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

[Jaegeuk Kim]

Hi Yunlong,

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.

So, how about adding SBI_BLOCK_OPS 

/* For s_flag in struct f2fs_sb_info */
enum {
	SBI_IS_DIRTY,				/* dirty flag for checkpoint */
	SBI_IS_CLOSE,				/* specify unmounting */
	SBI_NEED_FSCK,				/* need fsck.f2fs to fix */
	SBI_POR_DOING,				/* recovery is doing or not */
	SBI_NEED_SB_WRITE,			/* need to recover superblock */
	SBI_NEED_CP,				/* need to checkpoint */
===
	SBI_BLOCK_OPS,				/* doing block_operations */
===
};

How aboud avoiding f2fs_balance_fs() in __write_data_page() by:

	if (!is_sbi_flag_set(sbi, SBI_BLOCK_OPS) || !S_ISDIR(inode->i_mode))
		f2fs_balance_fs();

In block_operations(),
	set_sbi_flag(sbi, SBI_BLOCK_OPS);
	...
	clear_sbi_flag(sbi, SBI_BLOCK_OPS);

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