[Tux3] Deferred delete prototype for Ext2

Benjamin K. Stuhl benjamin.stuhl at colorado.edu
Tue Dec 2 21:14:25 PST 2008

On Tuesday 02 December 2008 21:16:13 Daniel Phillips wrote:
> I only had to make one hack to core vfs to make this work.  Essentially,
> we are changing the dentry cache from a volatile, read only cache to a
> writeback cache which is entirely consistent on its own, as opposed to
> just being an accelerator.  We always knew this was possible, because
> that is how RAMFS works.  But I needed to make it work when the cache
> is backed by a filesystem.  All I had to do here is add one new method,
> to prevent the dentry cache from forcibly removing a dentry from the
> cache that has been unlinked, but which is still in used for some hard
> to understand reason.  With my new hook (d_ops->hide) the dentry just
> stays in cache as a negative dentry and we take a reference count on it
> to make sure it does not disappear before our code has a chance to find
> it and remove the underlying directory entry.

Hi Daniel,
  While I'm certainly not qualified to comment on the _content_ of the patch, I 
have been watching Linux filesystem flamewars for a while... I _strongly_ 
suggest that you write to linux-fsdevel at vger about these VFS changes, and 
sooner rather than later. (It probably would be a good idea to directly CC at 
least Al Viro and Christoph Hellwig; Ted Ts'o, Christoph Lameter, Linus, and 
Andrew Morton are also good candidates.) Tux3 looks very promising, and I 
would hate to see it get tied up in avoidable VFS battles when it's otherwise 
ready for merging.

-- BKS

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