Re: btrfs dev del not transaction protected?

Qu Wenruo
2019-12-21T01:23:53Z

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On 2019/12/21 上午1:07, Marc Lehmann wrote:
>> Just while I was writing this mail, on 5.4.5, the _newly created_ btrfs
>> filesystem I restored to went into readonly mode with ENOSPC. Another
>> hardware problem?
>
> btrfs check gave me a possible hint:
>
> Checking filesystem on /dev/mapper/xmnt-cold15
> UUID: 6e035cfe-5b47-406a-998f-b8ee6567abbc
> [1/7] checking root items
> [2/7] checking extents
> [3/7] checking free space tree
> cache and super generation don't match, space cache will be invalidated

That's common, and not a problem at all.
Btrfs will rebuild the free space tree.

> [4/7] checking fs roots
> [no other errors]
>
> But mounting with clear_cache,space_cache=v2 didn't help, df still shows 0
> bytes free, "btrfs f us" still shows 3tb unallocated. I'll play around with
> it more...

Df reports 0 available is a bug and caused pinned down.
It's btrfs_statfs() can't co-operate with latest over-commit behavior.

This happens when there are some metadata operation queued.
It's completely a runtime false alert, had nothing incorrect on-disk.

I had a fix submitted for it.
https://patchwork.kernel.org/patch/11293419/

Thanks,
Qu

>

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