On 2020/5/16 20:50, Christoph Hellwig wrote: > On Sat, May 16, 2020 at 08:44:45PM +0800, Coly Li wrote: >> Yes you are right, just like REQ_OP_DISCARD which does not transfer any >> data but changes the data on device. If the request changes the stored >> data, it does transfer data. > > REQ_OP_DISCARD is a special case, because most implementation end up > transferring data, it just gets attached in the low-level driver. > Yes, REQ_OP_ZONE_RESET and REQ_OP_ZONE_RESET_ALL are quite similar to REQ_OP_DISCARD. Data read from the LBA range of reset zone is not suggested and the content is undefined. For bcache, similar to REQ_OP_DISCARD, REQ_OP_ZONE_RESET and REQ_OP_ZONE_RESET_ALL are handled in same way: If the backing device supports discard/zone_reset, and the operation successes, then cached data on SSD covered by the LBA range should be invalid, otherwise users will read outdated and garbage data. We should treat REQ_OP_ZONE_RESET and REQ_OP_ZONE_RESET_ALL being in WRITE direction. Coly Li
