LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Eric Sandeen <sandeen@redhat.com>
To: Theodore Tso <tytso@mit.edu>, Eric Sandeen <sandeen@redhat.com>,
	Eric Paris <eparis@redhat.com>,
	linux-kernel@vger.kernel.org, linux-ext4@vger.kernel.org
Subject: Re: general protection fault:  from release_blocks_on_commit
Date: Mon, 27 Oct 2008 19:08:37 -0500	[thread overview]
Message-ID: <49065805.1080303@redhat.com> (raw)
In-Reply-To: <20081027232843.GA9797@mit.edu>

Theodore Tso wrote:
> On Mon, Oct 27, 2008 at 05:26:47PM -0500, Eric Sandeen wrote:
>> Ted, you probably need some slab debugging on to hit it.
> 
> I had slab debugging enabled, but haven't been able to replicate it
> yet.  I'll do some more work to try to replicate it.
> 
>> I think the problem is that jbd2_journal_commit_transaction may call
>> __jbd2_journal_drop_transaction(journal, commit_transaction) if the
>> checkpoint lists are NULL, and this frees the commit_transaction.
> 
> I think you're right.  I would probably change the patch around so
> that after calling __jbd2_jurnal_drop_transaction(), we set
> commit_transaction to NULL, and then adding an "if
> (commit_transaction)" to the lines in questions; that way we keep the
> commit callback outside of the j_list_lock() spinlock.

Ok, I thought about that; sounds good.  will resend.

>> Also, I'm not certain that it matters, but the loop in 
>> release_blocks_on_commit() is kfreeing list entries w/o taking
>> them off the list; I suppose maybe this is safe if the whole thing
>> is getting discarded when we're done, but just to keep things sane,
>> would this make sense
> 
> There are plenty of other loops in the kernel where we go through the
> linked list and free all of the items on the list that don't bother to
> call list_del().  That was one of the things I checked when I created
> the patch.

Ok.

>> (also, I think we need to double-check use of
>> s_md_lock; it's taken when adding things to the list, but not when
>> freeing/removing ... if it's needed, isn't it needed on both ends...):
> 
> No, because the linked list is hanging off the transaction structure.
> While the transaction is active, multiple CPU's can be adding elements
> to the linked list.  But once the transaction has been committed, we
> don't have to worry about any one else trying to modify the linked list.
> 
>       	      	    	      	       	      - Ted

ok, just double checking.

Thanks,
-Eric

  reply	other threads:[~2008-10-28  0:09 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-10-21 18:03 Eric Paris
2008-10-27 18:19 ` Theodore Tso
2008-10-27 22:26   ` Eric Sandeen
2008-10-27 23:28     ` Theodore Tso
2008-10-28  0:08       ` Eric Sandeen [this message]
2008-10-28  1:52         ` Theodore Tso
2008-10-28  2:15           ` Eric Sandeen
2008-10-28  2:28           ` [PATCH, RFC] jbd2: Call the commit callback before the transaction could get dropped Theodore Tso
2008-10-28  2:41             ` Eric Sandeen
2008-10-28 13:46               ` Eric Paris

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=49065805.1080303@redhat.com \
    --to=sandeen@redhat.com \
    --cc=eparis@redhat.com \
    --cc=linux-ext4@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=tytso@mit.edu \
    --subject='Re: general protection fault:  from release_blocks_on_commit' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).