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[PULL,27/35] qemu-img.1: Image invalidation on qemu-img commit

Message ID 20171026131741.5059-28-kwolf@redhat.com
State New
Headers show
Series [PULL,01/35] block: don't add 'driver' to options when referring to backing via node name | expand

Commit Message

Kevin Wolf Oct. 26, 2017, 1:17 p.m. UTC 
From: Max Reitz <mreitz@redhat.com>

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>
Reviewed-by: Jeff Cody <jcody@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 qemu-img.texi | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)
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Patch

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}