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Message-ID: <20120308232041.GU3592@dastard>
Date: Fri, 9 Mar 2012 10:20:41 +1100
From: Dave Chinner <david@...morbit.com>
To: Jan Kara <jack@...e.cz>
Cc: LKML <linux-kernel@...r.kernel.org>, linux-fsdevel@...r.kernel.org,
Al Viro <viro@...IV.linux.org.uk>,
Christoph Hellwig <hch@...radead.org>, dchinner@...hat.com,
sandeen@...hat.com, Kamal Mostafa <kamal@...onical.com>,
Ben Myers <bpm@....com>, Alex Elder <elder@...nel.org>,
xfs@....sgi.com
Subject: Re: [PATCH 11/19] xfs: Convert to new freezing code
On Mon, Mar 05, 2012 at 05:01:09PM +0100, Jan Kara wrote:
> Generic code now blocks all writers from standard write paths. So we block all
> writers coming from ioctl and replace blocking of transactions on frozen
> filesystem with a debugging check. As a bonus, we get a protection of ioctl
> against racing remount read-only. We also convert xfs_file_aio_write() to a
> non-racy freeze protection.
....
> diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
> index 329b06a..6468a2a 100644
> --- a/fs/xfs/xfs_trans.c
> +++ b/fs/xfs/xfs_trans.c
> @@ -577,7 +577,6 @@ xfs_trans_alloc(
> xfs_mount_t *mp,
> uint type)
> {
> - xfs_wait_for_freeze(mp, SB_FREEZE_TRANS);
> return _xfs_trans_alloc(mp, type, KM_SLEEP);
> }
So what is there to stop internal XFS threads from starting
transactions when the filesystem is frozen? Previously this
SB_FREEZE_TRANS would guarantee even internal fucntions would get
stopped, but now there's nothing?
I do beleive that ext4 has the same problem (the issue reported with
the lazy inode init background thread), and I can see that any other
filesystem that can make modifications via internal triggers will
see the same problem - freeze doesn't block them any more...
Cheers,
Dave.
--
Dave Chinner
david@...morbit.com
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