From: Ric Wheeler <rwheeler@redhat.com>
To: Szeredi Miklos <miklos@szeredi.hu>
Cc: Valerie Aurora <valerie.aurora@gmail.com>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
viro@zeniv.linux.org.uk, Christoph Hellwig <hch@infradead.org>
Subject: Re: Union mounts comparison with overlay file system prototype?
Date: Fri, 25 Mar 2011 08:12:34 -0400 [thread overview]
Message-ID: <4D8C86B2.2060902@redhat.com> (raw)
In-Reply-To: <AANLkTikGybr-iynMG3T0TwY0aRSbMdDDB+D8QFnWgwA7@mail.gmail.com>
On 03/25/2011 07:38 AM, Szeredi Miklos wrote:
> On Thu, Mar 24, 2011 at 2:43 PM, Ric Wheeler<rwheeler@redhat.com> wrote:
>> Can one or both of you summarize what we union mounts and overlay do better
>> or worse? Do we need both or just one?
> The semantics are very similar, the differences are in the implementation.
>
> Union mounts:
>
> - whiteout/opaque/fallthrough support in filesystems
> - whiteout operation is atomic
> - no dentry and inode duplication
> - copy up on lookup and readdir
> - does not support union of two read-only trees
> - merged directory stored in upper tree
>
> Overlayfs
>
> - whiteout/opaque as xattrs
> - whiteout operation is not atomic
> - dentry and inode duplication(*)
> - only copy up on modification
> - supports union of two read-only trees
> - merged directory not cached(**)
>
> (*) it's possible to eliminate inode duplication of non-directories
> with some VFS modifications
> (**) caching should be possible to do
Thanks for the high level overview!
Ric
next prev parent reply other threads:[~2011-03-25 12:12 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-23 1:58 [PATCH 00/74] Union mounts version something or other Valerie Aurora
2011-03-23 1:58 ` [PATCH 01/74] VFS: Comment follow_mount() and friends Valerie Aurora
2011-03-23 1:58 ` [PATCH 02/74] VFS: Make lookup_hash() return a struct path Valerie Aurora
2011-03-23 1:58 ` [PATCH 03/74] autofs4: Save autofs trigger's vfsmount in super block info Valerie Aurora
2011-03-23 1:58 ` [PATCH 04/74] Documentation: Fix trivial typo in filesystems/sharedsubtree.txt Valerie Aurora
2011-03-23 1:58 ` [PATCH 05/74] whiteout/NFSD: Don't return information about whiteouts to userspace Valerie Aurora
2011-03-23 1:58 ` [PATCH 06/74] whiteout: Define opaque inode flags and operations Valerie Aurora
2011-03-23 1:58 ` [PATCH 07/74] whiteout: Add vfs_whiteout() and whiteout inode operation Valerie Aurora
2011-03-23 1:58 ` [PATCH 08/74] whiteout: Allow removal of a directory with whiteouts Valerie Aurora
2011-03-23 1:58 ` [PATCH 09/74] whiteout: tmpfs whiteout support Valerie Aurora
2011-03-23 1:58 ` [PATCH 10/74] ext2: Add ext2_dirent_in_use() Valerie Aurora
2011-03-23 1:58 ` [PATCH 11/74] ext2: Split ext2_add_entry() from ext2_add_link() Valerie Aurora
2011-03-23 1:58 ` [PATCH 12/74] whiteout: ext2 whiteout support Valerie Aurora
2011-03-23 1:58 ` [PATCH 13/74] whiteout: jffs2 " Valerie Aurora
2011-03-23 1:58 ` [PATCH 14/74] fallthru: Basic fallthru definitions Valerie Aurora
2011-03-23 1:58 ` [PATCH 15/74] fallthru: ext2 fallthru support Valerie Aurora
2011-03-23 1:58 ` [PATCH 16/74] fallthru: tmpfs " Valerie Aurora
2011-03-23 1:58 ` [PATCH 17/74] fallthru: jffs2 " Valerie Aurora
2011-03-23 1:58 ` [PATCH 18/74] VFS: Add hard read-only users count to superblock Valerie Aurora
2011-03-23 1:58 ` [PATCH 19/74] VFS: Make clone_mnt()/copy_tree()/collect_mounts() return errors Valerie Aurora
2011-03-23 1:58 ` [PATCH 20/74] VFS: Add CL_NO_SHARED flag to clone_mnt()/copy_tree() Valerie Aurora
2011-03-23 1:58 ` [PATCH 21/74] VFS: Add CL_NO_SLAVE " Valerie Aurora
2011-03-23 1:58 ` [PATCH 22/74] VFS: Add CL_MAKE_HARD_READONLY " Valerie Aurora
2011-03-23 1:58 ` [PATCH 23/74] union-mount: Union mounts documentation Valerie Aurora
2011-03-23 1:59 ` [PATCH 24/74] union-mount: Introduce MNT_UNION and MS_UNION flags Valerie Aurora
2011-03-23 1:59 ` [PATCH 25/74] union-mount: Add CONFIG_UNION_MOUNT option Valerie Aurora
2011-03-23 1:59 ` [PATCH 26/74] union-mount: Create union_stack structure Valerie Aurora
2011-03-23 1:59 ` [PATCH 27/74] union-mount: Add two superblock fields for union mounts Valerie Aurora
2011-03-23 1:59 ` [PATCH 28/74] union-mount: Add union_alloc() Valerie Aurora
2011-03-23 1:59 ` [PATCH 29/74] union-mount: Add union_find_dir() Valerie Aurora
2011-03-23 1:59 ` [PATCH 30/74] union-mount: Create d_free_unions() Valerie Aurora
2011-03-23 1:59 ` [PATCH 31/74] union-mount: Free union stack on removal of topmost dentry from dcache Valerie Aurora
2011-03-23 1:59 ` [PATCH 32/74] union-mount: Create union_add_dir() Valerie Aurora
2011-03-23 1:59 ` [PATCH 33/74] union-mount: Add union_create_topmost_dir() Valerie Aurora
2011-03-23 1:59 ` [PATCH 34/74] union-mount: Create IS_MNT_UNION() Valerie Aurora
2011-03-23 1:59 ` [PATCH 35/74] union-mount: Create needs_lookup_union() Valerie Aurora
2011-03-23 1:59 ` [PATCH 36/74] union-mount: Create check_topmost_union_mnt() Valerie Aurora
2011-03-23 1:59 ` [PATCH 37/74] union-mount: Add clone_union_tree() and put_union_sb() Valerie Aurora
2011-03-23 1:59 ` [PATCH 38/74] union-mount: Create build_root_union() Valerie Aurora
2011-03-23 1:59 ` [PATCH 39/74] union-mount: Create prepare_mnt_union() and cleanup_mnt_union() Valerie Aurora
2011-03-23 1:59 ` [PATCH 40/74] union-mount: Prevent improper union-related remounts Valerie Aurora
2011-03-23 1:59 ` [PATCH 41/74] union-mount: Prevent topmost file system from being mounted elsewhere Valerie Aurora
2011-03-23 1:59 ` [PATCH 42/74] union-mount: Prevent bind mounts of union mounts Valerie Aurora
2011-03-23 1:59 ` [PATCH 43/74] union-mount: Implement union mount Valerie Aurora
2011-03-23 1:59 ` [PATCH 44/74] union-mount: Temporarily disable some syscalls Valerie Aurora
2011-03-23 2:12 ` [PATCH 00/74] Union mounts version something or other Valerie Aurora
2011-03-24 13:43 ` Union mounts comparison with overlay file system prototype? Ric Wheeler
2011-03-25 11:38 ` Szeredi Miklos
2011-03-25 12:12 ` Ric Wheeler [this message]
2011-03-23 8:38 ` [PATCH 00/74] Union mounts version something or other Sedat Dilek
2011-03-24 22:40 ` Ben Hutchings
2011-03-25 2:32 ` Sedat Dilek
2011-03-30 14:30 ` David Howells
2011-04-01 16:48 ` Valerie Aurora
2011-04-21 13:09 ` David Howells
2011-04-24 21:48 ` Valerie Aurora
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4D8C86B2.2060902@redhat.com \
--to=rwheeler@redhat.com \
--cc=hch@infradead.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=miklos@szeredi.hu \
--cc=valerie.aurora@gmail.com \
--cc=viro@zeniv.linux.org.uk \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).