Re: ext4+quota+nfs issue

[Pavol Cvengros]

On 9/14/2009 8:52 PM, Aneesh Kumar K.V wrote:
> On Mon, Sep 14, 2009 at 07:50:56PM +0200, Jan Kara wrote:
>    
> >    I've found some time to look into this and I can see a few problems in
> > the code. Firstly, what may cause your problems:
> >    vfs_dq_claim_blocks() is called in ext4_mb_mark_diskspace_used(). But
> > as far as I can understand the code, ext4_mb_normalize_request() can
> > increase the amount of space we really allocate and thus we try to
> > allocate more blocks than we have actually reserved in quota. Aneesh, is
> > that right?
> >      
> ext4_mb_mark_diskspace_used use ac->ac_b_ex.fe_len which is NOT the normalized
> request len. it is min(allocated_len, original_len). So i guess that code
> should be safe
>
>
>    
> >    Secondly, ext4_da_reserve_space() seems to have a bug that it can reserve
> > quota blocks multiple times if ext4_claim_free_blocks() fail and we retry
> > the allocation. We should release the quota reservation before restarting.
> > Actually, when we find out we cannot reserve quota space, we could force
> > some delayed allocated writes to disk (thus possibly release some quota
> > in case we have overestimated the amount of blocks needed). But that's
> > a different issue.
> >      
> That would imply the file system was full. But the dumpe2fs ouput list
> large number of free blocks. But yes the code should have released the
> quota reservation before trying block reservation again.
>
>
>    

file system is fresh but unfortunately already used and I can't 
"re-format" it. Is there a way around this? I think that FS was created 
by "mkfs.ext4 -j /dev....."

> >    Thirdly, ext4_indirect_calc_metadata_amount() is wrong for sparse files.
> > The worst case is 3 metadata blocks per data block if we make the file
> > sufficiently sparse and there's no easy way around that...
> >
> >      
> -aneesh
>    

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