On Mon, May 08, 2017 at 11:46:14PM -0700, Nicholas A. Bellinger wrote: > That said, simply propagating up q->limits.max_write_zeroes_sectors as > dev_attrib->unmap_zeroes_data following existing code still looks like > the right thing to do. It is not. Martin has decoupled write same/zeroes support from discard support. Any device will claim to support it initially, and we'll only clear the flag if a Write Same command fails. So even if LBPRZ is not set you can trivially get into a situation where discard is supported through UNMAP, and you'll incorrectly set LBPRZ and will cause data corruption.
