[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH v4 0/7] qemu-img: Add salvaging mode to convert
From: |
Max Reitz |
Subject: |
Re: [Qemu-devel] [PATCH v4 0/7] qemu-img: Add salvaging mode to convert |
Date: |
Thu, 13 Jun 2019 21:52:37 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 |
On 07.05.19 22:35, Max Reitz wrote:
> Hi,
>
> This series adds a --salvage option to qemu-img convert. With this,
> qemu-img will not abort when it encounters an I/O error. Instead, it
> tries to narrow it down and will treat the affected sectors as being
> completely 0 (and print a warning).
>
> Testing this is not so easy, because while real I/O errors during read
> operations should be treated as described above, errors encountered
> during bdrv_block_status() should just be ignored and the affected
> sectors should be considered allocated. But blkdebug does not yet have
> a way to intercept this, and:
>
> (1) Just adding a new block-status event would be silly, because I don't
> want an event, I want it to fail on a certain kind of operation, on
> a certain sector range, independently of any events, so why can't we
> just do that? See patch 4.
>
> (2) If we just make blkdebug intercept .bdrv_co_block_status() like all
> other kinds of operations, at least iotest 041 fails, which does
> exactly that silly thing: It uses the read_aio event to wait for any
> read. But it turns out that there may be a bdrv_*block_status()
> call in between, so suddenly the wrong operation yields an error.
> As I said, the real fault here is that it does not really make sense
> to pray that the operation you want to fail is the one that is
> immediately executed after some event that you hope will trigger
> that operation.
> See patch 3.
>
> So patch 3 allows blkdebug users to select which kind of I/O operation
> they actually want to make fail, and patch 4 allows them to not use any
> event, but to have a rule active all the time.
>
> Together, we can then enable error injection for block-status in patch 5
> and make use of event=none iotype=block-status in patch 6.
Applied the series to my block branch, and fixed _filter_offsets in
patch 6 as suggested by Vladimir.
Max
signature.asc
Description: OpenPGP digital signature
[Prev in Thread] |
Current Thread |
[Next in Thread] |
- Re: [Qemu-devel] [PATCH v4 0/7] qemu-img: Add salvaging mode to convert,
Max Reitz <=