On 05/05/2015 13:48, Kevin Wolf wrote: > It depends. In its basic form, bdrv_discard() just means "I don't care > about the data any more". Then clearing the dirty bitmap is correct. > > The content is only important if the caller used discard to write zeros > because can_write_zeroes_with_unmap = true. Do we have any such callers > apart from qemu-img convert?
Yes, the SCSI command WRITE SAME with UNMAP = 1 (not coincidentially :)) calls discard too. Who knows what the guest used it for... However, write zeroes doesn't go through bdrv_co_discard, does it? Paolo
