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From: Andi Kleen <andi@firstfloor.org>
To: Mikulas Patocka <mpatocka@redhat.com>
Cc: Andi Kleen <andi-suse@firstfloor.org>,
	linux-kernel@vger.kernel.org, xfs@oss.sgi.com,
	Andi Kleen <andi@firstfloor.org>,
	Alasdair G Kergon <agk@redhat.com>, Milan Broz <mbroz@redhat.com>
Subject: Re: Device loses barrier support (was: Fixed patch for simple barriers.)
Date: Fri, 5 Dec 2008 01:48:49 +0100	[thread overview]
Message-ID: <20081205004849.GX6703@one.firstfloor.org> (raw)
In-Reply-To: <Pine.LNX.4.64.0812041756550.29638@hs20-bc2-1.build.redhat.com>

> And if barriers fail at random points, the user can't turn on disk cache 
> anyway (he would get data corruption if barrier write failed and hardware 

I think we already established earlier in the thread that there is no disk
corruption

> > > I'm wondering, where in fsync() does Linux wait for hardware disk cache to 
> > > be flushed? Isn't there a bug that fsync() will return before the cache is 
> > > flushed? I couldn't really find it. The last thing do_fsync calls is 
> > > filemap_fdatawait and it doesn't do cache flush (blkdev_issue_flush).
> > 
> > At least in fsync() on journaling fs the metadata update should push it.
> > 
> > -Andi
> 
> And what about fdatasync()?

I don't know. The surest way to find out is to instrument it and try.

-Andi
-- 
ak@linux.intel.com

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WARNING: multiple messages have this Message-ID (diff)
From: Andi Kleen <andi@firstfloor.org>
To: Mikulas Patocka <mpatocka@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>,
	linux-kernel@vger.kernel.org, xfs@oss.sgi.com,
	Alasdair G Kergon <agk@redhat.com>,
	Andi Kleen <andi-suse@firstfloor.org>,
	Milan Broz <mbroz@redhat.com>
Subject: Re: Device loses barrier support (was: Fixed patch for simple barriers.)
Date: Fri, 5 Dec 2008 01:48:49 +0100	[thread overview]
Message-ID: <20081205004849.GX6703@one.firstfloor.org> (raw)
In-Reply-To: <Pine.LNX.4.64.0812041756550.29638@hs20-bc2-1.build.redhat.com>

> And if barriers fail at random points, the user can't turn on disk cache 
> anyway (he would get data corruption if barrier write failed and hardware 

I think we already established earlier in the thread that there is no disk
corruption

> > > I'm wondering, where in fsync() does Linux wait for hardware disk cache to 
> > > be flushed? Isn't there a bug that fsync() will return before the cache is 
> > > flushed? I couldn't really find it. The last thing do_fsync calls is 
> > > filemap_fdatawait and it doesn't do cache flush (blkdev_issue_flush).
> > 
> > At least in fsync() on journaling fs the metadata update should push it.
> > 
> > -Andi
> 
> And what about fdatasync()?

I don't know. The surest way to find out is to instrument it and try.

-Andi
-- 
ak@linux.intel.com

  reply	other threads:[~2008-12-05  0:38 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <Pine.LNX.4.64.0812040009340.15169@hs20-bc2-1.build.redhat.com>
     [not found] ` <20081204100050.GN6703@one.firstfloor.org>
2008-12-04 14:00   ` Device loses barrier support (was: Fixed patch for simple barriers.) Mikulas Patocka
2008-12-04 14:00     ` Mikulas Patocka
2008-12-04 14:20     ` Andi Kleen
2008-12-04 14:20       ` Andi Kleen
2008-12-04 14:17       ` Mikulas Patocka
2008-12-04 14:17         ` Mikulas Patocka
2008-12-04 14:58         ` Andi Kleen
2008-12-04 14:58           ` Andi Kleen
2008-12-04 16:45           ` Mikulas Patocka
2008-12-04 16:45             ` Mikulas Patocka
2008-12-04 17:48             ` Andi Kleen
2008-12-04 17:48               ` Andi Kleen
2008-12-04 17:53               ` Christoph Hellwig
2008-12-04 17:53                 ` Christoph Hellwig
2008-12-04 19:37               ` Mikulas Patocka
2008-12-04 19:37                 ` Mikulas Patocka
2008-12-04 22:15                 ` Andi Kleen
2008-12-04 22:15                   ` Andi Kleen
2008-12-04 23:08                   ` Mikulas Patocka
2008-12-04 23:08                     ` Mikulas Patocka
2008-12-05  0:48                     ` Andi Kleen [this message]
2008-12-05  0:48                       ` Andi Kleen
2008-12-05  1:16                       ` Mikulas Patocka
2008-12-05  1:16                         ` Mikulas Patocka
2008-12-05  1:37                         ` Andi Kleen
2008-12-05  1:37                           ` Andi Kleen
2008-12-05  2:21                           ` Mikulas Patocka
2008-12-05  2:21                             ` Mikulas Patocka
2008-12-05  3:09                             ` Andi Kleen
2008-12-05  3:09                               ` Andi Kleen
2008-12-05 11:52                           ` Alan Cox
2008-12-05 11:52                             ` Alan Cox
2008-12-05 12:29                             ` Andi Kleen
2008-12-05 12:29                               ` Andi Kleen
2008-12-05  3:26                 ` Device loses barrier support Eric Sandeen
2008-12-05  3:26                   ` Eric Sandeen
2008-12-07  4:17             ` Device loses barrier support (was: Fixed patch for simple barriers.) Dave Chinner
2008-12-07  4:17               ` Dave Chinner
2008-12-05  5:44           ` Device loses barrier support Timothy Shimmin
2008-12-05  5:44             ` Timothy Shimmin
     [not found] <bFnGM-7mA-5@gated-at.bofh.it>
     [not found] ` <bFpyX-1jh-15@gated-at.bofh.it>
     [not found]   ` <bFquY-2x2-5@gated-at.bofh.it>
     [not found]     ` <bFsnc-51o-37@gated-at.bofh.it>
     [not found]       ` <bFuyC-7Zt-11@gated-at.bofh.it>
     [not found]         ` <bFvuI-L8-29@gated-at.bofh.it>
     [not found]           ` <bFwTJ-2oc-13@gated-at.bofh.it>
     [not found]             ` <bFxwq-3g7-1@gated-at.bofh.it>
     [not found]               ` <bFxGa-3pz-1@gated-at.bofh.it>
     [not found]                 ` <bFHvW-7up-5@gated-at.bofh.it>
     [not found]                   ` <bFHPd-84I-13@gated-at.bofh.it>
2008-12-05 18:21                     ` Device loses barrier support (was: Fixed patch for simple barriers.) Bodo Eggert
2008-12-05 18:21                       ` Bodo Eggert
2008-12-05 18:41                       ` Andi Kleen
2008-12-05 18:41                         ` Andi Kleen

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