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Re: Effect in guest of a hard read error from the host's storage ?
- To: Juergen Gross <jgross@xxxxxxxx>
- From: Anthony PERARD <anthony.perard@xxxxxxxxxx>
- Date: Fri, 8 Apr 2022 16:49:18 +0100
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- Cc: George Dunlap <dunlapg@xxxxxxxxx>, Simon Hobson <simon@xxxxxxxxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, xen-users <xen-users@xxxxxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>
- Delivery-date: Fri, 08 Apr 2022 15:50:26 +0000
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- List-id: Xen user discussion <xen-users.lists.xenproject.org>
On Thu, Apr 07, 2022 at 12:20:27PM +0200, Juergen Gross wrote:
> On 07.04.22 12:10, George Dunlap wrote:
> >
> >
> > On Sat, Apr 2, 2022 at 8:28 PM Simon Hobson <simon@xxxxxxxxxxxxxxxx
> > <mailto:simon@xxxxxxxxxxxxxxxx>> wrote:
> >
> > Not having experienced it on any of my Xen systems I’ve managed in the
> > past,
> > I just wanted to check what happens when the host’s storage encounters
> > an
> > unrecoverable read error ?
> > My expectation would be that the error would be passed up the chain
> > (host’s
> > OS, virtual disk emulator, guest OS disk driver, guest OS filesystem,
> > guest
> > OS program), appear as an unrecoverable error to the guest, and hence
> > passed
> > up to the program attempting to read the file - so really nothing
> > different
> > to the same error on bare metal.
> >
> > Has anyone encountered this, and can confirm if that’s how Xen+Linux
> > handles
> > it ?
> >
> >
> > Juergen / Roger / Anthony -- any idea what would happen with either
> > blkback or qdisk on a hard read error? (Or blktap, for that matter?)
>
> Any I/O error for a request issued via the PV block device protocol will be
> handed back to the frontend via a generic error "BLKIF_RSP_ERROR", which is
> handed back to the block layer as I/O error on the guest side.
It seems to be the same when the backend is "qdisk", QEMU sets the
request status to BLKIF_RSP_ERROR on I/O error.
--
Anthony PERARD
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