linux-kernel - Re: [PATCH 04/11] vfs: add renameat2 syscall

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Message-ID: <20140115103032.GD24171@tucsk.piliscsaba.szeredi.hu>
Date:	Wed, 15 Jan 2014 11:30:32 +0100
From:	Miklos Szeredi <miklos@...redi.hu>
To:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc:	torvalds@...ux-foundation.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, hch@...radead.org,
	akpm@...ux-foundation.org, dhowells@...hat.com, zab@...hat.com,
	jack@...e.cz, luto@...capital.net, mszeredi@...e.cz
Subject: Re: [PATCH 04/11] vfs: add renameat2 syscall

On Wed, Jan 15, 2014 at 07:11:16AM +0900, Tetsuo Handa wrote:
> Miklos Szeredi wrote:
> > +
> > +	if (flags)
> > +		return -EOPNOTSUPP;
> > +
> 
> If (at least for now) only ext4 interprets renameat2() flags,
> I think adding a new member to "struct inode_operations" and
> check it like
> 
> 	if (!old_dir->i_op->swapname)
> 		return -EOPNOTSUPP;
> 
> or

This is not just about swapname, but other rename variants too (non-overwriting
rename is also included in the patchset).

> 
> 	if (!(old_dir->i_op->supported_features & flags))
> 		return -EOPNOTSUPP;

Or rather old_dir->i_sb->s_type->fs_flags.  We access it due to
FS_RENAME_DOES_D_MOVE anyway.

I like this variant, because now filesystems need to explicitly add a flag to
*enable* the functionality and not a check to disable it.

Objections?

Thanks,
Miklos
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