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Re: [PATCH] XFS: Kill filestreams cache flush

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: [PATCH] XFS: Kill filestreams cache flush
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Sat, 2 Jan 2010 23:12:03 +1100
Cc: xfs@xxxxxxxxxxx
In-reply-to: <20100102115338.GA18502@xxxxxxxxxxxxx>
References: <1262399900-19110-1-git-send-email-david@xxxxxxxxxxxxx> <20100102115338.GA18502@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.18 (2008-05-17)
On Sat, Jan 02, 2010 at 06:53:38AM -0500, Christoph Hellwig wrote:
> On Sat, Jan 02, 2010 at 01:38:20PM +1100, Dave Chinner wrote:
> > The filestreams cache flush is not needed in the sync code as it
> > does not affect data writeback, and it is now not used by the
> > growfs code, either, so kill it.
> 
> I have to admit I never understood the purpose of this call.

I can't remember why it was put there, either. I may have even put
it there when I was getting filestreams ready for merge but I can't remember
at all...

> What xfs_fstrm_free_func does is:
> 
>  - clear the filesystems flag on the inode
>  - decrement pagf_fstrms
>  - drop references on the inode (and parent if known)
>  - free the filestream item
> 
> Nothing of that should matter for sync, although dropping inode
> references during sync might generally be a good idea.

Which means that sync destroys active filestreams associations and
that seems more broken to me than anything an active reference will
cause. I think just letting them time out is better than having them
destroyed by external operations. I'm happy to leave it there if you
want....

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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