From: Eric Sandeen <sandeen@redhat.com>
To: Johann Lombardi <johann@whamcloud.com>
Cc: linux-ext4@vger.kernel.org, Andreas Dilger <adilger@whamcloud.com>
Subject: Re: [PATCH] ext4: add support for multiple mount protection
Date: Tue, 12 Apr 2011 15:39:33 -0500 [thread overview]
Message-ID: <4DA4B885.6020004@redhat.com> (raw)
In-Reply-To: <1302631493-9778-1-git-send-email-johann@whamcloud.com>
On 4/12/11 1:04 PM, Johann Lombardi wrote:
> Prevent an ext4 filesystem from being mounted multiple times.
> A sequence number is stored on disk and is periodically updated (every 5
> seconds by default) by a mounted filesystem.
> At mount time, we now wait for s_mmp_update_interval seconds to make sure
> that the MMP sequence does not change.
> In case of failure, the nodename, bdevname and the time at which the MMP
> block was last updated is displayed.
>
> Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
> Signed-off-by: Johann Lombardi <johann@whamcloud.com>
> ---
> fs/ext4/ext4.h | 56 ++++++++-
> fs/ext4/super.c | 363 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
> 2 files changed, 416 insertions(+), 3 deletions(-)
>
There was a lot of skepticism about this last time, and I imagine there still is...
400 new lines of kernel code for this, and if the other machine is hung up for 5 seconds and doesn't update, it can still be multiply-mounted anyway, right?
BUG: soft lockup - CPU#0 stuck for 10s! anyone? :(
I don't see the value in it for upstream ext4, but then hey, ext4 rarely meets a feature it doesn't like ;)
-Eric
next prev parent reply other threads:[~2011-04-12 20:39 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-12 18:04 [PATCH] ext4: add support for multiple mount protection Johann Lombardi
2011-04-12 19:20 ` Bernd Schubert
2011-05-02 13:43 ` Johann Lombardi
2011-04-12 20:39 ` Eric Sandeen [this message]
2011-04-12 21:08 ` Andreas Dilger
2011-04-12 21:11 ` Johann Lombardi
2011-04-12 21:41 ` Bernd Schubert
2011-04-12 21:44 ` Eric Sandeen
-- strict thread matches above, loose matches on Subject: below --
2011-05-02 8:11 MMP update Johann Lombardi
2011-05-02 9:36 ` [PATCH] ext4: add support for multiple mount protection Johann Lombardi
2011-05-23 2:19 ` Ted Ts'o
2011-05-14 0:38 Johann Lombardi
2011-05-24 21:47 ` Ted Ts'o
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