Re: [v3][PATCH 5/5] Merge code for singleandmultiple-instancemounts

["Serge E. Hallyn" <serue@us.ibm.com>]

Quoting Sukadev Bhattiprolu (sukadev@linux.vnet.ibm.com):
...

> >From 2f7746f4df78ff57125c4714f0cd64e739ccf804 Mon Sep 17 00:00:00 2001
> From: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
> Date: Mon, 11 May 2009 13:11:11 -0700
> Subject: [PATCH] devpts: Correctly set default options
> 
> devpts_get_sb() calls memset(0) to clear mount options and calls
> parse_mount_options() if user specified any mount options. The memset(0) is
> bogus since the 'mode' and 'ptmxmode' options are non-zero by default.
> parse_mount_options() restores options to default anyway and can properly deal
> with NULL mount options.
> 
> So in devpts_get_sb() remove memset(0) and call parse_mount_options() even for
> NULL mount options.
> 
> Bug reported by Eric Paris: http://lkml.org/lkml/2009/5/7/448.

Would you almost say... Reported-by: ?  :)
> 
> Signed-off-by: Sukadev Bhattiprolu (sukadev@us.ibm.com)

Looks good.

Acked-by: Serge Hallyn <serue@us.ibm.com>

> ---
>  fs/devpts/inode.c |   18 ++++++++++++------
>  1 files changed, 12 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c
> index 63a4a59..b7a954e 100644
> --- a/fs/devpts/inode.c
> +++ b/fs/devpts/inode.c
> @@ -90,6 +90,15 @@ static inline struct super_block *pts_sb_from_inode(struct inode *inode)
>  #define PARSE_MOUNT	0
>  #define PARSE_REMOUNT	1
> 
> +/*
> + * parse_mount_options():
> + * 	Set @opts to mount options specified in @data. If an option is not
> + * 	specified in @data, set it to its default value. The exception is
> + * 	'newinstance' option which can only be set/cleared on a mount (i.e.
> + * 	cannot be changed during remount).
> + *
> + * Note: @data may be NULL (in which case all options are set to default).
> + */
>  static int parse_mount_options(char *data, int op, struct pts_mount_opts *opts)
>  {
>  	char *p;
> @@ -355,12 +364,9 @@ static int devpts_get_sb(struct file_system_type *fs_type,
>  	struct pts_mount_opts opts;
>  	struct super_block *s;
> 
> -	memset(&opts, 0, sizeof(opts));
> -	if (data) {
> -		error = parse_mount_options(data, PARSE_MOUNT, &opts);
> -		if (error)
> -			return error;
> -	}
> +	error = parse_mount_options(data, PARSE_MOUNT, &opts);
> +	if (error)
> +		return error;
> 
>  	if (opts.newinstance)
>  		s = sget(fs_type, NULL, set_anon_super, NULL);