linux-kernel - Re: [PATCH] f2fs: fix some cases with reserved

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Date:   Tue, 8 Aug 2017 14:08:15 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Yunlong Song <yunlong.song@...wei.com>, <jaegeuk@...nel.org>,
        <chao@...nel.org>, <yunlong.song@...oud.com>
CC:     <miaoxie@...wei.com>, <bintian.wang@...wei.com>,
        <linux-fsdevel@...r.kernel.org>,
        <linux-f2fs-devel@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] f2fs: fix some cases with reserved_blocks

On 2017/8/8 12:12, Yunlong Song wrote:
> Signed-off-by: Yunlong Song <yunlong.song@...wei.com>
> ---
>  fs/f2fs/recovery.c | 3 ++-
>  fs/f2fs/super.c    | 9 +++++----
>  2 files changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/f2fs/recovery.c b/fs/f2fs/recovery.c
> index a3d0261..e288319 100644
> --- a/fs/f2fs/recovery.c
> +++ b/fs/f2fs/recovery.c
> @@ -51,7 +51,8 @@ bool space_for_roll_forward(struct f2fs_sb_info *sbi)
>  {
>  	s64 nalloc = percpu_counter_sum_positive(&sbi->alloc_valid_block_count);
>  
> -	if (sbi->last_valid_block_count + nalloc > sbi->user_block_count)
> +	if (sbi->last_valid_block_count + nalloc +
> +			sbi->reserved_blocks > sbi->user_block_count)

I think we can treat reserved blocks as over-provision space in f2fs, so it
would be safe to store invalid data (may become valid during recovery) there.
Anyway, it OK to remain old condition judgment.

>  		return false;
>  	return true;
>  }
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index 4c1bdcb..c644bf5 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -946,6 +946,7 @@ static int f2fs_statfs(struct dentry *dentry, struct kstatfs *buf)
>  	u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
>  	block_t total_count, user_block_count, start_count, ovp_count;
>  	u64 avail_node_count;
> +	block_t avail_user_block_count;
>  
>  	total_count = le64_to_cpu(sbi->raw_super->block_count);
>  	user_block_count = sbi->user_block_count;
> @@ -953,16 +954,16 @@ static int f2fs_statfs(struct dentry *dentry, struct kstatfs *buf)
>  	ovp_count = SM_I(sbi)->ovp_segments << sbi->log_blocks_per_seg;
>  	buf->f_type = F2FS_SUPER_MAGIC;
>  	buf->f_bsize = sbi->blocksize;
> +	avail_user_block_count = user_block_count - sbi->reserved_blocks;
>  
>  	buf->f_blocks = total_count - start_count;
>  	buf->f_bfree = user_block_count - valid_user_blocks(sbi) + ovp_count;
> -	buf->f_bavail = user_block_count - valid_user_blocks(sbi) -
> -						sbi->reserved_blocks;
> +	buf->f_bavail = avail_user_block_count - valid_user_blocks(sbi);
>  
>  	avail_node_count = sbi->total_node_count - F2FS_RESERVED_NODE_NUM;
>  
> -	if (avail_node_count > user_block_count) {
> -		buf->f_files = user_block_count;
> +	if (avail_node_count > avail_user_block_count) {

Likewise f_blocks calculation, the f_files one doesn't need to consider
reserved_blocks.

Thanks,

> +		buf->f_files = avail_user_block_count;
>  		buf->f_ffree = buf->f_bavail;
>  	} else {
>  		buf->f_files = avail_node_count;
>