linux-kernel - Re: [RFC][PATCH v2] fuse: In fuse_flush only wait if someone wants the return code

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Message-ID: <YufuRyehrRquv+lk@tycho.pizza>
Date:   Mon, 1 Aug 2022 09:16:23 -0600
From:   Tycho Andersen <tycho@...ho.pizza>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     Al Viro <viro@...iv.linux.org.uk>, Oleg Nesterov <oleg@...hat.com>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Miklos Szeredi <miklos@...redi.hu>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [RFC][PATCH v2] fuse: In fuse_flush only wait if someone wants
 the return code

On Sat, Jul 30, 2022 at 12:10:33AM -0500, Eric W. Biederman wrote:
> +static int fuse_flush_async(struct file *file, fl_owner_t id)
> +{
> +	struct inode *inode = file_inode(file);
> +	struct fuse_mount *fm = get_fuse_mount(inode);
> +	struct fuse_file *ff = file->private_data;
> +	struct fuse_flush_args *fa;
> +	int err;
> +
> +	fa = kzalloc(sizeof(*fa), GFP_KERNEL);
> +	if (!fa)
> +		return -ENOMEM;
> +
> +	fa->inarg.fh = ff->fh;
> +	fa->inarg.lock_owner = fuse_lock_owner_id(fm->fc, id);
> +	fa->args.opcode = FUSE_FLUSH;
> +	fa->args.nodeid = get_node_id(inode);
> +	fa->args.in_numargs = 1;
> +	fa->args.in_args[0].size = sizeof(fa->inarg);
> +	fa->args.in_args[0].value = &fa->inarg;
> +	fa->args.force = true;

Seems like you need a

    fa->args.nocreds = true;

here or you'll hit the WARN() in fuse_simple_background().

Tycho