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Re: [Qemu-devel] [PATCH v19 09/16] block: Support dropping active in bdr
From: |
Fam Zheng |
Subject: |
Re: [Qemu-devel] [PATCH v19 09/16] block: Support dropping active in bdrv_drop_intermediate |
Date: |
Tue, 20 May 2014 11:53:12 +0800 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
On Mon, 05/19 13:38, Eric Blake wrote:
> 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
Looks they are not exclusive functional changes, I can rebase if it is merged
before this.
>
> > + *
> > + * 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) ?
Yes, thanks!
>
> > *
> > - * 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)
>
Yes, thanks!
Fam
- Re: [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
- [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