linux-kernel - Re: [PATCH] ovl: Fix condition check for workdir

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Date:	Fri, 9 Jan 2015 10:40:32 +0800
From:	hujianyang <hujianyang@...wei.com>
To:	Seunghun Lee <waydi1@...il.com>
CC:	<miklos@...redi.hu>, <linux-unionfs@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH] ovl: Fix condition check for workdir

On 2015/1/8 20:41, Seunghun Lee wrote:
> When file system is mounted read-only workdir is not needed.
> 
> Signed-off-by: Seunghun Lee <waydi1@...il.com>
> ---
>  fs/overlayfs/super.c | 35 +++++++++++++++++++++++------------
>  1 file changed, 23 insertions(+), 12 deletions(-)
> 
> diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
> index 84f3144..4e50617 100644
> --- a/fs/overlayfs/super.c
> +++ b/fs/overlayfs/super.c
> @@ -30,6 +30,7 @@ struct ovl_config {
>  	char *lowerdir;
>  	char *upperdir;
>  	char *workdir;
> +	bool is_rw;
>  };
>  
>  /* private information held for overlayfs's superblock */
> @@ -515,10 +516,11 @@ static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
>  	struct ovl_fs *ufs = sb->s_fs_info;
>  
>  	seq_printf(m, ",lowerdir=%s", ufs->config.lowerdir);
> -	if (ufs->config.upperdir) {
> +	if (ufs->config.upperdir)
>  		seq_printf(m, ",upperdir=%s", ufs->config.upperdir);
> +	if (ufs->config.is_rw)
>  		seq_printf(m, ",workdir=%s", ufs->config.workdir);
> -	}
> +
>  	return 0;
>  }
>  
> @@ -822,16 +824,27 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
>  
>  	sb->s_stack_depth = 0;
>  	if (ufs->config.upperdir) {
> -		/* FIXME: workdir is not needed for a R/O mount */
> +		err = ovl_mount_dir(ufs->config.upperdir, &upperpath);
> +		if (err)
> +			goto out_free_config;
> +
> +		sb->s_stack_depth = upperpath.mnt->mnt_sb->s_stack_depth;
> +	}
> +
> +	/* If the upper fs is r/o or nonexistent, we mark overlayfs r/o too */
> +	if (!upperpath.mnt || (upperpath.mnt->mnt_sb->s_flags & MS_RDONLY)) {
> +		ufs->config.is_rw = false;
> +		sb->s_flags |= MS_RDONLY;
> +	} else {
> +		ufs->config.is_rw = true;
> +	}

Hi Seunghun,

A partition can be mounted with ro flag. I think workdir is not
needed in this way either.

> +
> +	if (ufs->config.is_rw) {
>  		if (!ufs->config.workdir) {
>  			pr_err("overlayfs: missing 'workdir'\n");
>  			goto out_free_config;
>  		}
>  
> -		err = ovl_mount_dir(ufs->config.upperdir, &upperpath);
> -		if (err)
> -			goto out_free_config;
> -
>  		err = ovl_mount_dir(ufs->config.workdir, &workpath);
>  		if (err)
>  			goto out_put_upperpath;
> @@ -844,8 +857,8 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
>  			pr_err("overlayfs: workdir and upperdir must be separate subtrees\n");
>  			goto out_put_workpath;
>  		}
> -		sb->s_stack_depth = upperpath.mnt->mnt_sb->s_stack_depth;
>  	}
> +
>  	err = -ENOMEM;
>  	lowertmp = kstrdup(ufs->config.lowerdir, GFP_KERNEL);
>  	if (!lowertmp)
> @@ -884,7 +897,9 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
>  			pr_err("overlayfs: failed to clone upperpath\n");
>  			goto out_put_lowerpath;
>  		}
> +	}
>  
> +	if (ufs->config.is_rw) {
>  		ufs->workdir = ovl_workdir_create(ufs->upper_mnt, workpath.dentry);
>  		err = PTR_ERR(ufs->workdir);
>  		if (IS_ERR(ufs->workdir)) {
> @@ -914,10 +929,6 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
>  		ufs->numlower++;
>  	}
>  
> -	/* If the upper fs is r/o or nonexistent, we mark overlayfs r/o too */
> -	if (!ufs->upper_mnt || (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY))
> -		sb->s_flags |= MS_RDONLY;
> -
>  	sb->s_d_op = &ovl_dentry_operations;
>  
>  	err = -ENOMEM;
> 


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