Am 10.01.2019 um 14:20 hat Vladimir Sementsov-Ogievskiy geschrieben: > drv_co_block_status digs bs->file for additional, more accurate search > for hole inside region, reported as DATA by bs since 5daa74a6ebc. > > This accuracy is not free: assume we have qcow2 disk. Actually, qcow2 > knows, where are holes and where is data. But every block_status > request calls lseek additionally. Assume a big disk, full of > data, in any iterative copying block job (or img convert) we'll call > lseek(HOLE) on every iteration, and each of these lseeks will have to > iterate through all metadata up to the end of file. It's obviously > ineffective behavior. And for many scenarios we don't need this lseek > at all. > > So, let's "5daa74a6ebc" by default, leaving an option to return > previous behavior, which is needed for scenarios with preallocated > images. > > Add iotest illustrating new option semantics. > > Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
I still think that an option isn't a good solution and we should try use some heuristics instead. Kevin
