On Wed, Feb 21, 2024 at 2:43 PM Markus Armbruster <arm...@redhat.com> wrote:
> Hyman Huang <yong.hu...@smartx.com> writes: > > > Add comment in detail for commit 433957bb7f (qapi: > > Make parameter 'file' optional for > > BlockdevCreateOptionsLUKS). > > > > Signed-off-by: Hyman Huang <yong.hu...@smartx.com> > > --- > > qapi/block-core.json | 20 +++++++++++++++++++- > > 1 file changed, 19 insertions(+), 1 deletion(-) > > > > diff --git a/qapi/block-core.json b/qapi/block-core.json > > index ab5a93a966..42b0840d43 100644 > > --- a/qapi/block-core.json > > +++ b/qapi/block-core.json > > @@ -4973,7 +4973,25 @@ > > ## > > # @BlockdevCreateOptionsLUKS: > > # > > -# Driver specific image creation options for LUKS. > > +# Driver specific image creation options for LUKS. Note that > > +# @file is required if @preallocation is specified and equals > > +# PREALLOC_MODE_ON. The following three scenarios determine how > > +# creation logic behaves when @preallocation is either equal to > > +# PREALLOC_MODE_OFF or is not given: > > +# > > +# 1) When @file is given only, format the block device referenced > > +# by @file as the LUKS specification and trunk it to the @size. > > Do you mean "truncate it to @size"? > Yes, :( sorry for the spelling mistake. > > > +# In this case, the @size should reflect amount of space made > > +# available to the guest, so the trunk size must take account > > +# of that which will be used by the crypto header. > > +# > > +# 2) When @header is given only, just format the block device > > +# referenced by @header as the LUKS specification. > > +# > > +# 3) When both @file and @header are given, block device > > +# referenced by @file should be trunked to @size, and block > > +# device referenced by @header should be formatted as the LUKS > > +# specification. > > # > > # @file: Node to create the image format on, mandatory except when > > # 'preallocation' is not requested > > Let's see whether I understand. > > blockdev-create with "driver": "luks" can work in three different ways: > > 1. Create an image with a LUKS header > > 2. Create just a detached LUKS header > > 3. Create an image and a detached LUKS header > > Correct? > Yes > @file and @header are BlockdevRef, which means they refer to existing > images with arbitrary driver. Could be "file", "qcow2", or anything. > > Correct? > Yes > > To get 1., specify @file, but not @header. > > To get 2., specify @header, but not @file. > > To get 3., specify both. > > Specifying neither is an error. > > Correct? > Yes > In any case, @size is the logical size of the image (how much data it > can hold). > Yes > > With 1., the actual image size is a bit larger due to the LUKS header. > The @file image is resized to that size: if it's shorter, it's grown, if > it's longer, it's truncated. > Yes > With 2., @size is merely recorded in the detached LUKS header. > In LUKS1 specification, payload data size is not contained in the header, so in this case, @size is not recorded in the detached LUKS header. The creation logic just does the LUKS header formatting only. > > With 3., @size is recorded in the detached LUKS header, and the @file > image is resized as with 1. > Same reason as above, @size is not recorded and @file image is resized to @size exactly. > > Correct? > > Thanks for the comment, Yong -- Best regards
