Re: [RFC] VFS: data=ordered (was: [Advocacy] Re: 3ware 9650 tips)

[Matthew Wilcox]

On Mon, Jul 16, 2007 at 09:28:08PM +0300, Al Boldi wrote:
> Well, conceptually it sounds like a piece of cake, technically your guess is 
> as good as mine.  IIRC, akpm once mentioned something like this.

How much have you looked at the VFS?  There's nothing journalling-related
in the VFS right now.  ext3 and XFS share no common journalling code,
nor do I think that would be possible, due to the very different concepts
they have of journalling.

Here's a good hint:

$ find fs -type f |xargs grep -l journal_start
fs/ext3/acl.c
fs/ext3/inode.c
fs/ext3/ioctl.c
fs/ext3/namei.c
fs/ext3/resize.c
fs/ext3/super.c
fs/ext3/xattr.c
fs/ext4/acl.c
fs/ext4/extents.c
fs/ext4/inode.c
fs/ext4/ioctl.c
fs/ext4/namei.c
fs/ext4/resize.c
fs/ext4/super.c
fs/ext4/xattr.c
fs/jbd/journal.c
fs/jbd/transaction.c
fs/jbd2/journal.c
fs/jbd2/transaction.c
fs/ocfs2/journal.c
fs/ocfs2/super.c

JBD and JBD2 provide a journalling implementation that ext3, ext4 and
ocfs2 use.  Note that XFS doesn't, it has its own journalling code.

If you want XFS to support data=ordered, talk to the XFS folks.  Or
start picking through XFS yourself, of course -- you do have the source
code.

-- 
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."
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[RFC] VFS: data=ordered (was: [Advocacy] Re: 3ware 9650 tips)

[Al Boldi]

Matthew Wilcox wrote:
> On Mon, Jul 16, 2007 at 08:40:00PM +0300, Al Boldi wrote:
> > XFS surely rocks, but it's missing one critical component: data=ordered
> > And that's one component that's just too critical to overlook for an
> > enterprise environment that is built on data-integrity over performance.
> >
> > So that's the secret why people still use ext3, and XFS' reliance on
> > external hardware to ensure integrity is really misplaced.
> >
> > Now, maybe when we get the data=ordered onto the VFS level, then maybe
> > XFS may become viable for the enterprise, and ext3 may cease to be KING.
>
> Wow, thanks for bringing an advocacy thread onto linux-fsdevel.  Just what
> we wanted.  Do you have any insight into how to "get the data=ordered
> onto the VFS level"?  Because to me, that sounds like pure nonsense.

Well, conceptually it sounds like a piece of cake, technically your guess is 
as good as mine.  IIRC, akpm once mentioned something like this.

But seriously, can you think of a technical reason why it shouldn't be 
possible to abstract data=ordered mode out into the VFS?


Thanks!

--
Al

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