linux-kernel - Re: Entirely unexpected ENOSPC?

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Date:	Wed, 4 Mar 2009 13:50:53 -0500
From:	Josef Bacik <josef@...hat.com>
To:	Hugo Mills <hugo-lkml@...fax.org.uk>, linux-btrfs@...r.kernel.org,
	linux-kernel@...r.kernel.org, Chris Mason <chris.mason@...cle.com>
Subject: Re: Entirely unexpected ENOSPC?

On Wed, Mar 04, 2009 at 06:06:19PM +0000, Hugo Mills wrote:
>    Last night, this event jammed up a good chunk of my server:
> 
> Mar  4 01:51:36 vlad kernel: btrfs searching for 1716224 bytes, num_bytes 1716224, loop 2, allowed_alloc 1
> Mar  4 01:51:36 vlad kernel: btrfs searching for 860160 bytes, num_bytes 860160, loop 2, allowed_alloc 1
> [lots of this...]
> Mar  4 01:55:52 vlad kernel: btrfs searching for 4096 bytes, num_bytes 4096, loop 2, allowed_alloc 1
> Mar  4 01:55:52 vlad kernel: btrfs allocation failed flags 1, wanted 4096
> Mar  4 01:55:52 vlad kernel: space_info has 0 free, is full
> Mar  4 01:55:52 vlad kernel: block group 12582912 has 8388608 bytes, 8388608 used 0 pinned 0 reserved
> Mar  4 01:55:52 vlad kernel: 0 blocks of free space at or bigger than bytes is
> Mar  4 01:55:52 vlad kernel: block group 1103101952 has 1073741824 bytes, 1073741824 used 0 pinned 0 reserved
> Mar  4 01:55:52 vlad kernel: 0 blocks of free space at or bigger than bytes is
> [30 more lines of this]

So yeah thats expected, you ran out of space.  The key thing is this

Mar  4 01:55:52 vlad kernel: space_info has 0 free, is full

If space_info has 0 free and is full, then there is no space to allocate for it
and its completely used.  I'd recommend switching to the -rc7 kernel since that
has things in place to keep this from happening as often.  Thanks,

Josef
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