From mboxrd@z Thu Jan  1 00:00:00 1970
From: Amir Goldstein <amir73il@gmail.com>
Subject: Re: [PATCH v4 1/6] vfs: create vfs helper vfs_tmpfile()
Date: Mon, 6 Mar 2017 17:29:16 +0200
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To: "J. R. Okajima" <hooanon05g@gmail.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>, Al Viro <viro@zeniv.linux.org.uk>, linux-unionfs@vger.kernel.org, linux-fsdevel <linux-fsdevel@vger.kernel.org>

On Mon, Mar 6, 2017 at 4:59 PM, J. R. Okajima <hooanon05g@gmail.com> wrote:
> Amir Goldstein:
>> Factor out some common vfs bits from do_tmpfile()
>> to be used by overlayfs for concurrent copy up.
>
> Hmm, just to copy-up.
> I have no objection this factoring-out, but do you have any specific
> reason for overlayfs NOT to support i_op->tmpfile()?

No reason. Just someone has to do the leg work.

>
> If you try supporting it in the future, then the parameter open_flag may
> become a problem. I guess that you will make ovl_tmpfile() (currently
> not exist) to call vfs_tmpfile(), and pass dummy 0 as open_flag as
> overlayfs copy-up does. But such dummy parameter will make the created
> tmpfile un-linkable by a user I am afraid.
>

I don't think that's going to be a problem.
ovl_link() can probably make sure that I_LINKABLE is propagated to upper
inode before calling vfs_link() for a tmpfile.