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Date: Thu, 21 Mar 2013 12:03:20 +0100
From: Peter Lieven <pl@dlhnet.de>
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Subject: Re: [Qemu-devel] iscsi / block segfault regression
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To: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>
Cc: Kevin Wolf <kwolf@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, ronnie sahlberg <ronniesahlberg@gmail.com>

git bisect results:

lieven@lieven-pc:~/git/qemu$ git bisect bad
f500a6d3c2b9ef0bb06d0080d91d8ed3c1d68f58 is the first bad commit
commit f500a6d3c2b9ef0bb06d0080d91d8ed3c1d68f58
Author: Kevin Wolf <kwolf@redhat.com>
Date:   Mon Nov 12 17:35:27 2012 +0100

     block: Avoid second open for format probing

     This fixes problems that are caused by the additional open/close cycle
     of the existing format probing, for example related to qemu-nbd without
     -t option or file descriptor passing.

     Signed-off-by: Kevin Wolf <kwolf@redhat.com>

:100644 100644 c4f5566b5de6cfa371d7b60dd8b0e1a2da7fd55f 2ec3afebfe6a6c12b573cba9ad36de800623fe6a M	block.c


On 21.03.2013 11:45, Peter Lieven wrote:
> Hi,
>
> I currently try to debug a regression in git master with iscsi that happens with some iscsi volumes.
> I added debugging output to all aio calls into block/iscsi.c and it seems that immediately after
> brdv_open something is overwriting bs->opaque with a new pointer.
>
> ~/git/qemu$ x86_64-softmmu/qemu-system-x86_64 -k de -enable-kvm -m 1024 -drive format=iscsi,file=iscsi://172.21.200.31/iqn.2001-05.com.equallogic:0-8a0906-3c0f4e007-dce91829d0450add-lieven-storage-migration-test-hd0/0,if=virtio,cache=writeback,aio=native
>   -vnc :1 -boot dc -monitor stdio
> iscsi open start
> iscsi_full_connect_sync: iscsilun = 140063347224208, iscsilun->iscsi = 140063347225536, bs = 140063347221696, filename=iscsi://172.21.200.31/iqn.2001-05.com.equallogic:0-8a0906-3c0f4e007-dce91829d0450add-lieven-storage-migration-test-hd0/0
> iscsi open finish ret=0
> iscsi_aio_flush: iscsilun = 140063347230736, iscsilun->iscsi = 0, bs = 140063347221696, filename=iscsi://172.21.200.31/iqn.2001-05.com.equallogic:0-8a0906-3c0f4e007-dce91829d0450add-lieven-storage-migration-test-hd0/0
> iscsi_aio_flush_acb: iscsilun = 140063347230736, iscsilun->iscsi = 0, bs = 140063347221696, filename=iscsi://172.21.200.31/iqn.2001-05.com.equallogic:0-8a0906-3c0f4e007-dce91829d0450add-lieven-storage-migration-test-hd0/0
> Speicherzugriffsfehler (Speicherabzug geschrieben)
>
> bs address is unchanged, but iscsilun address is changed after connection it seems to an area with zeroed memory. the pointer to the iscsi context
> is thus NULL.
>
> iscsilun, iscsilun->iscsi and bs are addresses.
>
> Peter
>