Revert "libnvdimm: band aid btt vs clear poison locking"

This reverts commit 4aa5615e "libnvdimm: band aid btt vs clear
poison locking".

Now that poison list locking has been converted to a spinlock and poison
list entry allocation during i/o has been converted to GFP_NOWAIT,
revert the band-aid that disabled error clearing from btt i/o.

Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/nvdimm/claim.c

@@ -243,15 +243,7 @@ static int nsio_rw_bytes(struct nd_namespace_common *ndns,
 	}
 
 	if (unlikely(is_bad_pmem(&nsio->bb, sector, sz_align))) {
-		/*
-		 * FIXME: nsio_rw_bytes() may be called from atomic
-		 * context in the btt case and nvdimm_clear_poison()
-		 * takes a sleeping lock. Until the locking can be
-		 * reworked this capability requires that the namespace
-		 * is not claimed by btt.
-		 */
-		if (IS_ALIGNED(offset, 512) && IS_ALIGNED(size, 512)
-				&& (!ndns->claim || !is_nd_btt(ndns->claim))) {
+		if (IS_ALIGNED(offset, 512) && IS_ALIGNED(size, 512)) {
 			long cleared;
 
 			cleared = nvdimm_clear_poison(&ndns->dev, offset, size);