From: Christoph Hellwig <hch@infradead.org>
To: Trond Myklebust <trondmy@primarydata.com>
Cc: Christoph Hellwig <hch@infradead.org>,
"linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>,
"xfs@oss.sgi.com" <xfs@oss.sgi.com>
Subject: Re: [PATCH 10/12] NFS: Do not serialise O_DIRECT reads and writes
Date: Thu, 16 Jun 2016 02:12:41 -0700 [thread overview]
Message-ID: <20160616091241.GA15953@infradead.org> (raw)
In-Reply-To: <E6003989-FB5F-4FE8-A161-C6E52E031091@primarydata.com>
On Wed, Jun 15, 2016 at 03:45:37PM +0000, Trond Myklebust wrote:
> Serialisation is not mandatory in POSIX:
>
> http://pubs.opengroup.org/onlinepubs/9699919799/functions/write.html
>
> ???Writes can be serialized with respect to other reads and writes. If a read() of file data can be proven (by any means) to occur after a write() of the data, it must reflect that write(), even if the calls are made by different processes. A similar requirement applies to multiple write operations to the same file position. This is needed to guarantee the propagation of data from write() calls to subsequent read() calls. This requirement is particularly significant for networked file systems, where some caching schemes violate these semantics.???
That is the basic defintion, but once O_DSYNC and friends come into
play it gets more complicated:
next prev parent reply other threads:[~2016-06-16 9:12 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-14 19:05 [PATCH 01/12] NFS: Don't flush caches for a getattr that races with writeback Trond Myklebust
2016-06-14 19:05 ` [PATCH 02/12] NFS: Cache access checks more aggressively Trond Myklebust
2016-06-14 19:05 ` [PATCH 03/12] NFS: Cache aggressively when file is open for writing Trond Myklebust
2016-06-14 19:05 ` [PATCH 04/12] NFS: Kill NFS_INO_NFS_INO_FLUSHING: it is a performance killer Trond Myklebust
2016-06-14 19:05 ` [PATCH 05/12] NFS: writepage of a single page should not be synchronous Trond Myklebust
2016-06-14 19:05 ` [PATCH 06/12] NFS: Don't hold the inode lock across fsync() Trond Myklebust
2016-06-14 19:05 ` [PATCH 07/12] NFS: Don't enable deep stack recursion when doing memory reclaim Trond Myklebust
2016-06-14 19:05 ` [PATCH 08/12] NFS: Fix O_DIRECT verifier problems Trond Myklebust
2016-06-14 19:05 ` [PATCH 09/12] NFS: Ensure we reset the write verifier 'committed' value on resend Trond Myklebust
2016-06-14 19:05 ` [PATCH 10/12] NFS: Do not serialise O_DIRECT reads and writes Trond Myklebust
2016-06-14 19:05 ` [PATCH 11/12] NFS: Don't count O_DIRECT reads in the inode->i_dio_count Trond Myklebust
2016-06-14 19:05 ` [PATCH 12/12] NFS: Clean up nfs_direct_complete() Trond Myklebust
2016-06-15 7:16 ` [PATCH 11/12] NFS: Don't count O_DIRECT reads in the inode->i_dio_count Christoph Hellwig
2016-06-15 14:36 ` Trond Myklebust
2016-06-15 14:41 ` Christoph Hellwig
2016-06-15 14:50 ` Trond Myklebust
2016-06-15 14:53 ` Christoph Hellwig
2016-06-15 7:13 ` [PATCH 10/12] NFS: Do not serialise O_DIRECT reads and writes Christoph Hellwig
2016-06-15 14:29 ` Trond Myklebust
2016-06-15 14:48 ` Christoph Hellwig
2016-06-15 14:52 ` Trond Myklebust
2016-06-15 14:56 ` Christoph Hellwig
2016-06-15 15:09 ` Trond Myklebust
2016-06-15 15:14 ` Christoph Hellwig
2016-06-15 15:45 ` Trond Myklebust
2016-06-16 9:12 ` Christoph Hellwig [this message]
2016-06-15 7:09 ` [PATCH 07/12] NFS: Don't enable deep stack recursion when doing memory reclaim Christoph Hellwig
2016-06-15 7:08 ` [PATCH 06/12] NFS: Don't hold the inode lock across fsync() Christoph Hellwig
2016-06-15 14:47 ` Trond Myklebust
2016-06-15 14:54 ` Christoph Hellwig
2016-06-17 1:11 ` [PATCH 03/12] NFS: Cache aggressively when file is open for writing Oleg Drokin
2016-06-17 14:01 ` Trond Myklebust
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