[plug] NBD issues

[Brad Campbell]

Craig Ringer wrote:
> Hi folks
> 
> I'm running into some odd issues with NBD that I haven't seen before, 
> and was hoping someone might be able to shed some light.
> 
> If the NBD client I'm using dies without informing the server (ie a 
> hardware reset), the nbd server seems to fail to accept any more 
> connections from that IP. This is a bit of an issue, but not the only one.
> 
> I'm also seeing kernel oops-es when disconnecting an NBD device:
> 
> NBD_DISCONNECT
> NBD: receive - sock=-1041996592 at buf=-1041375512, size=16 returned 0.
> NBD: Recv control failed.(result 0)
> req should never be null
> nbd: shutting down socket
> Unable to handle kernel NULL pointer dereference at virtual address 
> 00000008
>  printing eip:
> c0193b4b
> *pde = 00000000
> Oops: 0000
> CPU:    0
> EIP:    0010:[<c0193b4b>]    Not tainted
> EFLAGS: 00010282
> eax: 00000000   ebx: c0311fb0   ecx: 00000001   edx: c1ef2000
> esi: c0311f90   edi: 00000001   ebp: 00000004   esp: c1eddf18
> ds: 0018   es: 0018   ss: 0018
> Process nbd-client (pid: 115, stackpage=c1edd000)
> Stack: c0262249 00000000 c191c4ac 00000001 00000000 00000000 00030002 
> 00000000
>        00000000 00000000 00000000 00000000 00000000 00000000 00000000 
> 00000000
>        00000000 00000000 00000000 00000000 00000000 00000000 00000000 
> 00000000
> Call Trace:    [<c01379df>] [<c013e251>] [<c0108967>]
> 
> Code: 8b 50 08 6a 03 50 ff 52 28 c7 46 0c 00 00 00 00 83 c4 0c 89

Eww.. thats a nasty stack trace..
Highlight the whole thing with gpm, fire up ksymoops and paste it into 
that, that may provide some insight as to where it's going pear shaped.

I have to say, since I got familiar with ksymoops and gdb my linux 
debugging life has gotten considerably easier.

Brad

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