Date: Tue, 29 Jul 2014 09:41:11 +0900
From: Changman Lee <cm224.lee@samsung.com>
To: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH 07/11] f2fs: enable in-place-update for fdatasync
Message-id: <20140729004111.GA442@lcm>
References: <1406328445-63707-1-git-send-email-jaegeuk@kernel.org>
 <1406328445-63707-7-git-send-email-jaegeuk@kernel.org>
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Hi Jaegeuk,

On Fri, Jul 25, 2014 at 03:47:21PM -0700, Jaegeuk Kim wrote:
> This patch enforces in-place-updates only when fdatasync is requested.
> If we adopt this in-place-updates for the fdatasync, we can skip to write the
> recovery information.

But, as you know, random write occurs when changing into in-place-updates.
It will degrade write performance. Is there any case in-place-updates is
better, except recovery or high utilization?

Thanks

> 
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
>  fs/f2fs/f2fs.h    | 1 +
>  fs/f2fs/file.c    | 7 +++++++
>  fs/f2fs/segment.h | 4 ++++
>  3 files changed, 12 insertions(+)
> 
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index ab36025..8f8685e 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -998,6 +998,7 @@ enum {
>  	FI_INLINE_DATA,		/* used for inline data*/
>  	FI_APPEND_WRITE,	/* inode has appended data */
>  	FI_UPDATE_WRITE,	/* inode has in-place-update data */
> +	FI_NEED_IPU,		/* used fo ipu for fdatasync */
>  };
>  
>  static inline void set_inode_flag(struct f2fs_inode_info *fi, int flag)
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 121689a..e339856 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -127,11 +127,18 @@ int f2fs_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
>  		return 0;
>  
>  	trace_f2fs_sync_file_enter(inode);
> +
> +	/* if fdatasync is triggered, let's do in-place-update */
> +	if (datasync)
> +		set_inode_flag(fi, FI_NEED_IPU);
> +
>  	ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
>  	if (ret) {
>  		trace_f2fs_sync_file_exit(inode, need_cp, datasync, ret);
>  		return ret;
>  	}
> +	if (datasync)
> +		clear_inode_flag(fi, FI_NEED_IPU);
>  
>  	/*
>  	 * if there is no written data, don't waste time to write recovery info.
> diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
> index ee5c75e..55973f7 100644
> --- a/fs/f2fs/segment.h
> +++ b/fs/f2fs/segment.h
> @@ -486,6 +486,10 @@ static inline bool need_inplace_update(struct inode *inode)
>  	if (S_ISDIR(inode->i_mode))
>  		return false;
>  
> +	/* this is only set during fdatasync */
> +	if (is_inode_flag_set(F2FS_I(inode), FI_NEED_IPU))
> +		return true;
> +
>  	switch (SM_I(sbi)->ipu_policy) {
>  	case F2FS_IPU_FORCE:
>  		return true;
> -- 
> 1.8.5.2 (Apple Git-48)
> 
> 
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