[Btrfs-devel] btrfs and git-reflog

Chris Mason chris.mason at oracle.com
Fri Jan 25 13:37:25 PST 2008

On Friday 25 January 2008, Theodore Tso wrote:
> On Fri, Jan 25, 2008 at 01:55:37PM -0500, Chris Mason wrote:
> > Since btrfs maintains both a name index and an inode index, I can
> > iterate over the name index (hash values) for use cases that require
> > telldir/seekdir.  At any rate, there are a variety of choices for
> > working around it, but I'm focusing on the disk format first ;)
> Well, there is a disk format way of handling the problem, and which is
> what JFS used; it simply maintained associated a separate "telldir"
> cookie for each file, and had separate b-tree which allowed for fast
> access each file given its telldir cookie.  btrfs could theoretically
> do something similar.  I'd suggest thinking about this as an optional
> feature, which would be enabled if full 100% reliable telldir/seekdir
> support is required, or for NFS servers.
> There are indeed workarounds, but unfortunately they all have
> downsides....

Hmmm, for seekdir and telldir, my understanding was that I was allowed to 
return entries more than once, especially in the face of changes to the 
directory in between calls.  


Does the JFS cookie allow you to get from the file to to the directory entry?  
We've got that now via backrefs.


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