On 8/6/22 5:49 AM, Zhang Boyang wrote: > Previously, for file-backed loop devices, REQ_OP_DISCARD and > REQ_OP_WRITE_ZEROES (without REQ_NOUNMAP) are implemented using > fallocate(FALLOC_FL_PUNCH_HOLE), which will cause the underlying file to > be sparse and disk space freed. The users have no choice to prevent this > this from happening. > > This patch introduces LO_FLAGS_NODEALLOC. With this flag set, > REQ_OP_DISCARD and REQ_OP_WRITE_ZEROES are forced to use > fallocate(FALLOC_FL_ZERO_RANGE). The disk space of underlying file is > kept allocated. This is useful if users, for example, want to use a > preallocated file as the backing file. Just in terms of readability, I would prefer if NO_DEALLOC is used consistently rather than NODEALLOC. The latter reads more like node-alloc to me. -- Jens Axboe
