linux-kernel - Re: [V9fs-developer] [PATCH 3/5] 9p: revert tsyncfs related changes

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Message-ID: <4D8FB93A.6020508@linux.vnet.ibm.com>
Date:	Sun, 27 Mar 2011 15:24:58 -0700
From:	Venkateswararao Jujjuri <jvrao@...ux.vnet.ibm.com>
To:	"Aneesh Kumar K. V" <aneesh.kumar@...ux.vnet.ibm.com>
CC:	v9fs-developer@...ts.sourceforge.net,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [V9fs-developer] [PATCH 3/5] 9p: revert tsyncfs related changes

On 03/27/2011 01:28 AM, Aneesh Kumar K. V wrote:
> On Fri, 25 Mar 2011 14:20:04 -0700, Venkateswararao Jujjuri<jvrao@...ux.vnet.ibm.com>  wrote:
>> On 03/25/2011 04:30 AM, Aneesh Kumar K.V wrote:
>>> Now that we use write_inode to flush server
>>> cache related to fid, we don't need tsyncfs.
>>> This help us to do a more efficient server flush
>>> for dotu protocol
>> Why are you singling out dotu only? won't it be applicable to dotl too?
>>
> With dotl we can have new operations and so we added tsyncfs. The
> primary goal is to add an operation that can flush server cache. We
> hooked that to sync(2) on the client. With dotu we cannot add new
> operations so we always forced the write on the server in case of dotu
> to O_SYNC. That is much slower than doing an fsync on write_inode. But
> whether doing an fsync on write inode is better than doing tsyncfs on
> sync(2) on client is something i haven't yet measured. Stefan Hajnoczi wants to
> see some numbers before we push tsyncfs in the server(qemu). We also don't
> want a kernel release with 9p operation which we may remove later. So
> the plan now is to get write_inode changes upstream in this merge window
> and later get numbers against tsyncfs/write_inode ->  fsync and add tsyncfs only
> if we see a benefit. BTW NFS use the write_inode approach.

Nice explanation. I looked at NFS and realized that they also follow 
write_inode approach.
So I think you should make it explict that this will be helpful to dotl 
also and may and TFSYNCFS
in the future if needed. With that I ack this.

Reviewed-by : Venkateswararao Jujjuri <jvrao@...ux.vnet.ibm.com>

> -aneesh

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