On 3/11/19 1:51 PM, Vladimir Sementsov-Ogievskiy wrote: > We already use (we didn't notice it) IN_USE flag for marking bitmap > metadata outdated, such as AUTO flag, which mirrors enabled/disabled > bitmaps. No we are going to support bitmap resize, so it's good to
s/No/Now/ > write IN_USE meaning with more details. > > Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com> > --- > docs/interop/qcow2.txt | 18 +++++++++++++++--- > 1 file changed, 15 insertions(+), 3 deletions(-) > > diff --git a/docs/interop/qcow2.txt b/docs/interop/qcow2.txt > index fb5cb47245..575a5f25e2 100644 > --- a/docs/interop/qcow2.txt > +++ b/docs/interop/qcow2.txt > @@ -589,7 +589,19 @@ Structure of a bitmap directory entry: > Bit > 0: in_use > The bitmap was not saved correctly and may be > - inconsistent. > + inconsistent. This inconsitency may touch both > bitmap inconsistency > + data and metadata, and this mean that bitmap state > + (its data and metadata) was changed but not stored > + back to the image. This flag doesn't relate to > format > + corruption, all fields are still correct from qcow2 > + point of view, they just may be outdated. > + > + Note: Currently, Qemu may change (additionally to > + bitmap data) @auto flag and size of the bitmap > during > + image resize. This mean, that not only bitmap data > + may be outdated if @in_use flag set, but also value > of > + @auto flag and bitmap size (which is indirectly > + referenced by @bitmap_table_size). Feels wordy. Maybe drop the second paragraph starting with Note, and merely use this for the first paragraph: The bitmap was not saved correctly and may be inconsistent. Although the bitmap metadata is still well-formed from a qcow2 perspective, the metadata (such as the auto flag or bitmap size) or data contents may be outdated. > > 1: auto > The bitmap must reflect all changes of the virtual > @@ -717,8 +729,8 @@ corresponding range of the virtual disk (see above) was > written to while the > bitmap was 'enabled'. An unset bit means that this range was not written to. > > The software doesn't have to sync the bitmap in the image file with its > -representation in RAM after each write. Flag 'in_use' should be set while the > -bitmap is not synced. > +representation in RAM after each write or metadata change. Flag 'in_use' > +should be set while the bitmap is not synced. > > In the image file the 'enabled' state is reflected by the 'auto' flag. If > this > flag is set, the software must consider the bitmap as 'enabled' and start > -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org
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