From: Paolo Bonzini <pbonzini@redhat.com>
To: Olaf Hering <olaf@aepfle.de>, Kevin Wolf <kwolf@redhat.com>,
Stefan Hajnoczi <stefanha@redhat.com>
Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org
Subject: Re: [Qemu-devel] bogus bdrv_check_request in bdrv_co_discard
Date: Wed, 9 Mar 2016 13:29:48 +0100 [thread overview]
Message-ID: <56E0173C.70407@redhat.com> (raw)
In-Reply-To: <20160309121139.GA21975@aepfle.de>
On 09/03/2016 13:11, Olaf Hering wrote:
> What is the purpose of the bdrv_check_request() call in bdrv_co_discard?
>
> It seems a frontend cant possibly know what the limit is in the
> qemu-of-the-day, I found no interface to propagate
> BDRV_REQUEST_MAX_SECTORS into the guest.
It depends on the backend. For example SCSI uses the block limits VPD
page. It has a default max-unmap-size of 1 GiB, which happens to be
smaller than BDRV_REQUEST_MAX_SECTORS too.
It probably should range check max_unmap_size and max_io_size against
BDRV_REQUEST_MAX_SECTORS, and reject anything bigger than that, though.
Paolo
> I think to handle nb_sectors > BDRV_REQUEST_MAX_SECTORS bdrv_co_discard
> has to split the request into smaller chunks, just as it does a few
> lines down in the function.
next prev parent reply other threads:[~2016-03-09 12:30 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-09 12:11 [Qemu-devel] bogus bdrv_check_request in bdrv_co_discard Olaf Hering
2016-03-09 12:29 ` Paolo Bonzini [this message]
[not found] ` <20160309144514.GA29027@aepfle.de>
2016-03-09 14:58 ` Kevin Wolf
2016-03-09 16:50 ` Olaf Hering
2016-03-09 17:03 ` Olaf Hering
2016-03-16 10:18 ` Olaf Hering
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