From: Al Viro <viro@ZenIV.linux.org.uk>
To: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: "J. R. Okajima" <hooanon05@yahoo.co.jp>,
Miklos Szeredi <miklos@szeredi.hu>,
Andrew Morton <akpm@linux-foundation.org>,
torvalds@linux-foundation.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, hch@infradead.org,
apw@canonical.com, nbd@openwrt.org, neilb@suse.de,
jordipujolp@gmail.com, ezk@fsl.cs.sunysb.edu,
dhowells@redhat.com, sedat.dilek@googlemail.com,
mszeredi@suse.cz
Subject: Re: [PATCH 0/9] overlay filesystem: request for inclusion (v17)
Date: Fri, 15 Mar 2013 12:12:20 +0000 [thread overview]
Message-ID: <20130315121220.GY21522@ZenIV.linux.org.uk> (raw)
In-Reply-To: <1363335318.2459.4.camel@dabdike>
On Fri, Mar 15, 2013 at 08:15:18AM +0000, James Bottomley wrote:
> It's the fact that a directory entry based whiteout limits the amount of
> change to the VFS, but has to be supported by underlying filesystems.
> The generic_dirent_fallthrough() mechanism is a nice way of hiding it,
> but there are still quite a few fs specific mods in the union mount tree
> because of this. Having to modify filesystems to me indicates the
> mechanism is a bit fragile. If we could do whiteouts purely in the VFS,
> so it would work for any filesystem (without needing filesystem
> modifications) that would seem to be a more robust approach. I'm not
> saying we can definitely do this in an elegant way ... I'm just saying
> that if someone comes up with it, it's obviously preferable.
The trouble with such mechanisms is that they tend to end up depending on
fairly non-trivial properties of underlying fs. Try aufs one on btrfs,
see how soon you spot the problem. It's nice when a method turns out
to be really redundant and implementable in uniform way via other methods
present; see fh_to_dentry history for example of situation where it hadn't...
next prev parent reply other threads:[~2013-03-15 12:12 UTC|newest]
Thread overview: 79+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-13 14:16 [PATCH 0/9] overlay filesystem: request for inclusion (v17) Miklos Szeredi
2013-03-13 14:16 ` [PATCH 1/9] vfs: add i_op->dentry_open() Miklos Szeredi
2013-03-13 22:44 ` Andrew Morton
2013-03-14 11:15 ` Miklos Szeredi
2013-03-13 14:16 ` [PATCH 2/9] vfs: export do_splice_direct() to modules Miklos Szeredi
2013-03-13 22:45 ` Andrew Morton
2013-03-13 14:16 ` [PATCH 3/9] vfs: export __inode_permission() " Miklos Szeredi
2013-03-13 14:16 ` [PATCH 4/9] vfs: introduce clone_private_mount() Miklos Szeredi
2013-03-13 22:48 ` Andrew Morton
2013-03-14 13:28 ` Miklos Szeredi
2013-03-13 14:16 ` [PATCH 5/9] overlay filesystem Miklos Szeredi
2013-03-13 22:53 ` Andrew Morton
2013-03-13 14:16 ` [PATCH 6/9] overlayfs: add statfs support Miklos Szeredi
2013-03-13 14:16 ` [PATCH 7/9] overlayfs: implement show_options Miklos Szeredi
2013-03-13 14:16 ` [PATCH 8/9] overlay: overlay filesystem documentation Miklos Szeredi
2013-03-13 23:06 ` Andrew Morton
2013-03-14 13:35 ` Miklos Szeredi
2013-03-13 14:16 ` [PATCH 9/9] fs: limit filesystem stacking depth Miklos Szeredi
2013-03-13 14:31 ` [PATCH 0/9] overlay filesystem: request for inclusion (v17) Sedat Dilek
2013-03-13 15:13 ` Sedat Dilek
2013-03-13 15:18 ` Miklos Szeredi
2013-03-13 15:26 ` Sedat Dilek
2013-03-13 15:53 ` Sedat Dilek
2013-03-13 16:10 ` Sedat Dilek
2013-03-13 16:21 ` Miklos Szeredi
2013-03-13 16:35 ` Sedat Dilek
2013-03-13 16:51 ` Sedat Dilek
2013-03-13 18:12 ` Robin Holt
2013-03-13 18:37 ` Felix Fietkau
2013-03-13 19:10 ` Sedat Dilek
2013-03-13 19:54 ` Eric W. Biederman
2013-03-13 19:58 ` Linus Torvalds
2013-03-13 20:27 ` Sedat Dilek
[not found] ` <CAB3woddVfZ9PdYPpzidJLBMmUeRx0Rxgb5Pc8bTM9U-tkcS_uA@mail.gmail.com>
2013-03-13 20:32 ` Sedat Dilek
2013-03-13 20:36 ` Phillip Lougher
2013-03-13 23:08 ` Andrew Morton
2013-03-14 13:43 ` Miklos Szeredi
2013-03-15 1:25 ` Al Viro
2013-03-15 4:15 ` J. R. Okajima
2013-03-15 4:44 ` Al Viro
2013-03-15 5:09 ` J. R. Okajima
2013-03-15 5:13 ` Al Viro
2013-03-15 8:15 ` James Bottomley
2013-03-15 12:12 ` Al Viro [this message]
2013-03-15 18:57 ` J. R. Okajima
2013-03-15 19:26 ` Erez Zadok
2013-03-15 20:30 ` Al Viro
2013-03-16 13:55 ` J. R. Okajima
2013-03-15 19:11 ` Linus Torvalds
2013-03-16 13:57 ` J. R. Okajima
2013-03-17 13:06 ` [PATCH 2/9] vfs: export do_splice_direct() to modules David Howells
2013-03-18 2:31 ` Dave Chinner
2013-03-18 15:39 ` Jan Kara
2013-03-18 21:53 ` Al Viro
2013-03-18 23:01 ` Al Viro
2013-03-19 1:38 ` Al Viro
2013-03-19 9:00 ` J. R. Okajima
2013-03-19 10:29 ` Miklos Szeredi
2013-03-19 17:03 ` Al Viro
2013-03-19 18:32 ` Miklos Szeredi
2013-03-19 21:24 ` Al Viro
2013-03-20 9:15 ` Miklos Szeredi
2013-03-19 11:04 ` David Howells
2013-03-19 11:40 ` Miklos Szeredi
2013-03-19 20:54 ` Jan Kara
2013-03-19 20:25 ` Jan Kara
2013-03-19 21:38 ` Al Viro
2013-03-19 22:10 ` Al Viro
2013-03-20 2:33 ` Al Viro
2013-03-20 19:52 ` Jan Kara
2013-03-20 21:48 ` Al Viro
2013-03-20 22:19 ` Jan Kara
2013-03-20 12:30 ` David Howells
2013-03-22 17:37 ` J. R. Okajima
2013-03-22 18:11 ` Al Viro
2013-03-22 18:21 ` Al Viro
2013-03-23 2:49 ` J. R. Okajima
2013-03-23 4:41 ` Al Viro
2013-03-23 5:37 ` J. R. Okajima
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