On Mon, 14 Jun 2010 12:47:23 +0200
Nagilum [off-list ref] wrote:

----- Message from neilb@suse.de ---------
     Date: Mon, 14 Jun 2010 09:15:18 +1000
     From: Neil Brown [off-list ref]
  Subject: Re: Problem re-shaping RAID6
       To: Jérôme Poulin [off-list ref]
       Cc: linux-raid [off-list ref]

quoted

Thanks.
I fixed this bug a slightly different way

-               blocks = ochunk/512 * nchunk/512 * odata * ndata / a;
+               blocks = (ochunk/512) * (nchunk/512) * odata * ndata / a;


See
http://neil.brown.name/git?p=mdadm;a=commitdiff;h=200871adf9e15d5ad985f28c349fd89c386ef48a

Those static numbers always make my nose wrinkle.
Don't we have the blocksize somewhere already? I'm also concerned what  
happens when true 4k sectors are used..

A sector will always be 512 bytes to Linux, even when we have drives that can
only do IO in multiples of 8 sectors.  Changing that would cause way to many
headaches.

Yes,  I could possibly use a define for '512'.  Some times that is
appropriate, but I thing 512 is so clearly "bytes_per_sector" it would just
add an unnecessary level of indirection.
It is a question of taste really - no right answers.

Thanks,
NeilBrown

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