On Tue, Jun 30, 2020 at 09:36:33AM -0400, Mike Snitzer wrote: > On Tue, Jun 30 2020 at 10:10am -0400, > Michal Suchánek <msucha...@suse.de> wrote: > > > On Tue, Jun 30, 2020 at 09:32:01AM -0400, Mikulas Patocka wrote: > > > > > > > > > On Tue, 30 Jun 2020, Michal Suchanek wrote: > > > > > > > The writecache driver does not handle asynchronous pmem. Reject it when > > > > supplied as cache. > > > > > > > > Link: https://lore.kernel.org/linux-nvdimm/87lfk5hahc....@linux.ibm.com/ > > > > Fixes: 6e84200c0a29 ("virtio-pmem: Add virtio pmem driver") > > > > > > > > Signed-off-by: Michal Suchanek <msucha...@suse.de> > > > > --- > > > > drivers/md/dm-writecache.c | 6 ++++++ > > > > 1 file changed, 6 insertions(+) > > > > > > > > diff --git a/drivers/md/dm-writecache.c b/drivers/md/dm-writecache.c > > > > index 30505d70f423..57b0a972f6fd 100644 > > > > --- a/drivers/md/dm-writecache.c > > > > +++ b/drivers/md/dm-writecache.c > > > > @@ -2277,6 +2277,12 @@ static int writecache_ctr(struct dm_target *ti, > > > > unsigned argc, char **argv) > > > > > > > > wc->memory_map_size -= (uint64_t)wc->start_sector << > > > > SECTOR_SHIFT; > > > > > > > > + if (!dax_synchronous(wc->ssd_dev->dax_dev)) { > > > > + r = -EOPNOTSUPP; > > > > + ti->error = "Asynchronous persistent memory not > > > > supported as pmem cache"; > > > > + goto bad; > > > > + } > > > > + > > > > bio_list_init(&wc->flush_list); > > > > wc->flush_thread = > > > > kthread_create(writecache_flush_thread, wc, "dm_writecache_flush"); > > > > if (IS_ERR(wc->flush_thread)) { > > > > -- > > > > > > Hi > > > > > > Shouldn't this be in the "if (WC_MODE_PMEM(wc))" block? > > That should be always the case at this point. > > > > > > WC_MODE_PMEM(wc) retrurns true if we are using persistent memory as a > > > cache device, otherwise we are using generic block device as a cache > > > device. > > > > This is to prevent the situation where we have WC_MODE_PMEM(wc) but > > cannot guarantee consistency because the async flush is not handled. > > The writecache operates in 2 modes. SSD or PMEM. Mikulas is saying > your dax_synchronous() check should go within a WC_MODE_PMEM(wc) block > because it doesn't make sense to do the check when in SSD mode.
Indeed, it's in the wrong if/else branch. Thanks Michal
