Re: quotas: failure on removing a file via SFTP/SSH

[ST <smntov@gmail.com>]

> >>> I'm trying to use quotas for a simple chrooted sftp setup, limiting
> >>> space for each user's subvolume (now for testing to 1M).
> >>>
> >>> I tried to hit the limit by uploading files and once it comes to the
> >>> limit I face following problem: if I try to free space by removing a
> >>> file via Linux sftp client (or Filezilla) - I get error:
> >>> "Couldn't delete file: Failure"
> >>>
> >>> Sometimes, but not always, if I repeat it for 3-5 times it does removes
> >>> the file at the end.
> >>> If I login as root and try to remove the file via SSH I get the error:
> >>> "rm: cannot remove 'example.txt': Disk quota exceeded"
> >>>
> >>> What is the problem? And how can I solve it?
> >>
> >> Kernel version first.
> >>
> >> If it's possible, please use latest kernel, at least newer than v4.10,
> >> since we have a lot of qgroup reservation related fixes in newer kernel.
> >>
> >> Then, for small quota, due to the nature of btrfs metadata CoW and
> >> relative large default node size (16K), it's quite easy to hit disk
> >> quota for metadata.
> > 
> > Yes, but why I get the error specifically on REMOVING a file? Even if I
> > hit disk quota - if I free up space - it should be possible, isn't it?
> 
> It's only true for fs modifying its metadata in-place (and use journal
> to protect it).
> 
> For fs using metadata CoW, even freeing space needs extra space for new
> metadata.
> 

Wait, it doesn't sound like a bug, but rather like a flaw in design.
This means - each time a user hits his quota limit he will get stuck
without being able to free space?!!

Thank you.