On Wed, Aug 1, 2012 at 2:57 PM, Eric Blake <ebl...@redhat.com> wrote: > On 07/31/2012 10:51 AM, Dong Xu Wang wrote: >> This is the implementation code for add-cow file format. Because image_file >> might be very huge, then we can't read entire bitmap into memory, we must use >> a cache. Since qcow-cache.c has implemted cache code, we can create our cache > > s/implemted/implemented/ > >> code based on it. > > Just wondering if Paolo's HBitmap code for drive-mirror might be a more > efficient way to implement your caching. > >> >> Signed-off-by: Dong Xu Wang <wdon...@linux.vnet.ibm.com> >> --- >> block/Makefile.objs | 1 + >> block/add-cow-cache.c | 206 +++++++++++++++++ >> block/add-cow.c | 599 >> +++++++++++++++++++++++++++++++++++++++++++++++++ >> block/add-cow.h | 101 +++++++++ >> block_int.h | 2 + > > Rather than adding a new implementation for code duplication, can you > refactor the existing implementation to be reusable, and update > qcow-cache.c to call into the common refactored code?
I looked at this and block/qcow2-cache.c seems fairly clean and generic. The only things that need to be parameterized are the s->l2_table_cache/s->refcount_block_cache and s->cluster_size. These can be fixed by adding fields to Qcow2Cache: size_t table_size; /* cached table size in bytes */ BlkDebugEvent flush_event; BlkDebugEvent load_event; Or maybe a table type enum (L2/refcount blocks/bitmap blocks). If Kevin agrees with extracting this from qcow2 (i.e. we can't add more qcow2-specific behavior easily in the future), then this looks doable. Stefan
