Re: Subject: [PATCH] SQUASHME: Move a check from nfs_pageio_do_add_request to nfs_generic_pg_test

From: Trond Myklebust <Trond.Myklebust@netapp.com>
To: Boaz Harrosh <bharrosh@panasas.com>
Cc: Benny Halevy <bhalevy@panasas.com>, linux-nfs@vger.kernel.org
Subject: Re: Subject: [PATCH] SQUASHME: Move a check from nfs_pageio_do_add_request to nfs_generic_pg_test
Date: Thu, 26 May 2011 16:11:29 -0400	[thread overview]
Message-ID: <1306440689.31601.7.camel@lade.trondhjem.org> (raw)
In-Reply-To: <4DDEB0DF.70409@panasas.com>

On Thu, 2011-05-26 at 22:58 +0300, Boaz Harrosh wrote: 
> On 05/26/2011 10:17 PM, Boaz Harrosh wrote:
> > 
> > desc->pg_bsize is negotiated with the MDS. But if we are doing
> > pnfs-IO it is not relevant.
> > 
> > While at it cleanup nfs_pageio_do_add_request() in light of the
> > less things it needs to do.
> > 
> > Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
> > ---
> >  fs/nfs/pagelist.c |   28 ++++++++++++++--------------
> >  1 files changed, 14 insertions(+), 14 deletions(-)
> > 
> > diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
> > index c795660..130b683 100644
> > --- a/fs/nfs/pagelist.c
> > +++ b/fs/nfs/pagelist.c
> > @@ -206,6 +206,16 @@ nfs_wait_on_request(struct nfs_page *req)
> >  
> >  static bool nfs_generic_pg_test(struct nfs_pageio_descriptor *desc, struct nfs_page *prev, struct nfs_page *req)
> >  {
> > +	/*
> > +	* FIXME: ideally we should be able to coalesce all requests
> > +	* that are not block boundary aligned, but currently this
> > +	* is problematic for the case of bsize < PAGE_CACHE_SIZE,
> > +	* since nfs_flush_multi and nfs_pagein_multi assume you
> > +	* can have only one struct nfs_page.
> > +	*/
> > +	if (desc->pg_bsize < PAGE_SIZE)
> > +		return 0;
> > +
> >  	return desc->pg_count + req->wb_bytes <= desc->pg_bsize;
> >  }
> >  
> > @@ -278,29 +288,19 @@ static bool nfs_can_coalesce_requests(struct nfs_page *prev,
> >  static int nfs_pageio_do_add_request(struct nfs_pageio_descriptor *desc,
> >  				     struct nfs_page *req)
> >  {
> > -	size_t newlen = req->wb_bytes;
> > -
> >  	if (desc->pg_count != 0) {
> >  		struct nfs_page *prev;
> >  
> > -		/*
> > -		 * FIXME: ideally we should be able to coalesce all requests
> > -		 * that are not block boundary aligned, but currently this
> > -		 * is problematic for the case of bsize < PAGE_CACHE_SIZE,
> > -		 * since nfs_flush_multi and nfs_pagein_multi assume you
> > -		 * can have only one struct nfs_page.
> > -		 */
> > -		if (desc->pg_bsize < PAGE_SIZE)
> > -			return 0;
> > -		newlen += desc->pg_count;
> > +		desc->pg_count += req->wb_bytes;
> 
> - 		desc->pg_count += req->wb_bytes;
> 
> >  		prev = nfs_list_entry(desc->pg_list.prev);
> >  		if (!nfs_can_coalesce_requests(prev, req, desc))
> >  			return 0;
> 
> + 		desc->pg_count += req->wb_bytes;
> 
> > -	} else
> > +	} else {
> >  		desc->pg_base = req->wb_pgbase;
> > +		desc->pg_count = req->wb_bytes;
> > +	}
> >  	nfs_list_remove_request(req);
> >  	nfs_list_add_request(req, &desc->pg_list);
> > -	desc->pg_count = newlen;

Wait. Why not just replace this line with

desc->pg_count += req->wb_bytes;

That should always be correct.

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@netapp.com
www.netapp.com