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[Xen-devel] [PATCH] Add sharing-check for blktap

To: "xen-devel" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: [Xen-devel] [PATCH] Add sharing-check for blktap
From: "Kasai Takanori" <kasai.takanori@xxxxxxxxxxxxxx>
Date: Fri, 17 Aug 2007 17:52:30 +0900
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Hi All,

When the same file is specified with blktap in two or more domains,
it is not checked regardless of the mode.

The configuration file is defined as follows.

Domain1 :
disk = [ ,"tap:aio:/xen/image/tmp/drive.img-1,xvdd,w" ]

Domain2 :
disk = [ ,"tap:aio:/xen/image/tmp/drive.img-1,xvdd,w" ]

Even if the same file is specified, the domain can be started.

# xm create -f Domain1
Using config file "./Domain1"
Started domain Domain1
# xm create -f Domain2
Using config file "./Domain2"
Started domain Domain2

Whether it is possible to share in the specified mode in file backend and physical device is checked.
However, blktap is not checked at all.

Domain1   Domain2    phy:       tap:
mode       mode     file:
  w         w       Error      Started
  w         r       Error      Started
  w         w!      Started    Started
  r         w       Error      Started
  r         r       Started    Started
  r         w!      Started    Started
  w!        w       Error      Started
  w!        r       Started    Started
  w!        w!      Started    Started

There is a possibility of breaking the file because it can
unconsciously share the same file by two or more domains.
We corrected to do the sharing-check for blktap similarly.
It was tested to check it similarly with all cases in this patch.

Signed-off-by: Takanori Kasai <kasai.takanori@xxxxxxxxxxxxxx>
Signed-off-by: Hirofumi Tsujimura <tsujimura.hirof@xxxxxxxxxxxxxx>

Best Regards

Takanori Kasai

Attachment: sharing-check-for-blktap.patch
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