From: Bill Kendall <wkendall@sgi.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: xfs@oss.sgi.com
Subject: Re: [PATCH] xfsdump: fix metadata restore on split files
Date: Mon, 31 Oct 2011 07:14:38 -0500 [thread overview]
Message-ID: <4EAE912E.7090303@sgi.com> (raw)
In-Reply-To: <20111028093716.GA23069@infradead.org>
On 10/28/2011 04:37 AM, Christoph Hellwig wrote:
> On Wed, Oct 26, 2011 at 06:24:43PM -0500, Bill Kendall wrote:
>> xfsrestore does not apply certain metadata until all of the file's
>> data has been restored. This allows, for example, files with the
>> immutable flag set to be restored properly.
>>
>> While testing multi-stream restores, I noticed that files split
>> across multiple streams did not have their metadata restored.
>> Looking into this further, it also applies to the single-stream
>> case where files are split across media files, such as when a
>> backup spans multiple tapes.
>>
>> The fix is to check to see if a file is completely restored
>> whenever we hit the end of a media file. The current code
>> is broken because it relies on all media files being applied
>> during the same restore session.
>>
>> This also moves the S_ISREG() check into restore_complete_reg()
>> rather than relying on callers to make the check.
>
> Uhh, that's a nasty bug for people storing large files over multiple
> tapes. Any chance we could get an xfstests test case for this?
I mischaracterized the existing bug, files split across tapes
are okay. The bug occurs when:
- a file ends right at the end of a tape in a multi-tape dump, and
- the next tape is not loaded during the same restore session
(i.e., the restore is interrupted and resumed later)
> Can we somehow simulate multiple tapes using small files?
We can simulate multiple tapes on a single tape by asking for a
small media file size. I've got a couple of tests which do this
which I'll post later today.
I don't have a test for the exact scenario above. That would
require using 2 tapes (or 2 files on small loopback filesystems)
and knowing the exact number of bytes that will fit in the dump
file, then working backwards to find a file size that will end
at the right spot on media. Sounds like a very fragile test. It
would break if, for example, a file in the filesystem being
dumped was written as 2 extents instead of 1.
I'll repost this patch with correct commit message.
Bill
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prev parent reply other threads:[~2011-10-31 12:14 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-26 23:24 [PATCH] xfsdump: fix metadata restore on split files Bill Kendall
2011-10-28 9:37 ` Christoph Hellwig
2011-10-28 13:35 ` Bill Kendall
2011-10-31 12:14 ` Bill Kendall [this message]
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