[Qemu-devel] [PATCH] qemu-img.1: Image invalidation on qemu-img commit

[Qemu-devel] [PATCH] qemu-img.1: Image invalidation on qemu-img commit

[Max Reitz]

qemu-img commit invalidates all images between base and top.  This
should be mentioned in the man page.

Suggested-by: Ping Li <pingl@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
---
 qemu-img.texi | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/qemu-img.texi b/qemu-img.texi
index ee5c5940d3..fdcf120f36 100644
--- a/qemu-img.texi
+++ b/qemu-img.texi
@@ -274,11 +274,10 @@ If the backing chain of the given image file @var{filename} has more than one
 layer, the backing file into which the changes will be committed may be
 specified as @var{base} (which has to be part of @var{filename}'s backing
 chain). If @var{base} is not specified, the immediate backing file of the top
-image (which is @var{filename}) will be used. For reasons of consistency,
-explicitly specifying @var{base} will always imply @code{-d} (since emptying an
-image after committing to an indirect backing file would lead to different data
-being read from the image due to content in the intermediate backing chain
-overruling the commit target).
+image (which is @var{filename}) will be used. Note that after a commit operation
+all images between @var{base} and the top image will be invalid and may return
+garbage data when read. For this reason, @code{-b} implies @code{-d} (so that
+the top image stays valid).
 
 @item compare [-f @var{fmt}] [-F @var{fmt}] [-T @var{src_cache}] [-p] [-s] [-q] @var{filename1} @var{filename2}
 
-- 
2.13.6

Re: [Qemu-devel] [Qemu-block] [PATCH] qemu-img.1: Image invalidation on qemu-img commit

[Jeff Cody]

On Thu, Oct 26, 2017 at 09:59:47AM +0200, Max Reitz wrote:
> qemu-img commit invalidates all images between base and top.  This
> should be mentioned in the man page.
> 
> Suggested-by: Ping Li <pingl@redhat.com>
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>  qemu-img.texi | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/qemu-img.texi b/qemu-img.texi
> index ee5c5940d3..fdcf120f36 100644
> --- a/qemu-img.texi
> +++ b/qemu-img.texi
> @@ -274,11 +274,10 @@ If the backing chain of the given image file @var{filename} has more than one
>  layer, the backing file into which the changes will be committed may be
>  specified as @var{base} (which has to be part of @var{filename}'s backing
>  chain). If @var{base} is not specified, the immediate backing file of the top
> -image (which is @var{filename}) will be used. For reasons of consistency,
> -explicitly specifying @var{base} will always imply @code{-d} (since emptying an
> -image after committing to an indirect backing file would lead to different data
> -being read from the image due to content in the intermediate backing chain
> -overruling the commit target).
> +image (which is @var{filename}) will be used. Note that after a commit operation
> +all images between @var{base} and the top image will be invalid and may return
> +garbage data when read. For this reason, @code{-b} implies @code{-d} (so that
> +the top image stays valid).
>  
>  @item compare [-f @var{fmt}] [-F @var{fmt}] [-T @var{src_cache}] [-p] [-s] [-q] @var{filename1} @var{filename2}
>  
> -- 
> 2.13.6
> 
>

Reviewed-by: Jeff Cody <jcody@redhat.com>

Re: [Qemu-devel] [PATCH] qemu-img.1: Image invalidation on qemu-img commit

[Kevin Wolf]

Am 26.10.2017 um 09:59 hat Max Reitz geschrieben:
> qemu-img commit invalidates all images between base and top.  This
> should be mentioned in the man page.
> 
> Suggested-by: Ping Li <pingl@redhat.com>
> Signed-off-by: Max Reitz <mreitz@redhat.com>

Thanks, applied to the block branch.

Kevin