On Wed, Feb 8, 2012 at 8:14 PM, Liu Bo <liubo2009@xxxxxxxxxxxxxx> wrote:
> On 02/09/2012 05:01 AM, Mitch Harder wrote:
>> On Wed, Jan 18, 2012 at 10:13 AM, Mitch Harder
>> <mitch.harder@xxxxxxxxxxxxxxxx> wrote:
>>> I have a Btrfs partition that is reliably reproducing premature ENOSPC
>>> when restoring the disk from a tar file, but it is only happening with
>>> zlib compression (lzo or no compression proceeds normally).
>>>
>>> I've had the same issue at least back through the 3.1 kernel series,
>>> and I've been having intermittent issues even further back.
>>>
>>> I am currently using a 3.2.1 kernel merged with Chris' latest
>>> integration branch.
>>>
>>> I've performed about 12 trials trying to explore various combinations
>>> of compress, compress-force, compress[-force]=[zlib,lzo] and
>>> autodefrag.
>>>
>>> If I use no compression, or if I explicitly declare lzo compression, I
>>> don't receive the premature ENOSPC when untarring my restoration
>>> archive to the empty partition.
>>>
>>> If I don't specify compression (zlib is the default) or specify zlib,
>>> I get consistent premature ENOSPC errors regardless of other
>>> combinations.
>>>
>>> I apologize if this is already general knowledge, but I couldn't see
>>> where this has been posted to the list before.
>>>
>>> As time allows, I will try to capture exactly where this ENOSPC is
>>> being issued in btrfs by inserting WARN_ON's in my local version
>>> where-ever ENOSPC is set.
>>
>> Some follow-up...
>>
>> I've injected some debugging code to isolate when the ENOSPC is being
>> generated when using zlib compression.
>>
>> When using zlib, I'm getting intermittent ENOSPC in the
>> may_commit_transaction() function in extent-tree.c at this point:
>>
>> if (delayed_rsv->size < bytes) {
>> spin_unlock(&delayed_rsv->lock);
>> return -ENOSPC;
>> }
>>
>> The typical values for (delayed_rsv->size < bytes) have been:
>> delayed_rsv->size ( = 0x60000) < bytes ( = 0x78000)
>>
>> This typically occurs when unzipping a section of my backup that
>> contains lots of small files that are probably being mostly in-lined.
>>
>> I don't see errors in this section when using lzo or no compression.
>
> Hi Mitch,
>
> Would you like to try this patch?
>
> thanks,
> liubo
>
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index 8603ee4..d83b15e 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -3483,28 +3483,34 @@ static int may_commit_transaction(struct btrfs_root *root,
> if (force)
> goto commit;
>
> - /* See if there is enough pinned space to make this reservation */
> - spin_lock(&space_info->lock);
> - if (space_info->bytes_pinned >= bytes) {
> + if (space_info != delayed_rsv->space_info) {
> + /*
> + * For DATA:
> + * See if there is enough pinned space to make this reservation
> + */
> + spin_lock(&space_info->lock);
> + if (space_info->bytes_pinned < bytes) {
> + spin_unlock(&space_info->lock);
> + return -ENOSPC;
> + }
> spin_unlock(&space_info->lock);
> - goto commit;
> - }
> - spin_unlock(&space_info->lock);
> -
> - /*
> - * See if there is some space in the delayed insertion reservation for
> - * this reservation.
> - */
> - if (space_info != delayed_rsv->space_info)
> - return -ENOSPC;
> -
> - spin_lock(&delayed_rsv->lock);
> - if (delayed_rsv->size < bytes) {
> + } else {
> + /*
> + * For METADATA:
> + * See if there is enough space(pinned and delayed insertion)
> + * to make this reservation
> + */
> + spin_lock(&space_info->lock);
> + spin_lock(&delayed_rsv->lock);
> + if (space_info->bytes_pinned + delayed_rsv->size < bytes) {
> + spin_unlock(&delayed_rsv->lock);
> + spin_unlock(&space_info->lock);
> + return -ENOSPC;
> + }
> spin_unlock(&delayed_rsv->lock);
> - return -ENOSPC;
> - }
> - spin_unlock(&delayed_rsv->lock);
> + spin_unlock(&space_info->lock);
>
> + }
> commit:
> trans = btrfs_join_transaction(root);
> if (IS_ERR(trans))
> --
> 1.6.5.2
>
>
Thanks for looking at this, but I'm still getting ENOSPC errors at the
same point after applying this patch.
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