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Re: [PATCH] xfs: Fix possible truncation of log data in xlog_bread_noali

To: Tony Lu <zlu@xxxxxxxxxx>
Subject: Re: [PATCH] xfs: Fix possible truncation of log data in xlog_bread_noalign()
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Tue, 5 Mar 2013 08:03:11 +1100
Cc: Mark Tinguely <tinguely@xxxxxxx>, Alex Elder <elder@xxxxxxxxxx>, "linux-kernel@xxxxxxxxxxxxxxx" <linux-kernel@xxxxxxxxxxxxxxx>, Chris Metcalf <cmetcalf@xxxxxxxxxx>, "xfs@xxxxxxxxxxx" <xfs@xxxxxxxxxxx>, Ben Myers <bpm@xxxxxxx>, Dave Chinner <dchinner@xxxxxxxxxx>, "linux-fsdevel@xxxxxxxxxxxxxxx" <linux-fsdevel@xxxxxxxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <BAB94DBB0E89D8409949BC28AC95914C47C4C19C@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
References: <BAB94DBB0E89D8409949BC28AC95914C47C485E5@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> <20130223000802.GB26081@dastard> <BAB94DBB0E89D8409949BC28AC95914C47C48702@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> <20130223235546.GA5551@dastard> <BAB94DBB0E89D8409949BC28AC95914C47C488D8@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> <20130224141017.GC5551@dastard> <BAB94DBB0E89D8409949BC28AC95914C47C49005@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> <5130CE9E.9080501@xxxxxxx> <51310E7A.1000905@xxxxxxx> <BAB94DBB0E89D8409949BC28AC95914C47C4C19C@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Mon, Mar 04, 2013 at 08:32:45AM +0000, Tony Lu wrote:
> Thanks for you following up.
> 
> My apologize that I just found that it is one change I made before
> that causes this problem. This change forces mkfs.xfs to format
> xfs partitions whose sectorsize were not smaller than 4096 bytes,
> which was due to a bug that earlier versions of xfs used (struct
> *page)->private(long) as a bitmap to represent each block's state
> within a page (the size of a page could be 64K or larger, then it
> needs 128 bit or more to represent each block's state within a
> page).

You do realise that bug doesn't affect x86-64 platforms as they
don't support 64k pages?

> This is reproducible on 2.6.38.6 kernel on X86. But I do not get
> why this change makes the xfs log inconsistent during
> mount/cp/umount operations.

Neither do I, and I don't care to look any further because the
problem is of your own making. In future, please check first that
the bug you are reporting is reproducable on a current upstream
kernel and userspace.

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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