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From: David Howells <dhowells@redhat.com>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: dhowells@redhat.com, viro@ZenIV.linux.org.uk,
	torvalds@linux-foundation.org, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org, bfields@fieldses.org,
	hch@infradead.org, akpm@linux-foundation.org, zab@redhat.com,
	jack@suse.cz, luto@amacapital.net, mszeredi@suse.cz
Subject: Re: [PATCH 00/13] cross rename v4
Date: Thu, 13 Feb 2014 16:42:50 +0000	[thread overview]
Message-ID: <20106.1392309770@warthog.procyon.org.uk> (raw)
In-Reply-To: <20140213162534.GB4026@tucsk.piliscsaba.szeredi.hu>

Miklos Szeredi <miklos@szeredi.hu> wrote:

> Regarding whiteouts, I raised a couple of questions that nobody answered
> yet, so let me ask again.
> 
> - If a filesystem containing whiteouts (fallthroughs, etc...) is mounted as
>   not part of a union, how are these special entities represented to
>   userspace?

I would suggest that whiteouts appear as otherwise negative dentries and that
they don't appear in getdents().

Fallthroughs are far more 'interesting'.  Maybe they should appear in
getdents() with a dentry type saying what they are, but give you EREMOTE or
something if you try to follow them.

Note that there is space in d_flags & DCACHE_ENTRY_TYPE for a whiteout type.
I would, however, mark fallthroughs by a separate flag.  So that the union
dentry will mirror the source dentry's type.

> - Can the user remove them?

Overwriting whiteouts and fallthroughs and unlinking fallthroughs I don't see
as a problem where they can be treated as normal negative dentries and normal
files in this regard.

However, what do you do about non-opaque directories that may or may not have
been unioned if you try and follow a dirent that would be a subdirectory that
hasn't been copied up?

David

  parent reply	other threads:[~2014-02-13 16:43 UTC|newest]

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-02-07 16:48 [PATCH 00/13] cross rename v4 Miklos Szeredi
2014-02-07 16:48 ` [PATCH 01/13] vfs: add d_is_dir() Miklos Szeredi
2014-02-07 17:36   ` J. Bruce Fields
2014-02-07 19:30   ` David Howells
2014-02-07 16:49 ` [PATCH 02/13] vfs: rename: move d_move() up Miklos Szeredi
2014-02-07 16:49 ` [PATCH 03/13] vfs: rename: use common code for dir and non-dir Miklos Szeredi
2014-02-07 16:49 ` [PATCH 04/13] vfs: add renameat2 syscall Miklos Szeredi
2014-02-07 16:49 ` [PATCH 05/13] vfs: add RENAME_NOREPLACE flag Miklos Szeredi
2014-02-07 16:49 ` [PATCH 06/13] security: add flags to rename hooks Miklos Szeredi
2014-02-07 16:49 ` [PATCH 07/13] vfs: lock_two_nondirectories: allow directory args Miklos Szeredi
2014-02-07 21:16   ` J. Bruce Fields
2014-02-11 15:32     ` Miklos Szeredi
2014-02-07 16:49 ` [PATCH 08/13] vfs: add cross-rename Miklos Szeredi
2014-02-07 22:40   ` J. Bruce Fields
2014-02-11 15:55     ` Miklos Szeredi
2014-02-07 16:49 ` [PATCH 09/13] ext4: rename: create ext4_renament structure for local vars Miklos Szeredi
2014-02-07 16:49 ` [PATCH 10/13] ext4: rename: move EMLINK check up Miklos Szeredi
2014-02-07 16:49 ` [PATCH 11/13] ext4: rename: split out helper functions Miklos Szeredi
2014-02-07 16:49 ` [PATCH 12/13] ext4: add cross rename support Miklos Szeredi
2014-02-11 21:23   ` Jan Kara
2014-02-07 16:49 ` [PATCH 13/13] vfs: merge rename2 into rename Miklos Szeredi
2014-02-07 22:46 ` [PATCH 00/13] cross rename v4 J. Bruce Fields
2014-02-11 15:57   ` Miklos Szeredi
2014-02-13 19:32     ` J. Bruce Fields
2014-02-10 10:51 ` Dave Chinner
2014-02-11 16:01   ` Miklos Szeredi
2014-02-12 17:18     ` Miklos Szeredi
2014-02-17  8:19       ` Dave Chinner
2014-02-17 18:04         ` Theodore Ts'o
2014-03-19 13:57         ` xfstest for renameat2 system call (was: [PATCH 00/13] cross rename v4) Miklos Szeredi
2014-04-08  1:23           ` Dave Chinner
2014-02-13 15:54 ` [PATCH 00/13] cross rename v4 David Howells
2014-02-13 16:25   ` Miklos Szeredi
2014-02-13 16:42   ` David Howells [this message]
2014-02-13 17:28     ` Miklos Szeredi
2014-02-13 18:21       ` Andy Lutomirski
2014-02-13 18:29       ` Linus Torvalds
2014-02-13 18:56         ` Miklos Szeredi
2014-02-13 19:20           ` Linus Torvalds
2014-02-13 19:02       ` David Howells
2014-02-13 19:32         ` Linus Torvalds
2014-02-13 20:17           ` Eric W. Biederman
2014-02-13 20:28           ` Miklos Szeredi
2014-02-24 17:12             ` Miklos Szeredi
2014-02-24 17:49               ` Linus Torvalds
2014-02-25  4:07               ` J. R. Okajima
2014-02-26 15:15               ` Jan Kara

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