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Re: [Qemu-devel] Fwd: qemu drive mirror assert fault

From: Paolo Bonzini
Subject: Re: [Qemu-devel] Fwd: qemu drive mirror assert fault
Date: Tue, 05 May 2015 13:49:57 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0

On 05/05/2015 13:48, Kevin Wolf wrote:
> It depends. In its basic form, bdrv_discard() just means "I don't care
> about the data any more". Then clearing the dirty bitmap is correct.
> The content is only important if the caller used discard to write zeros
> because can_write_zeroes_with_unmap = true. Do we have any such callers
> apart from qemu-img convert?

Yes, the SCSI command WRITE SAME with UNMAP = 1 (not coincidentially :))
calls discard too.  Who knows what the guest used it for...

However, write zeroes doesn't go through bdrv_co_discard, does it?


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