From: Dave Chinner <david@fromorbit.com>
To: dsterba@suse.cz, Liu Bo <bo.li.liu@oracle.com>,
linux-btrfs@vger.kernel.org, fdmanana@suse.com, kzak@redhat.com,
linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk
Subject: Re: i_version vs iversion (Was: Re: [RFC PATCH v2 1/2] Btrfs: add noi_version option to disable MS_I_VERSION)
Date: Tue, 23 Jun 2015 06:42:15 +1000 [thread overview]
Message-ID: <20150622204215.GA1557@dastard> (raw)
In-Reply-To: <20150618143856.GG6761@suse.cz>
On Thu, Jun 18, 2015 at 04:38:56PM +0200, David Sterba wrote:
> Moving the discussion to fsdevel.
>
> Summary: disabling MS_I_VERSION brings some speedups to btrfs, but the
> generic 'noiversion' option cannot be used to achieve that. It is
> processed before it reaches btrfs superblock callback, where
> MS_I_VERSION is forced.
>
> The proposed fix is to add btrfs-specific i_version/noi_version to btrfs,
> to which I object.
The issue is that you can't overide IS_I_VERSION(inode) because it
looks at the superblock flag, yes?
So perhaps IS_I_VERSION should become an inode flag, set by the
filesystem at inode instantiation time, and hence filesystems can
choose on a per-inode basis if they want I_VERSION behaviour or not.
At that point, the behaviour of MS_I_VERSION becomes irrelevant to
the discussion, doesn't it?
> xfs also forces I_VERSION if it detects the superblock version 5, so it
> could use the same fix that would work for btrfs.
XFS is a special snowflake - it updates the I_VERSION only when an
inode is otherwise modified in a transaction, so turning it off
saves nothing. (And yes, timestamp updates are transactional in
XFS). Hence XFS behaviour is irrelevant to the discussion, because
we aren't ever going to turn it off....
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
WARNING: multiple messages have this Message-ID (diff)
From: Dave Chinner <david@fromorbit.com>
To: dsterba@suse.cz, Liu Bo <bo.li.liu@oracle.com>,
linux-btrfs@vger.kernel.org, fdmanana@suse.com, kzak@redhat.com,
linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk
Subject: Re: i_version vs iversion (Was: Re: [RFC PATCH v2 1/2] Btrfs: add noi_version option to disable MS_I_VERSION)
Date: Tue, 23 Jun 2015 06:42:15 +1000 [thread overview]
Message-ID: <20150622204215.GA1557@dastard> (raw)
In-Reply-To: <20150618143856.GG6761@suse.cz>
On Thu, Jun 18, 2015 at 04:38:56PM +0200, David Sterba wrote:
> Moving the discussion to fsdevel.
>
> Summary: disabling MS_I_VERSION brings some speedups to btrfs, but the
> generic 'noiversion' option cannot be used to achieve that. It is
> processed before it reaches btrfs superblock callback, where
> MS_I_VERSION is forced.
>
> The proposed fix is to add btrfs-specific i_version/noi_version to btrfs,
> to which I object.
The issue is that you can't overide IS_I_VERSION(inode) because it
looks at the superblock flag, yes?
So perhaps IS_I_VERSION should become an inode flag, set by the
filesystem at inode instantiation time, and hence filesystems can
choose on a per-inode basis if they want I_VERSION behaviour or not.
At that point, the behaviour of MS_I_VERSION becomes irrelevant to
the discussion, doesn't it?
> xfs also forces I_VERSION if it detects the superblock version 5, so it
> could use the same fix that would work for btrfs.
XFS is a special snowflake - it updates the I_VERSION only when an
inode is otherwise modified in a transaction, so turning it off
saves nothing. (And yes, timestamp updates are transactional in
XFS). Hence XFS behaviour is irrelevant to the discussion, because
we aren't ever going to turn it off....
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
next prev parent reply other threads:[~2015-06-22 20:42 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-17 7:54 [RFC PATCH v2 1/2] Btrfs: add noi_version option to disable MS_I_VERSION Liu Bo
2015-06-17 7:54 ` [RFC PATCH v2 2/2] Btrfs: improve fsync for nocow file Liu Bo
2015-06-17 15:58 ` David Sterba
2015-06-18 3:27 ` Liu Bo
2015-06-24 18:21 ` David Sterba
2015-06-25 2:24 ` Liu Bo
2015-06-25 16:10 ` David Sterba
2015-06-17 15:33 ` [RFC PATCH v2 1/2] Btrfs: add noi_version option to disable MS_I_VERSION David Sterba
2015-06-17 15:52 ` Liu Bo
2015-06-17 17:01 ` David Sterba
2015-06-18 2:46 ` Liu Bo
2015-06-18 14:38 ` i_version vs iversion (Was: Re: [RFC PATCH v2 1/2] Btrfs: add noi_version option to disable MS_I_VERSION) David Sterba
2015-06-19 11:44 ` Karel Zak
2015-06-19 11:44 ` Karel Zak
2015-06-22 20:42 ` Dave Chinner [this message]
2015-06-22 20:42 ` Dave Chinner
2015-06-24 17:28 ` David Sterba
2015-06-23 16:32 ` Theodore Ts'o
2015-06-24 8:23 ` Liu Bo
2015-06-24 18:02 ` David Sterba
2015-06-24 23:17 ` Theodore Ts'o
2015-06-24 23:17 ` Theodore Ts'o
2015-06-24 23:59 ` Dave Chinner
2015-06-24 23:59 ` Dave Chinner
2015-06-25 18:46 ` J. Bruce Fields
2015-06-25 18:46 ` J. Bruce Fields
2015-06-25 22:12 ` Theodore Ts'o
2015-06-26 13:32 ` J. Bruce Fields
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