f2fs: add address space operations for data

This adds address space operations for data.

- F2FS supports readpages(), writepages(), and direct_IO().

- Because of out-of-place writes, f2fs_direct_IO() does not write data in place.
Signed-off-by: NJaegeuk Kim <jaegeuk.kim@samsung.com>

fs/f2fs/data.c

+/**
+ * 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
+
+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,
+};