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Re: [dm-devel] Bug#604049: linux-image-2.6.32-5-amd64: data corruption with promise stex driver and use of device-mapper layers (lvm/dm-crypt/..)

>-----Original Message-----
>From: Ben Hutchings [mailto:ben decadent org uk] 
>Sent: 2010年11月19日 21:34
>To: Ed Lin - PTU; Jens Axboe; dm-devel redhat com
>Cc: Markus Schulz; 604049 bugs debian org
>Subject: Re: Bug#604049: linux-image-2.6.32-5-amd64: data 
>corruption with promise stex driver and use of device-mapper 
>layers (lvm/dm-crypt/..)
>On Fri, 2010-11-19 at 20:26 +0100, Markus Schulz wrote:
>> Package: linux-2.6
>> Version: 2.6.32-27
>> Severity: critical
>> Tags: d-i upstream
>> Justification: causes serious data loss
>> any use of the stex.ko promise hw-raid controller driver with a
>> device-mapper layer produces data corruption (or filesystem 
>> like you can see in my dmesg).
>> i've asked Ed Lin (Maintainer of stex.c from promise) on 
>lkml and got the following answer:
>> > We found similar problem during test.
>> > The stex driver sets sg_tablesize as 32 (for st_yel it's 
>38) in the probe
>> > entry. It seems that this value was overridden by the 
>system if using
>> > dm/lvm, for unknown reason. The driver received requests with more
>> > sg items than registered. Sg item number could be as high 
>as 64. This
>> > is completely unexpected. The firmware could not handle such
>> > requests, and error occurred.
>I have little idea how this stuff is supposed to work, but it 
>looks like
>dm_dispatch_request() calls blk_insert_cloned_request() which calls
>blk_rq_check_limits() which checks the request against the maximum
>number of segments initialised from sg_tablesize.
>We can perhaps mitigate the data loss by checking the number 
>of segments
>again in scsi_dispatch_cmd(), but it won't really solve the problem.

I believe the cause of the problem has been found. An explanation
and a possible solution was posted at the linux-scsi mail list
and dm-devel redhat com 

The link is http://marc.info/?l=linux-scsi&m=129021716922966&w=2
So far no one responded. Any comment is welcome.

Ed Lin

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