C++ zero_user_segment函数代码示例

/*
 * Zero an extent within a page vector.  Offset is relative to the
 * start of the first page.
 */
static void zero_page_vector_range(int off, int len, struct page **pages)
{
	int i = off >> PAGE_CACHE_SHIFT;

	off &= ~PAGE_CACHE_MASK;

	dout("zero_page_vector_page %u~%u\n", off, len);

	/* leading partial page? */
	if (off) {
		int end = min((int)PAGE_CACHE_SIZE, off + len);
		dout("zeroing %d %p head from %d\n", i, pages[i],
		     (int)off);
		zero_user_segment(pages[i], off, end);
		len -= (end - off);
		i++;
	}
	while (len >= PAGE_CACHE_SIZE) {
		dout("zeroing %d %p len=%d\n", i, pages[i], len);
		zero_user_segment(pages[i], 0, PAGE_CACHE_SIZE);
		len -= PAGE_CACHE_SIZE;
		i++;
	}
	/* trailing partial page? */
	if (len) {
		dout("zeroing %d %p tail to %d\n", i, pages[i], (int)len);
		zero_user_segment(pages[i], 0, len);
	}
}

int f2fs_read_inline_data(struct inode *inode, struct page *page)
{
	struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
	struct page *ipage;
	void *src_addr, *dst_addr;

	if (page->index) {
		zero_user_segment(page, 0, PAGE_CACHE_SIZE);
		goto out;
	}

	ipage = get_node_page(sbi, inode->i_ino);
	if (IS_ERR(ipage)) {
		unlock_page(page);
		return PTR_ERR(ipage);
	}

	zero_user_segment(page, MAX_INLINE_DATA, PAGE_CACHE_SIZE);

	/* Copy the whole inline data block */
	src_addr = inline_data_addr(ipage);
	dst_addr = kmap(page);
	memcpy(dst_addr, src_addr, MAX_INLINE_DATA);
	kunmap(page);
	f2fs_put_page(ipage, 1);

out:
	SetPageUptodate(page);
	unlock_page(page);

	return 0;
}

static int rawfs_writepage(struct page *page, struct writeback_control *wbc)
{
	struct address_space *mapping = page->mapping;
	struct inode *inode;
	unsigned long end_index;
	char *buffer;
	int n_written = 0;
	unsigned n_bytes;
	loff_t i_size;

	if (!mapping)
		BUG();
	inode = mapping->host;
	if (!inode)
		BUG();
	i_size = i_size_read(inode);

	end_index = i_size >> PAGE_CACHE_SHIFT;

	if (page->index < end_index)
		n_bytes = PAGE_CACHE_SIZE;
	else {
		n_bytes = i_size & (PAGE_CACHE_SIZE - 1);

		if (page->index > end_index || !n_bytes) {
			zero_user_segment(page, 0, PAGE_CACHE_SIZE);
			set_page_writeback(page);
			unlock_page(page);
			end_page_writeback(page);
			return 0;
		}
	}

	if (n_bytes != PAGE_CACHE_SIZE)
		zero_user_segment(page, n_bytes, PAGE_CACHE_SIZE);

	get_page(page);

	buffer = kmap(page);

    /*	n_written = yaffs_wr_file(obj, buffer,
				  page->index << PAGE_CACHE_SHIFT, n_bytes, 0);
    */

    n_written = rawfs_write_file(inode, buffer, n_bytes,
        page->index << PAGE_CACHE_SHIFT);

	kunmap(page);
	set_page_writeback(page);
	unlock_page(page);
	end_page_writeback(page);
	put_page(page);

	return (n_written == n_bytes) ? 0 : -ENOSPC;
}

int f2fs_read_inline_data(struct inode *inode, struct page *page)
{
    struct page *ipage;

    ipage = get_node_page(F2FS_I_SB(inode), inode->i_ino);
    if (IS_ERR(ipage)) {
        unlock_page(page);
        return PTR_ERR(ipage);
    }

    if (!f2fs_has_inline_data(inode)) {
        f2fs_put_page(ipage, 1);
        return -EAGAIN;
    }

    if (page->index)
        zero_user_segment(page, 0, PAGE_CACHE_SIZE);
    else
        read_inline_data(page, ipage);

    SetPageUptodate(page);
    f2fs_put_page(ipage, 1);
    unlock_page(page);
    return 0;
}

int ext4_readpage_inline(struct inode *inode, struct page *page)
{
	int ret = 0;

	down_read(&EXT4_I(inode)->xattr_sem);
	if (!ext4_has_inline_data(inode)) {
		up_read(&EXT4_I(inode)->xattr_sem);
		return -EAGAIN;
	}

	/*
	 * Current inline data can only exist in the 1st page,
	 * So for all the other pages, just set them uptodate.
	 */
	if (!page->index)
		ret = ext4_read_inline_page(inode, page);
	else if (!PageUptodate(page)) {
		zero_user_segment(page, 0, PAGE_CACHE_SIZE);
		SetPageUptodate(page);
	}

	up_read(&EXT4_I(inode)->xattr_sem);

	unlock_page(page);
	return ret >= 0 ? 0 : ret;
}

static int f2fs_vm_page_mkwrite(struct vm_area_struct *vma,
						struct vm_fault *vmf)
{
	struct page *page = vmf->page;
	struct inode *inode = file_inode(vma->vm_file);
	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
	struct dnode_of_data dn;
	int err;

	f2fs_balance_fs(sbi);

	vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);

	f2fs_bug_on(sbi, f2fs_has_inline_data(inode));

	/* block allocation */
	f2fs_lock_op(sbi);
	set_new_dnode(&dn, inode, NULL, NULL, 0);
	err = f2fs_reserve_block(&dn, page->index);
	if (err) {
		f2fs_unlock_op(sbi);
		goto out;
	}
	f2fs_put_dnode(&dn);
	f2fs_unlock_op(sbi);

	file_update_time(vma->vm_file);
	lock_page(page);
	if (unlikely(page->mapping != inode->i_mapping ||
			page_offset(page) > i_size_read(inode) ||
			!PageUptodate(page))) {
		unlock_page(page);
		err = -EFAULT;
		goto out;
	}

	/*
	 * check to see if the page is mapped already (no holes)
	 */
	if (PageMappedToDisk(page))
		goto mapped;

	/* page is wholly or partially inside EOF */
	if (((page->index + 1) << PAGE_CACHE_SHIFT) > i_size_read(inode)) {
		unsigned offset;
		offset = i_size_read(inode) & ~PAGE_CACHE_MASK;
		zero_user_segment(page, offset, PAGE_CACHE_SIZE);
	}
	set_page_dirty(page);
	SetPageUptodate(page);

	trace_f2fs_vm_page_mkwrite(page, DATA);
mapped:
	/* fill the page */
	f2fs_wait_on_page_writeback(page, DATA);
	/* if gced page is attached, don't write to cold segment */
	clear_cold_data(page);
out:
	return block_page_mkwrite_return(err);
}

/*
 * NOTE: ipage is grabbed by caller, but if any error occurs, we should
 * release ipage in this function.
 */
static int f2fs_convert_inline_dir(struct inode *dir, struct page *ipage,
				struct f2fs_inline_dentry *inline_dentry)
{
	struct page *page;
	struct dnode_of_data dn;
	struct f2fs_dentry_block *dentry_blk;
	int err;

	page = grab_cache_page(dir->i_mapping, 0);
	if (!page) {
		f2fs_put_page(ipage, 1);
		return -ENOMEM;
	}

	set_new_dnode(&dn, dir, ipage, NULL, 0);
	err = f2fs_reserve_block(&dn, 0);
	if (err)
		goto out;

	f2fs_wait_on_page_writeback(page, DATA);
	zero_user_segment(page, MAX_INLINE_DATA, PAGE_CACHE_SIZE);

	dentry_blk = kmap_atomic(page);

	/* copy data from inline dentry block to new dentry block */
	memcpy(dentry_blk->dentry_bitmap, inline_dentry->dentry_bitmap,
					INLINE_DENTRY_BITMAP_SIZE);
	memset(dentry_blk->dentry_bitmap + INLINE_DENTRY_BITMAP_SIZE, 0,
			SIZE_OF_DENTRY_BITMAP - INLINE_DENTRY_BITMAP_SIZE);
	/*
	 * we do not need to zero out remainder part of dentry and filename
	 * field, since we have used bitmap for marking the usage status of
	 * them, besides, we can also ignore copying/zeroing reserved space
	 * of dentry block, because them haven't been used so far.
	 */
	memcpy(dentry_blk->dentry, inline_dentry->dentry,
			sizeof(struct f2fs_dir_entry) * NR_INLINE_DENTRY);
	memcpy(dentry_blk->filename, inline_dentry->filename,
					NR_INLINE_DENTRY * F2FS_SLOT_LEN);

	kunmap_atomic(dentry_blk);
	SetPageUptodate(page);
	set_page_dirty(page);

	/* clear inline dir and flag after data writeback */
	truncate_inline_inode(ipage, 0);

	stat_dec_inline_dir(dir);
	clear_inode_flag(F2FS_I(dir), FI_INLINE_DENTRY);

	if (i_size_read(dir) < PAGE_CACHE_SIZE) {
		i_size_write(dir, PAGE_CACHE_SIZE);
		set_inode_flag(F2FS_I(dir), FI_UPDATE_DIR);
	}

	sync_inode_page(&dn);
out:
	f2fs_put_page(page, 1);
	return err;
}

static int nfs_write_end(struct file *file, struct address_space *mapping,
			loff_t pos, unsigned len, unsigned copied,
			struct page *page, void *fsdata)
{
	unsigned offset = pos & (PAGE_CACHE_SIZE - 1);
	int status;

	dfprintk(PAGECACHE, "NFS: write_end(%s/%s(%ld), %[email protected]%lld)\n",
		file->f_path.dentry->d_parent->d_name.name,
		file->f_path.dentry->d_name.name,
		mapping->host->i_ino, len, (long long) pos);

	/*
	 * Zero any uninitialised parts of the page, and then mark the page
	 * as up to date if it turns out that we're extending the file.
	 */
	if (!PageUptodate(page)) {
		unsigned pglen = nfs_page_length(page);
		unsigned end = offset + len;

		if (pglen == 0) {
			zero_user_segments(page, 0, offset,
					end, PAGE_CACHE_SIZE);
			SetPageUptodate(page);
		} else if (end >= pglen) {
			zero_user_segment(page, end, PAGE_CACHE_SIZE);
			if (offset == 0)
				SetPageUptodate(page);
		} else
			zero_user_segment(page, pglen, PAGE_CACHE_SIZE);
	}

	status = nfs_updatepage(file, page, offset, copied);

	unlock_page(page);
	page_cache_release(page);

	if (status < 0)
		return status;
	return copied;
}

/*
 * Caller ensures that this data page is never allocated.
 * A new zero-filled data page is allocated in the page cache.
 *
 * Also, caller should grab and release a rwsem by calling f2fs_lock_op() and
 * f2fs_unlock_op().
 * Note that, ipage is set only by make_empty_dir, and if any error occur,
 * ipage should be released by this function.
 */
struct page *get_new_data_page(struct inode *inode,
                               struct page *ipage, pgoff_t index, bool new_i_size)
{
    struct address_space *mapping = inode->i_mapping;
    struct page *page;
    struct dnode_of_data dn;
    int err;
repeat:
    page = grab_cache_page(mapping, index);
    if (!page) {
        /*
         * before exiting, we should make sure ipage will be released
         * if any error occur.
         */
        f2fs_put_page(ipage, 1);
        return ERR_PTR(-ENOMEM);
    }

    set_new_dnode(&dn, inode, ipage, NULL, 0);
    err = f2fs_reserve_block(&dn, index);
    if (err) {
        f2fs_put_page(page, 1);
        return ERR_PTR(err);
    }
    if (!ipage)
        f2fs_put_dnode(&dn);

    if (PageUptodate(page))
        goto got_it;

    if (dn.data_blkaddr == NEW_ADDR) {
        zero_user_segment(page, 0, PAGE_CACHE_SIZE);
        SetPageUptodate(page);
    } else {
        f2fs_put_page(page, 1);

        page = get_read_data_page(inode, index, READ_SYNC);
        if (IS_ERR(page))
            goto repeat;

        /* wait for read completion */
        lock_page(page);
    }
got_it:
    if (new_i_size &&
            i_size_read(inode) < ((index + 1) << PAGE_CACHE_SHIFT)) {
        i_size_write(inode, ((index + 1) << PAGE_CACHE_SHIFT));
        /* Only the directory inode sets new_i_size */
        set_inode_flag(F2FS_I(inode), FI_UPDATE_DIR);
    }
    return page;
}

int ext4_bio_write_page(struct ext4_io_submit *io,
			struct page *page,
			int len,
			struct writeback_control *wbc)
{
	struct inode *inode = page->mapping->host;
	unsigned block_start, block_end, blocksize;
	struct ext4_io_page *io_page;
	struct buffer_head *bh, *head;
	int ret = 0;

	blocksize = 1 << inode->i_blkbits;

	BUG_ON(!PageLocked(page));
	BUG_ON(PageWriteback(page));

	io_page = kmem_cache_alloc(io_page_cachep, GFP_NOFS);
	if (!io_page) {
		set_page_dirty(page);
		unlock_page(page);
		return -ENOMEM;
	}
	io_page->p_page = page;
	atomic_set(&io_page->p_count, 1);
	get_page(page);
	set_page_writeback(page);
	ClearPageError(page);

	for (bh = head = page_buffers(page), block_start = 0;
	     bh != head || !block_start;
	     block_start = block_end, bh = bh->b_this_page) {

		block_end = block_start + blocksize;
		if (block_start >= len) {
			zero_user_segment(page, block_start, block_end);
			clear_buffer_dirty(bh);
			set_buffer_uptodate(bh);
			continue;
		}
		clear_buffer_dirty(bh);
		ret = io_submit_add_bh(io, io_page, inode, wbc, bh);
		if (ret) {
			set_page_dirty(page);
			break;
		}
	}
	unlock_page(page);
	put_io_page(io_page);
	return ret;
}

bool recover_inline_data(struct inode *inode, struct page *npage)
{
	struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
	struct f2fs_inode *ri = NULL;
	void *src_addr, *dst_addr;
	struct page *ipage;

	/*
	 * The inline_data recovery policy is as follows.
	 * [prev.] [next] of inline_data flag
	 *    o       o  -> recover inline_data
	 *    o       x  -> remove inline_data, and then recover data blocks
	 *    x       o  -> remove inline_data, and then recover inline_data
	 *    x       x  -> recover data blocks
	 */
	if (IS_INODE(npage))
		ri = F2FS_INODE(npage);

	if (f2fs_has_inline_data(inode) &&
			ri && (ri->i_inline & F2FS_INLINE_DATA)) {
process_inline:
		ipage = get_node_page(sbi, inode->i_ino);
		f2fs_bug_on(IS_ERR(ipage));

		f2fs_wait_on_page_writeback(ipage, NODE);

		src_addr = inline_data_addr(npage);
		dst_addr = inline_data_addr(ipage);
		memcpy(dst_addr, src_addr, MAX_INLINE_DATA);
		update_inode(inode, ipage);
		f2fs_put_page(ipage, 1);
		return true;
	}

	if (f2fs_has_inline_data(inode)) {
		ipage = get_node_page(sbi, inode->i_ino);
		f2fs_bug_on(IS_ERR(ipage));
		f2fs_wait_on_page_writeback(ipage, NODE);
		zero_user_segment(ipage, INLINE_DATA_OFFSET,
				 INLINE_DATA_OFFSET + MAX_INLINE_DATA);
		clear_inode_flag(F2FS_I(inode), FI_INLINE_DATA);
		update_inode(inode, ipage);
		f2fs_put_page(ipage, 1);
	} else if (ri && (ri->i_inline & F2FS_INLINE_DATA)) {
		truncate_blocks(inode, 0, false);
		set_inode_flag(F2FS_I(inode), FI_INLINE_DATA);
		goto process_inline;
	}
	return false;
}

/**
 * Called with lower inode mutex held.
 */
static int fill_zeros_to_end_of_page(struct page *page, unsigned int to)
{
	struct inode *inode = page->mapping->host;
	int end_byte_in_page;

	if ((i_size_read(inode) / PAGE_CACHE_SIZE) != page->index)
		goto out;
	end_byte_in_page = i_size_read(inode) % PAGE_CACHE_SIZE;
	if (to > end_byte_in_page)
		end_byte_in_page = to;
	zero_user_segment(page, end_byte_in_page, PAGE_CACHE_SIZE);
out:
	return 0;
}

static int f2fs_convert_inline_dir(struct inode *dir, struct page *ipage,
                                   struct f2fs_inline_dentry *inline_dentry)
{
    struct page *page;
    struct dnode_of_data dn;
    struct f2fs_dentry_block *dentry_blk;
    int err;

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

    set_new_dnode(&dn, dir, ipage, NULL, 0);
    err = f2fs_reserve_block(&dn, 0);
    if (err)
        goto out;

    f2fs_wait_on_page_writeback(page, DATA);
    zero_user_segment(page, 0, PAGE_CACHE_SIZE);

    dentry_blk = kmap_atomic(page);

    /* copy data from inline dentry block to new dentry block */
    memcpy(dentry_blk->dentry_bitmap, inline_dentry->dentry_bitmap,
           INLINE_DENTRY_BITMAP_SIZE);
    memcpy(dentry_blk->dentry, inline_dentry->dentry,
           sizeof(struct f2fs_dir_entry) * NR_INLINE_DENTRY);
    memcpy(dentry_blk->filename, inline_dentry->filename,
           NR_INLINE_DENTRY * F2FS_SLOT_LEN);

    kunmap_atomic(dentry_blk);
    SetPageUptodate(page);
    set_page_dirty(page);

    /* clear inline dir and flag after data writeback */
    truncate_inline_inode(ipage, 0);

    stat_dec_inline_dir(dir);
    clear_inode_flag(F2FS_I(dir), FI_INLINE_DENTRY);

    if (i_size_read(dir) < PAGE_CACHE_SIZE) {
        i_size_write(dir, PAGE_CACHE_SIZE);
        set_inode_flag(F2FS_I(dir), FI_UPDATE_DIR);
    }

    sync_inode_page(&dn);
out:
    f2fs_put_page(page, 1);
    return err;
}

void truncate_inline_data(struct inode *inode, u64 from)
{
	struct page *ipage;

	if (from >= MAX_INLINE_DATA)
		return;

	ipage = get_node_page(F2FS_I_SB(inode), inode->i_ino);
	if (IS_ERR(ipage))
		return;

	f2fs_wait_on_page_writeback(ipage, NODE);

	zero_user_segment(ipage, INLINE_DATA_OFFSET + from,
				INLINE_DATA_OFFSET + MAX_INLINE_DATA);
	set_page_dirty(ipage);
	f2fs_put_page(ipage, 1);
}

void read_inline_data(struct page *page, struct page *ipage)
{
    void *src_addr, *dst_addr;

    if (PageUptodate(page))
        return;

    f2fs_bug_on(F2FS_P_SB(page), page->index);

    zero_user_segment(page, MAX_INLINE_DATA, PAGE_CACHE_SIZE);

    /* Copy the whole inline data block */
    src_addr = inline_data_addr(ipage);
    dst_addr = kmap_atomic(page);
    memcpy(dst_addr, src_addr, MAX_INLINE_DATA);
    flush_dcache_page(page);
    kunmap_atomic(dst_addr);
    SetPageUptodate(page);
}