[Devel] Re: megaraid_mbox: garbage in file

[Vasily Averin]

Small update:

When I use
cat /vz/private/101/root/etc/ld.so.cache >/tmp/ttt
I've get "access beyond end of device" and garbage in buffers

Then I create the same scsi read command by using sgp_dd utils:
sgp_dd count=26 if=/dev/sg0 skip=871769260 of=/tmp/ttt.sgp
and get correct file content without any errors.

The only difference that I see is use_sg=3 for cat and use_sg=1 for dd.

dmesg with scsi debugs and output files are attached.

Node will be accessible for some time and I can perform some experiments. If
somebody wants I can request the customer about access on the node.

Thank you,
	Vasily Averin

SWsoft Virtuozzo/OpenVZ Linux kernel team

Vasily Averin wrote:
> James Bottomley wrote:
>>On Thu, 2006-05-04 at 22:48 +0400, Vasily Averin wrote:
>>>attempt to access beyond end of device
>>>sda6: rw=0, want=1044134458, limit=951401367
>>>Buffer I/O error on device sda6, logical block 522067228
>>That's not a SCSI error.  It's coming from the block layer and it means
>>that the filesystem tried to access beyond the end of the listed
>>partition.   Why that happened is anyone's guess.  I suspect the actual
>>filesystem is corrupt somehow, but how it came to be, I don't know.
> 
> James,
> 
> The issue is that the correctly finished scsi read command return me garbage
> (repeated 0 ...127 -- see hexdump in my first letter) instead correct file content.
> "attempt to access beyond end of device" messages occurs due the same garbage
> readed from the Indirect block. I found this garbage present in data buffers
> beginning at megaraid driver functions.
> 
> I would note that if I read the same file by using dd with bs=1024 or bs=512 --
> I get correct file content.
> 
> When I use kernel with 4Gb memory limit -- the same cat command return me
> correct file content too, without any garbage.
> 
> Question is what it is the strange garbage? Have you seen it earlier?
> Is it possible that it is some driver-related issue or it is broken hardware?
> And why I can workaround this issue by using only 4Gb memory?
> 
> Thank you,
> 	Vasily Averin
> 
> SWsoft Virtuozzo/OpenVZ Linux kernel team
> 

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