From: Christoph Hellwig <hch@infradead.org>
To: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: "J. Bruce Fields" <bfields@fieldses.org>,
Moazam Raja <moazam@gmail.com>,
linux-nfs@vger.kernel.org
Subject: Re: O_DIRECT, O_SYNC, or fsync() on NFS mounts?
Date: Sun, 21 Nov 2010 05:46:24 -0500 [thread overview]
Message-ID: <20101121104624.GA13874@infradead.org> (raw)
In-Reply-To: <1290201995.3135.63.camel@heimdal.trondhjem.org>
On Fri, Nov 19, 2010 at 04:26:35PM -0500, Trond Myklebust wrote:
> If the application requests O_DIRECT/O_SYNC or calls fsync(), we are
> required by POSIX to ensure the data is safe on disk. The presence of an
> NFS delegation does not change that requirement.
That's not quite correct. O_DIRECT for one is not actually specific in
Posix at all, and the documented Linux semantics only say that the
pagecache should not be used (even if it sometimes is with various
filesystems). There is not guarantee that data actually is on disk or
reachable, for that you need to add the O_SYNC/O_DYSNC flag in addition
or use fsync/fdatasync.
next prev parent reply other threads:[~2010-11-21 10:46 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-18 23:34 O_DIRECT, O_SYNC, or fsync() on NFS mounts? Moazam Raja
2010-11-19 19:24 ` Trond Myklebust
2010-11-19 19:55 ` Chuck Lever
2010-11-19 20:04 ` J. Bruce Fields
2010-11-19 21:26 ` Trond Myklebust
2010-11-19 21:48 ` J. Bruce Fields
2010-11-21 10:46 ` Christoph Hellwig [this message]
2010-11-21 19:31 ` Moazam Raja
2010-11-21 20:01 ` Trond Myklebust
[not found] ` <AANLkTi=AV20AsUKOGfVg6M92T8LfPLuuyrG_hQESw_RU@mail.gmail.com>
2010-11-20 23:54 ` Trond Myklebust
[not found] ` <AANLkTikFfdMWs0b4V1doVYUx1T96+ef8-dMUZf3v8cW9@mail.gmail.com>
2010-11-22 18:04 ` Trond Myklebust
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