Re: inode data not getting included in commits?

[Chris Mason <chris.mason@oracle.com>]

On Fri, 2008-12-19 at 12:08 -0800, Sage Weil wrote:

[ trigger data=ordered flush at commit time ]

>  
> > A third option is a different type of xattr operation that doesn't go to
> > disk until the metadata updates done at IO end time.
> > 
> > >From a performance point of view, it'll be much faster than slowing down
> > commit with data writes.
> > 
> > Can that work for you?
> 
> I suspect not, since multiple files are involved.  It's usually something 
> like
> 
>  write A
>  setxattr A
>  write B
>  setxattr C
> 
> and all need to be committed atomically.  The model really is a bundle of 
> arbitrary operations that commit atomically.
> 
> Slower commit times aren't as much of a concern because this is on the 
> storage backend, behind client caches and so forth.  I think it's 
> a reasonable price to pay for the stronger consistency.  
> 
> Hopefully it's not throwing too big a wrench into the data=ordered 
> machinery?  It sort of looks like this is already what you get when taking 
> a snapshot (I see the call to wait_ordered_extnets in commit_transaction 
> when snaps_pending).

If we make it optional, its fine by me to added a data=ordered flush at
commit time.

-chris