linux-ext4 - Re: [PATCH 1/2] ext4: journal all modifications in ext4_xattr_set

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Date:	Sat, 07 Nov 2009 12:22:13 -0700
From:	Andreas Dilger <adilger@....com>
To:	Theodore Tso <tytso@....edu>
Cc:	Eric Sandeen <sandeen@...hat.com>,
	ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH 1/2] ext4: journal all modifications in
 ext4_xattr_set_handle

On 2009-11-06, at 19:33, Theodore Tso wrote:
> On Fri, Nov 06, 2009 at 05:22:51PM -0700, Andreas Dilger wrote:
>> On 2009-11-06, at 15:35, Eric Sandeen wrote:
>>> Oh, and for those who haven't been following the bug, big
>>> thanks to Chris Mason for helping to look into this and coming
>>> up with the debugging patch that made it obvious...
>>
>> It would be great, IMHO, to have this debugging patch submitted to
>> the kernel also, and enabled under a CONFIG option.
>
> The debugging patch is only safe when the file system's block size ==
> page size.  I suppose we could leave a warning in Kconfig that the
> debugging option is only safe to be used when all of the file systems
> in the system have a 4k (or whatever the page size happens to be)
> block size, but it's probably better to clean up the patch so that
> it's only enabled on a mount option, and then only if the file system
> block size is the same as the page size.

Yes, definitely, but this covers about 90% of the filesystems in use,
so I don't see it as a big limitation.

>> I'd also be interested to see the "write shadow buffer to journal"
>> one-line patch that was discussed in the bug.
>
> Which patch are you referring to?


In bugzilla there was a comment from Chris:

         "Eric helped prove this is the case by testing a patch that  
always
          crcs and writes a stable duplicate of the metadata buffer  
instead
          of the metadata buffer itself (a one liner since the log  
code was
          already setup for this)."

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.

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