From: Trond Myklebust <trondmy@gmail.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Linux NFS Mailing List <linux-nfs@vger.kernel.org>
Subject: Re: [PATCH 6/7] nfs: take i_mutex during direct I/O reads
Date: Thu, 14 Nov 2013 15:43:21 -0500 [thread overview]
Message-ID: <C0D328CF-8E30-49E7-AE2C-A05EC463921B@gmail.com> (raw)
In-Reply-To: <20131114165042.013211118@bombadil.infradead.org>
On Nov 14, 2013, at 11:50, Christoph Hellwig <hch@infradead.org> wrote:
> We'll need the i_mutex to prevent i_dio_count from incrementing while
> truncate is waiting for it to reach zero, and protects against having
> the pagecache repopulated after we flushed it.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
Hi Christoph,
Why do we need to protect the page cache here? Using O_DIRECT and the page cache without some kind of application-specific synchronization method is technically not supported, since that violates close-to-open cache consistency.
What we _do_ want to support, though, is parallel reads and writes to the server by applications that know what they are doing. If we were to only protect the i_dio_count, then we could fix the truncate race, while continuing to allow parallelism. Is there any reason why we cannot do this?
Cheers
Trond
PS: I appear to be missing 7/7 in this patch series. Should I have seen it?
next prev parent reply other threads:[~2013-11-14 20:43 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-14 16:50 [PATCH 0/7] direct I/O fixes Christoph Hellwig
2013-11-14 16:50 ` [PATCH 1/7] nfs: fix size updates for aio writes Christoph Hellwig
2013-11-14 16:50 ` [PATCH 2/7] nfs: defer inode_dio_done call until size update is done Christoph Hellwig
2013-11-14 16:50 ` [PATCH 3/7] nfs: increment i_dio_count for reads, too Christoph Hellwig
2013-11-14 16:50 ` [PATCH 4/7] nfs: merge nfs_direct_read into nfs_file_direct_read Christoph Hellwig
2013-11-14 16:50 ` [PATCH 5/7] nfs: merge nfs_direct_write into nfs_file_direct_write Christoph Hellwig
2013-11-14 16:50 ` [PATCH 6/7] nfs: take i_mutex during direct I/O reads Christoph Hellwig
2013-11-14 17:00 ` Chuck Lever
2013-11-15 14:29 ` Christoph Hellwig
2013-11-14 20:43 ` Trond Myklebust [this message]
2013-11-15 14:32 ` Christoph Hellwig
2013-11-15 15:23 ` Trond Myklebust
2013-11-15 15:25 ` Christoph Hellwig
2013-11-15 15:34 ` Trond Myklebust
2013-11-15 15:37 ` Christoph Hellwig
2013-11-15 16:00 ` Trond Myklebust
2013-11-14 16:50 ` [PATCH 7/7] nfs: page cache invalidation for dio Christoph Hellwig
2013-11-14 18:35 ` Jeff Layton
2013-11-15 14:28 ` Christoph Hellwig
2013-11-15 14:52 ` Jeff Layton
2013-11-15 15:02 ` Christoph Hellwig
2013-11-15 15:33 ` Jeff Layton
2014-01-21 19:21 ` Jeff Layton
2014-01-22 8:24 ` Christoph Hellwig
2014-01-22 12:04 ` Jeff Layton
2014-01-24 15:50 ` Jeff Layton
2014-01-24 15:52 ` Jeff Layton
2014-01-24 17:11 ` Trond Myklebust
2014-01-24 17:29 ` Jeff Layton
2014-01-24 17:40 ` Trond Myklebust
2014-01-24 18:00 ` Jeff Layton
2014-01-24 18:46 ` Trond Myklebust
2014-01-24 21:21 ` Jeff Layton
2014-01-25 0:39 ` Trond Myklebust
2014-01-25 0:54 ` Jeff Layton
2014-01-25 1:05 ` Trond Myklebust
2014-01-25 1:11 ` Trond Myklebust
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