linux-kernel - Re: [PATCH v2] f2fs: wait IO writeback in commit_inmem

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Date:   Thu, 26 Apr 2018 09:36:44 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Chao Yu <chao@...nel.org>, <jaegeuk@...nel.org>
CC:     <linux-f2fs-devel@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] f2fs: wait IO writeback in commit_inmem_pages()

Hi Jaegeuk,

I just look into this flow again, found that in previous patch ("f2fs: fix to
wait page writeback during revoking atomic write") we have already called
f2fs_wait_on_page_writeback in __revoke_inmem_pages, so we don't need to call
redundant filemap_fdatawait here.

Anyway, let me merge these two patches.

Thanks,

On 2018/4/23 23:14, Chao Yu wrote:
> From: Chao Yu <yuchao0@...wei.com>
> 
> Thread A				Thread B
> - f2fs_ioc_commit_atomic_write
>  - commit_inmem_pages
>   - f2fs_submit_merged_write_cond
>   : write data
> 					- write_checkpoint
> 					 - do_checkpoint
> 					 : commit all node within CP
> 					 -> SPO
>   - f2fs_do_sync_file
>    - file_write_and_wait_range
>    : wait data writeback
> 
> In above race condition, data/node can be flushed in reversed order when
> coming a checkpoint before f2fs_do_sync_file, after SPOR, it results in
> atomic written data being corrupted.
> 
> This patch adds filemap_fdatawait() in commit_inmem_pages() to keep data
> and node of atomic file being flushed orderly.
> 
> Signed-off-by: Chao Yu <yuchao0@...wei.com>
> ---
> v2:
> - clean up codes suggested by Jaegeuk.
>  fs/f2fs/file.c    | 4 ++++
>  fs/f2fs/segment.c | 2 ++
>  2 files changed, 6 insertions(+)
> 
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index bac059474342..0cfa65c21d3f 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -217,6 +217,9 @@ static int f2fs_do_sync_file(struct file *file, loff_t start, loff_t end,
>  
>  	trace_f2fs_sync_file_enter(inode);
>  
> +	if (atomic)
> +		goto write_done;
> +
>  	/* if fdatasync is triggered, let's do in-place-update */
>  	if (datasync || get_dirty_pages(inode) <= SM_I(sbi)->min_fsync_blocks)
>  		set_inode_flag(inode, FI_NEED_IPU);
> @@ -228,6 +231,7 @@ static int f2fs_do_sync_file(struct file *file, loff_t start, loff_t end,
>  		return ret;
>  	}
>  
> +write_done:
>  	/* if the inode is dirty, let's recover all the time */
>  	if (!f2fs_skip_inode_update(inode, datasync)) {
>  		f2fs_write_inode(inode, NULL);
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 710d817c4350..31336fc54d8e 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -419,6 +419,8 @@ static int __commit_inmem_pages(struct inode *inode)
>  		__revoke_inmem_pages(inode, &fi->inmem_pages, true, false);
>  	} else {
>  		__revoke_inmem_pages(inode, &revoke_list, false, false);
> +
> +		err = filemap_fdatawait(inode->i_mapping);
>  	}
>  
>  	return err;
>