linux-block.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Eric Biggers <ebiggers@kernel.org>
To: Mike Snitzer <snitzer@redhat.com>
Cc: LVM2 development <lvm-devel@redhat.com>,
	markus.schade@gmail.com, ejt@redhat.com,
	linux-block@vger.kernel.org, dm-devel@redhat.com,
	joe.thornber@gmail.com, dm-devel@lists.ewheeler.net
Subject: Re: kernel BUG at drivers/md/persistent-data/dm-space-map-disk.c:178
Date: Tue, 14 Jan 2020 13:52:48 -0800	[thread overview]
Message-ID: <20200114215248.GK41220@gmail.com> (raw)
In-Reply-To: <20200107122825.qr7o5d6dpwa6kv62@reti>

On Tue, Jan 07, 2020 at 12:28:25PM +0000, Joe Thornber wrote:
> On Tue, Jan 07, 2020 at 10:46:27AM +0000, Joe Thornber wrote:
> > I'll get a patch to you later today.
> 
> Eric,
> 
> Patch below.  I've run it through a bunch of tests in the dm test suite.  But
> obviously I have never hit your issue.  Will do more testing today.
> 
> - Joe
> 
> 
> 
> Author: Joe Thornber <ejt@redhat.com>
> Date:   Tue Jan 7 11:58:42 2020 +0000
> 
>     [dm-thin, dm-cache] Fix bug in space-maps.
>     
>     The space-maps track the reference counts for disk blocks.  There are variants
>     for tracking metadata blocks, and data blocks.
>     
>     We implement transactionality by never touching blocks from the previous
>     transaction, so we can rollback in the event of a crash.
>     
>     When allocating a new block we need to ensure the block is free (has reference
>     count of 0) in both the current and previous transaction.  Prior to this patch we
>     were doing this by searching for a free block in the previous transaction, and
>     relying on a 'begin' counter to track where the last allocation in the current
>     transaction was.  This 'begin' field was not being updated in all code paths (eg,
>     increment of a data block reference count due to breaking sharing of a neighbour
>     block in the same btree leaf).
>     
>     This patch keeps the 'begin' field, but now it's just a hint to speed up the search.
>     Instead we search the current transaction for a free block, and then double check
>     it's free in the old transaction.  Much simpler.
> 

I happened to notice this patch is on the linux-dm/for-next branch
(https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=for-next&id=2137c0dcc04b24efb4c38d4b46b7194575718dd5)
and it has:

	Reported-by: Eric Biggers <ebiggers@google.com>

This is wrong, I didn't report this.  I think you meant to put:

	Reported-by: Eric Wheeler <dm-devel@lists.ewheeler.net>

- Eric (the other one)

  parent reply	other threads:[~2020-01-14 21:52 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-25 18:40 kernel BUG at drivers/md/persistent-data/dm-space-map-disk.c:178 with scsi_mod.use_blk_mq=y Eric Wheeler
2019-09-25 20:01 ` Mike Snitzer
2019-09-25 20:33   ` Eric Wheeler
2019-09-26 18:27   ` Eric Wheeler
2019-09-27  8:32     ` Joe Thornber
2019-09-27 18:45       ` Eric Wheeler
2019-12-20 19:54 ` [dm-devel] " Eric Wheeler
2019-12-27  1:47   ` [dm-devel] kernel BUG at drivers/md/persistent-data/dm-space-map-disk.c:178 Eric Wheeler
2019-12-28  2:13     ` Eric Wheeler
2020-01-07 10:35       ` [lvm-devel] " Joe Thornber
2020-01-07 10:46         ` Joe Thornber
2020-01-07 12:28           ` [dm-devel] [lvm-devel] " Joe Thornber
2020-01-07 18:47             ` Eric Wheeler
2020-01-14 21:52             ` Eric Biggers [this message]
2020-01-15  1:22               ` Mike Snitzer

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=20200114215248.GK41220@gmail.com \
    --to=ebiggers@kernel.org \
    --cc=dm-devel@lists.ewheeler.net \
    --cc=dm-devel@redhat.com \
    --cc=ejt@redhat.com \
    --cc=joe.thornber@gmail.com \
    --cc=linux-block@vger.kernel.org \
    --cc=lvm-devel@redhat.com \
    --cc=markus.schade@gmail.com \
    --cc=snitzer@redhat.com \
    /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
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
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).