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Message-ID: <49A1E3EB.8050708@garzik.org>
Date: Sun, 22 Feb 2009 18:46:51 -0500
From: Jeff Garzik <jeff@garzik.org>
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To: Theodore Tso <tytso@mit.edu>
CC: Pavel Machek <pavel@ucw.cz>, Eric Sandeen <sandeen@redhat.com>,
       Jan Kara <jack@suse.cz>,
       Fernando Luis V?zquez Cao <fernando@oss.ntt.co.jp>,
       Alan Cox <alan@lxorguk.ukuu.org.uk>,
       kernel list <linux-kernel@vger.kernel.org>,
       Jens Axboe <jens.axboe@oracle.com>, fernando@kic.ac.jp,
       Ric Wheeler <rwheeler@redhat.com>,
       Andrew Morton <akpm@linux-foundation.org>
Subject: Re: vfs: Add MS_FLUSHONFSYNC mount flag
References: <20090119120349.GA10193@duck.suse.cz> <1233135913.5399.57.camel@sebastian.kern.oss.ntt.co.jp> <20090128095518.GA16554@duck.suse.cz> <1234434811.15270.7.camel@sebastian.kern.oss.ntt.co.jp> <1234434970.15433.4.camel@sebastian.kern.oss.ntt.co.jp> <499458C1.90105@redhat.com> <20090212212304.GA7935@duck.suse.cz> <499494E2.3060006@redhat.com> <20090213022336.GH6922@mini-me.lan> <20090222141532.GC1586@ucw.cz> <20090222231914.GI17066@mit.edu> <49A1E2D3.9000304@garzik.org>
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Jeff Garzik wrote:
> Correctness should come before performance.  Linux has not had 
> credibility here, in the ATA+ext[23] space at least, and it is 
> embarrassing.


To be more clear / precise, this means actually performing the 
guarantees we claim to the user.  For example,

fsync(2) on ext2 should trigger a storage device writeback cache flush 
[or equivalent guarantee via FUA].

fsync(2) or journal commit on ext3 should trigger a flush [or equivalent 
guarantee via FUA].

Though, certainly, the user should be able to disable this strict 
behavior and trade correctness for performance.

	Jeff