linux-kernel - Re: [PATCH] f2fs: fix fdatasync

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Date:   Thu, 17 Nov 2016 10:51:37 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
CC:     <linux-f2fs-devel@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>, <chao@...nel.org>
Subject: Re: [PATCH] f2fs: fix fdatasync

Hi Jaegeuk,

On 2016/11/17 3:13, Jaegeuk Kim wrote:
> Hi Chao,
> 
> On Wed, Nov 16, 2016 at 08:12:11PM +0800, Chao Yu wrote:
>> For below two cases, we can't guarantee data consistence:
>>
>> a)
>> 1. xfs_io "pwrite 0 4195328" "fsync"
>> 2. xfs_io "pwrite 4195328 1024" "fdatasync"
>> 3. godown
>> 4. umount & mount
>> --> isize we updated before fdatasync won't be recovered
>>
>> b)
>> 1. xfs_io "pwrite -S 0xcc 0 4202496" "fsync"
>> 2. xfs_io "fpunch 4194304 4096" "fdatasync"
>> 3. godown
>> 4. umount & mount
>> --> dnode we punched before fdatasync won't be recovered
>>
>> The reason is that normally fdatasync won't be aware of modification
>> of metadata in file, e.g. isize changing, dnode updating, so in ->fsync
>> we will skip flushing node pages for above cases, result in making
>> fdatasynced file being lost during recovery.
>>
>> Introduce FDATASYNC_INO global ino cache for tracking node changing,
>> later fdatasync choose to flush nodes depend on ino cache state.
> 
> We don't need to add this additionally, and would be better to consider other
> major metadata as well.
> 
> How about this?

Seems it can't track file after evict?

Thanks,

> 
> ---
>  fs/f2fs/f2fs.h | 11 ++++++++++-
>  fs/f2fs/file.c |  2 +-
>  2 files changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index c9672a3..50ffa4f 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -1727,8 +1727,17 @@ static inline void f2fs_i_size_write(struct inode *inode, loff_t i_size)
>  		set_inode_flag(inode, FI_AUTO_RECOVER);
>  }
>  
> -static inline bool f2fs_skip_inode_update(struct inode *inode)
> +static inline bool f2fs_skip_inode_update(struct inode *inode, int dsync)
>  {
> +	if (dsync) {
> +		struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> +		bool ret;
> +
> +		spin_lock(&sbi->inode_lock[DIRTY_META]);
> +		ret = list_empty(&F2FS_I(inode)->gdirty_list);
> +		spin_unlock(&sbi->inode_lock[DIRTY_META]);
> +		return ret;
> +	}
>  	if (!is_inode_flag_set(inode, FI_AUTO_RECOVER))
>  		return false;
>  	return F2FS_I(inode)->last_disk_size == i_size_read(inode);
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index d48c120..50123c6 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -212,7 +212,7 @@ static int f2fs_do_sync_file(struct file *file, loff_t start, loff_t end,
>  	}
>  
>  	/* if the inode is dirty, let's recover all the time */
> -	if (!datasync && !f2fs_skip_inode_update(inode)) {
> +	if (!f2fs_skip_inode_update(inode, datasync)) {
>  		f2fs_write_inode(inode, NULL);
>  		goto go_write;
>  	}
>