Re: [PATCH] f2fs: provide f2fs_balance_fs to __write_data_page for dentry pages

[Jaegeuk Kim]

On 07/29, Yunlong Song wrote:
> f2fs_balance_fs of dentry pages is skipped in __write_data_page due to deadlock
> of gc_mutex in write_checkpoint flow. This patch enables f2fs_balance_fs for
> normal dentry page writeback to ensure there are always enough free segments.

Sorry, by the way, why do we need to do this? I subtly thought that dirty node
pages can be produce by redirtied inodes from what we've not covered through
filesystem calls. But, in dentry pages, we're controlling the number of dirty
pages, and calling f2fs_balance_fs in each directory operations.

Chao?

Thanks,

> 
> Reported-by: Chao Yu <yuchao0@xxxxxxxxxx>
> Signed-off-by: Yunlong Song <yunlong.song@xxxxxxxxxx>
> ---
>  fs/f2fs/checkpoint.c |  2 +-
>  fs/f2fs/data.c       | 67 +++++++++++++++++++++++++++++++++++++++++++++-------
>  fs/f2fs/f2fs.h       |  1 +
>  3 files changed, 61 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> index 3c84a25..2882878 100644
> --- a/fs/f2fs/checkpoint.c
> +++ b/fs/f2fs/checkpoint.c
> @@ -904,7 +904,7 @@ int sync_dirty_inodes(struct f2fs_sb_info *sbi, enum inode_type type)
>  	if (inode) {
>  		unsigned long cur_ino = inode->i_ino;
>  
> -		filemap_fdatawrite(inode->i_mapping);
> +		f2fs_filemap_fdatawrite(inode->i_mapping, is_dir);
>  		iput(inode);
>  		/* We need to give cpu to another writers. */
>  		if (ino == cur_ino) {
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index aefc2a5..ed7efa5 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -1475,7 +1475,7 @@ int do_write_data_page(struct f2fs_io_info *fio)
>  }
>  
>  static int __write_data_page(struct page *page, bool *submitted,
> -				struct writeback_control *wbc)
> +				struct writeback_control *wbc, bool do_balance)
>  {
>  	struct inode *inode = page->mapping->host;
>  	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> @@ -1578,7 +1578,7 @@ static int __write_data_page(struct page *page, bool *submitted,
>  	}
>  
>  	unlock_page(page);
> -	if (!S_ISDIR(inode->i_mode))
> +	if (do_balance)
>  		f2fs_balance_fs(sbi, need_balance_fs);
>  
>  	if (unlikely(f2fs_cp_error(sbi))) {
> @@ -1602,7 +1602,7 @@ static int __write_data_page(struct page *page, bool *submitted,
>  static int f2fs_write_data_page(struct page *page,
>  					struct writeback_control *wbc)
>  {
> -	return __write_data_page(page, NULL, wbc);
> +	return __write_data_page(page, NULL, wbc, true);
>  }
>  
>  /*
> @@ -1611,7 +1611,7 @@ static int f2fs_write_data_page(struct page *page,
>   * warm/hot data page.
>   */
>  static int f2fs_write_cache_pages(struct address_space *mapping,
> -					struct writeback_control *wbc)
> +					struct writeback_control *wbc, bool do_balance)
>  {
>  	int ret = 0;
>  	int done = 0;
> @@ -1701,7 +1701,7 @@ static int f2fs_write_cache_pages(struct address_space *mapping,
>  			if (!clear_page_dirty_for_io(page))
>  				goto continue_unlock;
>  
> -			ret = __write_data_page(page, &submitted, wbc);
> +			ret = __write_data_page(page, &submitted, wbc, do_balance);
>  			if (unlikely(ret)) {
>  				/*
>  				 * keep nr_to_write, since vfs uses this to
> @@ -1756,8 +1756,8 @@ static int f2fs_write_cache_pages(struct address_space *mapping,
>  	return ret;
>  }
>  
> -static int f2fs_write_data_pages(struct address_space *mapping,
> -			    struct writeback_control *wbc)
> +static int _f2fs_write_data_pages(struct address_space *mapping,
> +			    struct writeback_control *wbc, bool do_balance)
>  {
>  	struct inode *inode = mapping->host;
>  	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> @@ -1794,7 +1794,7 @@ static int f2fs_write_data_pages(struct address_space *mapping,
>  		goto skip_write;
>  
>  	blk_start_plug(&plug);
> -	ret = f2fs_write_cache_pages(mapping, wbc);
> +	ret = f2fs_write_cache_pages(mapping, wbc, do_balance);
>  	blk_finish_plug(&plug);
>  
>  	if (wbc->sync_mode == WB_SYNC_ALL)
> @@ -1813,6 +1813,57 @@ static int f2fs_write_data_pages(struct address_space *mapping,
>  	return 0;
>  }
>  
> +static int f2fs_write_data_pages(struct address_space *mapping,
> +			    struct writeback_control *wbc)
> +{
> +	return	_f2fs_write_data_pages(mapping, wbc, true);
> +}
> +
> +/*
> + * This function was copied from do_writepages from mm/page-writeback.c.
> + * The major change is changing writepages to _f2fs_write_data_pages.
> + */
> +static int f2fs_do_writepages(struct address_space *mapping,
> +				struct writeback_control *wbc, bool is_dir)
> +{
> +	int ret;
> +
> +	if (wbc->nr_to_write <= 0)
> +		return 0;
> +	while (1) {
> +		ret = _f2fs_write_data_pages(mapping, wbc, !is_dir);
> +		if ((ret != -ENOMEM) || (wbc->sync_mode != WB_SYNC_ALL))
> +			break;
> +		cond_resched();
> +		congestion_wait(BLK_RW_ASYNC, HZ/50);
> +	}
> +	return ret;
> +}
> +
> +/*
> + * This function was copied from __filemap_fdatawrite_range from
> + * mm/filemap.c. The major change is changing do_writepages to
> + * f2fs_do_writepages.
> + */
> +int f2fs_filemap_fdatawrite(struct address_space *mapping, bool is_dir)
> +{
> +	int ret;
> +	struct writeback_control wbc = {
> +		.sync_mode = WB_SYNC_ALL,
> +		.nr_to_write = LONG_MAX,
> +		.range_start = 0,
> +		.range_end = LLONG_MAX,
> +	};
> +
> +	if (!mapping_cap_writeback_dirty(mapping))
> +		return 0;
> +
> +	wbc_attach_fdatawrite_inode(&wbc, mapping->host);
> +	ret = f2fs_do_writepages(mapping, &wbc, is_dir);
> +	wbc_detach_inode(&wbc);
> +	return ret;
> +}
> +
>  static void f2fs_write_failed(struct address_space *mapping, loff_t to)
>  {
>  	struct inode *inode = mapping->host;
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 9280283..ea9bebb 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -2572,6 +2572,7 @@ void f2fs_invalidate_page(struct page *page, unsigned int offset,
>  int f2fs_migrate_page(struct address_space *mapping, struct page *newpage,
>  			struct page *page, enum migrate_mode mode);
>  #endif
> +int f2fs_filemap_fdatawrite(struct address_space *mapping, bool is_dir);
>  
>  /*
>   * gc.c
> -- 
> 1.8.5.2