[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH v19 09/16] block: Support dropping active in bdr
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH v19 09/16] block: Support dropping active in bdrv_drop_intermediate |
Date: |
Mon, 19 May 2014 13:38:52 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 |
On 05/11/2014 07:35 PM, Fam Zheng wrote:
> Dropping intermediate could be useful both for commit and stream, and
> BDS refcnt plus bdrv_swap could do most of the job nicely. It also needs
> to work with op blockers.
>
> Signed-off-by: Fam Zheng <address@hidden>
> ---
> block.c | 139
> ++++++++++++++++++++++++++++-----------------------------
> block/commit.c | 2 +-
> 2 files changed, 70 insertions(+), 71 deletions(-)
>
> -
> /*
> - * Drops images above 'base' up to and including 'top', and sets the image
> - * above 'top' to have base as its backing file.
> + * Drops images above 'base' up to and including 'top', and sets new 'base'
> as
> + * backing_hd of top's overlay (the image orignally has 'top' as backing
> file).
> + * top's overlay may be NULL if 'top' is active, no such update needed.
> + * Requires that the top's overlay to 'top' is opened r/w.
> + *
> + * 1) This will convert the following chain:
> + *
> + * ... <- base <- ... <- top <- overlay <-... <- active
> *
> - * Requires that the overlay to 'top' is opened r/w, so that the backing file
> - * information in 'bs' can be properly updated.
> + * to
> + *
> + * ... <- base <- overlay <- active
Jeff is working on allowing the user full control over the string
written into overlay; let's make sure these efforts are coordinated.
https://lists.gnu.org/archive/html/qemu-devel/2014-05/msg02949.html
> + *
> + * 2) It is allowed for bottom==base, in which case it converts:
> *
> - * E.g., this will convert the following chain:
> - * bottom <- base <- intermediate <- top <- active
> + * base <- ... <- top <- overlay <- ... <- active
> *
> * to
> *
> - * bottom <- base <- active
> + * base <- overlay <- active
> *
> - * It is allowed for bottom==base, in which case it converts:
> + * 2) It also allows active==top, in which case it converts:
Shouldn't this be 3) ?
> *
> - * base <- intermediate <- top <- active
> + * ... <- base <- ... <- top (active)
> *
> * to
> *
> - * base <- active
> + * ... <- base == active == top
> + *
> + * i.e. only base and lower remains: *top == *base when return.
> + *
> + * 3) If base==NULL, it will drop all the BDS below overlay and set its
and 4)
> + * backing_hd to NULL. I.e.:
> *
> - * Error conditions:
> - * if active == top, that is considered an error
> + * base(NULL) <- ... <- overlay <- ... <- active
> + *
> + * to
> + *
> + * overlay <- ... <- active
> *
> */
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
signature.asc
Description: OpenPGP digital signature
- [Qemu-devel] [PATCH v19 04/16] block: Replace in_use with operation blocker, (continued)
- [Qemu-devel] [PATCH v19 08/16] block: Parse "backing" option to reference existing BDS, Fam Zheng, 2014/05/11
- [Qemu-devel] [PATCH v19 09/16] block: Support dropping active in bdrv_drop_intermediate, Fam Zheng, 2014/05/11
- Re: [Qemu-devel] [PATCH v19 09/16] block: Support dropping active in bdrv_drop_intermediate,
Eric Blake <=
- [Qemu-devel] [PATCH v19 10/16] stream: Use bdrv_drop_intermediate and drop close_unused_images, Fam Zheng, 2014/05/11
- [Qemu-devel] [PATCH v19 11/16] commit: Use bdrv_drop_intermediate, Fam Zheng, 2014/05/11
- [Qemu-devel] [PATCH v19 12/16] qmp: Add command 'blockdev-backup', Fam Zheng, 2014/05/11
- [Qemu-devel] [PATCH v19 13/16] block: Allow backup on referenced named BlockDriverState, Fam Zheng, 2014/05/11
- [Qemu-devel] [PATCH v19 14/16] block: Add blockdev-backup to transaction, Fam Zheng, 2014/05/11
- [Qemu-devel] [PATCH v19 15/16] qemu-iotests: Test blockdev-backup in 055, Fam Zheng, 2014/05/11
- [Qemu-devel] [PATCH v19 16/16] qemu-iotests: Image fleecing test case 089, Fam Zheng, 2014/05/11