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Re: [Qemu-devel] [PATCH v2] block/raw-posix: detect readonly Linux block


From: Kevin Wolf
Subject: Re: [Qemu-devel] [PATCH v2] block/raw-posix: detect readonly Linux block devices using BLKROGET
Date: Wed, 06 Feb 2013 11:30:56 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120605 Thunderbird/13.0

Am 05.02.2013 16:12, schrieb Markus Armbruster:
> Stefan Hajnoczi <address@hidden> writes:
> 
>> Linux block devices can be set read-only with "blockdev --setro
>> <device>".  The same thing can be done for LVM volumes using "lvchange
>> --permission r <volume>".  This read-only setting is independent of
>> device node permissions.  Therefore the device can still be opened
>> O_RDWR but actual writes will fail.
>>
>> This results in odd behavior for QEMU.  bdrv_open() is supposed to fail
>> if a read-only image is being opened with BDRV_O_RDWR.  By not failing
>> for Linux block devices, the guest boots up but every write produces an
>> I/O error.
>>
>> This patch checks whether the block device is read-only so that Linux
>> block devices behave like regular files.
>>
>> Reported-by: Sibiao Luo <address@hidden>
>> Suggested-by: Paolo Bonzini <address@hidden>
>> Signed-off-by: Stefan Hajnoczi <address@hidden>
> 
> Reviewed-by: Markus Armbruster <address@hidden>

Thanks, applied to the block branch.

Kevin



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