On 03.07.20 17:58, Alberto Garcia wrote: > This works now at the subcluster level and pwrite_zeroes_alignment is > updated accordingly. > > qcow2_cluster_zeroize() is turned into qcow2_subcluster_zeroize() with > the following changes: > > - The request can now be subcluster-aligned. > > - The cluster-aligned body of the request is still zeroized using > zero_in_l2_slice() as before. > > - The subcluster-aligned head and tail of the request are zeroized > with the new zero_l2_subclusters() function. > > There is just one thing to take into account for a possible future > improvement: compressed clusters cannot be partially zeroized so > zero_l2_subclusters() on the head or the tail can return -ENOTSUP. > This makes the caller repeat the *complete* request and write actual > zeroes to disk. This is sub-optimal because > > 1) if the head area was compressed we would still be able to use > the fast path for the body and possibly the tail. > > 2) if the tail area was compressed we are writing zeroes to the > head and the body areas, which are already zeroized. > > Signed-off-by: Alberto Garcia <be...@igalia.com> > --- > block/qcow2.h | 4 +-- > block/qcow2-cluster.c | 81 +++++++++++++++++++++++++++++++++++++++---- > block/qcow2.c | 33 +++++++++--------- > 3 files changed, 94 insertions(+), 24 deletions(-)
Reviewed-by: Max Reitz <mre...@redhat.com>
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