From fa27c478102a6b5d1c6b02c005607ad9404b915f Mon Sep 17 00:00:00 2001 From: Max Reitz Date: Thu, 11 Jul 2019 15:29:35 +0200 Subject: doc: Preallocation does not require writing zeroes When preallocating an encrypted qcow2 image, it just lets the protocol driver write data and then does not mark the clusters as zero. Therefore, reading this image will yield effectively random data. As such, we have not fulfilled the promise of always writing zeroes when preallocating an image in a while. It seems that nobody has really cared, so change the documentation to conform to qemu's actual behavior. Signed-off-by: Max Reitz Message-id: 20190711132935.13070-1-mreitz@redhat.com Reviewed-by: Eric Blake Reviewed-by: Daniel P. Berrangé Reviewed-by: Maxim Levitsky Signed-off-by: Max Reitz --- docs/qemu-block-drivers.texi | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'docs') diff --git a/docs/qemu-block-drivers.texi b/docs/qemu-block-drivers.texi index 91ab0eceae..c02547e28c 100644 --- a/docs/qemu-block-drivers.texi +++ b/docs/qemu-block-drivers.texi @@ -31,8 +31,8 @@ Supported options: @item preallocation Preallocation mode (allowed values: @code{off}, @code{falloc}, @code{full}). @code{falloc} mode preallocates space for image by calling posix_fallocate(). -@code{full} mode preallocates space for image by writing zeros to underlying -storage. +@code{full} mode preallocates space for image by writing data to underlying +storage. This data may or may not be zero, depending on the storage location. @end table @item qcow2 -- cgit v1.2.3-55-g7522