From: Andrew Morton <akpm@osdl.org>
To: cel@citi.umich.edu
Cc: cel@netapp.com, linux-kernel@vger.kernel.org, trond.myklebust@fys.uio.no
Subject: Re: [PATCH 1/6] nfs: "open code" the NFS direct write rescheduler
Date: Fri, 19 May 2006 11:46:09 -0700 [thread overview]
Message-ID: <20060519114609.7b6d059d.akpm@osdl.org> (raw)
In-Reply-To: <446E104F.3060900@citi.umich.edu>
Chuck Lever <cel@citi.umich.edu> wrote:
>
> Andrew Morton wrote:
> > Chuck Lever <cel@netapp.com> wrote:
> >> + * Prevent I/O completion while we're still rescheduling
> >> + */
> >> + dreq->outstanding++;
> >> +
> >
> > No locking.
> >
> >> dreq->count = 0;
> >> + list_for_each(pos, &dreq->rewrite_list) {
> >> + struct nfs_write_data *data =
> >> + list_entry(dreq->rewrite_list.next, struct nfs_write_data, pages);
> >> +
> >> + spin_lock(&dreq->lock);
> >> + dreq->outstanding++;
> >> + spin_unlock(&dreq->lock);
> >
> > Locking.
> >
> > Deliberate?
>
> Yes. At the top of the loop, there is no outstanding I/O, so no locking
> is needed while updating "outstanding." Inside the loop, we've
> dispatched some I/O against "dreq" so locking is needed to ensure
> outstanding is updated properly.
>
OK. Well if I asked, then others will wonder about it. A comment would
cure that problem ;)
next prev parent reply other threads:[~2006-05-19 18:43 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-05-19 17:56 [PATCH 0/6] Support scatter/gather I/O in NFS direct I/O path Chuck Lever
2006-05-19 18:00 ` [PATCH 1/6] nfs: "open code" the NFS direct write rescheduler Chuck Lever
2006-05-19 18:10 ` Andrew Morton
2006-05-19 18:37 ` Chuck Lever
2006-05-19 18:46 ` Andrew Morton [this message]
2006-05-19 18:56 ` Chuck Lever
2006-05-19 18:00 ` [PATCH 2/6] nfs: remove user_addr and user_count from nfs_direct_req Chuck Lever
2006-05-19 18:00 ` [PATCH 3/6] nfs: Eliminate nfs_get_user_pages() Chuck Lever
2006-05-19 18:17 ` Andrew Morton
2006-05-19 19:18 ` Chuck Lever
2006-05-19 18:00 ` [PATCH 4/6] nfs: alloc nfs_read/write_data as direct I/O is scheduled Chuck Lever
2006-05-19 18:00 ` [PATCH 5/6] nfs: check all iov segments for correct memory access rights Chuck Lever
2006-05-19 18:22 ` Andrew Morton
2006-05-19 18:46 ` Chuck Lever
2006-05-19 19:36 ` Chuck Lever
2006-05-19 20:07 ` Andrew Morton
2006-05-19 18:25 ` Badari Pulavarty
2006-05-22 11:27 ` Andi Kleen
2006-05-19 18:00 ` [PATCH 6/6] nfs: Support vector I/O throughout the NFS direct I/O path Chuck Lever
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