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From: Chris Torek <torek@torek.net>
To: John-Mark Gurney <jmg@funkthat.com>
Subject: Re: MAXPHYS in md(4)
In-reply-to: Your message of "Mon, 21 Apr 2014 16:15:34 -0700."
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Date: Mon, 21 Apr 2014 17:27:03 -0600
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>Why?  GEOM modules are written on the assumption that no IO larger
>than MAXPHYS will ever be seen...  They allocate arrays of structures
>or other items based upon MAXPHYS, and will smash the stack/crash//do
>bad things if it receives an IO larger than MAXPHYS...
>
>The change would not break anything that isn't already broken (or
>working by luck)...
>
>Now if you're talking about wanting to increase MAXPHYS, there are many
>threads talking about what needs to be done about it, but that is
>completely different than this issue...

Yes, I was thinking of the latter.  It's not *completely*
different as it would be nice to let devices crank down the I/O
size if they have various address and/or byte-count limits.
(Not that I know of any *modern* devices with such limits.  I
see this is mentioned in old freebsd-arch discussions...)

Chris