From: Boaz Harrosh <bharrosh@panasas.com>
To: NeilBrown <neilb@suse.de>
Cc: "Darrick J. Wong" <darrick.wong@oracle.com>,
"Martin K. Petersen" <martin.petersen@oracle.com>,
"Theodore Ts'o" <tytso@mit.edu>,
linux-ext4 <linux-ext4@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [RFC PATCH 1/2] bdi: Create a flag to indicate that a backing device needs stable page writes
Date: Tue, 30 Oct 2012 16:58:41 -0700 [thread overview]
Message-ID: <509069B1.2040200@panasas.com> (raw)
In-Reply-To: <20121031091441.5fc6b412@notabene.brown>
On 10/30/2012 03:14 PM, NeilBrown wrote:
> On Tue, 30 Oct 2012 13:14:24 -0700 "Darrick J. Wong"
> <darrick.wong@oracle.com> wrote:
>
>> On Tue, Oct 30, 2012 at 08:19:41AM -0400, Martin K. Petersen wrote:
>>>>>>>> "Neil" == NeilBrown <neilb@suse.de> writes:
>>>
<>
> So I see a need for 2 flags here.
Yes that was my thought too. We need two flags. The FS should communicate
it's capabilities as well.
> The first one is set by the device or transport to say "I would prefer
> stable writes if possible".
> The second is set by the filesystem, either because it has its own needs, or
> because it sees the first flag set on the device and chooses to honour it.
> The VFS/VM would act based on this second flag, and devices like md/RAID5
> would set the first flag, and assume writes are stable if the second flag is
> also set.
>
> This implies that setting that second flag must be handled synchronously by
> the filesystem, so that the device doesn't see the flag set until the
> filesystem has committed to honouring it. That seems to make a mount (or
> remount) option the safest way to set it.
>
I think I do not like any mount option or any other tuneable. With the
block device stating it's needs and the FS confirming on it's capability
then I do not see how reverting that decision by admin can be any good.
Any overrides by an admin would then just be a bug.
> Comments?
>
> NeilBrown
>
Thanks
Boaz
next prev parent reply other threads:[~2012-10-30 23:58 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-26 10:19 semi-stable page writes Darrick J. Wong
2012-10-27 1:35 ` [RFC PATCH 1/2] bdi: Create a flag to indicate that a backing device needs stable " Darrick J. Wong
2012-10-29 18:13 ` Jan Kara
2012-10-29 18:30 ` Jan Kara
2012-10-29 23:48 ` NeilBrown
2012-10-30 0:10 ` Jan Kara
2012-10-30 0:34 ` NeilBrown
2012-10-30 13:38 ` Jan Kara
2012-10-30 21:49 ` NeilBrown
2012-10-30 4:10 ` Martin K. Petersen
2012-10-30 4:48 ` NeilBrown
2012-10-30 12:19 ` Martin K. Petersen
2012-10-30 20:14 ` Darrick J. Wong
2012-10-30 22:14 ` NeilBrown
2012-10-30 23:58 ` Boaz Harrosh [this message]
2012-10-31 8:56 ` Darrick J. Wong
2012-10-31 11:56 ` Jan Kara
2012-10-31 19:36 ` Darrick J. Wong
2012-10-31 23:12 ` Boaz Harrosh
2012-11-01 5:51 ` Darrick J. Wong
2012-11-01 6:25 ` Boaz Harrosh
2012-11-01 8:59 ` Jan Kara
2012-11-01 17:24 ` Boaz Harrosh
2012-11-01 22:42 ` Jan Kara
2012-10-30 22:40 ` Boaz Harrosh
2012-10-27 1:36 ` [RFC PATCH 2/2] mm: Gate stable page writes on the bdi flag Darrick J. Wong
2012-10-29 18:28 ` Jan Kara
2012-10-31 8:58 ` Darrick J. Wong
2012-10-29 22:01 ` semi-stable page writes Dave Chinner
2012-10-30 1:00 ` Theodore Ts'o
2012-10-30 23:30 ` Dave Chinner
2012-10-31 11:45 ` Jan Kara
2012-10-30 20:40 ` Darrick J. Wong
2012-10-30 23:43 ` Dave Chinner
2012-10-31 9:05 ` Darrick J. Wong
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