linux-kernel - Re: [PATCH] fuse: don't check for file->private

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Message-ID: <CAJfpegt2Xz0tGUygpN4eyb3g8EsFNWomsUUOmGBMj03ocOPVng@mail.gmail.com>
Date:	Thu, 13 Nov 2014 10:40:38 +0100
From:	Miklos Szeredi <miklos@...redi.hu>
To:	Martin Kepplinger <martink@...teo.de>
Cc:	fuse-devel <fuse-devel@...ts.sourceforge.net>,
	thierry.reding@...il.com,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	giedriuswork@...il.com,
	Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] fuse: don't check for file->private_data on open().

On Wed, Nov 12, 2014 at 5:31 PM, Martin Kepplinger <martink@...teo.de> wrote:
> The miscdevice core now sets file->private_data to the struct miscdevice
> so don't fail when this is not NULL.

Does it?  Look:

static int misc_open(struct inode * inode, struct file * file)
{
    ...
    if (file->f_op->open) {
        file->private_data = c;
        err = file->f_op->open(inode,file);
    }

It only sets ->private_data if the device provides an open method.
Fuse doesn't, so it's not clear what this patch is trying to fix.

Thanks,
Miklos


>
> Reported-by: Thierry Reding <thierry.reding@...il.com>
> Signed-off-by: Martin Kepplinger <martink@...teo.de>
> ---
> This is a question: what does this check provide and does overwriting
> file->private_data make any difference?
>
> Is open() by the user not allowed here, if file->private_data is set?
>
> thanks!!
>
>  fs/fuse/inode.c |    3 ---
>  1 file changed, 3 deletions(-)
>
> diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
> index 03246cd..562407e 100644
> --- a/fs/fuse/inode.c
> +++ b/fs/fuse/inode.c
> @@ -1092,9 +1092,6 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
>         }
>
>         mutex_lock(&fuse_mutex);
> -       err = -EINVAL;
> -       if (file->private_data)
> -               goto err_unlock;
>
>         err = fuse_ctl_add_conn(fc);
>         if (err)
> --
> 1.7.10.4
>
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