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Re: [Qemu-devel] [PATCHv3] qemu-img rebase: use empty string to rebase w
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCHv3] qemu-img rebase: use empty string to rebase without backing file |
Date: |
Mon, 15 Oct 2012 15:04:37 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:16.0) Gecko/20121009 Thunderbird/16.0 |
On 10/15/2012 02:50 PM, Alex Bligh wrote:
> This patch allows an empty filename to be passed as the new base image name
> for qemu-img rebase to mean base the image on no backing file (i.e.
> independent of any backing file). According to Eric Blake, qemu-img rebase
> already supports this when '-u' is used; this adds support when -u is not
> used.
>
> Signed-off-by: Alex Bligh <address@hidden>
> ---
> qemu-img.c | 26 ++++++++++++++++----------
> qemu-img.texi | 4 +++-
> 2 files changed, 19 insertions(+), 11 deletions(-)
Per http://wiki.qemu.org/Contribute/SubmitAPatch, it helps to add a
maintainer in cc; I'm guessing that this is most closely related to
block work, and therefore adding Kevin in cc.
Reviewed-by: Eric Blake <address@hidden>
>
> Also obtainable from:
> https://github.com/abligh/qemu.git
> Commit at:
>
> https://github.com/abligh/qemu/commit/49cd454aa09062b151710cc7afd4bb7fcf1070d0
>
> diff --git a/qemu-img.c b/qemu-img.c
> index f17f187..e817498 100644
> --- a/qemu-img.c
> +++ b/qemu-img.c
> @@ -1558,13 +1558,14 @@ static int img_rebase(int argc, char **argv)
> error_report("Could not open old backing file '%s'",
> backing_name);
> goto out;
> }
> -
> - bs_new_backing = bdrv_new("new_backing");
> - ret = bdrv_open(bs_new_backing, out_baseimg, BDRV_O_FLAGS,
> + if (out_baseimg[0]) {
> + bs_new_backing = bdrv_new("new_backing");
> + ret = bdrv_open(bs_new_backing, out_baseimg, BDRV_O_FLAGS,
> new_backing_drv);
> - if (ret) {
> - error_report("Could not open new backing file '%s'",
> out_baseimg);
> - goto out;
> + if (ret) {
> + error_report("Could not open new backing file '%s'",
> out_baseimg);
> + goto out;
> + }
> }
> }
>
> @@ -1580,7 +1581,7 @@ static int img_rebase(int argc, char **argv)
> if (!unsafe) {
> uint64_t num_sectors;
> uint64_t old_backing_num_sectors;
> - uint64_t new_backing_num_sectors;
> + uint64_t new_backing_num_sectors = 0;
> uint64_t sector;
> int n;
> uint8_t * buf_old;
> @@ -1592,7 +1593,8 @@ static int img_rebase(int argc, char **argv)
>
> bdrv_get_geometry(bs, &num_sectors);
> bdrv_get_geometry(bs_old_backing, &old_backing_num_sectors);
> - bdrv_get_geometry(bs_new_backing, &new_backing_num_sectors);
> + if (bs_new_backing)
> + bdrv_get_geometry(bs_new_backing, &new_backing_num_sectors);
>
> local_progress = (float)100 /
> (num_sectors / MIN(num_sectors, IO_BUF_SIZE / 512));
> @@ -1629,7 +1631,7 @@ static int img_rebase(int argc, char **argv)
> }
> }
>
> - if (sector >= new_backing_num_sectors) {
> + if (sector >= new_backing_num_sectors || !bs_new_backing) {
> memset(buf_new, 0, n * BDRV_SECTOR_SIZE);
> } else {
> if (sector + n > new_backing_num_sectors) {
> @@ -1675,7 +1677,11 @@ static int img_rebase(int argc, char **argv)
> * backing file are overwritten in the COW file now, so the visible
> content
> * doesn't change when we switch the backing file.
> */
> - ret = bdrv_change_backing_file(bs, out_baseimg, out_basefmt);
> + if (bs_new_backing)
> + ret = bdrv_change_backing_file(bs, out_baseimg, out_basefmt);
> + else
> + ret = bdrv_change_backing_file(bs, NULL, NULL);
> +
> if (ret == -ENOSPC) {
> error_report("Could not change the backing file to '%s': No "
> "space left in the file header", out_baseimg);
> diff --git a/qemu-img.texi b/qemu-img.texi
> index 8b05f2c..42ec392 100644
> --- a/qemu-img.texi
> +++ b/qemu-img.texi
> @@ -148,7 +148,9 @@ Changes the backing file of an image. Only the formats
> @code{qcow2} and
>
> The backing file is changed to @var{backing_file} and (if the image format of
> @var{filename} supports this) the backing file format is changed to
> address@hidden
> address@hidden If @var{backing_file} is specified as ``'' (the empty
> +string), then the image is rebased onto no backing file (i.e. it will exist
> +independently of any backing file).
>
> There are two different modes in which @code{rebase} can operate:
> @table @option
>
--
Eric Blake address@hidden +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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