From: Chris Mason <clm@fb.com>
To: Hugo Mills <hugo@carfax.org.uk>,
Btrfs mailing list <linux-btrfs@vger.kernel.org>
Subject: Re: Bug/regression: Read-only mount not read-only
Date: Mon, 30 Nov 2015 11:48:01 -0500 [thread overview]
Message-ID: <20151130164801.GD2162@ret.masoncoding.com> (raw)
In-Reply-To: <20151128134634.GF24333@carfax.org.uk>
On Sat, Nov 28, 2015 at 01:46:34PM +0000, Hugo Mills wrote:
> We've just had someone on IRC with a problem mounting their FS. The
> main problem is that they've got a corrupt log tree. That isn't the
> subject of this email, though.
>
> The issue I'd like to raise is that even with -oro as a point
> option, the FS is trying to replay the log tree. The dmesg output from
> mount -oro is at the end of the email.
>
> Now, my memory, experience and understanding is that the FS
> doesn't, and shouldn't replay the log tree on a RO mount, because the
> FS should still be consistent even without the reply, and
> RO-means-actually-RO is possible and desirable. (Compared to a
> journalling FS, where journal replay is required for a consistent,
> usable FS).
>
> So, this looks to me like a regression that's come in somewhere.
>
> (Just for completeness, the system in question usually runs 4.2.5,
> but the live CD the OP is using is 4.2.3).
We do need to replay the log tree, even on readonly mounts. Otherwise
files created and fsunk before crashing may not even exist.
We'll bail out of the log replay on readonly media, but otherwise the
replay always happens.
-chris
next prev parent reply other threads:[~2015-11-30 16:48 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-28 13:46 Bug/regression: Read-only mount not read-only Hugo Mills
2015-11-30 14:59 ` Austin S Hemmelgarn
2015-11-30 15:28 ` Hugo Mills
2015-11-30 16:00 ` Austin S Hemmelgarn
2015-11-30 16:48 ` Chris Mason [this message]
2015-11-30 17:06 ` Hugo Mills
2015-12-01 19:00 ` Chris Mason
2015-12-01 19:05 ` Eric Sandeen
2015-12-02 6:25 ` Russell Coker
2015-12-02 9:06 ` Qu Wenruo
2015-12-02 9:23 ` Qu Wenruo
2015-12-02 16:54 ` Eric Sandeen
2015-12-02 17:48 ` Austin S Hemmelgarn
2015-12-02 18:53 ` Hugo Mills
2015-12-02 22:48 ` Eric Sandeen
2015-12-02 23:40 ` Qu Wenruo
2015-12-02 23:51 ` Hugo Mills
2015-12-03 6:44 ` Duncan
2015-12-04 12:32 ` Austin S Hemmelgarn
2015-12-04 12:23 ` Austin S Hemmelgarn
2015-11-30 17:08 ` Austin S Hemmelgarn
2015-12-01 6:46 ` Qu Wenruo
2015-12-01 18:54 ` Chris Mason
2015-12-01 23:47 ` Qu Wenruo
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