From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: Al Viro <viro@ZenIV.linux.org.uk>
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 08:15:18 +0000 [thread overview]
Message-ID: <1363335318.2459.4.camel@dabdike> (raw)
In-Reply-To: <20130315051322.GX21522@ZenIV.linux.org.uk>
On Fri, 2013-03-15 at 05:13 +0000, Al Viro wrote:
> On Fri, Mar 15, 2013 at 02:09:14PM +0900, J. R. Okajima wrote:
>
> > If so, it has a big disadvantage for the layer-fs (or branch-fs) to have
> > to implement a new method for whiteout.
> >
> > Overlayfs implements whiteout as symlink+xattr which consumes an
> > inode. And you don't like it, right?
> > What I showed is another generic approach without xattr where the new
> > method to whiteout is unnecessary.
>
> I'm yet to see the reason that would make implementing that method a big
> disadvantage, TBH...
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.
James
next prev parent reply other threads:[~2013-03-15 8:15 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 [this message]
2013-03-15 12:12 ` Al Viro
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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