Re: ext4 extends implementation question

[Alberto Fuentes <alberto.fuentes@qindel.com>]

On 01/10/2012 11:31 PM, Arno Schuring wrote:
> afuentes (alberto.fuentes@qindel.com on 2012-01-10 10:33 +0100):
> > What happens when you run out of space to allocate new extends in
> > ext4? is not allowed to write anymore even tho there are tons of
> > blocks available?
>
> I'm unsure what you mean. Extents is only an optimization strategy for
> allocating contiguous blocks. If there are no contiguous blocks, ext4
> falls back to allocating singular blocks, but with normal usage
> patterns you should never get "tons of blocks available" with none of
> them contiguous.
>
> At least, that's how I understand it. Are you getting allocation
> failures with still plenty of space available?
>
>
> Regards,
> Arno

This is how i see it

[X][ ][ ][ ][ ][ ][ ][ ][ ][ ][ ][ ]
[X][X][X][X][ ][ ][ ][ ][ ][ ][ ][ ]
[X][X][X][X][X][X][X][X][ ][ ][ ][ ]
[X][X][ ][ ][ ][ ][ ][ ][ ][ ][ ][ ]
[X][X][X][ ][ ][ ][ ][ ][ ][ ][ ][ ]
[-][-][-][-][-][-][-][-][-][-][-][-]
[-][-][-][-][-][-][-][-][-][-][-][-]

row= extends
[x]= used
[ ]= allocated
[-]= free

after allocating two more extends in this scenario, what happens when it 
wants to write again?

thanks!
aL