bug#36908: parted optimal alignment fails minimal alignment check

[Brian C. Lane]

On Sat, Aug 03, 2019 at 12:26:56PM +0000, George Fedorov wrote:
> Hi,
> 
> 
> I was directed here by the page at 
> https://www.gnu.org/software/parted/bugs.shtml ; is there any bugreport 
> tracker where one can file a bug instead ?
> 
> 
> Anyway, here's the problem ( manifested in parted 3.2 coming with Ubuntu 
> 18.04 and checked vs. a manual build of the sources from 
> http://ftp.gnu.org/gnu/parted/parted-3.2.tar.xz  ):


The 3.2 tar is *really* old at this point and should not really be used.

[snip]


> As it turns out, the root of all evil comes from here :
> 
> 
> =====
> 
> # cat /sys/block/sdi/queue/optimal_io_size
> 33553920
> =====
> 
> 
> So parted is not to blame, but the system. But from the user's point of view, 
> it is quite hard to figure this out. And certainly the user deserves to know 
> the actual values that parted considers to be of best performance -- I mean, 
> pa->offset and pa->grain_size from parted.c::print_partition_alignment() 
> shall probably be exposed in some way -- at least when it comes to a warning 
> like the one above.


In commit 1726dbb4cd2dc4b19fe8d3c4b94e172fc0bd2c7c I added a message
that describes the failure with a bit more detail. It will print
something like:

<start> % <grain_size> != <offset>

I'm guessing Ubuntu doesn't have that patch, and the 3.2 tarball is
getting *really* old at this point (which is why I'm working toward a
3.3 release soon).

Brian

-- 
Brian C. Lane (PST8PDT) - weldr.io - lorax - parted