On 31/03/2016 22:17, Alex Bligh wrote: >> > In qemu, read+FUA just triggers blk_co_flush() prior to reading; but >> > that's the same function it calls for write+FUA. > That's harmless, but unnecessary in the sense that current documented > behaviour doesn't require it. Perhaps it should? > > I suppose TRIM etc. should support FUA too?
TRIM is an advisory operation, so it doesn't make sense to force access to the medium. The closest you could get would be to add FUA to WRITE_ZEROES. But since WRITE_ZEROES is not a particularly common operation there isn't much to gain compared to FLUSHing after the write has completed; in fact SCSI doesn't have a FUA bit on its WRITE SAME command. Paolo
