);
	up_read(&sbi->bio_sem);
	return -EFAULT;
	}

	submit_bio(type, bio);
	up_read(&sbi->bio_sem);

	/* wait for read completion if sync */
	if (sync) {
	lock_page(page);
	if (PageError(page))
	return -EIO;
	}
	return 0;
	}

	/**
	* This function should be used by the data read flow only where it
	* does not check the "create" flag that indicates block allocation.
	* The reason for this special functionality is to exploit VFS readahead
	* mechanism.
	*/
	static int get_data_block_ro(struct inode *inode, sector_t iblock,
	struct buffer_head *bh_result, int create)
	{
	unsigned int blkbits = inode->i_sb->s_blocksize_bits;
	unsigned maxblocks = bh_result->b_size >> blkbits;
	struct dnode_of_data dn;
	pgoff_t pgofs;
	int err;

	/* Get the page offset from the block offset(iblock) */
	pgofs = (pgoff_t)(iblock >> (PAGE_CACHE_SHIFT - blkbits));

	if (check_extent_cache(inode, pgofs, bh_result))
	return 0;

	/* When reading holes, we need its node page */
	set_new_dnode(&dn, inode, NULL, NULL, 0);
	err = get_dnode_of_data(&dn, pgofs, RDONLY_NODE);
	if (err)
	return (err == -ENOENT) ? 0 : err;

	/* It does not support data allocation */
	BUG_ON(create);

	if (dn.data_blkaddr != NEW_ADDR && dn.data_blkaddr != NULL_ADDR) {
	int i;
	unsigned int end_offset;

	end_offset = IS_INODE(dn.node_page) ?
	ADDRS_PER_INODE :
	ADDRS_PER_BLOCK;

	clear_buffer_new(bh_result);

	/* Give more consecutive addresses for the read ahead */
	for (i = 0; i < end_offset - dn.ofs_in_node; i++)
	if (((datablock_addr(dn.node_page,
	dn.ofs_in_node + i))
	!= (dn.data_blkaddr + i)) \|\| maxblocks == i)
	break;
	map_bh(bh_result, inode->i_sb, dn.data_blkaddr);
	bh_result->b_size = (i << blkbits);
	}
	f2fs_put_dnode(&dn);
	return 0;
	}

	static int f2fs_read_data_page(struct file file, struct page page)
	{
	return mpage_readpage(page, get_data_block_ro);
	}

	static int f2fs_read_data_pages(struct file *file,
	struct address_space *mapping,
	struct list_head *pages, unsigned nr_pages)
	{
	return mpage_readpages(mapping, pages, nr_pages, get_data_block_ro);
	}

	int do_write_data_page(struct page *page)
	{
	struct inode *inode = page->mapping->host;
	struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
	block_t old_blk_addr, new_blk_addr;
	struct dnode_of_data dn;
	int err = 0;

	set_new_dnode(&dn, inode, NULL, NULL, 0);
	err = get_dnode_of_data(&dn, page->index, RDONLY_NODE);
	if (err)
	return err;

	old_blk_addr = dn.data_blkaddr;

	/* This page is already truncated */
	if (old_blk_addr == NULL_ADDR)
	goto out_writepage;

	set_page_writeback(page);

	/*
	* If current allocation needs SSR,
	* it had better in-place writes for updated data.
	*/
	if (old_blk_addr != NEW_ADDR && !is_cold_data(page) &&
	need_inplace_update(inode)) {
	rewrite_data_page(F2FS_SB(inode->i_sb), page,
	old_blk_addr);
	} else {
	write_data_page(inode, page, &dn,
	old_blk_addr, &new_blk_addr);
	update_extent_cache(new_blk_addr, &dn);
	F2FS_I(inode)->data_version =
	le64_to_cpu(F2FS_CKPT(sbi)->checkpoint_ver);
	}
	out_writepage:
	f2fs_put_dnode(&dn);
	return err;
	}

	static int f2fs_write_data_page(struct page *page,
	struct writeback_control *wbc)
	{
	struct inode *inode = page->mapping->host;
	struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
	loff_t i_size = i_size_read(inode);
	const pgoff_t end_index = ((unsigned long long) i_size)
	>> PAGE_CACHE_SHIFT;
	unsigned offset;
	int err = 0;

	if (page->index < end_index)
	goto out;

	/*
	* If the offset is out-of-range of file size,
	* this page does not have to be written to disk.
	*/
	offset = i_size & (PAGE_CACHE_SIZE - 1);
	if ((page->index >= end_index + 1) \|\| !offset) {
	if (S_ISDIR(inode->i_mode)) {
	dec_page_count(sbi, F2FS_DIRTY_DENTS);
	inode_dec_dirty_dents(inode);
	}
	goto unlock_out;
	}

	zero_user_segment(page, offset, PAGE_CACHE_SIZE);
	out:
	if (sbi->por_doing)
	goto redirty_out;

	if (wbc->for_reclaim && !S_ISDIR(inode->i_mode) && !is_cold_data(page))
	goto redirty_out;

	mutex_lock_op(sbi, DATA_WRITE);
	if (S_ISDIR(inode->i_mode)) {
	dec_page_count(sbi, F2FS_DIRTY_DENTS);
	inode_dec_dirty_dents(inode);
	}
	err = do_write_data_page(page);
	if (err && err != -ENOENT) {
	wbc->pages_skipped++;
	set_page_dirty(page);
	}
	mutex_unlock_op(sbi, DATA_WRITE);

	if (wbc->for_reclaim)
	f2fs_submit_bio(sbi, DATA, true);

	if (err == -ENOENT)
	goto unlock_out;

	clear_cold_data(page);
	unlock_page(page);

	if (!wbc->for_reclaim && !S_ISDIR(inode->i_mode))
	f2fs_balance_fs(sbi);
	return 0;

	unlock_out:
	unlock_page(page);
	return (err == -ENOENT) ? 0 : err;

	redirty_out:
	wbc->pages_skipped++;
	set_page_dirty(page);
	return AOP_WRITEPAGE_ACTIVATE;
	}

	#define MAX_DESIRED_PAGES_WP 4096

	static int f2fs_write_data_pages(struct address_space *mapping,
	struct writeback_control *wbc)
	{
	struct inode *inode = mapping->host;
	struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
	int ret;
	long excess_nrtw = 0, desired_nrtw;

	if (wbc->nr_to_write < MAX_DESIRED_PAGES_WP) {
	desired_nrtw = MAX_DESIRED_PAGES_WP;
	excess_nrtw = desired_nrtw - wbc->nr_to_write;
	wbc->nr_to_write = desired_nrtw;
	}

	if (!S_ISDIR(inode->i_mode))
	mutex_lock(&sbi->writepages);
	ret = generic_writepages(mapping, wbc);
	if (!S_ISDIR(inode->i_mode))
	mutex_unlock(&sbi->writepages);
	f2fs_submit_bio(sbi, DATA, (wbc->sync_mode == WB_SYNC_ALL));

	remove_dirty_dir_inode(inode);

	wbc->nr_to_write -= excess_nrtw;
	return ret;
	}

	static int f2fs_write_begin(struct file file, struct address_space mapping,
	loff_t pos, unsigned len, unsigned flags,
	struct page pagep, void fsdata)
	{
	struct inode *inode = mapping->host;
	struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
	struct page *page;
	pgoff_t index = ((unsigned long long) pos) >> PAGE_CACHE_SHIFT;
	struct dnode_of_data dn;
	int err = 0;

	/* for nobh_write_end */
	*fsdata = NULL;

	f2fs_balance_fs(sbi);

	page = grab_cache_page_write_begin(mapping, index, flags);
	if (!page)
	return -ENOMEM;
	*pagep = page;

	mutex_lock_op(sbi, DATA_NEW);

	set_new_dnode(&dn, inode, NULL, NULL, 0);
	err = get_dnode_of_data(&dn, index, 0);
	if (err) {
	mutex_unlock_op(sbi, DATA_NEW);
	f2fs_put_page(page, 1);
	return err;
	}

	if (dn.data_blkaddr == NULL_ADDR) {
	err = reserve_new_block(&dn);
	if (err) {
	f2fs_put_dnode(&dn);
	mutex_unlock_op(sbi, DATA_NEW);
	f2fs_put_page(page, 1);
	return err;
	}
	}
	f2fs_put_dnode(&dn);

	mutex_unlock_op(sbi, DATA_NEW);

	if ((len == PAGE_CACHE_SIZE) \|\| PageUptodate(page))
	return 0;

	if ((pos & PAGE_CACHE_MASK) >= i_size_read(inode)) {
	unsigned start = pos & (PAGE_CACHE_SIZE - 1);
	unsigned end = start + len;

	/* Reading beyond i_size is simple: memset to zero */
	zero_user_segments(page, 0, start, end, PAGE_CACHE_SIZE);
	return 0;
	}

	if (dn.data_blkaddr == NEW_ADDR) {
	zero_user_segment(page, 0, PAGE_CACHE_SIZE);
	} else {
	err = f2fs_readpage(sbi, page, dn.data_blkaddr, READ_SYNC);
	if (err) {
	f2fs_put_page(page, 1);
	return err;
	}
	}
	SetPageUptodate(page);
	clear_cold_data(page);
	return 0;
	}

	static ssize_t f2fs_direct_IO(int rw, struct kiocb *iocb,
	const struct iovec *iov, loff_t offset, unsigned long nr_segs)
	{
	struct file *file = iocb->ki_filp;
	struct inode *inode = file->f_mapping->host;

	if (rw == WRITE)
	return 0;

	/* Needs synchronization with the cleaner */
	return blockdev_direct_IO(rw, iocb, inode, iov, offset, nr_segs,
	get_data_block_ro);
	}

	static void f2fs_invalidate_data_page(struct page *page, unsigned long offset)
	{
	struct inode *inode = page->mapping->host;
	struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
	if (S_ISDIR(inode->i_mode) && PageDirty(page)) {
	dec_page_count(sbi, F2FS_DIRTY_DENTS);
	inode_dec_dirty_dents(inode);
	}
	ClearPagePrivate(page);
	}

	static int f2fs_release_data_page(struct page *page, gfp_t wait)
	{
	ClearPagePrivate(page);
	return 0;
	}

	static int f2fs_set_data_page_dirty(struct page *page)
	{
	struct address_space *mapping = page->mapping;
	struct inode *inode = mapping->host;

	SetPageUptodate(page);
	if (!PageDirty(page)) {
	__set_page_dirty_nobuffers(page);
	set_dirty_dir_page(inode, page);
	return 1;
	}
	return 0;
	}

	const struct address_space_operations f2fs_dblock_aops = {
	.readpage = f2fs_read_data_page,
	.readpages = f2fs_read_data_pages,
	.writepage = f2fs_write_data_page,
	.writepages = f2fs_write_data_pages,
	.write_begin = f2fs_write_begin,
	.write_end = nobh_write_end,
	.set_page_dirty = f2fs_set_data_page_dirty,
	.invalidatepage = f2fs_invalidate_data_page,
	.releasepage = f2fs_release_data_page,
	.direct_IO = f2fs_direct_IO,
	};