From: "Berthier, Emmanuel" <emmanuel.berthier@intel.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>
Subject: RE: fsync() does not flush all the file
Date: Fri, 2 Sep 2011 10:53:11 +0000 [thread overview]
Message-ID: <65CD3FC07F3BF942ABE211646D72D77001C474@IRSMSX102.ger.corp.intel.com> (raw)
In-Reply-To: <20110902081312.GA20157@infradead.org>
> From: linux-fsdevel-owner@vger.kernel.org [mailto:linux-fsdevel-owner@vger.kernel.org] On Behalf Of Christoph Hellwig
> On Fri, Sep 02, 2011 at 07:59:56AM +0000, Berthier, Emmanuel wrote:
> >
> > I've reproduced the issue on a PC with Ubuntu 10.04, but as the SSD drive contains cache, it's clear that this configuration can't guaranty the > immediate flushing of the file on the flash memory.
> >
> > A new info of today: the issue disappears if I call fflush() before fsync(): all the file is well flushed at a time.
> > The problem is that this is not the behavior of Sqlite3.6.2 (I've trace sys calls with strace, no fflush() on journal) (same for last 3.7.7.1).
> >
> > Who's wrong? FS or Sqlite?
>
> Oh. that actually sounds very much like a bug in sqlite.
>
> If you use the fread/fwrite family of userspace-buffered stream I/O you
> do need the fflush call to actually make the written data visible to the
> kernel, fsync has no chance to pick it up before that.
>
> It really surprise me sqlite uses fwrite for its intent log, as loggin
> generall is absolutely latency an integrity critical, and the streaming
> I/O APIs just make that more complicated.
You're right, I used fprintf(). After replacing these calls by write() ones, no more issue!
And yes, Sqlite uses write() calls also.
Thanks a lot!
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prev parent reply other threads:[~2011-09-02 10:53 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-01 18:12 fsync() does not flush all the file Berthier, Emmanuel
2011-09-01 21:50 ` Christoph Hellwig
2011-09-02 7:59 ` Berthier, Emmanuel
2011-09-02 8:13 ` Christoph Hellwig
2011-09-02 10:53 ` Berthier, Emmanuel [this message]
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