Re: [Qemu-devel] [PATCH v4 1/3] block/qcow2: refactoring of threaded encryption code

[Kevin Wolf <kwolf@redhat.com>]

Am 13.09.2019 um 16:07 hat Maxim Levitsky geschrieben:
> On Fri, 2019-09-13 at 14:01 +0000, Vladimir Sementsov-Ogievskiy wrote:
> > 13.09.2019 15:59, Maxim Levitsky wrote:
> > > This commit tries to clarify few function arguments,
> > > and add comments describing the encrypt/decrypt interface
> > > 
> > > Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
> > > ---
> > >   block/qcow2-cluster.c |  9 ++++---
> > >   block/qcow2-threads.c | 62 ++++++++++++++++++++++++++++++++++---------
> > >   block/qcow2.c         |  5 ++--
> > >   block/qcow2.h         |  8 +++---
> > >   4 files changed, 61 insertions(+), 23 deletions(-)
> > > 
> > > diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
> > > index f09cc992af..46b0854d7e 100644
> > > --- a/block/qcow2-cluster.c
> > > +++ b/block/qcow2-cluster.c
> > > @@ -463,8 +463,8 @@ static int coroutine_fn do_perform_cow_read(BlockDriverState *bs,
> > >   }
> > >   
> > >   static bool coroutine_fn do_perform_cow_encrypt(BlockDriverState *bs,
> > > -                                                uint64_t src_cluster_offset,
> > > -                                                uint64_t cluster_offset,
> > > +                                                uint64_t guest_cluster_offset,
> > > +                                                uint64_t host_cluster_offset,
> > >                                                   unsigned offset_in_cluster,
> > >                                                   uint8_t *buffer,
> > >                                                   unsigned bytes)
> > > @@ -474,8 +474,9 @@ static bool coroutine_fn do_perform_cow_encrypt(BlockDriverState *bs,
> > >           assert((offset_in_cluster & ~BDRV_SECTOR_MASK) == 0);
> > >           assert((bytes & ~BDRV_SECTOR_MASK) == 0);
> > >           assert(s->crypto);
> > > -        if (qcow2_co_encrypt(bs, cluster_offset,
> > > -                             src_cluster_offset + offset_in_cluster,
> > > +        if (qcow2_co_encrypt(bs,
> > > +                             host_cluster_offset + offset_in_cluster,
> > > +                             guest_cluster_offset + offset_in_cluster,
> > 
> > oops, seems you accidentally fixed the bug, which you are going to fix in the next
> > patch, as now correct offsets are given to qcow2_co_encrypt :)
> > 
> > and next patch no is a simple no-logic-change refactoring, so at least commit message
> > should be changed.
> 
> Yep :-( I am trying my best in addition to fixing the bug, also clarify the area to
> avoid this from happening again.
> 
> What do you think that I fold these two patches together after all?

No, just make sure that your refactoring patch is really just
refactoring without semantic change, i.e. make sure to preserve the bug
in this patch.

Maybe you should actually have two refactoring patches (this one without
the addition of offset_in_cluster, and patch 2) and an additional
one-liner for the actual fix.

Kevin