ENOSPC Regression

ENOSPC Regression

[Mitch Harder]

I'm encountering premature ENOSPC issues recently where my Btrfs
testing partition will either prematurely return an ENOSPC, or lock up
the operations trying to access the partition.

I have bisected the problem to this commit:
http://git.kernel.org/?p=linux/kernel/git/mason/btrfs-unstable.git;a=commit;h=914ee295af418e936ec20a08c1663eaabe4cd07a
(Btrfs: pwrite blocked when writing from the mmaped buffer of the same page)

I am encountering the problem on a small-ish 3.5 GB Btrfs partition.
I can replicate the problem with and without compression.  I can also
replicate the problem with and without reformating the partition.

For most operations I run on this partition, Btrfs is performing
without error.  But when I compile openmotif-2.3.3 on a kernel that is
after the above referenced commit, I'll get either an ENOSPC error or
the partition locks up.

When I encounter a lock-up issue, there are no errors in dmesg, and no
delayed processes are showing (unless I try to run an additional
operation on that partition, such as 'ls', which will subsequently
show up as delayed).  However, the build process for openmotif-2.3.3
appears frozen, and several processes related to the build are shown
as running, and will not even respond to 'kill -s 9 <pid>'

The partition only has about 500 MB of data when I encounter the
problems, and openmotif-2.3.3 typically only requires about 30-60 MB
to compile.

However, running 'btrfs fi show' indicates that btrfs has attempted to
reserve all the space on the disk for data and metadata.  When running
a kernel prior to the above referenced commit, btrfs will compile
openmotif-2.3.3 without needing to reserve much extra space on the
partition.

Let me know if you would like any additional information or tests.

Re: ENOSPC Regression

[Josef Bacik]

On Fri, Feb 11, 2011 at 07:21:47AM -0600, Mitch Harder wrote:
> I'm encountering premature ENOSPC issues recently where my Btrfs
> testing partition will either prematurely return an ENOSPC, or lock up
> the operations trying to access the partition.
> 
> I have bisected the problem to this commit:
> http://git.kernel.org/?p=linux/kernel/git/mason/btrfs-unstable.git;a=commit;h=914ee295af418e936ec20a08c1663eaabe4cd07a
> (Btrfs: pwrite blocked when writing from the mmaped buffer of the same page)
> 
> I am encountering the problem on a small-ish 3.5 GB Btrfs partition.
> I can replicate the problem with and without compression.  I can also
> replicate the problem with and without reformating the partition.
> 
> For most operations I run on this partition, Btrfs is performing
> without error.  But when I compile openmotif-2.3.3 on a kernel that is
> after the above referenced commit, I'll get either an ENOSPC error or
> the partition locks up.
> 
> When I encounter a lock-up issue, there are no errors in dmesg, and no
> delayed processes are showing (unless I try to run an additional
> operation on that partition, such as 'ls', which will subsequently
> show up as delayed).  However, the build process for openmotif-2.3.3
> appears frozen, and several processes related to the build are shown
> as running, and will not even respond to 'kill -s 9 <pid>'
> 
> The partition only has about 500 MB of data when I encounter the
> problems, and openmotif-2.3.3 typically only requires about 30-60 MB
> to compile.
> 
> However, running 'btrfs fi show' indicates that btrfs has attempted to
> reserve all the space on the disk for data and metadata.  When running
> a kernel prior to the above referenced commit, btrfs will compile
> openmotif-2.3.3 without needing to reserve much extra space on the
> partition.
> 
> Let me know if you would like any additional information or tests.

Can you try my btrfs-work tree and see if you still have the same problem?
Thanks,

Josef

Re: ENOSPC Regression

[Mitch Harder]

On Fri, Feb 11, 2011 at 10:22 AM, Josef Bacik <josef@redhat.com> wrote:
> On Fri, Feb 11, 2011 at 07:21:47AM -0600, Mitch Harder wrote:
>> I'm encountering premature ENOSPC issues recently where my Btrfs
>> testing partition will either prematurely return an ENOSPC, or lock =
up
>> the operations trying to access the partition.
>>
>> I have bisected the problem to this commit:
>> http://git.kernel.org/?p=3Dlinux/kernel/git/mason/btrfs-unstable.git=
;a=3Dcommit;h=3D914ee295af418e936ec20a08c1663eaabe4cd07a
>> (Btrfs: pwrite blocked when writing from the mmaped buffer of the sa=
me page)
>>
>> I am encountering the problem on a small-ish 3.5 GB Btrfs partition.
>> I can replicate the problem with and without compression. =A0I can a=
lso
>> replicate the problem with and without reformating the partition.
>>
>> For most operations I run on this partition, Btrfs is performing
>> without error. =A0But when I compile openmotif-2.3.3 on a kernel tha=
t is
>> after the above referenced commit, I'll get either an ENOSPC error o=
r
>> the partition locks up.
>>
>> When I encounter a lock-up issue, there are no errors in dmesg, and =
no
>> delayed processes are showing (unless I try to run an additional
>> operation on that partition, such as 'ls', which will subsequently
>> show up as delayed). =A0However, the build process for openmotif-2.3=
=2E3
>> appears frozen, and several processes related to the build are shown
>> as running, and will not even respond to 'kill -s 9 <pid>'
>>
>> The partition only has about 500 MB of data when I encounter the
>> problems, and openmotif-2.3.3 typically only requires about 30-60 MB
>> to compile.
>>
>> However, running 'btrfs fi show' indicates that btrfs has attempted =
to
>> reserve all the space on the disk for data and metadata. =A0When run=
ning
>> a kernel prior to the above referenced commit, btrfs will compile
>> openmotif-2.3.3 without needing to reserve much extra space on the
>> partition.
>>
>> Let me know if you would like any additional information or tests.
>
> Can you try my btrfs-work tree and see if you still have the same pro=
blem?
> Thanks,
>
> Josef
>

I've built and tested the 2.6.38-rc1 kernel from the master branch of
git://git.kernel.org/pub/scm/linux/kernel/git/josef/btrfs-work.git,
and I am still getting the same issue.

I've just noticed there is another thread going on about this same prob=
lem.

I'll just pile on that thread if I come across something new.
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