Yong Huang <yong.hu...@smartx.com> writes: > 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.
Writing good documentation in a second language is *hard*. All we can reasonably expect from contributors to try their best. And then we improve the text together in review. Just like we do for code :) >> > +# 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. Is @size unused then? >> 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
