linux-kernel - Re: [PATCH 0/17] Make O_SYNC handling use standard syncing path (Version 2)

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Date:	Mon, 24 Aug 2009 11:29:05 +0200
From:	Jan Kara <jack@...e.cz>
To:	Jamie Lokier <jamie@...reable.org>
Cc:	Jan Kara <jack@...e.cz>, LKML <linux-kernel@...r.kernel.org>,
	hch@....de, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 0/17] Make O_SYNC handling use standard syncing path
	(Version 2)

On Sat 22-08-09 17:27:11, Jamie Lokier wrote:
> Jan Kara wrote:
> > The patch set unifines O_SYNC handling with standard fsync() path.  After this,
> > we have just one place forcing a single file to disk so filesystems like ext3 /
> > ext4 don't have to force a transaction commit in ext?_file_write for O_SYNC
> > files / IS_SYNC inodes.  The code is also cleaner this way (actually about 150
> > lines shorter), we don't sync the inode several times as it happened previously
> > etc.
> 
> Afaik, O_SYNC requires just the written data to be committed to disk,
> but fsync() requires all dirty data for the file (including written by
> other processes / descriptors) to be committed to disk.
> 
> So doing the equivalent of fsync() after write might be the wrong
> thing to do.
  It's OK, we essentially end up doing fdatasync() on the range of the file
where the write happened. So no unnecessary writing happens.

									Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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