From: Theodore Tso <tytso@mit.edu>
To: Curt Wohlgemuth <curtw@google.com>
Cc: Valerie Aurora <vaurora@redhat.com>,
ext4 development <linux-ext4@vger.kernel.org>
Subject: Re: Odd "leak" of extent info into data blocks?
Date: Tue, 8 Sep 2009 15:40:45 -0400 [thread overview]
Message-ID: <20090908194045.GQ22901@mit.edu> (raw)
In-Reply-To: <6601abe90909081121p17b154a4s2e6852da2b71951f@mail.gmail.com>
On Tue, Sep 08, 2009 at 11:21:11AM -0700, Curt Wohlgemuth wrote:
> Hi Valerie:
>
> On Tue, Sep 8, 2009 at 10:56 AM, Valerie Aurora<vaurora@redhat.com> wrote:
> > Hey, did you figure this out? If not, I want to have a bug open
> > somewhere.
>
> Yes, sorry. I was going to post a patch for this, but have been
> waiting to verify that it really fixes the issue. And see the thread
> started by Frank Mayhar about fsync issues as well...
>
> The problem is a race, between the last write to a to-be-freed
> metadata block (to update the extent header) and the block being
> marked free in the on-disk/buddy bitmaps. Note that this only happens
> without a journal, since *with* a journal the ordering is done
> correctly.
Just to clarify, this a race that shows up even without an unclean
shutdown, right?
> Without a journal, the block buffer_head is written to, the
> buffer_head is marked dirty, and the bitmaps are updated via
> ext4_free_blocks(). In rare cases, the block is re-allocated for
> another inode and written to -- subsequently, the writeback mechanism
> will then flush the dirty extent header back to disk. That's why it
> looks like "leaked extent data" in the data block.
If this shows up even without an unclean shutdown, then it sounds like
the problem is a missing bforget() call.
- Ted
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next prev parent reply other threads:[~2009-09-08 19:40 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-08-22 23:10 Odd "leak" of extent info into data blocks? Curt Wohlgemuth
[not found] ` <20090908175605.GB7801@shell>
2009-09-08 18:21 ` Curt Wohlgemuth
2009-09-08 19:40 ` Theodore Tso [this message]
2009-09-08 21:18 ` Curt Wohlgemuth
2009-09-08 23:36 ` Theodore Tso
2009-09-09 4:00 ` Curt Wohlgemuth
2009-09-09 15:19 ` Theodore Tso
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