Re: [PATCH 3/4] loop: Add 'lo_logical_blocksize'

[Hannes Reinecke]

On 11/01/2016 03:01 PM, Christoph Hellwig wrote:
> On Mon, Oct 31, 2016 at 08:37:18PM +0100, Hannes Reinecke wrote:
> > Add a new field 'lo_logical_blocksize' to hold the logical
> > blocksize of the loop device.
>
> Why do we use the same flag for both block sizes?  If there is a good
> reason for that it should be documented and both should be in the same
> patch.
_Actually_ the flag enables you to set the logical blocksize.
However, if you want to set the logical blocksize you also have to set a 
matching physical blocksize.
And the physical blocksize itself isn't settable, rather taken from the 
underlying device/filesystem/whatever.
So the flag itself does not have a dual purpose, it's just out of 
necessity that you have to set the physical blocksize if you want to 
change the logical blocksize.

And I got pushback when I proposed to set the physical blocksize always,
so I made it dependent on the LO_BLOCKSIZE flag, too.

Cheers,

Hannes
--
Dr. Hannes Reinecke		      zSeries & Storage
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