Date: Wed, 25 Sep 2002 11:29:12 -0700 (PDT) From: Julian Elischer <julian@elischer.org> To: Mark Santcroos <marks@ripe.net> Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: vmware reads disk on non-sector boundary Message-ID: <Pine.BSF.4.21.0209251114130.46717-100000@InterJet.elischer.org> In-Reply-To: <20020925173453.GA1347@laptop.6bone.nl>
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vmware used the blocking ("b" devices) interface to disks that do
blocking for you.
Some well meaning but misguided individuals removed block devices
without providing an alernate way of doing this. It should be possible
to do the equivalent of a vn device that accepts misalligned
accesses and reblocks them, but I'll leave that to those whose
job it is to finish.
On Wed, 25 Sep 2002, Mark Santcroos wrote:
> Vmware2 stopped running from both md and ad devices. Virtual disks still
> work. It is caused by a read that is not on sector boundary.
>
> Should a program be able to read non-sector sized chunks from a raw disk
> yes or no? What is the desired behaviour?
The desired bahaviour is that it works. No programs shouldn't do it,
but they sometimes do, particularly LINUX programs.. (e.g. vmware)
and the chances that we get linux authors to change is really small.
(Particulary vmware who have been particularly stubborn)
>
> The fact that this did work, was it a bug or did this come out due to some
> other change. The stacktrace from read(2) is below.
>
> Any input welcome, it's about time that vmware runs again on -current.
>
> Mark
>
>
> dscheck(c7528a70,c0c20800,4,c7528a70,c28f0800) at dscheck
> diskstrategy(c7528a70,10,4,c0c20800,c0c2086c) at diskstrategy+0x7f
> readdisklabel(c23f4e00,c28f0800,1,c23d4000,c23f4e4c) at readdisklabel+0xb8
> dsopen(c2347e00,2000,0,c23d9588,c23d9200) at dsopen+0x1e6
> diskopen(c2347e00,1,2000,c23e0cc0,c26c4700) at diskopen+0x15f
> spec_open(cdac9a2c,cdac9ac8,c027796b,cdac9a2c,c0911c50) at spec_open+0x150
> spec_vnoperate(cdac9a2c,c0911c50,1,100,c23e0cc0) at spec_vnoperate+0x18
> vn_open_cred(cdac9bcc,cdac9ccc,0,c26c4700,cdac9cb8) at vn_open_cred+0x3eb
> vn_open(cdac9bcc,cdac9ccc,0,1,cdac9b04) at vn_open+0x29
> kern_open(c23e0cc0,8048639,0,1,0) at kern_open+0x1e3
> open(c23e0cc0,cdac9d10,c,c23e0cc0,3) at open+0x30
> syscall(2f,2f,2f,bfbffae4,bfbffaec) at syscall+0x2ca
> Xint0x80_syscall() at Xint0x80_syscall+0x1d
>
> --
> Mark Santcroos RIPE Network Coordination Centre
> http://www.ripe.net/home/mark/ New Projects Group/TTM
>
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