From: Mike Snitzer <snitzer@redhat.com>
To: Eric Biggers <ebiggers@kernel.org>
Cc: LVM2 development <lvm-devel@redhat.com>,
markus.schade@gmail.com, Joe Thornber <ejt@redhat.com>,
linux-block <linux-block@vger.kernel.org>,
device-mapper development <dm-devel@redhat.com>,
Joe Thornber <joe.thornber@gmail.com>,
Eric Wheeler <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 20:22:35 -0500 [thread overview]
Message-ID: <CAMM=eLfODVMDtGahspZsGsBM5Ty_dt+8idJVTyeudzHZQqsDdA@mail.gmail.com> (raw)
In-Reply-To: <20200114215248.GK41220@gmail.com>
On Tue, Jan 14, 2020 at 4:53 PM Eric Biggers <ebiggers@kernel.org> wrote:
>
> 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)
Fixed it up, not sure how that happened, sorry about that!
prev parent reply other threads:[~2020-01-15 1:22 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
2020-01-15 1:22 ` Mike Snitzer [this message]
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='CAMM=eLfODVMDtGahspZsGsBM5Ty_dt+8idJVTyeudzHZQqsDdA@mail.gmail.com' \
--to=snitzer@redhat.com \
--cc=dm-devel@lists.ewheeler.net \
--cc=dm-devel@redhat.com \
--cc=ebiggers@kernel.org \
--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 \
/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).